Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.
Heat Pump Minimum Ambient To Protect Compressor
PGB1
Member Posts: 92
Hello All!
My question concerns the minimum safe operating temperature for a heat pump outdoor unit. Our unit is 17 years old and has only been used for cooling. We heat hydronically. Ideally, I'd like heat pump mode available should the hydronic system be shut down for repair.
My refrigeration work life was limited to chiller units and refrigeration over 100 tons. Small units, like my house's, are not something with which I'm familiar. My R-22 experience is also limited to friends-and-family freebies and installing this unit.
I hope you don't mind lending guidance to amateurs like me.
The outdoor unit is Haier brand. it's 2-1/2 tons and uses R-22 with mineral oil. The compressor (Bristol H20J293ABCA) is reciprocating (piston) type and has an immersion crankcase heater (wattage is unknown). Expansion is by a TXV and there is a suction accumulator for cooling cycles. The 'evaporator-when-cooling' coil is in a Hi-Velocity brand air mini-duct handler. It's their RCM series thick style coil.
Haier no longer offers a Low Ambient Kit, which, if my memory is correct, was a headmaster valve.
My thought was to install a Snap-Disc type of control that would open at the appropriate temperature. I'd splice it into the compressor/outdoor fan combined contactor's coil.
I realize that in cooling season, I'd have to bypass it or swap it for an open at 65-F unit.
(Haier specifies 65-F in cooling mode and does not mention safe minimum temperature for heating mode, other than to say to use their low ambient kit).
What is a good temperature for the control to open? Also, rather than have the control inside the electrical compartment sensing air temp, would it be better on the suction-when-heating line?
Thank You for helping & sharing knowledge.
Paul
My question concerns the minimum safe operating temperature for a heat pump outdoor unit. Our unit is 17 years old and has only been used for cooling. We heat hydronically. Ideally, I'd like heat pump mode available should the hydronic system be shut down for repair.
My refrigeration work life was limited to chiller units and refrigeration over 100 tons. Small units, like my house's, are not something with which I'm familiar. My R-22 experience is also limited to friends-and-family freebies and installing this unit.
I hope you don't mind lending guidance to amateurs like me.
The outdoor unit is Haier brand. it's 2-1/2 tons and uses R-22 with mineral oil. The compressor (Bristol H20J293ABCA) is reciprocating (piston) type and has an immersion crankcase heater (wattage is unknown). Expansion is by a TXV and there is a suction accumulator for cooling cycles. The 'evaporator-when-cooling' coil is in a Hi-Velocity brand air mini-duct handler. It's their RCM series thick style coil.
Haier no longer offers a Low Ambient Kit, which, if my memory is correct, was a headmaster valve.
My thought was to install a Snap-Disc type of control that would open at the appropriate temperature. I'd splice it into the compressor/outdoor fan combined contactor's coil.
I realize that in cooling season, I'd have to bypass it or swap it for an open at 65-F unit.
(Haier specifies 65-F in cooling mode and does not mention safe minimum temperature for heating mode, other than to say to use their low ambient kit).
What is a good temperature for the control to open? Also, rather than have the control inside the electrical compartment sensing air temp, would it be better on the suction-when-heating line?
Thank You for helping & sharing knowledge.
Paul
0
Comments
-
-
Thank You for taking time to reply, yellow dog.yellowdog said:Was the unit sized for heating? It may be a trial and error basis to find what outdoor temperature the system is still capable of covering the heat loss of the house.
No, it's not sized for heating. It's sized for cooling and is heat pump capable only by circumstance.
I will Only use it in heating mode if the hydronic system is down for repair or maintenance.
I think of it as an ~8,800 watt space heater. On a cold day, the building won't reach design temp., but it'll be ~30-k BTU closer.
My ambient temperature worry is to prevent damaging the compressor, such as from backwards liquid slugging or oil migration. The easiest way would be a thermostatic device, such as a snap disc that opens at whatever temperature is safe.
Paul
PS:
The reason that the outdoor unit is heat pump capable is because, when I was to purchase a condensing unit for cooling, the supply house asked me to try a Haier for evaluation purposes. They supplied the heat pump model. It came in about half the price of their lowest, builder's model (Goodman). The only extra I had to spend was the swap for a bi-directional filter drier.
0 -
-
-
-
-
Thank You All for helping and for the advice. It is very much appreciated.
I found it odd that the manual didn't specify a minimum outdoor temperature for heating mode, other than to sell the Low Ambient Kit (a Headmaster valve, if I remember correctly).
PC7060 mentioned a control circuit to handle the switchover. Incorporating this would be a rather simple project if we decide to use the heat pump for primary heating. (We're spoiled and prefer the silence of the hydronic. And there's nothing like hugging a radiator after working outside all day.)
Thank You Each Again!
Paul
1
Categories
- All Categories
- 86.3K THE MAIN WALL
- 3.1K A-C, Heat Pumps & Refrigeration
- 53 Biomass
- 422 Carbon Monoxide Awareness
- 90 Chimneys & Flues
- 2K Domestic Hot Water
- 5.4K Gas Heating
- 100 Geothermal
- 156 Indoor-Air Quality
- 3.4K Oil Heating
- 63 Pipe Deterioration
- 916 Plumbing
- 6K Radiant Heating
- 381 Solar
- 14.9K Strictly Steam
- 3.3K Thermostats and Controls
- 54 Water Quality
- 41 Industry Classes
- 47 Job Opportunities
- 17 Recall Announcements