I have a Honeywell furnace and when it starts the exhaust fan kicks on then the flame starts (it's a propane furnace) it warms up between 30 seconds to a minute then the main blower kicks on but it blows out cold air for about 3 to 4 minutes before it starts to blow out warm air and about 6 minutes before it gets hot. I'm wondering if there is a regulatory or resister that is bad it has been wasting a lot of propane running like this.

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    What's the model of the furnace? Some units have adjustable blower controls, that allow you to change the delay.
    – Tester101
    Dec 9, 2017 at 1:20
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    This is normal there is no way to heat all the air in the ductwork, the only way I know how to eliminate this is mini splits or baseboard heaters in each room.
    – Ed Beal
    Dec 9, 2017 at 1:32
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    Where does your ductwork run? Attic? Unheated crawlspace? It might be that insulation needs to be added. I've seen heat duct blow artic air as they start because the ducts are uninsulated and running thru attic space. If you don't understand forced air furnaces it might be helpful to pay a well known and respected heating and cooling company to come and help you evaluate how to improve the system.
    – Tyson
    Dec 9, 2017 at 15:18
  • There's really no "heating up" involved with a modern furnace. The reason there's a delay is so that the various component systems can come on in the appropriate order and be tested for safety. Almost as soon as the burners are running fully the fan should come on.
    – isherwood
    Jun 13, 2018 at 19:23

1 Answer 1


No, that sounds like it's running correctly. If you want to adjust the timing, you can install an On Delay Timer on your circulation fan. You can use the ICM251 Fan Blower Control - Dual On/Off Delay Timer. It has an Adjustable Time Delay, and a 20 amp 120 volt relay built in. The On delay lets air reach proper level prior to energizing fan, and the off delay purges ducts of residual air to increase efficiency.

Fan Delay Spec Sheet

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    Depending on the furnace, it may already have an adjustable blower control.
    – Tester101
    Dec 9, 2017 at 1:20
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    There will always be some cold air coming from the ductwork (or hot in the summer) no matter how long the heat/cooling system is running , some systems run at a low speed for several minutes so the cool/ hot air flow is not as noticeable but it takes time with a forced air system, no way around this.
    – Ed Beal
    Dec 9, 2017 at 1:36

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