google learning thermostat not blowing hot air

[Cwang110]

Hi

I recently installed a google learning thermostat and it is not blowing hot air on heat setting. I cannot really tell if it is blowing cold air because it is 17 Celcius degrees inside but I am sure the fan is able to be turned on.

Below are my wiring:

Old PECO thermostat wiring: (wish I had a Honeywell, so many tutorials online)

New with google thermostat:

Here is a picture of my heating system:

 

Things I have tried so far and none of it fixed my heating issue:

1. connect RH to RC

2. connect only Y1 or W1 and turned on, still blowing cold

3. put back my old thermostat, it wasn't not blowing hot air, too. It could be that I didn't set it up properly because I didn't screw it back on the wall and wiring are all loose.

4. tried to set the thermostat, turn on both heat and fan, still no hot airing blowing

5. talked to a HVAC guy online, and tried to bypass some wiring for a manual operation, connected RH and Y1, for a short period time, it was blowing air but I can't feel what air it was

Things I could still try:

1. find a wire to bypass RC and RH (but I know it is not recommended to bypass wiring for nest)

2. open up my HVAC and see if there is a fuse that has been burned, and if so, get a new one.

To be honest, I am someone with zero hands-down experience on working any home project and this is overwhelming to me. I have tried and researched for many troubleshooting videos/threads and if it is not going anywhere, I might just need to seek help from a professional. (Also been very hard to contact a professional with smart home installation experience)

Any advice is helpful. Thanks.

 

[CoolingWizard]

First of all, I need to give you some education on a thermostat and its terminals and what they actually control.

your old thermostat appears to be wired as a conventional HVAC system. That is to say you have a compressor outside that is for the air conditioning, you have some forced air delivery system and you probably have a gas furnace as your heat source.

residential thermostat, terminals, and their functions:

R, Rh, Rc - Power IN. The HVAC control system operates on 24V AC. There is a step-down thermostat that converts 240VAC or 120VAC to the needed 24VAC.
Y, Y1, and Y2. This is control of the outdoor compressor.

W, W1, W2 this controls the heating system.
G this controls the blower fan. Typically set to AUTO, or ON.

C this is the 24VAC Power Common

O/B This is the Heat Pump reversing valve control; switches modes from Heat to Cool or Cool to Heat.

Your system uses R, G, Y, W and C.

Red Wire to Rc

White wire to Y1; Cooling

Orange Wire to W1: Heating

Black Wire To C: Power Common

When the thermostat decides it needs to call for heat, it connects the R to W. That means it sends the incoming 24VAC to the furnace control board. This will initiate the heating cycle. it makes no sense that the HVAC person you called told you to connect the R to the Y. To test the heating system, R needs to connect to W. Now let’s talk about the heating cycle.
The heating cycle starts with an induction fan that turns on to remove any gas that might be left in the heat exchanger. This induction fan creates a negative pressure in the burner box, which is sensed by a pressure switch when the pressure switch closes, it sends a signal to the control board to start the ignition process. This will cause a igniter to heat up. When the control board senses the igniter is hot, it turns on the gas valve and the flame sensor will signals the flame is burning. If the control board does not get a signal from the flame sensor, it will shut everything down and goes into a soft lockout. After a few minutes, the system restarts the heating cycle again. If we don’t get a flame ratified within three attempts, the furnace will do a hard lockout which will require service technician to come and reset it. The temperature has to rise to about 200° before it will signal the blower to turn on.

You seem to have a Nest Learning Thermostat is that correct?

Ken, The AC Cooling Wizard

[Cwang110]

Hi Ken,

Thank you for the detailed explanation. I have a better understanding of what each wire does now.

I do have a nest learning thermostat, and here is the link of where I purchased it: https://www.bestbuy.ca/en-ca/product/google-nest-wi-fi-smart-learning-thermostat-3rd-generation-whit...

If my wiring is correct, what are some next steps I can try to run my heat? or it is a sensor issue?

Thanks,

[CoolingWizard]

I would recommend a test of R wire (Red) and W wire (Orange) Now technically, you’re always encourage to turn the power off before you do this, but it can be done a little bit simple. Remove your face plate of your nest thermostat and then gently push in the connector and pull the red wire out and pull the white wire out of a W. Then what I use is what I have is a couple of alligator clips and I clip one to the red and one to the white and it makes the connection and turns on the heating system. I do this, technically in the furnace when I’m testing furnaces to see how they’re working. You can temporary connect the two wires together. Power will flow from the R wire to the W wire and as long as you’re not touching anything else you won’t be shocked by the 24V AC power. You might need a something to hold the two wires together and then wait to see if your heating system starts up and you get warm air coming out. Now, if you do not get any warm air coming out, this will signal a problem with your furnace itself and will require an HVAC technician to visit and determine the cause of the heating system failure.

Ken, The AC Cooling Wizard

[Cwang110]

Hi Ken,

Thank you for your advice.

So I tried to connect the power wire and the heating wire, and there was no wind blowing. I can hear there is a clicking sound from my furnace trying to kick start but no air is blowing. Also, checked my furnace and there is no error message. I got myself a few alligator clips so I believe the wires are well-connected.

I connect my power wire and fan wire, there would be cold air blowing out. So would you recommend that I connect my power, fan, and heat wire together and see if I can jump-start it?

Thanks,

[CoolingWizard]

Well, this sounds like there is a problem with your furnace. When you connect R to W, this signals the furnace control board to initiate the heating cycle. You should not have to turn on the blower. When you say you hear your furnace clicking, do you ever hear the burners lighting? Remember, the burners need to light and the heat exchanger box to rise in temperature before the blower fan turns on. When you set the thermostat to heat and set it to a warmer temperature, a couple degrees, at the furnace the first thing you were here will be what sounds like a motor running. It’s a small induction fan that like I said, it creates a negative air pressure inside the firebox exhausting any leftover unburnt gas that might be present. This runs for probably a good 30 to 50 seconds before the control board receives a signal that there’s negative pressure inside the firebox. At that point, you will hear a click when the control board initiates the igniter. there are a couple types of igniters. some are called hot surface igniter‘s HSI, some are spark, igniter‘s. You might hear the gas flowing but you won’t hear a click or anything like that when the gas is turned on. Once the control board since it’s the HSI is it the correct temperature it will turn on the gas and you will hear the you were here the “whoof” of the gas when it lights. Once the gas is Vernon, it takes about 30 to 40 seconds before the blower fan will turn on. On your furnace, that little green light, you see near the top left, it will blink a code if the system doesn’t achieve one of the steps of the ignition cycle. Again, you only need to connect R to W for this all to work. If it does not work, there is a problem in your furnace without a doubt.

Ken, The AC Cooling Wizard

[Cwang110]

Hi Ken,

Thank you for your advice but my furnace was working fine before switching to the google thermostat. Not sure switching the thermostat would cause any issues with my furnace.

I was suspecting a wiring issue or a nest setting issue. An appointment has been scheduled with a technician to come and have a look. I think my worst option would be to abandon my google thermostat and go back to my old thermostat.

Thank you for your help anyways. I have learned a few new things. HVAC is a fascinating system 🙂

[Jhonleanmel]

Hey folks, 

We appreciate your help here, @CoolingWizard.
@Cwang110, I wanted to follow up and see if you are still in need of any help. How was the appointment with the technician?

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

[Jhonleanmel]

Hey there,

Checking back in should you still have some questions here. Let us know by replying to this thread. 

Best, 
Mel

[Cwang110]

Hi Mel, 

Thanks for checking in. 

Unfortunately, it's not going well. I scheduled with Bestbuy Geeksquad for installation and they never showed up. Right now, I am planning to reinstall my old thermostat and hope it will work. Will return google thermostat as it was not a pleasant experience to deal with. I deeply regretted switching to google thermostat and will not recommend it to my friends. 

[Jhonleanmel]

Hi Cwang110,

We deeply appreciate you sharing your thoughts and experiences, and we'll take it as feedback. We hope we can change your mind in the future. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Best,

Mel