Nest e73 no power

[Terry_Z]

Hello everyone!

This topic my be beating to death already but I'm having issues with the Nest e73 code. Here's the story: 

I recently converted my house from oil to gas, all new boiler and hot water tank. Also, no cooling is connected and no common wire only two white and red wires. My system is an indirect system, my old oil system used indirect also but I rarely had issues with the nest during my oil years. So the way the new system works is that, if I'm my water drops below a certain temp the boiler kicks on but at the same time if I have my heat on the heat will turn off and the system will focus on heating the water back to temp. So I've noticed that when that happens the nest doesn't register the Rc wire and throws the e73 while the water heats up once the water finishes heating up the nest goes back to normal without turning it on and off. 

So my scenario is, when the water turns on to heat to temp but the boiler was in the middle of heating the house to temp which cause the nest to go to e73. But once the water is up to temp, the nest doesn't kick back to the set temp. Is there a way to keep power to the nest? I am far from being handy with electricity and don't want to blow my new system. Any advise?? 

Thank you

Terry 

[zoeuvre]

Hi Terry_Z, 

Oh no! I'm sorry to hear that your thermostat is giving you E73 code. The Nest thermostat is experiencing temporary power loss due to the operation of your new gas system, especially when water heating takes priority over heating. To prevent the E73 code, ensure the thermostat receives continuous power even when water heating takes precedence.

The most reliable solution is to have a C wire installed. The C wire provides a constant source of power to the thermostat. This might require running an additional wire from the HVAC system to the thermostat location. Consulting a professional HVAC technician would be advisable to assess the feasibility of adding a C wire in your specific setup. If running a new wire is not feasible, you can utilize a Nest Power Connector. The Nest Power Connector allows you to use the existing wiring as a power source for the thermostat. It essentially harnesses power from the heating system and provides it to the thermostat. Also, ensure that the wiring connections at both the thermostat and the HVAC system are secure and properly seated. Loose or faulty wiring connections can cause intermittent power issues. If you are uncertain about the wiring or any electrical aspects, it is recommended to consult a professional technician.

It's important to note that working with electrical components can be potentially hazardous if you're not experienced. If you're uncomfortable or unsure about the wiring and electrical aspects, it's best to seek assistance from a qualified HVAC technician who can assess your system and provide appropriate guidance and solutions.

Let us know if you have any other questions.

Best,

Zoe