Minimum ambient temp to start gshp

seandarcy

I have a 5 year old water furnace gshp in a pa summer house. The house is closed and drained. I'd like to reopen it this month, but the manual says ambient temp has to be above 45 to run the gshp. Ambient temp is 25-30. But this makes no sense to me. Why does it matter the temp of the air blowing across the heat exchanger ? The refrigerant is cooled too much for the cycle to work ? At 25 degrees ?

Thanks for any help.

EBEBRATT-Ed

I am assuming you are connected to a closed loop system with antifreeze in it. Is this true or do you have a system connected to a pond or open well with pond or well water?

seandarcy

Open loop. Well water @ 250 ft. About 50 F. How would this make a difference ?

SuperJ

I've heard the same thing, something about low condenser temperatures causing refrigeration problems. The TX valve only has so much range in temperatures. Sorry I don't not the details.

I think you could cheat and restrict the airflow to the coil (put a piece of cardboard in place of most of the RA filter) to artificially keep the coil temps/pressures up in low ambient conditions. (or leave the panel of the fan compartment slightly open to the room so the fan is only pulling a bit of air through the coil).

EBEBRATT-Ed

@seandarcy , if you are using the heat pump for heating in low ambient conditions as it heats the air in the home it will be cooling the well water. Without enough "load" on the unit due to the low temperature in the house you cold cause the well water to drop below freezing

GW

It seems like it has to do with the compressor temperature, I would just let her rip.

JUGHNE

Do you have back up electric heat strips? That or some other heat could warm the house up close to that 45 degree mark.
Then start the HP.
There should be a freeze stat protector on the heat pump which would shut it down before damaging the coil.

Most heating systems are designed to maintain heat in a house that is already warm. They have all fall/winter to maintain and not start from scratch.

seandarcy

EBEBRATT-Ed said:

@seandarcy , if you are using the heat pump for heating in low ambient conditions as it heats the air in the home it will be cooling the well water. Without enough "load" on the unit due to the low temperature in the house you cold cause the well water to drop below freezing

But I've got an open loop. Intake is an aquifer @ 250' , effluent to pond.

GW

Just run a small 5000btu heater in the room where the heat pump is for a bit, get a little warmth. Or if your extra good, point the heater at the compressor, warm that puppy up. Then let her rip.

Mark Eatherton

The problem is that at that temperature, it will super condense and slug the compressor with liquid, no?

I'd use the emergency electric heat to bring the space up to the minimum before starting the compressor. Unless warranty is not an issue...

ME

EBEBRATT-Ed

Unless I am reading this wrong 25-30 indoor temp and 50 deg condenser water = trouble

JUGHNE

How is the water well winterized? Does is drain down when off?
How do you winterize the heat exchanger coil for winter?