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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8134
Experience:  Furnace, A/C and heat pump specialist.
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I have two dual-stage units very recently installed I have

Customer Question

I have two dual-stage units very recently installed
I have asked the a/c technician to change the control system so that if the thermostat fan setting is set to "ON", the fan will ALWAYS run at full speed.
Is this possible? He doesn't know how to do it
The model number of one of the units is 4TXC8004DS3HCAA
Submitted: 9 months ago.
Category: HVAC
Expert:  Webb-Guy replied 9 months ago.

In order to do this you will need to check the schematics of the fan itself. Do you happen to know what fan you have? There are wires that select which speed you are wanting to use/

Customer: replied 9 months ago.
I was hoping you would have access to the schematics...
Expert:  Webb-Guy replied 9 months ago.

Unfortunately I don't so I will open this up for you.

Expert:  airheatman replied 9 months ago.

I am a different expert. This model is on the evaporator coil. PLease give me the model on the air handler/furnace. I will grab a manual on the unit.You most likely have a variable speed fan so this will be controlled by dip switches in air handler.

Expert:  airheatman replied 9 months ago.

If you have a gas furnace model lumber will be inside furnace in burner compartment so I can provide guidance with this specific unit.Model will be on a label just above burners on right or left inside panel

Customer: replied 9 months ago.
Sorry for the delay - I have been out of town.
I could not find any other model info, but I do have the schematic from the 3-ton unit. I suspect the 5-ton unit will have the same:
Expert:  airheatman replied 9 months ago.

Just got back in town myself.

OK on FAN ON mode at thermostat,your furnace will run fan on LOW HEAT or first stage speed.

To speed fan up you will adjust DIP switches SW7 and SW8 Both will need to be in OFF position

These settings are same for 3 ton and 5 ton

Expert:  airheatman replied 9 months ago.

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