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SnazzyGTP · Oct 28, 2005, 06:32 PM

Hi,

I've got a strange problem with my thermostat. Recently I purchased a Noma programmable thermostat (Mod#52-2558-8) and installed it replacing the existing analog control. Problem is it resets randomly about 1-2 times a day. My setup is (don't laugh) an Olsen gas furnace (Mod#BAS125) which is about 38 years old, and a White Rodgers Fan Centre (Mod#8A05A-101). I'm planning on replacing the furnace once I save up some cash, but I'd really like to get to the bottom of this resetting problem. I have already exchanged the first thermostat for a second unit of the same model number. I still need to check, but I think when the fan mode is set to Auto it never kicks on when the heat turns on - so I set it to ON.

Any help would be greatly appreciated.

TIA
Darren

labman · Oct 28, 2005, 08:06 PM

Sounds like 2 separate problems. If when the thermostat resets, it resets to a default, it could be due to losing power because of a bad connection. Could be anywhere from the wiring at the thermostat clear back to the breaker box. The older mechanical systems would pause and then continue after a momentary loss of power. Modern, solid state stuff forgets what it was doing. Some of them have a battery back up.

The fan problem could be a limit switch. They are wired not to come on until a limit switch in the furnace heats up. A second limit switch should shut off the gas if the blower doesn't come on.

bradhope31 · Dec 6, 2007, 07:38 PM

Hello,

I'm new to this site so please forgive any ignorance. I have virtually the same problem as Snazzy.

I, too, purchased the same Noma prog. Tstat (Model THM303M or Canadian Tire code: 52-2558-8) and it is randomly resetting itself. I originally purchased it back in June and all summer it was working just fine with the A/C. Ever since switching over to heat it has been randomly resetting itself. I exchanged it for the exact model earlier this week and now I'm experiencing the same problems. In the summer we had an HVAC technician come check out our system because the A/C wouldn't come on. He tested all the wires and his conclusion was that our tstat was garbage and we needed a new one. That's when I bought the Noma.

I realize that most tstats have the typical setup for wiring (W, Y, G, RC, RH, etc.) but what about the wiring in the house. The colours don't exactly match. I have a:

White wire attached to W
Orange wire attached to Y
Green wire attached to G
Black wire attached to RH
Red wire attached to RC

Does that make sense? Are there any problems with that setup that would contribute to my current problem?

The furnace comes on and it heats the house fine... the problem is the resetting. The default setting for Sleep (10pm - 6am) is 17.5 C or 63 F which is really cold!! My wife and I could suck it up but we have a 2 year old who has woken up with purple lips because the system resets in the middle of the night sometimes and we're totally unaware.

Any and all help would be greatly appreciated. Hopefully I've given enough information.
Thanks so much for taking the time to read this.
Brad.

Originally Posted by SnazzyGTP

Hi,

I've got a strange problem with my thermostat. Recently I purchased a Noma programmable thermostat (Mod#52-2558-8) and installed it replacing the existing analog control. Problem is it resets randomly about 1-2 times a day. My setup is (don't laugh) an Olsen gas furnace (Mod#BAS125) which is about 38 years old, and a White Rodgers Fan Centre (Mod#8A05A-101). I'm planning on replacing the furnace once I save up some cash, but I'd really like to get to the bottom of this resetting problem. I have already exchanged the first thermostat for a second unit of the same model number. I still need to check, but I think when the fan mode is set to Auto it never kicks on when the heat turns on - so I set it to ON.

Any help would be greatly appreciated.

TIA
Darren

alex0451 · Feb 26, 2009, 08:43 AM

I also have the resetting issue but I found the source of the problem. A relay in your system is probably creating a surge on your 24v system that gets through your thermostat relay and reset your thermostat. I found yesterday that if I manually start the fan relay by shorting the wire connection screw with a screw driver (bad connection that creates spark and surge) is automatically reset the thermostat. This problem should be easy to corrected by adding a MOV (Varistor) on the AC line(+-5$). I will try that this weekend and I will keep you updated.