I have a question about my heat pump- any pros that can help?

I don't want to go to great lengths to explain it unless someone wants to take a crack at it.

What's the question?

?

I have a 10 SEER heat pump that was installed in 1991 or so. My house sat empty for about 3 years, and the unit was ran very little if any.

When remodeling, I pinched the thermostat wire and had to replace a section of wire. I am certain that I have good connectivity and the wires are correct. In pinching the wire, I burned out the transformer for the 24v source for the thermostat. I called a HVAC guy I knew, he had one, I put it in.

While he was out, I had him check my freon level with some gauges, my air seemed like it took a long time to cool the house down. He put some in, I don't know how much.

Everything was fine until the next day, overnight we had an electrical storm, my capacitor went bad. Installed new capacitor, with the help of the same guy. Unit ran fine for 5 min, he left and the outside compressor shut down very hard, made the most awful clank bang hiss sound. The fan motor start coil had burned out due to running half speed on the bad capacitor. I got a new fan motor and installed it. It is now on a separate capacitor due to a change in the design of the fan motor.

All of that was a few weeks ago and ~$300. The AC cools fine as far as I can tell. But while working outside, I can hear the compressor shut down. Every 10th time, it makes that same bang clank hiss just after shut down, it sounds like the thing is falling apart. I starts right back up and runs fine, but the noise really concerns me.

When the guy charged my AC, the filer was dirty from my deconstruction mess. I didn't realize it was so dirty, otherwise I'd have done something else. I am wondering if it could be overcharged?

You would need to put a manifold gauge set on it to determine its pressure. A noisy compressor might be the result of a lack of oil or possibly there might be loose mounts. The entire unit would wobble in that case.

I have a set of 134a gauges, but I assume the ports are different?

If you have too much freon sometimes you get what you call liquid slugging. I've been out of the AC for sometime now. But if I remember what causes that hard sound is that you are getting liquid into the compressor instead of gas. Just like a gas engine your AC compressor can not compress liquid. It is made to compress gas. About a ratio of 10 to 1. Dirty filters can cause this by not letting enough air across the coils. Or over charged. Also check your indoor evaporator coils. They may have gotten clogged sometime. They have the little fins and that is where the air needs to pass obstructive. You might be able to clean them with a brush and a hose or spray bottle. Best thing is to have an expert do it. Also on let's say a 94 deg. day the suction line coming out of the outdoor condenser which is the big one should be cold to the touch. You may have to remove the insulation. This is felt right after the line comes out of the unit. The small line should be warm. This is the high side. Low side pressure might be around 70 something and the high side 150 +. But this is just an average. On a high humid day it can be different.

The gauge set for R-12 is also used for R-22 which is likely what your heat pump uses if it has a refrigerant charge. And around 70 for the low side is about right. High side will vary depending on ambient and coil efficiency but 150-175 is a good place for it to be.

Unfortunately, I don't have R12 gauges, only 134a.

I did (safely and legally, of course) remove some freon and the harsh shutdowns stopped.

I have been pondering another thing- what if I misted a fine spray of water on the coils while the compressor was running to help its efficiency? I found a company that makes a unit that does that, but what about a retrofit on my unit?

What the noise sounds like is slugeed or overcharged. You might have to do is you might want to have it serviced. Which is wash the evaporator coil, clear or clean condensate drain, check or replace filter. The filter should be changed or washed every thirty days, unless using pletaed filter. The Condenser should be cleaned washed down with water and a cleaning solution. Last have the pressures checked.On a 90 degree day you should have pressures 70 to 75 low pressure and 185 to 220 on the high side. If all that fails you might have to a hard start capacitor but if all that fails you might be having issues with the compreesor it self. The freon in the system should be R-22 it will not be R-134a which is used for wine cooler or automotive a/c.


Christopher Piacente
HVAC Techanican & Boiler Mechanic

Well, it started making noise after it was serviced :rolleyes: He is a guy I've known for a while, a good ole boy kind of thing. My filter was clogged with dust from deconstruction inside the house at the time he checked the freon level. He added some freon at that point, and the noise started right after that. Removing some freon fixed that hard shut down noise. I have since rinsed out the outside unit, still need to clean the inside coil.

What would you think about misting water on the outside coil to help with efficiency?

I have an ice maker water valve that I can use and would plan to use hollow cone agricultural spray nozzles. But, the water valve needs 110v AC to operate- I don't know of any source for that at the unit.

It will improve efficiency for a while, but there are issues of scaling etc...

Bring this back to life-

Since the freon level was reduced in the unit, the hard shutdowns are gone- but now that I am running the unit in reverse for heat, "frost" builds up on the coils, then when it shuts down, the "frost" melts running out on the concrete. Its not cold by any means here, but I am not really sure what that means.

My newer heat pump at my house that I sold didn't do that, so I am guessing its not normal. :dunno:

Thats normal for some heat pumps. On some models the reversing valve switches from heat to AC for a brief amount of time to melt the frost or ice build up. It's when it does not melt the ice that you got problems. But when it gets too cold your running on your electric resistance heat for the most part anyway.