I tried installing Nest 3rd Gen Thermostat for heating-only (Triangle Tube Hot Water Gas Boiler), but I am getting an error that 'no power to Rh wire detected (e74). I have only two wires in the old thermostat and I connected them to Rh and W1. Tech Info on the thermostat shows Voc as 23.08 V, Vin as 5.95 V and lin as 20mA. I know, all equipments are properly connected to the power, but it seems voltage is too low for Nest to detect.
Does Voc need to be above 24 V? How can I make Nest work for controlling the heating in my house?
The triangle tube does not have a C terminal so only way is to get a wall plug in 24v AC transformer and then connect it to RC and C on the nest.
Do you have any extra wires in the cable going to the nest?
If you do then you can put the transformer near the boiler and connect it to the 2 extra wires going to the nest and put them in Rc and C.
I wanted to stop by and see how I could help.
Thanks for assisting, @Houptee.
@rtyagi99, Your system may not provide enough or any power to the thermostat or a specific wire (causing the thermostat to fail to complete a circuit and display the report). I also found an article with some troubleshooting steps for when your thermostat shows any help codes. Let us know if you need more help.