11-03-2022 06:25 PM
Hi folks,
Hoping you can help me- I tried for multiple hours yesterday to get my 3rd Gen learning thermostat to work, but I keep getting the E74 no power to RH issue.
my old thermostat works fine - I have switched back to it - and it’s heating as expected. (I have an American standard gas furnace, An outdoor Lennox AC unit, and there’s a jumper cable between R and RC on the old thermostat)
any ideas?
11-03-2022 07:52 PM
SantiJS, try this first, on the nest backplate, put the red wire in Rc. Afterwards, check the EQUIPMENT status. To do this, open MENU, rotate dial to EQUIPMENT and select. You will see a Nest backplate and the wire the nest has detected. If the wedge is green, it is OK. If it is Yellow, it is not recognized or tested yet. So, here is a little explanation of the HVAC control system.
Rc and Rh or R, is the Power IN from the step down transformer. Why is there separate Heating and Cooling power IN? Sometime the heating system is a separate system. Most standard thermostat are setup with the primary input for power on the cooling side with a jumper wire to the heating Rh. The Thermostat takes that incoming power and send out the control wires for the heating, cooling and fan. The Power COMMON is the C terminal. The Heating call is sent on the W or W1 terminal. And Cooling call is sent on the Y or Y1 terminal. The Blower Fan is sent on the G terminal.
Ken, The AC Cooling Wizard
11-07-2022 11:22 AM
Hey folks,
We appreciate your help here, @CoolingWizard.
@SantiJS, I wanted to follow up and see if you are still in need of any help. Please let me know if you are still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.
Thanks,
Mel
11-10-2022 02:22 PM
Hi folks,
I wanted to follow up and see if you are still in need of any help. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further.
Thanks,
Edward
11-14-2022 02:12 PM
Hi SantiJS,
I'm just checking in to make sure that you've seen our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.
Thanks,
Edward