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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.
 

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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.
 

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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.
 

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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.
 

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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.

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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?

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