How does electric heat work?

[Charles]

Not very well, I am finding.

I don't mean the physics of it. I know that current I goes through resistor R and the power in = power out which is I-squared R. Each kW in gives about 3400 BTU/hr of heat.

I have baseboard heat with "Chromalox" thermostats. There is about an

8-degree difference between turn on and turn off. Methinks the current does some heating of the thermostat itself, as the heat turns off before the room reaches anywhere near the dialed temperature.

Temps here are in degrees F.

For instance, I have one thermostat set at 78, the temp near it is 63 and the heat still turns on and off. Another in the bedroom is set at

73, the temp never gets much above 64 and the heat still cycles on and off.

Until a year ago I always lived in houses with forced air gas heat. At least at the thermostat, the temp never varied much from 68. Other parts of the house might get cold if it got really cold outside, but not like this house with electric heat, where it is always colder inside when it is colder outside, with the same thermostat settings.

Thermostats were likely installed 30 years ago. Presumably there is no relay so all current going through baseboard also goes through the thermostat. Or is there a relay in the baseboard heater?

Someone on misc.rural suggest I replace the thermostats. Someone else suggested I post here.

Suggestions?

Thanks,

Charles.

[Edwin Pawlowski]

First I'd see if there is dirt or dust in the stat. If not, I'd try replacing one of them and see if it works properly then. Caution, they may be line voltage so be sure to check the power.

[Colbyt]

Ignore the degree markings on the thermostats. They are never correct. They might as well be number 1,2,3. Buy a couple of cheap thermometer. Adjust the stupid dial till you reach your comfort level or the desired temperature on the purchased thermometer. Thereafter the heat should not cycle more than 2 degrees over or under. If it does than you might need to replace something.

Colbyt

[rck]

I bought a line voltage thermostat, wall mounted, and it is very accurate. As noted, the temperature controls which are mounted on the baseboards are not calibrated to any specific temperature. I have a small baseboard heater in the bathroom and the thermostat reads, "Low, Med, High".

Bob

[Charles]

I don't know if these are line voltage or not, but they are calibrated in degrees F.

They seem to be sort of accurate but I get the feeling they are being heated when the heat is on.

Charles.

[Charles]

I plan to turn the power off before replacing any of them. I think I know what breaker turns off what as I used a clamp-on ammeter to track that down.

thanks.

Charles.

[Jeff Wisnia]

Many mechanical thermostats do have a small low resistance heater in them, usually connected in series with a low voltage relay coil load they are switching. Those heaters are knowb as "anticipators".

When the thermostat contacts are closed that heater produces a little heat inside the thermostat housing, causing the thermostat to open a bit before the rising room temperature would make it open without that heater.

That system "anticipates" the additional increase in room temperature caused by the heat remaining in the electric heaters, radiators or hydronic baseboard units, which at shutoff are at temperatures higher than the room air.

some of those anticipator heaters have an adjustable slider which can be moved to vary the resistance through which the thermostat current passes, enabling "tuning" of the system to better match the temperature overshoot of the heating system.

From your description, it sounds like there may be anticipators in those thermostats which are doing their jobs a little bi too well. Have a look see for them

HTH,

Jeff

Unless those are really BF thermostats, I'd expect there to be a relay somewhere. Without a better description, it'd be hard to tell for sure.

[Joe Bobst]

You may get some benefit from using ceiling fans for circulation of the air to avoid temperature stratification. Relocation of the thermostats may also be beneficial. Try to find a good quality thermometer while you're at it. HTH

Joe

[Greg]

My thinking exactly Joe. Forced air heat tends to equalize the temp and stabilize it (assuming good duct design). When you just have point sources and depend on convection alone you will always get hot spots.

[TURTLE]

This is Turtle.

First move the thermostat from just above the baseboard heat where it will heat the area above it very fast and cut off prematurely. Never install a thermostat just above the base board heater for it will never work right.

I have been called out on 3 base board heater in the last 10 years and everyone the thermostat was mounted just above the heater. They say the same thing you said here everytime.

TURTLE

[Charles]

Turtle,

The thermostats are on the other side of the room, nowhere near the baseboard heaters themselves.

Charles.

[Gary R. Lloyd]

Yep. Sounds like an anticipator problem to me.

Gary R. Lloyd CMS HVACR Troubleshooting Books/Software

[TURTLE]

Thgis is Turtle.

Check the Antisipator in the thermostat to see if you can get a longer cycle on them.

TURTLE

[Doug Warner]

My second house had electric heat (in MA). I found that my feet were always cold, while it was nearly 80 degrees at the ceiling. There was nothing to mix up the air and even out the temperature. =20 If I had to do it again, I'd have ceiling fans in every room.

To reply, please remove one letter from each side of "@" Spammers are VERMIN. Please kill them all.

[xrongor]

My second house had electric heat (in MA). I found that my feet were always cold, while it was nearly 80 degrees at the ceiling. There was nothing to mix up the air and even out the temperature. If I had to do it again, I'd have ceiling fans in every room.

yup. ceiling fan make huge difference