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.