How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask BillyHvac Your Own Question
BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22543
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
Type Your HVAC Question Here...
BillyHvac is online now
A new question is answered every 9 seconds

We have a lennox model g40uh-48b-090x-11. The recirculating

Customer Question

We have a lennox model g40uh-48b-090x-11. The recirculating fan keeps going on even when the thermostat is not set to heat, cool or fan. When we have the heat setting on and the house reaches temperature the fan goes on periodically blowing cool air into the room.
I understand the blower will stay on for a short time after the heat burner goes off (temperature reached).
Is there a control to shut off the recirculating air fan?
Thank you
Mark Karbon
Submitted: 1 year ago.
Category: HVAC
Expert:  BillyHvac replied 1 year ago.


What thermostat make and model are you using?

Customer: replied 1 year ago.
honeywell t8001c
Customer: replied 1 year ago.
I called Honeywell and they said if I ake the thermostat off and the fan is still running it is the hvac unit
Expert:  BillyHvac replied 1 year ago.


the thermostat does not do this...and the furnace does not do this.

The only way this furnace can do this is if there is an optional ventilation system (erv or hrv) hooked up for outdoor air....or...the circuit board is defective in the furnace.

I do not understand the techs comment unless you have an optional hrv?

Customer: replied 1 year ago.
Please explain HRV ERV. We have the unit in our attic and the compressor for air is outside. The fan that we cannot control is in the unit in the attic.
Expert:  BillyHvac replied 1 year ago.

There are some homes tat ave an optional energy recovery ventilator or also known as heat recovery ventilator. This is a separate unit that draws outdoor air into the home while exhausting stale air.

If you can post a pic of the furnace with doors off I can tellyou....BUT less than 5% home have these. I am actually thinking you have a bad ciircuit board but I want to cover the bases

Customer: replied 1 year ago.
I cannot access the unit in the attic due to my age. The cooling and heating functions work fine. Is this device which I think we are in the 5% mode a part of the unit in the attic or would this be a seperate device (probably in the attic)
Expert:  BillyHvac replied 1 year ago.

it would be a separate unit with piping to the outside and then piping to the duct work of furnace.

Can you read the tech report or tell me what the report was?

Customer: replied 1 year ago.
found a/c working fine. System has an air circulating fan. Turns on at sporadic times during the day. Nothing else said other then telling us that he can by pass or stop this fan by disconnecting for $300
Expert:  BillyHvac replied 1 year ago.

Sounds very suspect to me.

This furnace does not have a feature like that and the thermostat does not either.

If under home warranty the circuit board would be replaced. I think this is worth a look at by the company again.

I would call them back and relay that you are not understanding what part he says needs bypassed and why it is not under warranty if something is wrong. Even ask for another tech to make a courtesy call.

Something does not sound right......Plus I can think of nothing that would take $300 to disconnect

Customer: replied 1 year ago.
My wife just told me that he said we have this system based on seeing a 2nd ventilation system behind the wall intake vent. Now I hear he didn't go up in the attic. Can this additional system be identified by seeing a 2nd small vent w/filter inside the main wall intake?
Customer: replied 1 year ago.
I should have said a 2nd filter not 2nd ventilatin system
Expert:  BillyHvac replied 1 year ago.

now I am even more suspect if he did not go to attic to check the main unit.

Do you have another control other than the thermostat anywhere?

Customer: replied 1 year ago.
Expert:  BillyHvac replied 1 year ago.

than I really cannot see how a circulation fan operation could be determined without going into the attic.??