Heat pump timer?

**Bill Anglin** · 01-10-2012, 08:46 PM

Did an inspection on a Armstrong heat pump. The home also has a pellet stove that the seller uses as primary source of heat so the heat pump was turned off at the thermostat. I turned the heat on and after several minutes of no response from the unit, I wrote in the report that the unit did not respond to normal operating controls at the thermostat and I recommend further evaluation and repair as necessary. The HVAC specialist found that the unit and the thermostat has a timer. He said the timers were set too high and the unit would not have started for approx 8 minutes. I have no idea what he is talking about and cant think of why a timer would be needed. Anyone with knowledge on this subject please enlighten me. I have inspected several heat pumps but they all seam to turn on as soon as I call for heat.

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**Bruce King** · 01-10-2012, 10:10 PM

Never heard of that type timer. Sounds like a special install to suit a homeowner/engineer type.

Some systems wait several minutes when switching manually from cool to heat or vice versa. Some variable speed A/H's also have selections for small delays (30 sec to 90 sec) before turning on or off the indoor fan.

I had one that would not turn on once and the agent called the owners who had already moved out. They said it had a timer but were wrong, it ended up being a bad t-stat as I found out later.

James Duffin · 01-12-2012, 05:55 AM

My guess is that the 8 minute delay is to allow the pellet stove to heat the house on a call for heat. If after 8 minutes the house is still below setpoint the heat pump will come on and run.

**Jim Luttrall** · 01-12-2012, 10:53 AM

Originally Posted by James Duffin

My guess is that the 8 minute delay is to allow the pellet stove to heat the house on a call for heat. If after 8 minutes the house is still below setpoint the heat pump will come on and run.

ditto

**Raymond Wand** · 01-12-2012, 11:10 AM

I wouldn't think the pellet stove has anything to do with the heat delay of the themsostat.

Having a pellet stove they do not throw out heat right away, they take awhile before the blower even comes on.

**Jim Luttrall** · 01-12-2012, 04:16 PM

Originally Posted by Raymond Wand

I wouldn't think the pellet stove has anything to do with the heat delay of the themsostat.

Having a pellet stove they do not throw out heat right away, they take awhile before the blower even comes on.

With any alternate heat source as the primary, I would want the secondary source (heat pump) to be delayed to give the primary source time to recover before bringing on the secondary. Not everyone wants instantaneous heat response.

**H.G. Watson, Sr.** · 01-13-2012, 04:06 PM

Its january, and you're up north. I'm guessing it had been rather cool outside the night before and possibly was still quite cool when you switched the thermostat, and the HP wasn't making a call for heat in some tiime. Outdoor feedback interface. I'd also be surprised there to be no heats in the HP for backup. Pellet stove as "primary" might be how the homeowner operates, but not the "system" installed for habitation.

A pre-heater defroster has to have a chance to thaw things out before it goes into operation suspect outside wasn't cold enough for backup heat, but too cool for the HP to immediately kick in for operation.

**Rod Butler** · 01-17-2012, 09:21 AM

Watson has a good point. There may be a compressor heater that has to engage to pre-heat the oil before the unit will start. Especially if the system has been in the OFF position and not just turned down.

David Bell · 01-22-2012, 07:45 AM

Originally Posted by Rod Butler

Watson has a good point. There may be a compressor heater that has to engage to pre-heat the oil before the unit will start. Especially if the system has been in the OFF position and not just turned down.

The crankcase heater and low ambient control will operate regardless of thermostat position on every system I have seen.

Darren Augustine · 01-26-2012, 03:34 AM

you said the heat pump was turned off at the thermostat. Was it a digital thermostat? if so the thermostat has a 5 minute timer when turned on. Sometimes waiting for that 5 minutes seems like an hour.To adjust the timer you go into the thermostat setup. If the thermostat was on and just turned down to a lower temp it should turn the heat pump on quickly. New heat pumps also have a timer in the defrost board so if you have a manual thermostat the compressor will be protected from cycling.