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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8527
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Honeywell Wifi RTH 8580 WF temperature keeps increasing

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Just installed a honeywell wifi rth 8580 wf. It went smoothly connected to the internet and started running immediately. I noticed all day the indoor temperature was increasing. It was set on 75 for the last 5 hours but its 82 degrees in the house.. The setting is on auto and has been running constantly

Hello, welcome to JustAnswer. !!

There is a very good chance that the thermostat is working perfectly but that the air conditioning system itself is not. We can check that out.

First tell me how the system cooled the house before you fit then new thermostat.

Next, tell me if the outside unit runs all of the time, or is cycling on and off.

Next tell me if the fattest copper tube attached to the outside unit is running cool when the outside unit is running or not.

We can go from there.

Customer: replied 4 years ago.
Had a tune up yesterday and discussed with the technician my concerns. Thought the thermostat was cheap and not reading properly. So earlier today the fan wuld run but was not cooling. Now after double checking the wiring the fan would not turn on. While I was typing this about 10 mins after flipping the switch the fan started running. Now just waiting to see if it will start cooling
Hello again, if the fan starts running, it would be good if you could go outside and see if the unit outside is running, that part is what makes the cooling work.

If its not running, then its a problem with the controls.

Tell me if you put the new wifi thermostat on or if the HVAC service people put it on.

We can go from there.
Customer: replied 4 years ago.
I installed it. The outside unit is not running.
Thanks, tell me if this is the thermostat you have please,

And tell me which color or wires you had coming out of the wall and which terminals you connected each wire to.

We can go from there
Customer: replied 4 years ago.
that is the correct model. So i have a green that i then followed the instructions for if you don't have a C wire. I plugged the green into the C. Then the yellow to Y, white to W, there is a jumper between R and RC with the red wire going into RC. This is all done on the wall thermostat. I then went downstairs to the unit and mone the green wire that was located in G to C. It originally had a jumper wire from the C to Y so now that I was putting the green wire in the C spot. I then moved the jumper wire to connect the G and Y. Along with the Yellow to the Y and the white in the W. Red to the red.
My old thermostat had the green going to G. Red to RC. White to W and Yellow to Y
Hello again, you need to wire it as shown on the diagram green to green, and run a new separate wire for C. C goes to the opposite side of the 24v transformer from R inside the furnace

Look closely at the wire bundle thats pulled, it may have an extra wire that is not being used.

G is needed to run the fan, C and R are needed to power the thermostat.

If you do not have a fifth wire in the wire bundle, we can discuss other options

that would involve a jumper between Y and G at the furnace thermostat terminal strip and connecting G to C and and running G to the opposite side of the 24v transformer that R originates from

If you wire it that way then you will get a voltage read of 24v between R and C at the thermostat

Let me know if that makes sense, we can go from there.
Customer: replied 4 years ago.
We don't have a 5h wire that is accessible. Can we go with the 2nd option

Yes, we can go to the second option

Let me know how it goes

If C contacts R directly at any point it will blow the transformer fuse. if there is no fuse it will burn out the transformer. be careful about that C must only go directly to the other 24v terminal from red, so that 24v reads between them,

Be careful about that


Customer: replied 4 years ago.
Ok I put everything back to how it was with the old thermostat.
Ok back to the 1 st option because i didn't think the wire was long enough but might be able to make it work.
So if i connct the 5th wire to the C downstairs at the furnance terminal then there is currently a wire there that is running outside of the bundle to a separate red and white wire. I believe this is the wire that should not come into contact with the red that is in the R slot. I won''t need to touch it since its already connected. Then at the thermostat connect the 5th wire to the C and move the green to the G
Thats not it

look my previous instructions over again, and take no short cuts.

Turn the power off to the furnace

Connect green to C at the thermostat

then find green where it attach's inside the furnace, and remove it from the terminal.... attach a new piece of wire using a wire nut and run it to the transformer... but not where the red is attached, the terminal next to it. so that you get a 24v read between the two when you turn the power back on

then put a jumper between Y and G at the furnace terminal strip

we cannot do it some other way because of a shortage of wire. we do not have that luxury

if you do it some other way you can damage the transformer or the control card, or the new thermostat

Customer: replied 4 years ago.
I give up tonight. I am putting the new one on and going to bed. AND calling a professional tomorrow. Thank you for all your patience and assistance.

Good idea, this can be tricky business

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