# how long to wait between heat and A/c



## donhawley (Sep 26, 2016)

Is there an idustry standard for how long to wait before firing a furnace after the A/C has been shut off. Or turning on an A/C after test firing a furnace?


----------



## HVAC Service Mentor (Sep 24, 2016)

*How long?*

There is no need to wait between operation of furnace and AC or vice versa.

The thermostat may enforce a 5 minute time delay between switching between HEAT and COOL.

The main thing is that you allow both the furnace and AC to operate long enough so that the residual heat from the furnace and the residual "cold" and moisture from the AC coil have the opportunity to dissipate and return to normal before you take any performance measurements such as supply air temperature or refrigerant pressures, etc.

This should normally take about 15 minutes of steady run time.

-Eric


----------



## jedy22k (Dec 19, 2016)

If I am not wrong is about 5 to 10 minutes?


----------

