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Furnace turned on while thermostat set to AC

2 years ago

We recently moved into a house and been there for 2 weeks. Our heating system is gas and we used our AC unit for the first time yesterday from 4pm and on. All of a sudden at 1015pm we hear our gas heating furnace turn on in basement. i go to check furnace pull cover off and the barrel in front of the pilot flame Is blowing a huge flame thru it. None of the other barrels are lit. Any reason or advice of why the furnace woulda turned on, even though our thermostat was set to AC? I ran outside and our ac unit wasn’t on, but cold air was blowing thru the vents still, which Obvy was the residual cold air being pushed out so not wasted. But I was told when we moved in, the pilot snd flames will never have anything to do with AC when it is set to AC?

we’re worried something is malfunctioning, due to the furnace turning on and the one big flame being pushed thru The barrel in front of pilot flame...

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Comments (5)

mike_home
2 years ago
Do you own this house or rent it? If you own it then you need to call a service tech to investigate what is happening and do a preventative maintenance check. The HVAC system should have been checked during the home inspection. From the description it sounds like the furnace is in need of repair.

If you are a renter then you need to tell the landlord the furnace and AC are not working properly.
HU-230097092
Original Author
2 years ago
Homeowner....I’m going to run ac system as normal again and once air actually kicks on, see how long it runs, see what fan is doing, see if furnace is doing anything, and once it shuts down , I will check to see if the furnace does anything aka turn on of any sort again blowing any kind of flames....if it kicks on again will def be calling service tech to come check it out.
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OK, we are getting a more clear picture. Let me give you a concrete example. If the temperature inside is 75, it does not matter if the thermostat is set to 55 or 72, the heat will not go on. You can turn the t-stat to 55 or all the way down in the summer and it should not make much or any difference. That stated, I see that where my father is in upstate NY temps in the 40s are expected tonight. In a very poorly insulated structure, your heat might go on set to 55 and it is summer :-) I'll be there next week and I am looking forward to spending some time in a more hospitable climate. Tigerdunes is trying to figure out what kind of system you have. Is your water heater separate or does the same boiler provide both heat and hot water for the taps (domestic hot water)? If you have an all in one system, you should expect your boiler to kick on to provide hot water. There may be ways to improve the efficiency of the system so you will want to educate yourself and this is a good place to find help. Enjoy your new home. You will need good, knowledgable regular service with an oil burner. Ask around and find out who people like and make sure you get it cleaned and checked annually if you stay with oil heat. Traditionally, companies that sell oil and service equipment schedule regular service calls in the summer because they are not as busy delivering oil then.
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mike_home
2 years ago
Where are you located? Do you know if you if have a heat pump and gas furnace dual fuel system? If you have a dual fuel system, and you have been having cold nights and followed by an unusually warm day, it is possible the furnace might be turning on when the outdoor temperature drops. Usually the thermostat is wired so when it is set to cooling the furnace cannot turn on. Your furnace may have a feature to allow independent heating and cooling set points and operate the furnace and AC operate when needed. Have the service tech review this with you.
HU-230097092
Original Author
2 years ago
Located in doylestown PA. We turned our air on for first time yesterday and noticed at 1015pm, after the air ran its cycle, we heard furnace in basement turn on. I checked outside so unit, that was off. The fan was still on blowing the residual cold air out of vents. But when I went to check furnace downstairs after hearing it turn on, I pulled cover off, and one flame was blasting a full flame into the barrels. None of the other flames or barrels were lit. I regret not taking a video. The furnace and flame was only on for about 10-15 minutes then shut off. There is no heat pump. We have a nest Thermostat.
mike_home
2 years ago
I was in Doylestown PA three weeks ago for the first time. It is a beautiful area.

The Nest may have been set up to do what you have described. You may have a 2-stage furnace which may explain why your are not seeing all of the burner tubes light up.

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