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Heat pump/oil burner combo

John Kogel

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I could use a bit of enlightenment here. Not a lot, just a bit. [:)]

The house has been vacant for a few months, and the listing realtor has turned off the furnace because the tank is empty. The purchase of 5 gallons of oil would be a burden? Also, the new heat pump is not working, needs service, per the realtor. I had my hands full with the rest of the place anyway, so was happy to defer the heat system to an expert. So this question is to further my education, hopefully.

The oil furnace is nearly 50 years old. A 2 year young Heat pump has been added, with the indoor portion perched above the oil burner. They are using the old blower fan to push air through both units, I believe. There is one programmable thermostat upstairs. There is a Heathkit control unit and a Westinghouse control unit all daisy-chained to the old furnace controls and the heat pump.

Does this look like a Mickey Mouse mish-mash of products, or is it a typical way to control a heat pump and a backup furnace?

I am thinking maybe the controls have been tampered with, or gone faulty, knocking out the heat pump. It is a nearly new Carrier unit, and it shouldn't have just quit on its own. Maybe with the heat pump off, the poor old oil furnace was ordered up, so it burned up the last of the oil.

Or vice versa, could running out of oil for the backup heat cause the heat pump to shut down? What is most likely to cause this system to quit?

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In all the inspections I've done I've only seen one setup that had a heat pump with an oil furnace for backup.

It was all controlled by one thermostat, the same type that would usually control a heat pump/ electric furnace setup.

I went through the usual testing procedures that you would do for a heat pump / electric furnace combo. The system operated the same way (except for oil furnace instead of elec furnace). The oil furnace kicked in when make up heat was demanded. The oil furnace also operated exclusively when the thermostat was set to emergency heat.

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If you go to the thermostat and manually activate the fan and the fan operates, then the issue could be what they call the dual fuel board or the fossil fuel board. If this circuit board goes out, then the system has no way of knowing to tell the heat pump or the auxiliary heat system to activate. If you manually attempt to activate the fan and it does not operate you have an issue with voltage getting to the system. If the thermostat does not have an emergency heat option, there is a real strong probability that the thermostat was not designed for a heat pump and hence will not activate a heat pump.

Down here we don't see oil furnaces, but we do see gas furnaces and electric furnaces as auxiliary heat sources with heat pumps and they operate and are checked as John mentioned.

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Thanks. I wish I'd had an extra 15 minutes to apply power to the thermostat and the blower. My clients would have liked to know if the $10,000 heat pump is going to work for them. I had hoped to check it out at least a bit, but there were multiple issues with the rest of the place, and the sellers realtor had sent this message, problems with both units.

If someone called for auxiliary heat and the oil furnace refused to light, would the thermostat switch over to the heat pump or would the system lock up until reset?

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