Line voltage t-stat issue


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Old 11-22-21, 09:51 AM
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Line voltage t-stat issue

I have a Honeywell line voltage t-stat RLV3150 controlling a 2500 watt, 240V electric baseboard, installed 1/18/2016. Twice in the last week I've come into a cold room. The display shows that it's calling for heat, but baseboard is dead cold. In both cases I was able to fix it by turning the breaker off for several seconds, then back on. Any idea what's going on? Am I looking at the beginning of the end? Thanks for any help you can give me.

Edit: So far I have opened up the t-stat and cleaned it and cleaned the baseboard
 
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Old 11-22-21, 10:04 AM
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Turn the 'stat all the way on & measure the voltage across the contacts. At this 10A current a working wall switch would have about 0.03v across it.
Substantially more voltage across your stat contacts points to worn contacts or low spring pressure forcing the contacts together.

You could try fine sandpaper.

Unfortunately I don't yet have data for the contact resistance of stats or relays.
 
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Old 11-22-21, 10:21 AM
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That is a digital line voltage two wire thermostat. There is no relay or moving contacts inside.

You will need to pull the thermostat out of the wall and check across the two leads while it's in operation. Put your probes inside the wirenuts for testing. More than likely it's a thermostat issue because I'm pretty sure if the heater was defective the thermostat would go dark.
 
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Old 11-22-21, 10:33 AM
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My bad.

A working Triac when on & passing current should probably read a volt or so across it.
 
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Old 11-22-21, 10:41 AM
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Thanks bulova! Unfortunately, that's a bit above my pay grade. If it happens again, I may just replace it.

Does anyone have any opinions on which type t-stat lasts longer, electronic or mechanical? 6 years sure isn't much life, at least compared to my home low voltage Honeywell t-stat.
 
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Old 11-22-21, 10:57 AM
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There aren't many digital line voltage thermostats.
I don't know of any that use a relay. (mostly because of the size)
 
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Old 11-22-21, 11:11 AM
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Maybe I'm using the wrong terminology. I see two kinds of line voltage t-stats at the big box stores. What I call mechanical have a round knob that turns to adjust temperature; the other type has a digital display and you push buttons to adjust temperature. That's about the extent of my knowledge of stats and how they function!
 
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Old 11-22-21, 05:28 PM
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The digital ones have no moving parts and are silent.

The ones with the round knob are mechanical. They click when they approach setpoint.
They use mechanical contacts that arc and will wear out.

The mechanical units have been around much longer but I don't know if they are as long lasting now. In my opinion a mechanical unit is fine. You aren't saving any energy if the thermostat is more accurate. Every dollar you spend in electric heat is delivered in the home.
 
 

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