# HONEYWELL thermostat wiring



## morngon (Mar 30, 2016)

I just bought a RTH221 honeywell thermostat to replace my old T6575D1009 model.
i am trying to connect wires, but i don't have the G wire.
i have blue and other wires.

can someone tell me how to do it correctly?

thanks!


----------



## user_12345a (Nov 23, 2014)

1. You mounted the thermostat plate up side down.

2. Your old t-stat has atypical wiring for a unit with atypical controls. Going by letters could get you in deep trouble.

The way the unit it operates is most likely different from a basic 1 stage gas furnace/ac - the stat must be configured to energize the right terminals in each mode of operation.

For example most t-stats don't directly impact fan speed, yours does. In most setups G is the fan terminal - the fan speed selection is based on the mode of operation.


----------



## user_12345a (Nov 23, 2014)

Best bet is to get the model number of the old stat and cross reference it. You won't find the right stat at a retail chain.


----------



## beenthere (Oct 11, 2008)

Whoa, stop. Your old thermostat is a line voltage thermostat for fan coils. That new RTH221 is a low voltage/24 volt thermostat. Can't be used on your system.


----------



## gregzoll (Dec 25, 2006)

What is wrong with the existing thermostat? There is a reason why Honeywell.com offers a "Find replacement" option on their website. If the current one is no longer working, you need the TB6575A1000/U from Honeywell to replace it. https://customer.honeywell.com/en-US/pages/Product.aspx?cat=HonECC Catalog&pid=TB6575A1000/U


----------



## gregzoll (Dec 25, 2006)

beenthere said:


> Whoa, stop. Your old thermostat is a line voltage thermostat for fan coils. That new RTH221 is a low voltage/24 volt thermostat. Can't be used on your system.


I am beginning to wonder if people just rip the packaging open and toss everything. There is a reason why they come with the books. Before I even install any thermostat for someone that asks me to do it for them, I an sitting with the book and either a cup of coffee or a beer to familiarize myself with it.

It is neat that of course Honeywell does have a great way for people that want to change their thermostat, to be able to find a match. I am thinking that the OP was walking around the Big Box and grabbed the first one.

When I stopped by the local Electrical warehouse this past week to pick up a new disco for my outdoor A/C unit, because of course you cannot just buy the guts, you have to buy the whole box. They had a whole three shelves of nothing but Honeywell Thermostats.


----------



## jeffmattero76 (Jan 4, 2016)

gregzoll said:


> What is wrong with the existing thermostat? There is a reason why Honeywell.com offers a "Find replacement" option on their website. If the current one is no longer working, you need the TB6575A1000/U from Honeywell to replace it. https://customer.honeywell.com/en-US/pages/Product.aspx?cat=HonECC Catalog&pid=TB6575A1000/U


Why does that link not work? When I click on it I get an error message?

Sent from my LG-D415 using Tapatalk


----------



## gregzoll (Dec 25, 2006)

jeffmattero76 said:


> Why does that link not work? When I click on it I get an error message?
> 
> Sent from my LG-D415 using Tapatalk


Probably because you are trying to access it from the Tapatalk app. Download Chrome if you do not already have it and set Tapatalk to use it, instead of the Tapatalk app for web browsing.


----------



## jeffmattero76 (Jan 4, 2016)

Thanks.

Sent from my LG-D415 using Tapatalk


----------



## jeffmattero76 (Jan 4, 2016)

While we are on thermostats... I have two gas hot air furnaces un my home and two Honeywell 7 day programmable thermostats that were installed by a local, well known hvac firm. When first installed by the owner, both t stats worked fine. The owner died and the son took over the business. The spn worked with the dad for a few years. In any case, after coming over to fo a checkup and repair, when i put the fan on ON rather than AUTO the blower does not turn on. I hadn't moticed it until months later since I only use that feature in the summer and the repair was done in October. Can you tell me which wire goes to which terminal on the board? At the t stat end everything seems to be wired correctly. The furnace is a Ruud.

Sent from my LG-D415 using Tapatalk


----------



## yuri (Nov 29, 2008)

G is the wire that turns on the fan and may be broken at the board if it got bumped during the checkup. Check the G terminal/wire.


----------



## jeffmattero76 (Jan 4, 2016)

Thanks

Sent from my LG-D415 using Tapatalk


----------



## yuri (Nov 29, 2008)

Yur Welcome:wink2:


----------



## jeffmattero76 (Jan 4, 2016)

Yuri to be clear the blower works as it should when in the AUTO position. However, when in the ON position it doesn't come on. Is that still the G wire?

Sent from my LG-D415 using Tapatalk


----------



## yuri (Nov 29, 2008)

Yes. The Y wire turns on the AC and fan at the same time and the heat does the same.


----------



## jeffmattero76 (Jan 4, 2016)

Great. Thanks again. I hope to get to this today.

Sent from my LG-D415 using Tapatalk


----------

