Nest no power to rh wire

Nest no power to rh wire. E74 error shows up when there is no power to the RH wire Nest. The loose connection of the RH wire can cause this.

The drain pan can be clogged, causing no power. The float switch can trip and be responsible for the power loss in the RH wire.

I was setting my Nest thermostat to match my home, but then an E47 error appeared on the thermostat.

I checked what E47 in the Nest thermostat could mean, but before that, the problem was stated on the thermostat, so I didn’t need to check the meaning.

The thermostat displayed that there wasn’t any power to the RH wire. I checked the RH wire for issues and googled a bit about RH wire power issues.

The RH issues causing power loss were various in number. I checked for issues and cleared the RH wire power issue.

Nest no power to rh wire

Having a Nest thermostat assist you in all seasons is pretty great. The Nest thermostat works with advanced temperature and controls the house.

The RH wire is red in color, and it is for power transporting. Having Nest thermostat issues is bad. Transformer 24×7 is responsible for pricing the RH wire power. The RH wire having no power is common.

The RH wire itself can get loose. The clogging of the drain pipe can lead to no power in the RH wire as well. The condensate pump can also be clogged.

The condensate pump is present with the HVAC. Cleaning the condensate pump and other clogged points can help.

Power supply

power supply

Before viewing the RH wire, the power supply checking is a great idea. Start by checking if the power to the RH is coming from the system or not. Start by checking the switch that gives power to the system.

The switch should be in the power board or the fuse box. Check the switch. Make sure the switch inside the fuse box or the circuit box is on.

If not, turn the switch on manually. There might be two switches rather than one.

One switch in the box will be for heating, and the other, you can guess, is for cooling. Turn both switches on if the power is to be checked. If the switches are on, check the fuse and the breakers.

The fuse from the box may be missing or is a melted one that can’t give power to the RH wire. The breaker won’t be melted like the fuse, but the breaker can be tripped too.

Check if the breakers and the fuse have their functionality. If they don’t replace them both. Having a missing fuse can be a drag.


r wire

Actually, the R wire should be checked before the power to the R wire is checked. Looking at the R wire isn’t difficult. You should test the R wire later after checking its physical condition.

The physical condition includes the damages that the wire has encountered because of rough use or long-term use. Check for frayed in the wire and see other physical damages like scratches or cover damage.

Twists in the R wire can be a pain too. If you find physical damage to the R wire, then the wire won’t work without reaping.

You can cover the parts that have cover loss with electrical tape, but the R wire broken from inside cannot be repaired.

Replace the R wire if you have a resource to buy it. Twists in the wire can be removed by starting it. After straining, place the R wire back in its position.

Drain pipes

drain pipes

If the R-wire is okay and the power from breakers is fine, then check the drain pipes.

I know the drain pipes may look like they have nothing to do with power, but the drainpipes of the Nest thermostat have more to do with power than you think.

I connect power and drain pipes in the Nest thermostat with each other, and the drain pipes directly affect it.

The drainpipes should be open, and the draining should be smooth for the RH wire to get the power. Check the draining of the drain pipes and see if the draining is slow or if the draining isn’t being done.

If the draining is slow, the RH wire may still have power, but if there is no draining in the drainpipes, then clogging is causing the drainpipes to not let the draining continue, and the clearing of the drainpipes is required.

Condensate pump

The drain lines are connected to the condensate pump. The pump is also very important for power. If the pump is pushing, the drain line stops working, and if the pumps stop pushing, the drain lines won’t work.

Without the drain lines, the power in the RH wire will also stop working. This means that the pump to the drain lines is a crucial working thing, and the power won’t be useful without the pump.

If the pump of the thermostat is not working, then the power will be a disaster, and the RH wire doesn’t get to have any flow. To make the RH receive the power, it should the pump of the thermostat should be fixed.

The condensate pump is present near the HVAC system. The condensate pump may be irreparable. So replace the whole pump and connect the new pump to the drain line.

Float switch

float switch

There is a  float switch present in the device. The float switch is for safety. The float switch is useful in preventing damage to the thermostat. Condensation begins to gather when the thermostat is made to work.

A particular level of the contestation is assigned to the thermostats, and the thermostat works safely on this condensation level. The set limit of condensation is given by the manufacturer for the thermostat’s safety.

The condensation level rising above the set condensation level is not a great thing. Defects in the thermostat will start appearing if the condensation limit is breached.

The condensate overflow trips the float switch, and the thermostat with a tripped float switch powers off. The air conditioner won’t work either.

The humidification process becomes discontinued. This can get annoying as the temperature won’t remain the same. Removing the clogs will also get the float switch to work.



Sometimes the charge to the thermostat is fine, but the thermostat doesn’t work because the thermostat hasn’t been working for more than 12 hours.

The thermostat may need to be charged manually to receive the power back as the thermostat may be completely out of power.

Manual charging requires the use of a USB cable. A USB-enabled device is needed so the thermostat can be plugged into it.

A charging station or a desktop computer is enough to have the thermostat manually. You can use a USB adapter as well. Manually charge the thermostat until it is charged.


Nest thermostat can have many issues as the Nest thermostat handles a lot of things. The power and the charging method for the manual trick are mentioned above.

The condensation issues and the drain line of the thermostat or the air conditioner have been discussed as well.

Nest thermostat problems with its RH wire are pretty common. The RH wire without power won’t supply. Replacing the RH can be useful. Thanks for reading!

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