Electric Heat

[jerjwillelec]

I have a customer complaining about the electric heat in her apartment. She claims when the (in line) thermostat is set on 60, that the room heats up to around 70 - 75. She also claims her electric bill has gone up compared to previous winters.

This room is approximately 300 square ft. There is a 240 volt 2500 watt baseboard heater on one wall and a 240 volt 500 watt baseboard heater on the other wall.

I have replaced the thermostat (even though I didn't 100% feel that was the problem) and it continues to do the same. The t-stat is a Mears M601 single line break 22 amp rated. I realize this style of t-stat will have a varying range of degree fluctuation, but I wouldn't expect it to be more than a degree or two (maybe 3).

The 2500 watt heater element has 25.5 ohms of resistance (cool). The 500 watt heater element has 123.5 ohms of resistance (cool). The supply voltage to both heaters is 247 volts. By doing the math, this says the 2500 watt heater is only producing 2402 watts of heat and the 500 watt heater producing 494 watts of heat.

My question is this... do electric baseboard heaters loose efficiency over time creating a "hot spot" and causing the electric bill to go up or is this all in her head?

 

[mxslick]

Wrong question...

Wrong question...

Your question really needs to be why is the room heating up beyond the t'stat setting...

And with the resistance readings you've given, I'm willing to bet that there is a short to ground in one or both of those elements.

Given:

Heat when not called for;
Higher electric bills;
Wattage computations don't jib;
and the single line t-stat;

Break out an amprobe and check both line wires off the breaker with the stat at it's lowest setting and I'll bet you'll find a good current flow still happening. Anything other than 0 amps means element shorted to ground.

 

[code_compliant]

IMHO you did everything you can do by changing the t-stat. It appears he heaters are still good, they're not the problem.

I've never heard of hot spots on electric baseboard, I'm not sure it matters as all the heat is dissipated indoor anyway.

My wife will often comment that the house feels colder (or warmer) today than yesterday. I then walk over to the indoor weather station and comment that it's the same 69.5 degrees as it was yesterday.

 

[JohnJ0906]

Have you done actual temperature measurements? (I mean, is it actually 70 or 75 deg in the room when the stat is set on 60?)

As far as the bill going up, has the utility rate gone up?

 

[code_compliant]

Break out an amprobe and check both line wires off the breaker with the stat at it's lowest setting and I'll bet you'll find a good current flow still happening. Anything other than 0 amps means element shorted to ground.

I agree and stand corrected.

 

[jerjwillelec]

Have you done actual temperature measurements? (I mean, is it actually 70 or 75 deg in the room when the stat is set on 60?)

Yes, the temperature is actually 70 - 75.

 

[jerjwillelec]

Break out an amprobe and check both line wires off the breaker with the stat at it's lowest setting and I'll bet you'll find a good current flow still happening. Anything other than 0 amps means element shorted to ground.[/QUOTE]

Good idea, I will try this.

 

[peter d]

I would not pay any attention to the electric bill going up complaint. There are so many other factors that can affect an electric bill. Furthermore, we've had a bitterly cold winter so far, so I would expect a home that has electric heat to have a higher electric bill so far, especially if you are in the northern tier of the country.

As for the t-stat, the simple bimetallic stats are not very accurate at all. The solution, if at all possible, is to install a new Aube or Honeywell triac thermostat. They are accurate to +/- 0.3 degrees if I remember correctly. They pulse the output of the heater in 15 second intervals so the heat does not swing wildly as it does with a conventional bimetallic stat. Unfortunately they do not make these stats in an inline version so you would have to wire a wall mount stat if this is even an option.