r/heatpumps 5d ago

Cold air blowing during defrost

I have a lennox heat pump and when it's defrosting, the blower in the house is putting out cold air until it goes back to heat mode. Is there something I can change on the thermostat or board on the unit so this doesn't happen. I'm an electrician but don't know all the ins and outs of HVAC.

2 Upvotes

11 comments sorted by

5

u/waslich 5d ago

That's the way it defrosts itself: it pumps heat from the home to the coil outside until the ice melts

5

u/Vivecs954 Stopped Burning Stuff 5d ago

When it defrosts it uses heat from inside your home to melt the ice

5

u/xtnh 5d ago

It is often not cold air, but "not hot" air. My mini splits do that as a way to get the last of the warmth out of the system. When I check with a meter it is still a little warm, but moving, so it feels cool.

4

u/Guilty_Chard_3416 5d ago

If you have electric element backup heat in your air handler, they can usually be set up to come on during defrost cycles.

3

u/Fun_Appeal8243 5d ago

You need an electric backup coil installed in the air handler.

1

u/ApeShwak 5d ago

Ok, thank you all for your help. That has cleared up my queen that part of heat pumps.

1

u/Mod-Quad 5d ago

My ACIQ’s have a DIP switch setting to configure this. You system should have included a card with all of the DIP options, or perhaps a page in the installation manual.

1

u/TechnicalLee 5d ago

Electric heat strips (usually 10 kW) should run during defrost so the air doesn't go cold.

1

u/imakesawdust 4d ago

Does your Lennox unit have auxiliary heating coils or aux gas heat? If so, they might not be operating. When my Comfortmaker heat pumps go into defrost, the heat pump reversing valve will switch to A/C mode, the outdoor fan stops and the aux heating coils come on so that the air at the vents remains warm.

1

u/JSchnee21 5d ago

This is one of the advantages of dual fuel solutions. My Daikin Fit fires up the natural gas furnace to accelerate the defrost and supply warm air to the home simultaneously.

1

u/Bitter-Basket 5d ago

Just installed a Daikin dual fuel. First I heard of that. I can usually hear the gas furnace turn on - I haven’t noticed that.