Furnace blows cold air intermittently

Pawan

I have an American Standard high-efficiency 2-stage natural gas furnace, about 5 years old. The furnace is controlled by a single-stage thermostat, so I believe that the W1 and W2 connections on the furnace must be jumpered together.



The furnace seems to work normally except that 2-3 times during the day, it starts to blow out recirculated air, without any heat. This continues for about a half-hour, during which time the house loses about a degree or two of heat. The furnace then turns itself off. After a few minutes, it turns itself on again, and then there IS heat. I would obviously like the keep the house temperature as constant as possible, but I'm not sure if there is a problem with the furnace, or if something just needs adjustment. Obviously, though, it should either be off, or blowing hot air, not recirculating it for a half-hour by itself as the house gets colder. I don't recall this happening in prior seasons.



My thermostat can control temperature swings to within a quarter degree, so that can't be the problem. I'd appreciate any advice anyone more knowledgeable than myself could give me. Thanks in advance.

unclejohn

Filter Change

Sounds like your furnace is going off on limit. Check you air filter.

Pawan

Air filter

I have an electronic air filter, cleaned recently.

unclejohn

Time to get out

The book. You should have a idiot light some where on the furnace thats flashing you a error code. Check it out.

Pawan

Two red flashes

At the time the furnace is blowing cold air, I see two slow green flashes followed by 2 quick red ones. According to the book the 2 red flashes means "Retries or recycles exceeded". When the furnace resumes heating, I see the normal flashes of 20 green followed by one red. When the furnace is at rest, the flashing is normal too.



The ignitor on this furnace was replaced a couple of years ago. is it possible that the replacement ignitor is working intermittently?

unclejohn

Haven't seen

To many intermittent ignitors. Try cleaning the flame sensor.

Tim McElwain

Open the blower compartment door

and see if you can find the make and model number of the Elecronic Fan Timer or Integrated Control if I have that I can give you some idea as to what may be happening.



On the call for heat does the combustion air blower come on? Then does the igniter come on and glow? If so what happens after that?

Pawan

W1 to W2 jumper missing.

Sorry about the slow response. I was trying to figure out if there was a pattern to what the furnace was doing, and there is.



First of all, the only manufacturer's label I could see inside was on the gas flow control, which is a Gemini 36054-202. The blower motor did have a label, but it was impossible to read because of the way it was located.



The furnace operates normally in all respects, except for one thing. Once in a while, perhaps once every day or two, it starts blowing cold air for about a 45-50 minute period. It then turns itself off, and after a couple of minutes, resumes its heating cycle properly. While it's blowing cold air, the thermostat calls for heat, but the furnace will not respond, even if I put the temperature way up. If I manually turn the system off at the thermostat, and then re-start after a few minutes, it operates normally. Or, if I just let it finish it's period of blowing cold air, then it seems to reset everything properly again by itself.



I did notice one thing when I looked closely at the electrical board on the furnace. This is a 2-stage furnace, but the W1 and W2 connections are not jumpered together, as I thought they would be. The only connection to the thermostat is with the W1 connector. The installation manual requires a jumper between W1 and W2 when connected to a single-stage thermostat, but the installer clearly missed that. Could that be the source of this problem? If so, I can fix that easily.



A Happy New Year to all, and thanks again for your help.