Nest thermostat, ruud air handler, rheem heat pump. Always blows cold air.

[THEREALGDG]

New system handler, pump, Nest learning tstat. 

Always blows cold air, switched O/B no change. Confirmed wires at air handler and mapped to tstat.

Have 24v at Red wire (tstat) and air handler/heat pump.

Heat pump: changed sensors and board, confirmed capacitor good. No change.

Any ideas?

[Todbone · Accepted solution]

There are a lot of things it could be. First, is the outdoor unit running in heat mode? If so, the big copper line connected to it should be getting hot. If it's cold, then the unit is running in A/C. Rheem & RUUD systems have their reversing valves energized in heat mode, which means you have to tell the thermostat to energize it on "B" not "O". 

[Todbone · Accepted solution]

There are a lot of things it could be. First, is the outdoor unit running in heat mode? If so, the big copper line connected to it should be getting hot. If it's cold, then the unit is running in A/C. Rheem & RUUD systems have their reversing valves energized in heat mode, which means you have to tell the thermostat to energize it on "B" not "O". 

[THEREALGDG]

Thanks for your response.

As I wrote originally, I have switched the settings, via the tstat settings, to B fom O and back with no change in the result. That is set TSTAT to Heat, AH blows cold air through vents. 

[CoolingWizard]

The Raheem Heat Pump needs the thermostat to send power on the O wire to energize the Reversing Valve to put the outdoor unit into Heating Mode.  Are you an DIY HVAC tech? You say this is a new system and you stated “changed sensors and board, and Capacitor Ok” 

If this system system is “New” as you stated, the HVAC company that installed it should have tested it.  If the nest thermostat is set up improperly, and you call for cool, it might heat, if you’re calling for heat then it’s cooling then your settings for the reversing valve might be backwards, however if you call for cooling and it cools and you call for heating and it cools, then all likelihood the reversing valve solenoid has gone bad. This would cause a valve not to operate and it would be stuck in cooling mode.  Has this heat pump system ever operated properly?

Can you take a picture of the Nest backplate with the wires connected and upload here please.

Ken, The AC Cooling Wizard

[THEREALGDG]

Maybe I'm a DIY HVAC tech, I'm not sure. But I did perform those tasks on the HP. The coil sensor swap because there's a known problem with the sensor on a new RP1424-that may have changed as the unit is now 6 months old. I bought a new board just in case. Yes, the O wire needs to be powered and unpowered for the reversing valve to switch positions. 

So the install was mostly done by a HVAC company but the TSTAT wasn't. Basically the company ceased to exist shortly after their install. I put a Honeywell TSTAT up and the cooling seemed to work fine. Now, it's Fall and need heat. 

After your post, I did two things: changed the filter and ran it in Cool mode. Now, in Cool mode it blows hot air when I set the tstat to cool at a temp lower than inside ambient. Now, that indicates that the Heat and Cool wires are switched as you suggested. Now, to figure out where? According to Rheem/Ruud specs and NEST the tstat is set up correctly, I'll post picture in an hour. The AH shows correct color connections from tstat to AH. 

You'll probably want to see the tstat connections but what do you think at this point?

Txs, Gary

[THEREALGDG]

I can't seem to upload image of wiring on NEST. Here's the connections: 

R=Rc

BL=OB

G=G

Y=Y1

W=W1

BRN=C

Ruud/Rheem uses BRN for common and BL for OB

A new finding: the LED1 is now flashing. A few days ago both LEDs were flashing.

Code description

LED 1 LED 2 Control Board Status
OFF OFF No Power
ON ON Coil Sensor Failure
OFF ON Ambient Sensor Failure
FLASH FLASH Normal
OFF FLASH Low Pressure Lockout (short test pins to reset)
FLASH OFF High Pressure Lockout (short test pins to reset)

Where are the test pins?

[CoolingWizard · Accepted solution]

Hello Therealgdg,

When the HVAC industry first created heat pumps, they designed them with reversing valve that would either default to heating or default cooling. The concept was in The south, they would default to cooling and in the north they would default to heating. In this approach if the reversing valve solenoid failed, in the northern region you would still have heat, and in the southern regions you would still have Cooling. However it wasn’t long before the industry just would either do it one way or the other without concept of where the ship those units. It was cheaper to make it and send it north and south. So some manufactures make O models in some manufacturers make B models.

you need to go into the setting of the Nest Thermostat settings and change the function of the O wire. You need to:

1. enter menu

2. Rotate ring to EQUIPMENT, Select? The nest should show you a picture of your black claim showing all the wires that are connected. You should see a wire on OB saying heat pump.

3. verify the back plane picture of equipment detected is correct then tap continue. You should see a screen that says your system, heat pump heating heat pump cooling and fan.

4. Select continue

5. you will now see equipment settings, rotate ring to heat pump and select

6. You will now be asked a question about does your heat pump use an O wire or a B wire.

7. select B, the less common one, and then select DONE.

Now, go back into EQUIP!ENT and perform a HEATING Test. Keep in mind that when your system switches from heating to cooling, the system must be off for approximately for 5 to 8 minutes before trying again. The system controller will lock out any changes from heat to cooling back to back. now if you are blowing cold air still, and when I say cold I mean cold as in refrigerated, then turn the system off, wait 10 minutes, turn the system on and switch to cooling mode and see if it puts out warm air or if it also puts out cold air.

if indeed you have a high-pressure lockout, what you can do to reset it is find the circuit breaker going to the outdoor unit, turn that circuit breaker off for five minutes, then turn that breaker back on and it will reset. we cannot do any of these tests until the system is in a normal status.

Ken, The AC Cooling Wizard

[THEREALGDG]

Yes, the high-pressure lockout condition was resolved by turning off AH and HP. Waiting 5 minutes and then turning back on.

Although I thought I had previously tested the recommendation made by Ken, The Air Cooling Wizard, following his steps exactly resulted in a successful heat test and subsequent heat pump operation. The only thing different was the new air filter.

So in summary Ken fixed it and thank you very much!

Maybe, though, it should be Ken, The Cooling and Heating Wizard. 

[Markjosephp]

Hi folks,

You've been a massive help, Ken. Hats off to you!

@THEREALGDG, I'm glad that you've got the answer you're looking for—give yourself a pat on the back for a job well done!

Since we've come to a solution, I'm going to lock this thread within 24 hours. If you have any other concerns or questions, please feel free to create a new post.

Best regards,

Mark