Recently installed furnace blows cold air at first
This is regarding a new home that I moved into in July of 2022. We have a new Goodman model GMES800805CN furnace. When the unit clicks on to begin warming, it belows cold air for 4 to 6 minutes and then finally starts blowing warm air. I am trying to determine if I can cut down or even completly eliminate the cold air altogther at the beginning of each heat cycle? One of my thoughts would be if I could increase the time before the blower starts. I am not sure if this unit supports that ability or not? Or if there are other suggestions of things to look at?
Is it a gas furnace? Does the burner light as soon as the thermostat calls for heat? Is the air warmer than ambient but just not warm enough to feel wam or is it actually not being heated at all?0
Are you running a deep set back?
Are the return ducts exposed to very cold air?
It's possible to increase the 'on' time for the blower, but you need to measure and test air flow and temperature rise to best determine if that is feasible, or if you have a duct work deficiency.
Sounds like you went thru a whole winter like this.
You're going to need a tech eventually. And with AC season coming up might be time for a competent tech who understands airflow to give the entire system a once over.steve0
I will do my best to answer the comments posted so far. Yes, this is a gas furnace that is in our attic. I need to confirm if the burner light is going right after the thermostat calls for heat. I suppose it is possible there is too much of a delay for igniting the burner. The air does feel warm eventualy that is coming out of the vents. It is just anoying that it takes a while to feel that warm.
We will need to have a tech review our duct work and test our air flow and temperature rise. And yes we did put up with the way the system has been running for the whole winter. I think we were wishfully hoping the problem would fix itself.
We have had the company out that installed the unit. But they have not been able to find anything wrong. And their troubleshooting skills have not been the best. Then tend to throw parts at a situatuon until they accendentialy fix the issue.0
This information is available from the installation manual. It seems that there is only a 30 second circulator fan delay from proof of flame to the circulator blower start.
Circulator blower is energized on high heat speed following
a fixed thirty second blower on delay
It appears that you have no adjustment for blower on delay in the control system.Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics0
There are other blower adjustments that may help to midigate your ussue. There will always be some amount of cold air when the circulator blower start up in the winter due to the duct location in the attic. There are CFM adjusting switches that may provide faster warm up of the air flow thru the duct system. You can increase the amount of insulation around your ductwork. Since your furnace is equipped with a variable speed circulator blower motor, you can maintain a slow (usuallly unnoticable) constant air flow by placing the thermostat to "FAN ON" during the heating season. This will keep the ductwork from getting too cold between operating cycles. I have been told that with the lowest CFM setting for "FAN ON" the ECM type blower motor will use varry little electricity.
You can try several different blower CFM switch settings and FAN ON/FAN AUTO combinations to see what works best for you. But once you set it, try it for a few days before you decide that it is not working for you. Good Luck with your new heater.
Mr. EdEdward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics0
Hi, You should expect some cool air when the furnace starts up as there will be cool air in the ductwork. The best fix for this is to install grilles and adjust fan speed so the air doesn't blow on you. Done right, you shouldn't even feel the air movement. This matters because it not only makes things more comfortable, it also allows slightly warm air to heat your place. Barely warm air blowing on you might feel cool because it can increase your personal evaporative loss. Hope that makes sense! 🤓
The fifth dot. down on the right shows a fixed 30 second delay from proof of flame to blower start up.
The 4-6 minutes of cold air is a problem. The furnace will go through trial For ignition, and if it doesn't pass all the tests, it will try again. It might try 3 to 5 times (not familiar with your model) before it goes into a hard lockout. During these failed trials, the blower will come on at high speed as a safety. Usually the blower will stop, before a new trial for ignition is started but maybe your model doesn't.
Your furnace seems to be working on the second or third trial. It's something that NEEDS to be addressed.1
At start up, there is a delay for the blower to turn on while the furnace heats up. At a certain temp the blower turns on. There are sensors or dip switches that control the blower on and off delays. Might check that.0
What HVACNUT said.
Could be flame sensor needs cleaned or pressure switches open because of cold start.
Will probably get worse to where it will do hard lock out.0
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