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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22541
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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Installing a new thermostat for a heat pump. It's a

Customer Question

Installing a new thermostat for a heat pump. It's a Honeywell rth7500d. Problem is I have 10 wires coming out of the wall and not sure where they all match up.
Submitted: 11 months ago.
Category: HVAC
Customer: replied 11 months ago.
We have W, W2, Y, O, G, R, coming out of black wire in the wall and R, Y2, Black, and G coming out of the white wire in the wall
Expert:  Sean replied 11 months ago.

Jen, I am a expert here, Your question has been reported, This can be quite difficult when you start having this many wires, What kind of thermostat did you remove?

Customer: replied 11 months ago.
It was an old hai rc100 thermostat
Expert:  Sean replied 11 months ago.

Im looking now. Did you remove all the wires?

Customer: replied 11 months ago.
We put the labels on when removing. The g listed above was in the F slot.
Customer: replied 11 months ago.
The green wire was attached to the f port on the thermostat I mean.
Expert:  Sean replied 11 months ago.

Im looking at old thermostat manual now, I see no F slot, i am not familiar with the Hai rc100 t-stat Im going to opt out and let another professional help, I know from experience where most of the wires go but regarding the few I don't it can cause issues if there placed wrong and Im not wanting to take that chance

Customer: replied 11 months ago.
Ok thanks.
Expert:  BillyHvac replied 11 months ago.


My name is Billy.

Very simply, on the older thermostats F meant FAN...which is what the G terminal/green wire does.. So Old F = New G.

What other wires do you need help with?

Customer: replied 11 months ago.
I have too many wires basically. There are 2 main cords coming out of wall. 1 has 4 wires (red, green, black, white). Other has 6 wiresRed marked r
Green marked f
Orange marked o
White marked c (it was in the c slot per the wiring they had)
Yellow marked y
Sort of brown/cream marked w2
Customer: replied 11 months ago.
New thermostat has 9 slots
Expert:  BillyHvac replied 11 months ago.


out of all those many were actually hooked up?

Most of the time there are extra wires in the cables.

Customer: replied 11 months ago.
All of them. Looks like a blue is not used on the one side. I didn't count that one.
Expert:  BillyHvac replied 11 months ago.

I understand now.

You have dual stage cooling and multistage heat. The thermostat you have (rth7500) will not accommodate all the features you have on your system.

So we have 2 choices....dumb the system down by combining features or get a new thermostat capable of multiple stages. have 2 stages cooling...we would have to dumb the unit down and put 2 wires from 2 stages together to make one stage....I do not recommend doing this but it is an option.

You will need a thermostat that says 2h/2c...and one with emergency heat capability.

So basically your system has more features than the 7500 can provide for.

Customer: replied 11 months ago.
Ok. Makes sense. I think we would prefer to get a new thermostat. If we have access to all those features, seems silly to take them away.Really appreciate the information and you help. You probably saved me hours of running in circles.Thanks!
Expert:  BillyHvac replied 11 months ago.

You are very welcome and you are making the right choice.

If you have questions when you get the new thermostat let me know.

Make sure new thermostat is :

Heat pump compatible

Has emergency heat option

2 stage heat and 2 stage cool at a minimum.

If you see 3 and 4 stage that is fine...we just do not use the extra staging. Just rate service to close