Thermostat "heating" light is always on


  #1  
Old 09-16-14, 10:39 PM
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Thermostat "heating" light is always on

Like the title says ... as of just recently, maybe a few days now, the indicator light is always on (the one that turns on when the heat kicks in). I didn't change anything, it just started happening.

- Thermostat: White-Rodgers 1F97-371, about 8 years old, this is the "main stat" that is acting up
- Munchkin boiler, outdoor reset
- No A/C in the house, no fans etc, the thermostat just tells the boiler to fire up
- Two zones, the second zone is RFH running on a little Tekmar 510
- Each stat seems to be working perfectly fine, well except for the light on the 1F97; I mean the boiler faithfully obeys their commands.

What I've tried, with no change in the behavior:
- replace the three AA batteries in the 1F97 (it runs on batteries, not a wire)
- clean the battery contacts with rubbing alcohol
- shut everything down and reset the breaker that it all runs on.
- full reset to factory values on the 1F97
- inspected the circuit board with a magnifier for obvious burn marks or popped elements

There is some green corrosion inside one battery holder, maybe in the past a battery leaked in there and left some residue. The solder tracks nearby to it on the PCB are not as shiny as all the others, but they are not broken.

Is the circuit board maybe messed up and I should be on the lookout to replace the 1F97? Not really interested in having it fail while we are away in November and the house is empty, etc.
 

Last edited by sbarr11; 09-16-14 at 11:22 PM.
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Old 09-18-14, 11:59 AM
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Anybody?

It's a really simple setup: just two wires at the stat, they go to the boiler. Currently there is also one jumper at the stat. When the thermostat closes the circuit, the boiler fires up and, via a relay tells the circulators to start circulating.

Everything is working fine except the little "heat is on" light is always illuminated, no matter what.

Do I need a new thermostat?

I'm assuming the thermostat is bad, just looking for confirmation (or not)
 
  #3  
Old 09-18-14, 01:05 PM
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Are you sure about the stat model number?
I don't even see an L terminal.
 
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Old 09-18-14, 01:23 PM
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Here is the model number, the light shining happily with the room 4 degrees above the setpoint (the boiler is not on, however), and the wiring.
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Old 09-18-14, 05:33 PM
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http://www.alpinehomeair.com/related...sersManual.pdf

Sounds like a faulty stat.

3
The yellow indicator glows when
the system is operating
Does the yellow indicator glow when you disconnect the wire from your W terminal?
 
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Old 09-18-14, 07:43 PM
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By the way, thanks for helping out.

The yellow indicator does not glow when I throw the breaker, nor when I disconnect the W wire.
 
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Old 09-19-14, 05:08 AM
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I'd inspect the control wire connections at the boiler end and if nothing looks shorted, I'd replace the stat.
 
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Old 09-19-14, 08:18 AM
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Hey I also checked the voltage at the stat, it reads 28.1 Volts. I trust my multimeter, it is decent quality and relatively new. I will inspect the boiler end more carefully tonight.

Is 28V within spec, or could the problem be that the boiler's control board is sending too high of a voltage?
 

Last edited by sbarr11; 09-19-14 at 09:58 AM.
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Old 09-19-14, 04:20 PM
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I usually measure around 27 volts so your voltage is fine.
 
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Old 10-05-14, 09:27 AM
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Follow-up: I never officially determined the problem with the old stat but I replaced the thermostat with a wifi model, a White-Rogers/Emerson Sensi, model 1F86U-42WF.

The Sensi seems great, the wireless is easy to set up and to work with, one thing didn't seem to work so I emailed tech support and within a few hours I had it working. The one negative to this replacement for me is that it is not easy to know when the heat is on, there is no glowing light just one small word ("heating") added to the display screen.
 
 

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