Unusual noise in copeland scroll. With vids.

[fastline]

This is a 2.5T Tempstar system. Was decommissioned for approx 4yrs and reinstalled in an older home. When system was installed, it was verified there was a very small leak on the vapor side port and an oring cap solved it at that time. 2.5yrs later, system is slightly low on charge. This was originally a heat pump but because the reversing valve was junk and heat mode was not needed, I cut the valve out and plumbed it out to only operate as an AC.

This is my personal system. Scroll has always had some vibration on cooler days below about 60F. I was considering this noise slugging but not super sure. System would pull down about 20*F across the A coil and otherwise purr like a kitten. If I can solve the vibration issue, it should be fine for a long time.

Vids: First is right after unit starts and you can hear it calm down and purr. Second vid is same cycle but 20min later. Noise in vid is highly amplified but you get the idea. In cool weather though, it is bad enough that I will not allow it to run or will cycle it once and kill it for the evening.

http://youtu.be/ltAyLsciWX8
http://youtu.be/cvpJWj3eyKw

System specs right now are:
Pressures 185/50
Ambient - 80F
Suction line temp - 68F
Liquid line temp - 84F
Delta T across A - 15F

[monkey spanners]

Piston or txv?

Suction superheat seem high, wonder if systems got a restriction?
(theres usually a chart somewhere teling you what the design subcooling or superheat should be depending on the expansion device type)

But the noise sounds like a tired scroll to me, job to tell without standing next to it.

(I'm assuming you're running R22...)

[aramis]

You are right, suction pressure is a little low, it wouldn’t surprise me the indoor coil is not in good shape either.

It doesn’t sound like slugging but more like an acoustic problem caused by vibration.

Scroll vibration is higher with wear and lower charge does not help either.

You should tighten the base, probably replace grommets, maybe change (or install) tube clamps and tighten all screws or rivets.

If neighbors complain about the noise you could install acoustic foam to cover the wooden walls.

[fastline]

The A coil was cleaned when installed a couple years ago. I may go ahead and reinspect it though. It is a fixed capillary system. No TXV.

[Magoo]

I agree with Arimus,
start by replacing rubber compressor mounts /gromets as they do settle and harden with age.

[fastline]

I had a guy I know out and he figured it was a piston type system and it was well hidden in the A coil somewhere. Certainly not a TXV. We charged the system a bit, took about 1.5lbs. System is now running near spec per the charge sheet on the condenser and is doing an 18* dT over the A coil right now. We were about 53% humidity in the house.
He did not think it was slugging and thought it was a vibration issue on the compressor but he also did not hear it when it was really talking. Cooler weather will make it talk more which I would think would be indicative of slugging but maybe the oscillating sound is what drives away from a slugging issue?

[aramis]

I had a guy I know out and he figured it was a piston type system and it was well hidden in the A coil somewhere. Certainly not a TXV. We charged the system a bit, took about 1.5lbs. System is now running near spec per the charge sheet on the condenser and is doing an 18* dT over the A coil right now. We were about 53% humidity in the house.
He did not think it was slugging and thought it was a vibration issue on the compressor but he also did not hear it when it was really talking. Cooler weather will make it talk more which I would think would be indicative of slugging but maybe the oscillating sound is what drives away from a slugging issue?

A piston compressor with worn piston pin sounds less with high compression ratio (hot weather) and more with low compression ratio (cold weather).

The noise comes from the piston pin hitting for every direction change of the running gear, in extreme cases the piston will hit the valve plate because the piston still goes up while the rod already started the down stroke.

The wear comes from long times working with high compression ratio which prevents the piston pin to lubricate and causes wear both in the piston and the rod.

Good news it is not slugging, bad news is the only solution would be to change the piston-rod set ... or compressor.

Insulating against noise covering the compressor could help.

[fastline]

Sorry, I was referring to a piston throttle valve in the A coil. The compressor is guaranteed a copeland scroll, not a piston. When I installed the A coil, I did not see any kind of valving and because it was a heat pump, there was some unusual plumbing there. I figured it was a fixed orifice capillary but a friend thought otherwise. be either way, there was nothing that would indicate TXV.

[aramis]

Don't be sorry, I am! ... for the confusion and I'm not used to call a fixed orifice a "piston".

It should be near the distributor.

[fastline]

I think there is some confusion on my part as to what throttling system is being used in the A coil but regardless, it is not a TXV type. I still think it is fixed capillary but whatever. It seems to be working for now. lol

[mikeref]

Sounds to me to be more of a compressor mechanical issue.
When compressor reaches normal running temperature, the noise is louder.
You can place a sheet of cardboard over the condenser fan after compressor has been running for 10 minutes or so, and listen for the noise to increase as the compressor has to work harder against higher head pressure.

[monkey spanners]

Don't be sorry, I am! ... for the confusion and I'm not used to call a fixed orifice a "piston".

It should be near the distributor.

I think its called a piston as it is able to move in its housing slightly, in cooling it will move so that the refrigerant has to go through the metering hole in the middle but in heating it will move back to allow unrestricted flow round the outside, a similar set up in the outdoor unit (or txv and check valve) takes care of expansion of the refrigerant in heating mode.

[fastline]

It is the funniest thing but actually the compressor runs MUCH smoother when it is hot out. Almost no start up noises and smooth as a new one. When it is cooler outside is when it makes noise. That is mostly why I was targeting slugging on this one. It will hit 90* today so if you like, I can probably provide vids of both warmer and cooler performance.

[Gary]

System specs right now are:
Pressures 185/50
Ambient - 80F
Suction line temp - 68F
Liquid line temp - 84F
Delta T across A - 15F


I had a guy I know out and he figured it was a piston type system and it was well hidden in the A coil somewhere. Certainly not a TXV. We charged the system a bit, took about 1.5lbs. System is now running near spec per the charge sheet on the condenser and is doing an 18* dT over the A coil right now.

What are the new numbers since the changes were made?

[Gary]

Charge it until the saturated condensing temp (SCT) is 30F above outdoor temp, then show us the new numbers.

To be more specific:

Step 1: Ballpark charge to SCT 30F above outdoor temp (30F TD).
Step 2: Adjust indoor fan speed to achieve evap delta-T (dT) of 20F (as close as practical). Lowering fan speed raises dT and vice versa.
Step 3: Adjust refrigerant charge to 12-16F superheat at evap exit.
Step 4: Repeat steps 2 and 3 as needed.

Note: Lower evap dT (assuming proper superheat) gives you higher efficiency and higher humidity. Higher dT gives you lower efficiency and lower humidity. There is an energy price for moisture removal. 20F dT should be just about right.

[fastline]

New numbers are
Ambient 75F
Suction - 51F
Liquid - 82F
dT over coil - 18F

Charge was added via superheat to 15*
Pressures - 205/66
Spec on condenser sheet was 206/68 so we are damn close to that.


Fan speed is on high and argument on delta was that there is a guaranteed new filter in it and before it likely had some filter restriction. It was determined this house is dirtier than most and requires very regular filters.

[Gary]

New numbers are
Ambient 75F
Suction - 51F
Liquid - 82F
dT over coil - 18F

Charge was added via superheat to 15*
Pressures - 205/66
Spec on condenser sheet was 206/68 so we are damn close to that.


Fan speed is on high and argument on delta was that there is a guaranteed new filter in it and before it likely had some filter restriction. It was determined this house is dirtier than most and requires very regular filters.

Okay... it looks to be running well. If you find you have a humidity problem, you might want to lower the indoor fan speed.

[Gary]

Does the system have an accumulator?
Is the indoor unit elevated above the outdoor unit?

[fastline]

There is not an accumulator that I am aware of. There are a couple copper bulbs in the liquid side in the condenser that I figure are factory driers (we added another filter drier in the line set.

The air handler is indeed above the condenser so any liquid coming from the A coil would easily get back to the compressor IMO. air handler is updraft so A coil sits about 5ft off the floor level, line set runs under the floor back to condenser. Vapor line elevates about 12" in the condenser.

Since many units have the A coil well below the condenser, I questioned whether it would be an issue. Friend of mine did not see any benefit to putting a sag in the line set or adding an accumulator. Not sure though. I still think the cool weather = increase noise would indicate slugging. IMO, a compressor would be louder in the heat with higher heat pressures if it was a compressor issue.

[Gary]

During the off cycle, liquid refrigerant will migrate to the coldest point, which is usually the evaporator. This liquid can drain by gravity down the suction line to the compressor inlet, washing out the oil on start-up. If possible, have the suction line go up above the evap coil and then down to the compressor. This helps trap the liquid in the coil. The alternative is to catch the liquid in an accumulator.

[Gary]

... line set runs under the floor back to condenser.

The suction line should be pitched in the direction of flow to help the oil return.