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Specs to look for in choosing right thermostat for ceiling radiant heat

Specs to look for in choosing right thermostat for ceiling radiant heat


  #1  
Old 01-24-11, 11:21 PM
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Specs to look for in choosing right thermostat for ceiling radiant heat

Hi everybody,

I would like to buy a replacement thermostat for the ceiling radiant heat in my 1972-built apartment (just moved in). But, Iím not sure what specs to look for because Iím not knowledgeable about electrical matters.

My old thermostat is a GE (Model 3AHT40A1B2). It is labeled: non-inductive; 120/240V A-C, 22.0 AMP; 277 VOLT A-C, 18.0 AMP. It is connected by two wires, red and black. The corresponding circuit breaker consists of two switches numbered ď20Ē on each (tied together).

My question is: What specs must I look for in choosing the right thermostat?

I prefer a digital thermostat, but I canít find any with the same specs. They all seem to have a lower amp rating than my old GE thermostat.

For example, I looked at the Honeywell RLV430, which says it cannot be used with a resistive load over 14.6 A. I donít know the resistive load of my heater, so can I still use the RLV430? Or would that be dangerous?

Thanks!
 
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Old 01-25-11, 05:35 AM
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Do you have an Amp Probe meter to take some amp reading to see what the heater is pulling?
 
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Old 01-25-11, 12:03 PM
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No, I don't have an amp probe meter.

I have found a couple of mechanical thermostats with specs that match my old GE thermostat.

Honeywell T4398A1021
Product

LuxProducts LV1
Amazon.com: Lux Products BBLV1-005L Line Voltage Single Pole Heat Thermostat, Sterling White: Home Improvement

Maybe I should just use one of the above mechanical thermostats, and forget about getting a digital one?

Thanks.
 
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Old 01-25-11, 12:12 PM
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You can use either one of them.. Do you have any specs or info on the electric heating system you have now?
 
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Old 01-25-11, 12:27 PM
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Unfortunately, no. We just moved in, and the previous owner did not leave us with any information. Since the heat system is embedded in the ceiling, I'm assuming I can't examine it.

Thanks.
 
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Old 01-25-11, 12:33 PM
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Ok, then safe to just get a new stat with the matching amp or find someone who has a amp probe and take some readings.
 
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Old 01-27-11, 09:14 AM
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So I got the Lux LV1 single pole thermostat with ratings (22 amps @ 125 VAC, 22 amps @ 250/277 VAC) that match/exceed the old GE thermostat.

I removed the old one, and noticed that tags on the wires coming out of the box say: GE, HW1120C1, 1200 W, 240V. I assume these are the specs for the radiant heat.

The LV1ís manual says to connect the line wire to the top screw on the thermostat and the load wire to the bottom screw.

I have two wires that connected to the old GE thermostat: red and orange. I used a multimeter to test them, and they both turned out to be hot (readings around 115). That confused me, because I thought only the line wire was supposed to be hot, and the load wire was supposed to be neutral. Is this a problem?

So my questions is: Since I canít tell which wires are line versus load, does it matter how I connect them to the LV1? In other words, is it ok if the connections are reversed?

Thanks!
 
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Old 01-27-11, 11:11 AM
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With that info you gave on the specs, the heater is pulling about 10 amps.

The 240v, both lines are going to be hot.

You can hook up either line to "LV1".
 
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Old 01-27-11, 01:52 PM
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Thank you, Jay11J for your help. Appreciate it.

This single pole, 240V heater system doesn't seem very safe. If there is current through the heater all the time, then one can get shocked if one somehow touches the heater even if it's not on. I suppose the best thing to do is to shut off the breaker switch when not in use.
 
  #10  
Old 01-27-11, 03:20 PM
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Glad to help out.

They are a few other things out there with a single pole switch, so that's why it's always important to turn off the main breaker when you service something.

The unit itself won't be "hot" just if you touched the wires itself. If you want to be safe, you can shut the breaker in the summer months. That's what I did when we had an apt. with the electric base board heat.
 
 

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