BS: Thermostats

Subject: low voltage (15 to 30) CT87A,BJ, ROUND
From:
Date: 14 Oct 05 - 10:33 AM

question there are 3 poles R,W,Y WJAT KINDA WIRE DO I NEED 2 PAIR? what guage wire do i need its 45 feet from t-stat and connectiona at each end please

Subject: RE: BS: Thermostats
From: dianavan
Date: 06 Oct 05 - 07:41 PM

open mike - I didn't have musch choice. Who said monopolies were illegal?

Subject: RE: BS: Thermostats
From: JennyO
Date: 06 Oct 05 - 04:05 AM

wonder if I should tackle the hissing toilet next. :>)

Dianavan - so you are being bothered by the "flush of a distant toilet"? Seems to be a lot of that round here :-)

Anyway, I'm glad the thermostat's been turned down on this thread. Things were getting a bit hot for a while....

Subject: RE: BS: Thermostats
From: open mike
Date: 06 Oct 05 - 01:26 AM

unfortunte that you supported the honeywell company..
because they make triggers for nuclear weapons..
and often it is their products and componenets
that are transported by the white (nuke) trains

oh well, hard to seperate yourself from the military
industrial complex because it is, well, complex.

Subject: RE: BS: Thermostats
From: dianavan
Date: 06 Oct 05 - 01:16 AM

Thank-you, J in K -

I'm warm and cozy now. Sure have learned alot. Thanks for teaching me so much! I'm feeling quite brave now and wonder if I should tackle the hissing toilet next. :>)

d

Subject: RE: BS: Thermostats
From: JohnInKansas
Date: 05 Oct 05 - 07:05 PM

dianovan -

DON'T BUY ANOTHER THERMOSTAT.

The new Honeywell CT50 thermostat you just installed IS EXACTLY THE SAME as the "round" Honeywell T87F that you removed, except:

1. The CT50 isn't "round."
2. The T87F probably costs more.



ONE STEP AT A TIME:

I'm more confused than ever!

Welcome to mudcat.



My heating system is a gas fired boiler that gravity feeds hot water (not steam) to the radiators

We thought we had that figured out. I'm glad you've confirmed it.




It appears that the CT50A is for gas or oil only - according to the manual.

The usual use for the CT50A is for turning a gas or oil burner on/off. That just means that most people who buy one will use it that way. The installation instruction sheet that comes with the "round one" you removed SAYS EXACTLY THE SAME THING.

The ONLY thing that distinguishes a "gas or oil" thermostat from a "convection hot water" thermostat in most cases is where they set the anticipator before they put it in the box.

Since most people who buy either a CT50 or an T87F will use it to turn a gas or oil burner valve on/off, the anticipator will be set to ".2," "0.2," (or for some other brands to "200,") because most burner valves will require about two tenths of an ampere, (or 200 milliamperes) at 20 or 30 volts, to be turned on/off.

If you go seek out a "different thermostat" for a convection circuit water heating system, you are quite likely to get THE SAME THERMOSTAT with the anticipator pre-set to about ".8," "0.8," or "800" because common low-volt water shutoff solenoids (valves) usually require about eight tenths of an ampere to turn on/off. It will likely have a slightly different "detail model number," and will cost you a bit more or a bit less depending on the mood of the guy who wrote the latest "how much can we screw them for this" list.



I am also quite unsure about the anticipator. As I mentioned before, I had read it should be at 8 for a gravity fed hot-water system. You seemed to confirm in a previous post that this was correct. I have only a single metal arm called the anticipator.

A typical setting for a gravity fed (convection) hot-water system would be ".8" or "0.8". The ONLY THING that matters is how much current is required to pass through the switch in the thermostat, to turn on the valve that lets the water flow when you need to warm the room.

Please note: IT DOESN'T MATTER VERY MUCH in most cases.

1. Any setting that results in the room getting warmer when it should get warmer, and doesn't result in the room getting warmer when it should not get warmer, is okay.

2. Setting the anticipator more precisely may make you more comfortable, and potentially can save a bit of fuel, but it's extremely tedious and time consuming to "adjust" one, so most people use a default setting.

3. Setting the anticipator ALL THE WAY to one end, IF the valve actually requires a fair amount of current, may result in burnout of the anticipator or in reduced life of the thermostat. All the way to the other end won't hurt the thermostat, but it's hard to tell that end from 'tother end, so just "don't go all the way 'less it's for a good reason." Your mother told you that years ago.

WHAT SHOULD YOU DO ABOUT YOUR ANTICIPATOR

1. If your heat comes on and eventually goes off (and eventually comes back on again) you don't really have to do anything.

2. If your old thermostat hasn't been changed, you can look at it and set the anticipator on your new one to the same number it used.

3. If you can find the valve that actually turns on the water to provide heat, you can look at its nameplate to see how much current it needs, and set the anticipator to a matching number.

4. You can make a guess, and hope, and it will probably be okay. With your system about 0.8 or so should be a good guess unless you find that you need to use a different value to make things work. Since it's an old, and apparently "homemade" system, the original cobbleruper might have used an unusual valve that needs something a bit different, although it's unlikely.

Eventually, when you decide whether you're comfy or need to actually be concerned:

1. If the heat doesn't stay "turned on" long enough, it will cycle on and off frequently but may "never quite get there" in terms of making you feel warm enough. Move the anticipator to a slightly higher number and give it a day to see if it helped.

2. If the heat stays "turned on" too long, the room may overshoot to a "too warm" condition every time the thermostat flips, but then may get "too cool" before it flips again. Move the anticipator to a slightly lower number and give it a day to see if it helped.

Adjusting to anything other than default settings usually is so time consuming (calendar time) that something breaks before you finish and you have to start over. That's why they sell "gas/oil burner" control thermostats with the anticipator preset to 0.2, and "convection water valve" control thermostates, with a different part number and different price and with the preset at 0.8. If you can turn the screw (or slide the lever) they're the EXACT SAME PART - except for the package, the name, the price, the color, the shape, the adverts, etc. ad nauseum.

And they (nearly) all have illegible installation instructions.

John

Subject: RE: BS: Thermostats
From: dianavan
Date: 04 Oct 05 - 10:24 PM

John in Kansas -

I'm more confused than ever! My heating system is a gas fired boiler that gravity feeds hot water (not steam) to the radiators. It appears that the CT50A is for gas or oil only - according to the manual.

I am also quite unsure about the anticipator. As I mentioned before, I had read it should be at 8 for a gravity fed hot-water system. You seemed to confirm in a previous post that this was correct. I have only a single metal arm called the anticipator.   

I think I'm going crazy and the Honeywell manuals that you linked are useless. Just when I get to the information I need, part of the page is missing! When I go to the boiler, the thermostat is hooked to a little metal box on top of the boiler and it is absolutely plain with no markings except the Honeywell name.

I know this is not straightforward for many reasons. The man who owned the house before me was from Germany and worked in a shipyard. You would not believe this system (or the house for that matter). Its 100 years old, straight grain, first growth fir, re-inforced with concrete and steel. The heating system is really old and obviously home-made but it does work beautifully if I can just get a grip on this thermostat. The boiler (one of two remaining in Vancouver) is actually a feature of the house (men are in awe) but I have been told that you need to be a member of the boiler makers union to run this system. :>)

I am now like a dog with a bone and I won't give up. At this point, I am tempted to buy a new (old style) round thermostat exactly like the one I replaced. At least I know that it is made for a hot water system and I can read the temperature in degrees.

Now I know why the old owner said, "If it isn't broken, don't fix it"! I should have known better.

Thanks for all your help.

Subject: RE: BS: Thermostats
From: kendall
Date: 04 Oct 05 - 06:35 PM

Ok,, Jon, Good enough. Few people come to me for the truth anyway.

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 04 Oct 05 - 05:36 PM

Well I thought I tried Kendall with the thickness of a wire (the conductor) one.

Please don't get me wrong BTW. I do not think you are "dangerous" in the sense you would wilfully harm anyone (I "know" you as a nice guy who once sent me a small "pc mic" out of nothing but kindess - If I gave the impression I believe you are "evil" or something like that, I'm sorry - and will spell it out that I believe no such thing of you and believe you to be kind hearted). Whether I'd turn to you for tech advice is another matter - not sure I'd really even turn to myself for that!

Subject: RE: BS: Thermostats
From: kendall
Date: 04 Oct 05 - 04:47 PM

You never did answer my question.

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 04 Oct 05 - 09:31 AM

I thought we were out of it Kendall? Seems to me you can not even obey your very own:

Ok, time to put it to rest.

Subject: RE: BS: Thermostats
From: kendall
Date: 04 Oct 05 - 08:39 AM

Talk about A tempest in a teapot.

Subject: RE: BS: Thermostats
From: JohnInKansas
Date: 04 Oct 05 - 08:33 AM

dianovan -

The T87F 3855 that you replaced is the "classic standard" round dial thermostat (and coincidentally the same one Kendall's HVAC installer used). The T87F is essentially the same thermostat - for your purposes - as your replacement, the CT50A4775.

Since it is an attempt to retain the original Honeywell Thermostat "look" the T87F is not really adaptable to modern (cheap) manufacture, and usually sells for more than functionally equivalent thermostats of more modern design, but people still like the look. It doesn't do anything that your new one can't do for you.

T87F and CT50 are "base model numbers," and the "digits that follow" may describe additional features. You apparently need a simple ON/OFF thermostat for heating only, so the cheapest thing you can find that does this (and fits your room decor) is the appropriate one for you. You have the CT50 so it's obviously cheapest now to keep what you've got, and there's no real reason to look for something else - unless you have something you haven't mentioned like a humidifier or air conditioner to deal with.

The only remaining quibble is with the "adjustment of the two(?) screws" that Kendall refered to. As Kendall indicated (correctly) if these are set too far wrong they can prevent the thermostat from turning on the heat. Some thermostats do have separate adjustments for heating and for cooling. The basic CT50A/CT51A thermostat has only one, but "variants" of the basic model may have both.

The additional detail you should check, now that you're up and working, is that the "anticipator" should NOT be set all the way to one end as a general rule.

The anticipator is essentially a rheostat. Moving the pointer changes the length of a small resistive wire to change the amount of heat it generates. If you move the pointer all the way to the low resistance end, you have a very short wire carrying a lot of current, and it will (sometimes) eventually burn itself up and/or degrade the (usually plastic) board that it's mounted on - and then you'll need a new thermostat. If you move it all the way to the other (high resistance) end, it will not generate the heat needed to provide the function for which it's intended.

If you still have your old thermostat and it hasn't been "readjusted" you can look at it to see where its anticipator was set. You should try setting your new one to the same number.

If you don't still have the old one, or if you've played with it and changed the setting, the number that should be set is the "current rating of the primary control device" that the thermostat connects to (in the basement). This device will probably be a valve of some sort on your system, and probably is the thing that actually turns the water flow on and off. (This is not the transformer.) For a typical gas heating system, the gas valve would probably be at about 0.2 (0.2 amps or 200 ma on the valve nameplate) but for a water valve it may be more like 0.8. (I'm assuming that heating of the water is controlled separately, and your room temperature controller just turns the water flow on/off.)

Since thermostats of this kind are most commonly used on gas burner control systems, the "factory setting" for the anticipator was probably at 0.2. If your water control valve needed an 0.8 setting the current (0.8 amps) when the switch closes would heat the anticipator so fast that the thermostat shut itself off before you could tell it came on. This is probably what was happening before you "turned the screws."

If the anticipator is set too high, the thermostat won't turn off until room temperature actually gets high enough flip the mercury switch. Heat stored in the radiators will continue to dump into the room, and you'll get an unnecessarily large temperature cycle. When you have more than about 2 degrees F (1 degree C or so) variation in room temperature, most people respond by feeling "cold" when the temp is at the low side of the swing, so they push the thermostat up. Waste of fuel.

Once you're close to a good setting, you can make SMALL adjustments to get even temperatures, but you should let the room temperature stabilize for at least 5 to 10 hours before making another adjustment. Instructions for your thermostat suggest that if the temperature cycles over too wide a temperature range (furnace stays on too long) you should move the anticipator lever clockwise. If the furnace cycles on and off too frequently, move it counterclockwise. Make SMALL adjustments, and wait for it to settle before making another one. This can take days (or weeks) to get really right if you're too fussy. Don't worry too much about it if the heat comes on and you're comfortable.

Your new thermostat should have included a brief "Installation Instructions" sheet that probably (no guarantee) includes instructions on all this. Honeywell makes good products, but does a really shitty job of providing tech information on their websites. In the event the instruction sheet wasn't there you might look at:

CT50A Installation Instructions (610 KB .pdf) in English, but really ratty.

CT50 Installation Instructions (2.72 MB .pdf) the same stuff, in Enlish, much larger download, a little clearer pictures but still poor.

With either of these, unless you have a great imagination, you'll probably want to print them and patch the pieces together before you try to make sense of them.

For clear pictures (the same ones) you can also download the Spanish version I linked at 02 Oct 05 - 04:39 AM. All three of these appear to be the "same instructions" but only the Spanish one is really legible.

John

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 03 Oct 05 - 09:05 PM

Jeri, i think the heart might not be content with the Honeyqell I fond. Maybe as RB suggest, a weaaaker one is neded, but I'm sure people can get hurt.

RG is right by the way over millimps killing.. The voltage is the force that may push those tiny figures through the resistance of the body.

Subject: RE: BS: Thermostats
From: Jeri
Date: 03 Oct 05 - 08:48 PM

Jon, I don't know if information on this model is relevant and I know it's not dianavan's, but the directionf for this one (Adobe Acrobat) say to check calibration, the first thing you do is remove the cover. You can then fiddle with the dial and the ring to your hearts content. There is no imminent danger of zapping.

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 03 Oct 05 - 08:32 PM

Yes Diana (and please believe me that I'm really glad you are safe). Can you not see that I could not have found you the stat I gave you in the link I supplied and maybe (in all innocence) have hurt you?

That it did not happen seems somewhat less relaavant to me.

Subject: RE: BS: Thermostats
From: dianavan
Date: 03 Oct 05 - 08:24 PM

Jon - There are many, many models of Honeywell thermostats. Mine doesn't look anything like the one in your link.

When I finally found a picture of the old one, it was the same voltage as the new one which was 30V max.

It has now been callibrated and it seems to be working. I also checked to make sure it was level. It was.

Diana

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 03 Oct 05 - 07:58 PM

I don't think it is the voltage either jeri,, but I do think you can take the cover off a UK Honeywell stat and find 230-240 of them behind you.

If such matters should not be of concern, I will apologise.

Subject: RE: BS: Thermostats
From: Jeri
Date: 03 Oct 05 - 07:13 PM

Jon, I don't think it's the voltage. I think that calibration is something that shouldn't cause you to worry about dying. And no, dianavin didn't ask how to level a thermostat, but kendall said, "And, it must be perfectly level. If it is off just a bit, it wont work." That right there should have made me think there was a leg or several being pulled. Good one, Sparky.

The companies who deliver the gas have installation and repair guys. I'd ask somebody professional. Or you can invite kendall over. You know CPR?

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 03 Oct 05 - 06:59 PM

Kendall, I'm rolling on the floor laughing at that but OK, no point in keeping up an unhappy forum - I can go along with that.

Subject: RE: BS: Thermostats
From: kendall
Date: 03 Oct 05 - 06:46 PM

Ok, time to put it to rest.
I knew exactly what I was doing. ok?

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 03 Oct 05 - 05:48 PM

I do think though Jeri (poss as indicated by Richard Bridge - ie. 110 is a sort of safety voltage for site work, etc) that Americans might be generally more casual about taking covers of things than UK people. That could be a cultural one, coming from we do have that higher voltage.

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 03 Oct 05 - 05:38 PM

Jeri, I have re-read and see no indication that leveling one (never seen a mercury one BTW) was being asked for, idea or country or anything. Perhaps you can find for me that in the first post. I just find someone with problems with a Honeywell.

Hints?

Subject: RE: BS: Thermostats
From: Jeri
Date: 03 Oct 05 - 05:28 PM

I suppose levelling a thermostat or calibrating it (attached to wall, with its cover off) would put you in danger of electrocution too? That's what started all of this.

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 03 Oct 05 - 04:48 PM

misssed my linkk

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 03 Oct 05 - 04:46 PM

Kendall I'm going from a UK background but I can assure you I could go out and buy any buy any number of things that could burn you. If you got it wrong. I could for examle go out and buy this honeywell and have the 230- 240V. I think the sense comes in in the knowing what might be behind it - simple rule, you isolate things from the mains before messing. And a job such as changing 2 wires on a thrermostat (to fit a new one) should be safe for anyone as long as it isn't live when doing the job. Replacing a socket or light switch isn't hard either but personally I'd rather ensure it is switched of at the mains first.

Can't go out and buy a gun though.

Subject: RE: BS: Thermostats
From: kendall
Date: 03 Oct 05 - 03:56 PM

No, but Jon has upset me some.

Subject: RE: BS: Thermostats
From: Richard Bridge
Date: 03 Oct 05 - 02:54 PM

Kendall, have you upset tehm lately?

Subject: RE: BS: Thermostats
From: kendall
Date: 03 Oct 05 - 02:27 PM

Jon, don't you think it unlikely that the furnace company would suggest I mess with the wiring if they thought I could get burned?

Subject: RE: BS: Thermostats
From: Richard Bridge
Date: 03 Oct 05 - 11:37 AM

It's the volts that jolts, but the mills (milliamps) that kills.

240v mains won't usually kill you so long as you don't manage to create a situation in which you can't let go or turn it off. If you have a weak heart it might. If you hold one wire with your left hand and one with your right, then it can be dangerous because the current crosses the chest (and therefore the heart).

240v can give you a nasty burn that if deep will take a long time to heal. Been there, done that. If you fiddle with electrical stuff enough, sooner or later you will make a mistake and get a good belt, but you usually survive and learn.


Let's not get paranoid here. What you really do need to worry about is 3-phase and if you get two bits of equipment on different phases you can get 415 volts between them. And the maths of it is a whole different ball game so a mistake becomes likelier. Unless you are a professional, do not do 3-phase!

Take extra care with even 240v in kitchens - you are surrounded by good conductors, and good earths. I once bought a house where the previous owner had succeeded in wiring up a spur to feed the ignition circuit in the gas cooker with phase and neutral reversed (and no earth at all). And it was next to the sink. The really really worrying thing was that he was a nuclear engineer, and if his standards were as high at work, the consequences did not bear thinking about.

Over here 110v is used as a safety level voltage for site work (big step down transformers) on the basic theory that 110v is not (all that) likely to kill, even among muddy puddles.

Subject: RE: BS: Thermostats
From: kendall
Date: 03 Oct 05 - 11:26 AM

I've been challenged. I expect an answer.

Subject: RE: BS: Thermostats
From: dianavan
Date: 02 Oct 05 - 09:49 PM

Hey, Jon, relax - I did check out the Honeywell site before I asked for help. Neither my old model or my new model thermostat appeared on that site.

Subject: RE: BS: Thermostats
From: The Fooles Troupe
Date: 02 Oct 05 - 09:46 PM

Enjoy yourself?

;-)

Subject: RE: BS: Thermostats
From: kendall
Date: 02 Oct 05 - 09:39 PM

Like I said, what other dangerous advice have I given?

Subject: RE: BS: Thermostats
From: Joe Offer
Date: 02 Oct 05 - 07:45 PM

Dianavan - it sounds like you have your problem solved. Remember that a thermostat is basically an on-off switch. If you have a very simple thermostat, it may not use power at all (it just serves as a switch for the relay that turns the heater off and on). Simple thermostats turn on at a certain temperature, and turn off when a certain temperature is reached. Usually, the range is set at one or two degrees so it's not a constant on-off-on cycle.
-Joe Offer-

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 02 Oct 05 - 06:13 PM

Seem to have missed some of my intended post...


Try this page for example. You will find quite clearly that for the same watts, I'd need thinner, not thicker wire for if I used higher voltage..

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 02 Oct 05 - 05:44 PM

OK Kendall I will come back just for this:

There is no way that such small wires could carry enough voltage to harm you.

Are you aware that the current may be more important when thinking of the wires and if you have a higher voltage you may use thinner wire to carry the same wattage? Would W=I^2R mean anything to you? They don't (at least in the UK) have such high voltages on the distribution like pylons because a high voltage needs a thicker wire you know.

Subject: RE: BS: Thermostats
From: kendall
Date: 02 Oct 05 - 05:07 PM

When the heating company installed my thermostat, a Honeywell T87F, it did not work properly. I called them and they couldn't get to me right away so they suggested I make sure the thermostat was level. It wasn't, so I made it level. I also touched the tiny wires that activate the thing, and as you can see, I'm still alive. There is no way that such small wires could carry enough voltage to harm you.
Now I'm curious, what other dangerous advice have I given, Jon?

Now, I admit I'm not much on computers, but how does that carry over to thermostats?

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 02 Oct 05 - 03:44 PM

Opps, dianvan. see we cross posted. Maybe finding that page before asking here.... Whatever, I'm out of this one.

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 02 Oct 05 - 03:42 PM

Fair enoough Dianavan - no point in my repeating a concern.

John, in the UK, they have tried to make us safer! There is these days a little thing called "Part P" floating around" making life more difficult for an odd jobber (at home) like me - some stuff needs testing by an electrician now (or maybe yoou risk house insurance),

Whether it will improve the Brit gene pool or not
, I'm, uncertain but I think you will find cowboys (hey aint that an American term - used in the UK a lot - slipshod builders, etc. poss con men...- though and in this way in terms of me using it as a joking response to your joking) will still get through.

Subject: RE: BS: Thermostats
From: dianavan
Date: 02 Oct 05 - 03:27 PM

Jon - As you can see by this page, http://yourhome.honeywell.com/Consumer/Cultures/en-US/Products/Thermostats/Non-Programmable/Non-Digital/Default.htm

Thermostats are broken into two categories:

1. professional

2. do-it-yourself

I think what you are saying is that in Britain, only professionals should attempt this. In North America, they seem to think that we have enough know-how to do it ourselves, if it is low-voltage.

I don't think Honeywell would risk a law suit.

BTW - I am impressed with the wide range of products that Honeywell manufactures and no longer believe that my thermostat is cheap junk. Seems to me that they are a very reputable company.

Subject: RE: BS: Thermostats
From: JohnInKansas
Date: 02 Oct 05 - 03:09 PM

Jon:

From one of my previous:

By implementing these restrictions in building codes, it is apparently hoped, by some of our leaders, that eventually the US will have even more "surviving idiots" than the rest of the world. It seems to be working...

Just trying to improve the Brit gene pool....

(joking of course)

John

Subject: RE: BS: Thermostats
From: dianavan
Date: 02 Oct 05 - 03:00 PM

I finally found the model number of my old, Honeywell thermostat (T87F 3855) and it is 24V which is very helpful information. I realize now that I want to return to this very effecient, old standard type.

The only numbers I could find on the transformer (also Honeywell) were A409B1X0) which did not prove to be very helpful. I couldn't find anything on the net. I think the problem may be that its such an old system that they probably don't even make the parts anymore.

Jon -

I don't see what's wrong with asking for help on the cat. I think that most people here are able to help with all kinds of questions. Members seem to have a wide variety of experience and knowledge. I certainly rcvd. the info. I needed and it has saved me a pile of money.

I have no idea how a UK member would have interpreted the info but it was good enough for me.

Since I'm a single mom with very little money to hire tradesman, I often have to do my own work. I make some mistakes but I haven't hurt myself yet. I'm pretty cautious and know when I am over my head. I think that its good to learn about the heating system in your home and not to rely on others to do the work. Same goes for plumbing. Sure, if its a big job, I hire somebody. Its my home and whenever possible, I take responsibility for minor repairs. Whenever I solve a problem (such as this one) my self confidence soars and I enjoy my home even more.

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 02 Oct 05 - 12:09 PM

Dainavan, my worry is just that we can (maybe mostly me) dive into these questions so easily and even if what JIK says is (and I've no reason to dispute this) correct, some UK 'Catter could have read and finding rather more than a 24V control circuit.

I can't help the feeling these matters are better dealt with more professional places. As you know we are in different countires but UK, I used this one for bits of help at times. Not sure what is like now but it did have some good working tradesmen in,

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 02 Oct 05 - 11:53 AM

Aye John but I do have difficulty with

IF THE VOLTAGE at the wires is more than 30V it will probably be line voltage, 110 VAC or more and you would probably have killed yourself by now, or at least melted some wire.

Meaning anything other than a recognition that it is possible to kill oneself.

Subject: RE: BS: Thermostats
From: JohnInKansas
Date: 02 Oct 05 - 04:39 AM

dianovan -

The only thing very specific to your thermostat that I've found at Honeywell's website is an operator's manual that, unfortunately for me, appears to be available only in Spanish. If that's helpful, and you didn't get one with the thermostat, it's a 2.4MB .pdf download at CT50 Operating Manual. It focuses on the CT51, which appears to be a little fancier than the CT50, but it covers both; and it does look like it tells you how to check the nameplate(s) on the stuff in the basement to confirm that you have the right thermostat for your setup - if you can read the Español. Even without reading, you can tell quite a bit from the pictures.

The 30V rating for the Honeywell CT50 is a maximum rating, and this thermostat shouldn't care if any lower voltage is used. It would, in fact, probably work for a while at significantly higher voltage, although staying within the ratings is recommended. All it does is open and close a single connection when it's connected in the two wire configuration you're using. If there aren't any sparks or smoke when it turns off, and it doesn't get too hot when it's on, it will work; although outside the ratings it may not work for very long.

The "professional" way to tell if the thermostat is on or off would be to clip a voltmeter on the terminals where it's connected. Your voltmeter should show "thermostat line voltage" (probably about 24V) when the switch is open (furnace off) and near zero when the switch closes (furnace on).

The cover on your new thermostat is a pull-off kind, and the thermostat will work just as well with the cover off as with it on. The CT50 is the common mercury switch type. If you can see the mercury switch, just look at which end of the glass tube the shiny blob is in. If it's in one end and the furnace is off, moving it to the other end (by setting a different temp) should turn the furnace on. You can probably run down, check, and get back upstairs to turn it back down before all the butter melts.

As long as you can turn the furnace on/off by changing the setting on the thermostat, you can be pretty confident that it will do its own thing when you set it and forget it.

I did get an indication elsewher at Honeywell that your "anticipator" screw for the heat turn-on should probably be set at about "8" for hot water systems. Setting the rheostats all the way to zero can let a lot of current through them, which can burn them up. No mention at that source about where the other one should be, but somewhere around "2" or "3" should be safe enough.

John

Subject: RE: BS: Thermostats
From: dianavan
Date: 02 Oct 05 - 03:32 AM

Like I said, I'm still not sure the problem has been solved but I should know by tomorrow night if it is working. I still haven't heard it turn off and on automatically according to the room temperature. One of the problems is that the boiler is in the basement and I don't hear a thing. I am constantly running up and down the stairs to see if its on or off. Could it be that the bimetal coil is malfunctioning?

The new thermostat is a 30vac and of course I threw away the old one and have no idea if it is the right voltage. It may have been a 24 to 27 Vac since it was Honeywell's round classic. My old one is not like the picture on the web because it only controls the heat, not a cooling system, too. How do I know how many volts are coming into the thermostat?

Don't worry, Jon, I am so scared of electricity my kids make fun of me. The last thing I want is an electrical zap. I'm not playing with the wires, just checking them, adjusting the calibration and trying to make sure that the new thermostat is compatible with my heating system.

Thanks for your help and for your consideration.

Subject: RE: BS: Thermostats
From: JohnInKansas
Date: 02 Oct 05 - 02:50 AM

Jon -

The diagram to which you referred may be common in the UK, but except in exceptional circumstances would not be legal under the building codes in most US municipalities, or in most of Canada, at least for residential use. (I haven't looked lately, but at my last casual browsing of Canadian codes, they appear to be much like the common US ones.) Any connection that carries line voltage must be enclosed in a "junction box." Any access to any metal part that carries line voltage must require the removal of one or more "permanent fasteners" such as metal screws or bolts. This pretty much precludes using a surface mount device, like the thermostats described, at line voltage.

Line voltage thermostats are used in the US, but usually only for electric baseboard/underfloor systems and some heat pump systems. Where line voltage is used, the thermostat itself usually is embedded into the wall in an electrical junction box. Even for these systems, current rules in most areas would require that the "thermostat" in your diagram be replaced by a "relay" or in some cases a "contactor" which would in turn be switched on/off by a low-volt thermostat hung in the occupied areas of the residence.

By implementing these restrictions in building codes, it is apparently hoped, by some of our leaders, that eventually the US will have even more "surviving idiots" than the rest of the world. It seems to be working...

You also asked about the use of bimetal thermostat sensors. The "sensing" in the simple mercury switch thermostats used here is usually done by a bimetal strip, usually a coil that looks like a clock spring, with a glass tube containing a slug of mercury hung at the outer end of the coil. As the temp falls the coil winds tighter and tilts the tube so that the mercury runs to one end and connects two embedded wire ends. A cute feature is that when the mercury runs to the turnon end it applies an additional torque to the coil, so that the temperature has to rise a bit past the original switch point before the blob runs back. Automatic snap-action.

The two adjustment pointers mentioned by Kendall (01 Oct 05 - 09:04 AM) are called "anticipator" adjustments and are usually on a couple of small rheostats that apply a bit of extra heat near the bimetal coil. One heats the coil a little when the mercury switch is OFF (for the heat circuit) - making the switch turn on at a little lower room temp, and the other heats it a different bit when the switch is ON, also making it turn off at a different slightly lower than room temp. This lets you adjust the "gap" in temperature between when the furnace turns on and when it turns off, although it may shift the calibration between switch point temp and indicated room temp if used too agressively. Digital thermostats generally have similar adjustments, although they often work by applying a voltage bias to a thermister circuit.

The "OFF Side" anticipator adjustment would normally be critical only if you're using the thermostat for heating and cooling. (Older 2-wire 'stats often only had a single anticipator.) In a heat-only setup, setting the Off-side one too high could get an "off below on" condition, but it's really unlikely. It does sound as if dianovan may have managed it. If one or both of these is set too far off, you'll often see fairly wide temperature excursions. If the heat comes on at 68F (20C?) and stays on until the room hits 75F (24C?) you're likely to feel like you're enjoying the benefits of menopause. Some twiddling may be in order. A swing of about 2F (1C) is generally considered acceptable, although some sensitive souls have trouble even with that.

Simple flat leaf bimetals with "dry contacts" may be more common in line-voltage setups, but it's really difficult to get sensitive temperature adjustment with sufficient "snap" to prevent arcing of the contacts. They're commonly used here for water heaters and such, where adjustment in 10 or 20 degree F increments is sufficient, but seldom seen - so far as I'm aware - in room temp setups.

I've been told that A/C is uncommon in the UK, but it's one of the easiest ways to get rid of that muggy humidity, and in moderate temperatures shouldn't be too expensive to run. I'd suspect it will become more common when more Brits have been exposed to it here... I've even seen A/C equipped houses in Seattle - proof positive that it's becoming more common in foreign places.

John

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 01 Oct 05 - 09:34 PM

I still haven't received a shock. Maybe I'm just lucky.

Maybe you are stupid enough to not realise it is possible that you couuld have been dealinng with voltages that cold zap you.

If it is intended as sarcasm, try tracing the volatge throough any of the examples I gave you from Honeywell and tell me the it is not likely that the voltage you hit might not be V230 at the stat.

Please trace you route and publice it here if you think such reasoning of mine is BS, or admit these things CAN be dangerous - give me one or other rationalisation from the diagrams

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 01 Oct 05 - 08:47 PM

Yes but Daina, Kendalls coments (as often are the case - look at his computer messups for one) are often the most dangerous of all. Glad this worked out but really and honestly I would not trust that guy to change a fuse (I would on the other hand think KIK would follow the UK wiring diagrams I gave without being troubled - have more than a touch of belief in his tech ability and to be able to apply it in various areas if needed). Simple, maybe on this one,,, Thank God.

Subject: RE: BS: Thermostats
From: dianavan
Date: 01 Oct 05 - 08:35 PM

I'm still alive and guess what? Its often the simplest of things that prove effective.

The winner of the solution is - Kendall, "Remove the cover. You should see two tiny pointers. If they have not been calibrated, that would account for the thing not working. They must be on different ends of the scale to work right."

Yes, it does help to calibrate the damn thing.

Anyway, it seems to be working now. I'll give it a couple of days to prove itself. The next step will be to buy a room thermometer and follow your directions, JohninKansas.

Thanks everybody, so much - and don't worry, as much monkeying as I have done, I still haven't received a shock. Maybe I'm just lucky.

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 01 Oct 05 - 07:26 PM

Funny reading this thread BTW. And I'm guilty too here... At one extreme we have recogintiion that some of these devices (although it seems rarer in the US) could quite literaly kill you and at the other a seemingly casual just take the cover off.

Perhaps that again higlights the dangers (and I stress I'm aware I contributed) of asking this type tech question on a primarily music forum.

Between us all (and with very informative comments from John in K too) the reality to me (at least if it was common UK systems) is that we could have "killed some fucker" here and all with good intentions.

Subject: RE: BS: Thermostats
From: JohnInKansas
Date: 01 Oct 05 - 04:43 PM

Honeywell makes it hard to identify specific models on their website, but the CT50 has terminals marked "R" and "W" that should be used if your wall only has two wires running out of it. At least that's the answer the Honeywell Thermostat Wizard gave me.

The only other thing that needs to be checked is that you don't have one of those "line voltage" systems mentioned above. If you have a voltmeter, the two wires - without the thermostat connected - should show something less than 30V AC (probably 24V or near that). If the voltage at the wires is less than 30V, hook them up to the R and W terminals and you should be working.

IF THE VOLTAGE at the wires is more than 30V it will probably be line voltage, 110 VAC or more and you would probably have killed yourself by now, or at least melted some wire. If you don't have a voltmeter handy, you may be able to tell from the markings on the old thermostat whether it was a normal (30V) one or a special high voltage unit. If you're adventurous, you can see if the voltage at the wires will light an ordinary household light bulb. I'd expect it won't.

The thermometers built in on thermostats seldom read the same as the markings on the dial/lever you use to adjust them, unless some care is taken in calibrating things. A small separate thermometer mounted nearby should work just as well as a built in one. The trick is to:

1. let the room temperature stabilize.
2. read the temperature on the thermometer.
3. set the thermostat knob/lever to the temperature on the thermometer. If the heat clicks on rotate the entire thermostat (usually ccw) so that it's off.
4. rotate the thermostat on the wall carefully (usually cw) until it just clicks on the heater. This adjusts the levelling of the switch so that it comes on at the temperature on the knob/lever. (A test lamp or voltmeter is handy to tell when the thing switches.)
5. tighten the thermostat mounting screws.

The simpler option is to read the temp from your separate thermometer, and just nudge the thermostat knob/lever a little at a time in the direction you want the temp to go.

John

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 01 Oct 05 - 04:09 PM

Dunno dianavan, seem to be more variations on systems than I'd realised when I'd first posted and going by bits of UK experience...

I think it's best left to someone who has dealt with your systems.

Subject: RE: BS: Thermostats
From: dianavan
Date: 01 Oct 05 - 01:56 PM

Before I start monkeying with this, the thermostat is a model

CT50A4775, Class 2, 30 V max. Two wires R and W.

Do I have the right model for a gravity fed, hot water system with a gas-fired boiler? There are two wires.

My old thermostat was a honeywell (round) with a thermometer to measure room temp. and a dial.

The new Honeywell seems to have only on and off.

Maybe I need a different thermostat. I want to know the room temperature and I want to be able to control it.

Help, please, before I do something I might regret.

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 01 Oct 05 - 12:17 PM

One other point of course is that I don't imagine air conditioning (as in the cooling side) being something you would find often in a UK house.

Subject: RE: BS: Thermostats
From: dianavan
Date: 01 Oct 05 - 12:09 PM

Thanks, so much for all of your guidance.

I will get busy this afternoon. Hopefully I don't make a mistake!

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 01 Oct 05 - 12:00 PM

(but instead of a timer, like that programmable stats - Honewell do one too - can't find that diagram at the moment though)

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 01 Oct 05 - 11:59 AM

Interesting John... I would have guessed most mechanical stats I've seen (UK) would be using a bimetal strip.

I didn't know of the low voltage control system. I've not touched many
or looked at many wiring diagrams but the ones I have have been 240V (UK of course). Our own is now effectively the Honeywell Y plan shown here.

Subject: RE: BS: Thermostats
From: JohnInKansas
Date: 01 Oct 05 - 11:48 AM

Common US thermostat manufacturers include Honeywell, Robertshaw/LUX, White-Rodgers, General Controls, Johnson Controls, and Jameson. There are several others. For most purposes they can be considered interchangeable, although various installers may have their favorites. Only the "brand names" are US. They'll most likely be made in Taiwan, Mexico, China, Indonesia etc., with instructions written by someone in India, Turkistan, or S. Africa by an ESL marketing specialist, and the "US" company probably belongs - directly or indirectly - to a British Holding Conglomerate (LLC).

Nearly all thermostats work off a transformer, often located near the device being controlled. The standard voltage in the US is 24VAC, although 6, 12, and 30 volts have been used. The most common applications assume that the transformer voltage will be switched on and off to the device the thermostat is controlling; but many heat pump systems and electric (baseboard and under-floor) require a special device to switch "line voltage" (110/220 VAC in the US). These line voltage types will sometimes use an internal battery to power the temperature sensing circuit. Battery powered thermostats can generally be used on any system, but since you have to bring the switched voltage to the thermostat there's little practical reason to do so if it's a low-voltage control line.

Many thermostats use a "mercury switch" on a bimetal coil to sense temperature, and these require - as kendall notes - that the thermostat be mounted with a specific orientation and be "perfectly level." If your new thermostat is of this kind it should have had a "permanent label" noting "CONTAINS MERCURY DISPOSE PROPERLY" (an OSHA/EPA mandated label). More "modern" digital thermostats frequently use thermister sensors that shouldn't be too sensitive to orientation, although a level mounting is probably a good idea.

Thermostat wiring - what comes out of the wall - is commonly 2, 4, or 5 wires. Many "digital" thermostats require at least the 4-wire connection, since the sensing circuit must be powered independent of the controlled circuit (2 wires each). Thermostats with a battery to power the sensing circuit may be usable on a 2-wire system, but non-battery-powered digitals likely will not work. (There are exceptions.) If you've only got 2 wires, you're probably better off with a simple (ugly) mercury switch type thermostat.

Most recently offered thermostats accommodate 4 or 5 wire connection. The 5th wire allows a single thermostat to control both heating and cooling. If you have a 4-wire installation and have inadvertently connected the "furnace hot" lead to the "A/C hot" terminal, you'll get the effect described that you can make it turn on, but it will never shut itself off and you can make it turn off but it will never turn itself on.

John

Subject: RE: BS: Thermostats
From: kendall
Date: 01 Oct 05 - 09:07 AM

And, it must be perfectly level. If it is off just a bit, it wont work.

Subject: RE: BS: Thermostats
From: kendall
Date: 01 Oct 05 - 09:04 AM

Remove the cover. You should see two tiny pointers. If they have not been calibrated, that would account for the thing not working. They must be on different ends of the scale to work right.

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 01 Oct 05 - 07:33 AM

And re the continuity test, I've a feeling you are Canada but N America anyway so might well have a "Radio Shack" near you. If you haven't got one, go out and get youself a cheap mulitmeter - I'd suggest a digital one as they are more robust. I think my own (UK) cost about £20 but you could easily 1/2 that. I do use mine for a bit more than this but they are handy to have around even if all you want to do is confirm whether a fuse is blown or to find if a battery really has some voltage, etc.

My meter (and maybe most now do) has a continuity setting that gives a bleep but one with just ohms (which they all have) is fine. A switch like the thermostat should be showing close to infinate resistance when open/off and close to zero when closed/on.

Joe mentioned the bulb one. You need a battery for that. You just make a circuit so that the swich is the thing you want to test. Your light shold come on when the thermostat is on.

One big thing in all this though is make sure your thermostat is not connected to the mains in any way when you try to test it. Take it off the wall and have no mains connected. If it is a type relying on mains for a timer or programmer, I'd suggest you leave it alone or get a professional in unless you are fully sure of what you are doing I think even on your 110V (certainly is on our 240) a mistake could be fatal and at a minimum very unpleasant.

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 01 Oct 05 - 05:21 AM

Wrong page - We went for this type

Subject: RE: BS: Thermostats
From: GUEST,Jon
Date: 01 Oct 05 - 05:18 AM

Put the old one back if you still have it.

What type of stat is it? A manual one with a knob? You can usualy get some clue as to whether the they are swiching as you probably would be able to gear a click as you rotate the dial. Joe Offers method is more reliable though - s simple continuity test.

You could well find you have a faulty unit but I believe Honewell are OK. I've a feeling they are American but thier heating controls are widely used in the UK.

Don't know what other makes you might get. Our own is one of these Danfoss-Randall ones. Works fine. I fitted the controls a year or more back as there was no room stat, no cylider stat, and no zone valve for the hot water side of the circuit, going radio conroled to avoid wiring tasks I didn't fancy. We have made significant savings in oil consumption since moving from the system that was just controlled by timer to this.

Subject: RE: BS: Thermostats
From: Joe Offer
Date: 01 Oct 05 - 02:33 AM

Hi, Dianavan - Honeywell is one of the standards, and they're usually thought to be pretty good - there aren't all that many brands available. What model number is it?
How many wires do you have to hook to the thermostat? Have you tried reversing them?
How does the thermostat get power? - from the wires, or does it need a supplemental battery?
Is there a timer on the thermostat?
The basic test is to disconnect the thermostat from the furnace and connect a low-voltage light or meter to it. Then, rotate the dial and see when it goes off and on - test is just a bit different with digital thermostats, but works on the sam principle.
Give us the model number of the thermostat, and I (or somebody) should be able to come up with advice for you.
-Joe Maintenance-

Subject: BS: Thermostats
From: dianavan
Date: 01 Oct 05 - 12:39 AM

I need advice, quick!

I recently replaced my old thermostat with a new one. The old one
was old and ugly but it worked. The new one is a Honeywell and it looks nice but it doesn't work.

I know, if it ain't broke, don't fix it but...

The new Honeywell seems to have only two temperatures, hot and cold (off and on). The thermometer doesn't work and the temperature is not controlled automatically. I need a new thermostat very soon or I'm gonna freeze.

I have a gas powered, hot water system that works just fine. Its just that I can't seem to regulate it. Someone said its because the thermostat is cheap junk from China.

Is there anyone who makes a good thermostat? How much does it cost?