The Mudcat Café TM
Thread #92381   Message #1764838
Posted By: JohnInKansas
20-Jun-06 - 02:16 PM
Thread Name: BS: Rainbow Vacuums
Subject: RE: BS: Rainbow Vacuums
The Rainbow is apparently similar to one that acquired a degree of popularity in the late 1940s under the (US) brand name "RexAir." My family used one for nearly 20 years, and it was an excellent machine.

The one at the first link appears to have some "modern features" that the old Rex didn't, such as the "powered head" for carpets. Whether it's the same design internally isn't easily discernible from the pictures.

The RexAir was marketed as a "modern technology" and actually used a five stage axial turbine as an air pump. It "moved the air" significantly better than competing vacs of the era, and was impressively quieter. Since it used water as the filter medium, small amounts of liquid could be cleaned up with it, although the water container had limited capacity and large suckups could overfill it.

As to the hazard of using water inside an electrical device, remember that most electrical devices are full of metal parts that are better conductors than water. It's a safe design, and in usable condition - or it's not. The presence of internal water doesn't change anything. Vacuuming a damp carpet with another kind of vacuum - one not designed to contain water - is probably more likely to present a hazard than using one containing a working water filtration system.

If you're concerned about the current condition of the vac you've acquired, you might be able to find a shop that could run a "HiPot test" of the kind used for safety certifications. This involves applying a "high" voltage (50 V or greater) to each side of the electrical circuit and measuring the resistance to external parts. Equipment for this test is not commonly on hand at the average wire-stringer shop though. A shop that advertises motor rewinding might have the equipment.

An ordinary VOM should be able to show any obvious defect. From each "hot" prong of the plug to "external metal" you should show a minimum of 10 MegOhm resistance. (Some codes require even more than 10Meg.) If the plug has a ground prong, and if it is connected to an internal ground in the vac, resistance should be "very low" between that prong and metal parts of the vac housing. More recent designs typically isolate the electrical ground from exposed parts, using what's called "double-insulated" design (in the US) and if it's wired in this style all of the plug prongs should show high (>10M) isolation.

Simply plugging into a working GFI outlet probably is a sufficient test for a vac of this kind that "looks good." If the GFI doesn't trip, you can be reasonably assured that there's no leakage current. Note that even if the device is in good shape, an "inductive load" like a large motor can cause a phase shift sufficient to trip a GFI. If the GFI doesn't trip, the vac should be safe. If it does trip, the vac may still be safe, but you'll want to use other methods to be sure.