Nest for garage thermostat

[Shiltsy]

Good morning from tropical Minnesota, where we are expecting highs in the 40s today!

I recently installed a Next thermostat in my garage to control 45k BTU Reznor. I liked the cool factor, but also the ability to control heat remotely, schedule, etc...

From what I can tell, unless I put the Nest in "Away" mode I can't schedule it automatically for temps below 50 degrees. What I'd like to do is drop to about 40 overnight and then heat up to 55 before we leave for work in the morning.

Any ideas would be appreciated!

 

[Denwood]

Does nest have a temperature adjustment? The Ecobee3 stats we use drop to 44F, but you have 10F of adjustment, so you can bias the temp to 34F if you want. If Nest has a similar adjustment, that might be the easiest path.

 

[Shiltsy]

Cool, I have will have to check that out.

As it turn out, I have bigger issues! There is no Common "C" wire in my two wire setup to the Reznor UDAP 45, so the furnace was cycling all night but won't run properly with Nest.

Basically, I need to run another wire to provide 24V to the Nest C terminal. Just not sure where to steal that 24v off the furnace.

 

[Denwood]

You may need to add a 24volt power source using a plugin "wall wart" or transformer. Any Hvac shop will have 24volt transformers to provide the constant power you need. Nest tries to power-steal which as you observed may wreak havoc with your HVAC. A proper 24V power supply is the way to do it. If you have the option of swapping out for an Exobee3..I'd suggest it. It does require a C wire though.

 

[Bighead38]

Cool, I have will have to check that out.

As it turn out, I have bigger issues! There is no Common "C" wire in my two wire setup to the Reznor UDAP 45, so the furnace was cycling all night but won't run properly with Nest.

Basically, I need to run another wire to provide 24V to the Nest C terminal. Just not sure where to steal that 24v off the furnace.

Have this problem with Honeywell at home. Let me know what you do.

 

[Denwood]

This is pretty much what you need to do if there is no 24VAC source at the heater.

Having a quick look at this: http://www.reznorhvac.com/files/I-UDA & APD Series (12-14) smallest.pdf

It looks like the Reznor has a C terminal, but not brought out to the rear terminal strip. So you can check and see if you have 24VAC between C and R on the circuit panel inside. If so, run your C wire from there. The stats use very little power so should not be an issue at all for the Reznor.

 

[Shiltsy]

Kenwood - thanks so much! The G terminal on the back of the heater seemed to have constant 24v (tested with voltmeter) but when I ran that to C on the Nest, the furnace just constantly cycled on/off.

The good news is that I just had the furnace installed last week, so I'm going to have the guys come out and run the 24v from inside the furnace out to that terminal strip. Should solve my problem.

For now, I moved the Nest inside to use for the house... what a cool/novel little device!

 

[majerus]

This might work for you, Go to settings on the nest, then "away" press on the nest set the low to 40 for away, and the high to whatever you want it to be. Then on the schedule menu set the temp to "50" for say 6am m-f or whatever you want. Then validate its kicking into away as needed. Good luck