Nest Thermostat Heat Function Not Working

[Dev4]

I have a Nest 3rd gen. learning thermostat that has been connected to a Bard W24H2-A00 heat pump. I have maybe only used the heater one time since 2019 and I think the heat worked correctly. Anyhow, today I tried it turn on the heat and instead of heat, I get cold air (like its cooling).

According to the instructions on my Bard HVAC unit "“B” terminal is the reversing valve input. The reversing valve must be energized for heating mode."

My instructions also state that for Heat Pump Heating: Energize Y, G, B

Below are pic of the wiring on my Nest unit as well as the low voltage board of the Bard HVAC unit. I believe everything to be connected correctly. I have also tried changing the heat mode to both O and B with no luck - both result in cold air (like it's cooling).

So it appears that either my reversing valve is not functioning or the Nest thermostat is not functioning correctly.

Any HVAC / Nest folks have any other suggestions?

*Tried both O and B heat pump modes with no luck

*Tried factor reset with no luck

[Patrick_Caezza]

@Dev4 

Have you tried this yet?

If your system starts to blow cool air when your Nest thermostat is in Heat mode (or if it blows warm air when its in Cool mode), change the settings for orientation of your heat pump.

Nest Learning Thermostat and Thermostat E

1.  On your thermostat, go to Settings.
2. Select Equipment.
3. Select Continue > Continue.
4. Select Heat Pump.
5. The Nest Thermostat defaults to an O setting for heat
   pumps. 
   • If the O option is highlighted, select B.
   • If the B option is highlighted, select O.
6. Test your heating and cooling again to make sure the issue is resolved.

[Dev4]

@Patrick_Caezza

Yes, I have tried that with no luck sadly.

*Tried both O and B heat pump modes with no luck

*Tried factor reset with no luck

[Patrick_Caezza]

@Dev4 

Who is the manufacturer, and what is the model number?

[Dev4]

@Patrick_Caezza

See original post for more details -

MFG: Bard

Model: W24H2-A00 heat pump

According to the instructions on my Bard HVAC unit "“B” terminal is the reversing valve input. The reversing valve must be energized for heating mode."

My instructions also state that for Heat Pump Heating: Energize Y, G, B

[CoolingWizard]

I pulled out my service manual, blew off the dust and found this about the Bard W24H2 wall mounted packaged heat pump. I hope it helps.  Strange that my manual describes and defrost control board, and you picture is a simple terminal strip.  The service manual states the reversing valve of that unit is on W1 of the defrost control board. I would look for the DFC and see how this terminal strip is wired to the DFC. Look for a W1 or RV on the DFC and where it is cross connected on the terminal board.

The AC Cooling Wizard

[Dev4 · Accepted solution]

The issue was that the harness to the reversing valve was unplugged!

[CoolingWizard]

Oh my goodness. Was this used unit you purchased recently?

AC Cooling Wizard 

[Dev4]

No, it was a brand new unit which was installed in 2019.

[Jake]

Hey Dev4,

Thanks for the help CoolingWizard, and Patrick_Caezza.

I am glad to hear you were able to resolve the issue, and everything is good to go from here. With that being the case, I am going to go ahead and lock the thread in 24 hours. Let me know if you have any further questions, as I would be happy to reivew.

Best regards,

Jake