Heat Pump Pumpdown AND Recovery.
Yes, I mean "AND."
Maybe I've never pumped down a heat pump unit before.
I would have thought I have, but if I did, I didn't have
problems and didn't think much about it. Likewise for
But yesterday, I was involved with an air-handler removal so
I ended up attempting both a pumpdown and a recovery
on a split heat pump. (Goodman. No, I didn't bother
with the model number.) Ambient was about 60 F. Inside
dry bulb was maybe 65.
First, the low-side pressure would not fall below about
30 psi for at least 10 minutes so I decided something was
up. I called up two seasoned techs and they thought the
low ambient, 60 F, should not matter. And yes, I had
the system running via the tstat in cooling mode with
the high-side service valve tightly closed--at least the
allen bolt was tight. So after not having any clues, I
decided maybe the service valve was leaking and decided
to do a recovery. (The installers were anxious to remove
the old air-handler so I had to do something resembling
My Appion G5 is usually really fast, but yesterday the system
finally got down to about 25 psi and sat there for maybe a half
hour. There was some icing on the suction line
and a bit of frosting on the reversing valve. Shuttting it off
for 20 minutes and then starting it back up seemed to
stir up some progress, so the pressure dropped to about 15 psi
then went back to 25 and then slowly worked back down.
What am I ignoring? I figured that with the liquid line
service valve closed, the heat pump orifice played no
part in anything, so the whole thing should be just
like an A/C-only system. Obviously I'm doing some
Thank you for any enlightenment.
Sounds to me like the compressor may have bad valves, and/or it was grossly overcharged. How much refrig did you take out?
Sounds like you had a lot of freezon in there. Also possibly a bad compressor.
That is actually a good test for you to use if you think you could have bad valves.
In cool ambients it also takes a long time it seems to get from say 30 down to close to 0.
In your case I would have done the following.
Pumped it down as much as I could and recover the rest. Should have been quick that way.
Then the installers can get to it whiles you recover the condenser if necessary.
Sounds to me that maybe the internal pressure relief valve was opening or you just have bad valves. As far as the recovery is concerned you could have a lot of refrigerant trapped in the oil which can take longer to recover. Sometimes I will apply heat to the compressor shell on cold days to speed up the recovery.
The things-going-badly theme carried to my charging scale.
I did weigh the recovery tank before I started, and I was
weighing it as it slowly recovered, but then the 9V battery
in my scale controller (Fieldpiece wireless scale) died.
But the unit label said it held just shy of 14 lbs, not counting
the rather long--two-story house--lineset, 223 ounces.
Uh, no, I don't carry spare 9 V batteries. But I have not
recovered any other unit to the recovery tank, so I just
need to weight the tank. I know it initially weighed 25 pounds.
I had taken out at least 6 pounds before the battery died.
The outside unit looked fairly new. The previous owner
had replaced just it, not the air-handler. The new owner
didn't even run the unit, I think. The house is vacant.
He simply wants to go with gas heating, plans to keep
the condenser. (I guess we'll wire the reversing valve
to the contactor coil?)
I go back tomorrow to braze the lineset at the evap coil.
And I think I will be charging it, so we shall see. I really
hope it DOESN'T have bad valves.
I should mention scrolls don't have valves.
For future reference, if you have a system like this that won't pump down, close both valves, then you only have to pump down the coil and line set, which goes for vacuum pumping also as most of the refrig is still in the cond.
As a follow-up, I went back to this unit today to finish up.
I brazed up the new evap coil and pressure tested with
nitrogen. Even the nitrogen seemed to empty slowly,
so I opened both lines at the condenser, sealed them
up, and ran nitrogen in both directions. It seemed normal
enough. I then put it all back together, evacuated,
charged with the prescribed 14+ pounds, and passed the
HERS test. Perhaps the large capacity and the accumulator
just makes things seem a lot different than most systems.
Thanks for the efforts to help.
Were you only recovering from the vapor port?
No. I think the problem was a combination of sheer volume and icing
Originally Posted by beenthere
at the suction service valve. But I was recovering from the liquid line
service valve as well as the suction one.
Next time you are pumping down refrigerant open the high and low side gauges both. This will allow refrigerant to flow through your gauges if there is a restriction in your indoor metering device. Also speeds up the pump down process
Also next time you are recovering refrigerant, take a heat gun to that accumulator and heat that refrigerant out of the system. Makes it faster.
Are you sure your hoses are depressing valve cores adequately?
Originally Posted by georgelass
It's not uncommon for a unit not to pump down all the way & it doesn't mean there is anything wrong with the compressor especially if there is a long line set involved. Either way I've found the fastest thing to do in that situation is just take the recovery can, hook it up to the high side while the unit is running normally & let it pump a few lbs. into the can. After you lighten the freon load a little it usually pumps into a vacuum real quick. You don't even have to bother hooking up the recovery unit. I've done it hundreds of times with rarely a problem.
An engineer designs what he would never work on.
A technician works on what he would never design.