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sporkman 11-21-2010 11:56 AM

Electric Baseboard Heat - relay problem?
 
Hello,

I'm in an apartment with electric baseboard heat. There are two units which each are wired to a relay in the garage - one circuit for each, one relay for each. The relay is controlled by a standard thermostat.

The temperature in the apartment has been swinging wildly - with the thermostat set at about 70F, the temperature can go as low as 66 and as high as 80. Thinking this might just be a quirk of the old mechanical thermostat combined with the fact that there's probably about 2x as much capacity as needed for this studio, I bought a cheap Honeywell digital thermostat.

The problem remains...

One thing I noticed today as the temperature reached nearly 84F is that one strip of baseboard heaters was staying on way, way longer than the other after the thermostat cut off power. According to the manual for the Honeywell 814 relay, the relay does have a built-in delay on both turn on and turn off - this is accomplished with a bimetal switch.

Could the bimetal delay doodad be the root of the problem? I know there's one per circuit, and I know in the past I've noticed a different delay on each set of heaters.

I have to partially DIY this because my landlord would either not do anything or send out someone totally unskilled. If I can pinpoint the relay as the source, then he can buy the part and pay an electrician to install it. The relay is at least 30 years old.

beenthere 11-21-2010 01:55 PM

It could be the relay. It could also be the hole in the wall where the thermostat wires come through.

sporkman 11-21-2010 03:56 PM

Quote:

Originally Posted by beenthere (Post 538130)
It could be the relay. It could also be the hole in the wall where the thermostat wires come through.

Oh, also I did go ahead and disconnect the thermostat for one test - the one set of heaters continued to produce heat...

I did think of the new thermostat being more finicky about drafts or something, but I've narrowed it down to just one section of the heaters. The way the relay is wired is that there's a single input from the thermostat and then two relays internally - one for the west side of the apartment, one for the east. I turned off the breaker for the west side heaters and the east continues to function normally.

Apparently the relay also has a "bimetal" strip that is used as some type of delay mechanism - perhaps that's stuck.

But can I pretty much assume after narrowing it down to one heater strip/circuit that the thermostat is OK and that the relay is what's going nuts?

beenthere 11-21-2010 04:45 PM

Fairly safe to believe that.

The bimetal may be getting weak, and unable to move back to the open position anymore. or the relay can be going bad as in generating heat itself and keeping the bimetal warm/hot.

However. Although I know that relay can go out anytime it wants.

Your landlord may want to say it went out because you wired up your new thermostat wrong, and damaged it.

Be carefull how you approach him about this. And you may not want to tell your diagnostic procedure to the guy he sends to fix it. Since that guy works for him. And reports to him.

sporkman 11-21-2010 06:01 PM

Thanks for the info, I appreciate it.

The landlord drama is what it is. His goal is to never pay for outside help, mine is to have the heat working with some assurance it's safe. I'm not totally thrilled that one of the failure modes of the relay is to run the heat continuously... I was just out of the country for two weeks, if this would have happened then, that would have been bad. As far as I know the heating units themselves don't have any cutoff. They've been painted over so many times that I can find no indication of a make/model.

If he wants to blame this on the thermostat, that's kind of nuts. It's two wires - close the connection, heat goes on - open the connection, heat goes off. But if playing dumb is the best bet, I can do that. :) I will tell him the truth - I had to cut the breaker to stop the heat.

I'm having a hard time dating this place - it's a large standalone 2-car garage with a full second floor that's now an apartment. All the original power outlets are 3-prong, so I think that puts it somewhere after 1970. The unpainted drywall in the garage is tan/brown rather than white or grey. The floor tiles are asbestos, which I think dates it to before the 80's. The heating units look to be part of the original construction - all the wiring for them is properly routed behind the drywall, as is the thermostat wire. I guess my point here is that the relay unit is probably at least 30 years old...

yuri 11-21-2010 06:21 PM

Is it one of these relays, 841 instead of 814:

http://customer.honeywell.com/Honeywell/UI/Pages/Catalog/ComponentCategory.aspx?Catalog=Homes&Category=Rela ys_33134&ChannelID={2EB2F178-20ED-44E0-97FB-CCFB4218DD64}

sporkman 11-21-2010 06:38 PM

Quote:

Originally Posted by yuri (Post 538262)
Is it one of these relays, 841 instead of 814:

Yes, I was repeatedly making that mistake on the model #. If I had to guess, I'd say the 841E:

http://customer.honeywell.com/techli...0s/60-2004.pdf

That doc sort of suggests that there's not a true "relay" in there. It says that on the thermostat calling for heat, a heater in the enclosure causes the bimetal to basically push a switch. Perhaps I need to pull the cover off this just to see what's in there.

I hate getting anywhere near AC. Makes me super-jittery.

yuri 11-21-2010 06:43 PM

NO. Do you want to get electrocuted/damage it /cause it to arc and spark and start a fire/burn the place down/ be liable?? I work on electric furnaces and we are talking SERIOUS amounts of current and high voltage here. At least they are not obsolete. Now call the rentalsman and have them lean on the landlord. Tell the rentalsman you feel it is unsafe as one of the heaters won't shut off/is running wild.


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