Heat Pump shuts off completely when calling for auxiliary heat? Help!


Old 12-08-16, 08:05 PM
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Heat Pump shuts off completely when calling for auxiliary heat? Help!


I installed an Aprilaire 8466 heat pump t-stat during the summer and apparently I have something, in regards to heat or auxiliary heat, hooked up wrong. Your quick help would be appreciated as the unit is stuck in aux. heat mode and not functioning.

This is how I have it wired.

Red wire= RC and R via jumper
Yellow wire= Y
Green wire= G

I'm confident all of these are correct.....

Brown wire= C (common).

I'm fairly confident this is correct because if I remove the batteries there is still power to the t-stat.

I just don't know about the following.

White wire= W. This is supposed to be Heat.

Blue wire= O/B. This should be reversing valve

The heat pump has been functioning properly until tonight as temp are really dropping and it wants supplemental heat. However when it calls for auxiliary heat the unit shuts down completely, nothing. I moved the white wire to the t-stat W2 terminal, which is supposed to be auxiliary heat, but nothing happened.

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Old 12-09-16, 10:01 AM
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Do you have a gas or electric furnace? If it's gas then the heat pump will shut down when the burners are on.
Did you set the switch on the back of the stat to HP?

Last edited by skaggsje; 12-09-16 at 10:10 AM. Reason: added
Old 12-09-16, 10:47 AM
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What brand is the heat pump condensor ?
Old 12-10-16, 05:24 AM
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Hello All,

I appreciate the input. Let me give some requested details and an update.

1) It is a Tappan FT5BD-042K (3.5 ton) all electric heat pump outdoor condenser and indoor air handler, with 10kw heat strip. I didn't open up the unit to confirm the heat strip but the unit is marked as having it installed and there is paperwork on the unit for it.

2) Yes, I have the t-stat set as being a Heat Pump. My Aprilaire manual didn't have the programing listed in it though, so I couldn't check additional settings the other night. I installed one at our other house (for sale) and was able to change some of the programing.

a) I changed the fan control mode (02) to electric, whereas the t-stat controls the fan. It was set to gas/oil in which case the equipment controlled the fan.

The unit seems to be running proper now with the exception the heat strip never comes on. It doesn't come on in normal mode in an assisting role nor does it come on in auxiliary heat mode, whereas it is solely responsible for heating. The blower will run but it is just recirculating the air. No heat.

b) I changed the t-stat reversing valve setting to "energized in heating". I do have a wire connected to the O/B terminal, btw. However, the unit goes into cooling mode with such. So I set it back to default "energized in cooling".

I'm assuming I should have a wire connected to the W2 terminal which is auxiliary heat but I don't know which wire to move???

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