E195 When Other Zones Call for Heat

[Wakunga]

I recently installed a Nest Thermostat E for one of my zones for a multi-zoned boiler system. I also installed a Nest Power Connector since I do not have a 'C' wire. The other zones just have traditional thermostats. The Nest works fine until one of the other zones calls for heat. Then I get a 'E195: No power to R wire' error. Once the other zones shut off, the zone with the Nest Thermostat E works fine again. My zone board is made by Argo. Any feedback is appreciated.

[zoeuvre]

Hi Wakunga, 

Thanks for reaching out, and I'm sorry to hear that your thermostat is showing an E195 error code. “No power to R wire” or the E195 error code on your Nest Thermostat E means there is an issue with the power supply going to the R wire. Perhaps in your multi-zoned boiler system, when another zone called for heat, it broke up the electricity supply to the R wire and became an error. A few questions: When was the thermostat installed? Who installed the thermostat? Did the issue happen during the installation or after the installation? And do you use a single-wire or double-wire transformer? Also, follow these:

1. Go to the breaker box and check if the breakers flipped.
   • If yes, ask the customer to reset the breakers.
2. Check your system’s drip pan or drain tubes.
3. Check the condition of the HVAC fuse.
4. Check if you have an energy savings box.
   • Search for an energy savings box near the electric meter (possibly near their air conditioner).
   • Search for a small box with 2 lights on it (one light is red, the other is usually green). This box allows the utility company to cycle the customer’s air conditioner off and on during certain peak times of the day.
5. Check your air filter.
6. Gather the power readouts from the thermostat.
   • Go to Settings > Technical Info > Power.
     • Battery
     • VOC
     • VIN
     • lIN
7. Make sure the thermostat wires are properly stripped and seated in the thermostat base.

Keep us posted. We're happy to help.

Best,

Zoe 

[Wakunga]

Hi Zoe, 

I believe the problem may be related to a 'priority switch' associated with one of the other zones on the boiler. For me, it is the zone that handles the hot water tank. I think that when the ‘E195’ occurs it is because the hot water zone value is open and taking priority over all other zones. Once that zone closes then the ‘E195’ goes away. It has probably always been that way but now with the Google Nest, I notice that challenge by getting the ‘E195’ error. I'm not sure if there is a fix or it is just something I need to live with.

Here are the answers to your questions (in bold):

When was the thermostat installed? [11/11/23]

Who installed the thermostat? [Me]

Did the issue happen during the installation or after the installation? [After, I noticed it when the hot water zone is calling for heat]

And do you use a single-wire or double-wire transformer? [Not sure I understand, I am using a Google Power Connector, so I am using a single wire coming off the COM connector]

Also, follow these:

1. Go to the breaker box and check if the breakers flipped. [No Breaker Issues]
• If yes, ask the customer to reset the breakers.
2. Check your system’s drip pan or drain tubes. [No Issues]
3. Check the condition of the HVAC fuse. [No Issues]
4. Check if you have an energy savings box. [No Energy Savings Box]
• Search for an energy savings box near the electric meter (possibly near their air conditioner).
• Search for a small box with 2 lights on it (one light is red, the other is usually green). This box allows the utility company to cycle the customer’s air conditioner off and on during certain peak times of the day.
5. Check your air filter. [This is a closed loop boiler system, no air filter]
6. Gather the power readouts from the thermostat.
• Go to Settings > Technical Info > Power.
• Battery - 3.851 V
• VOC – 33.98V
• VIN – 32.39V
• lIN – 20 mA (i)

Thanks for your feedback

[zoeuvre]

Hi there, 

Gotcha. Is your previous thermostat still available? If yes, could you try to reinstall it? This will help us determine if the issue is with the thermostat or the HVAC system.

1. Turn off the power to the HVAC system at the breaker box again.
2. Take a photo of the wires so they can remember the terminals to use.
3. Install each wire to its correct terminal.
4. Turn the power back on.
   • If the reinstallation of the previous thermostat fixes the issue and the system comes back on, process a replacement thermostat base for the Nest Thermostat.

Let us know how it goes.

Best,

Zoe