Oil Pressure problems with a 06D compressor

[Kraeusen]

We inherieted this job from a company that hacked the installation.

The problem was and still is that it trips on oil failure. We tried to correct all the things that we found wrong that would contribute to this problem. Mainly, low load conditions.

We increased the supply air duct size. Cleaned the Evap and fan wheel. Repiped the oil lift lines on the suction side as per manufacturers recommendation.

The superheat is reading high 25 degF on both circuits. Sight glass is full. The feeler blubs are now tight which they were not before. There was no filter driers. We added one.

This is a 10 ton system. Carrier 38AQ012. 2 circuit HP.

The suction pressure ranges between 50-60 and the head is around 200 psi. The oil pressure is 4 psi differental.

Someone suggested that dip tube broke off inside the compressor. But if that was the case why is the oil leaving the compressor? How do you check the oil dip tube? The trouble shooting chart doesn't mention this.

We are ready to change the compressor but we don't want to have the same problem after we get done so. It is no fun being a parts changer. :(

Any input would be greatly appreciated.

[overhaul]

you're probably going to have to remove compressor drain the oil and remove the belly pan. This was you can inspect the pick up screan and tubing. My guess is copper fillings or the pick up fell off.

[Kraeusen]

you're probably going to have to remove compressor drain the oil and remove the belly pan. This was you can inspect the pick up screan and tubing. My guess is copper fillings or the pick up fell off.

If we pull the compressor and turn it over to do this while it is on the roof.. can the dip tube be repaired in the field?

PS thanks for the quick response.

[Jarredsdad]

A little confusing info here.

Carlyle says that comp oil switch is 8 - 11 cut in and 4 - 8 cutout diff.

Carrier IOM (from 1989) says Oil switch set point 9 psig. Differential 2 8. <-Notice space. I think there maybe a dash between the 2 and 8 that didn't copy. However + _ and .'s are all legible.

How much oil in sight glass?

I'd run it in oil recovery, loaded, and get as much oil back as possable.

Pic looks like that comp will not be fun to pull.

Much less flip over and open/ inspect.

[Dallas Duster]

Your oil pressure seems way low have you checked you valve plates?

[JRINJAX]

Recover the refrigerant out of the compressor and pull the oil pump cover off. Remove the allen screws that hold on the Tang. Now unbolt the front bearing head and it will slide out in your hands. Check bearing head for galling.
If no galling is present, it might be worth installing a new bearing head with a high volume oil pump.

[maxpower]

why is the oil leaving the compressor?


Can you see this happening? Is the sight glass oil level going down as its running? If you can see this happening,you need a new compressor. Its pumping itself out. Rings/cylinders are bad.

[maxpower]

why is the oil leaving the compressor?


Can you see this happening? Is the sight glass oil level going down as its running? If you can see this happening,you need a new compressor. Its pumping itself out of oil. Rings/cylinders are bad.

[Tech Rob]

JRINJAX has a good idea there.

Run it loaded up, recover the gas, drain the oil in the crank, and see what the oil looks like.

Pull heads, oil pump/bearing head and look for wear on the circumference of the shaft or a broken oil pump drive.

Wear on the shaft on that end usually indicates main bearing wear, seeing as that's the end closest to the oil pump.

While you have the oil pump off, you may be able to see the inlet screen or tube inside the crank.

[Kraeusen]

Thanks for all the input my peeps. My carlyle book states oil pressure should run at 18-26 psi. So, I'm way low at 4 psi. Originally thought compressor or oil pump problem, went with option # 2 figuring it'd probably be thousands of dollars cheaper for the customer. Have maybe opened one compressor in seven years, don't often work on compressors of this size and when I do, compressors are usually in good working order. So... looking at valve plates may not help me as I wouldn't know what to look for. Galling of the cylinder walls and shaft? Not sure what that means, something like scoring, metal on metal wear? Did look in oil sump when pump was changed out. There were alot of copper filings, they were infinitely small so I figured it was okay, but did siphon as much out as possible. Didn't get a good look at the oil screen as pipes, etc. were in the way. I usually am running it fully loaded as the space temp. usually is in the upper 70's. The oil level starts at 3/4 sight glass and within maybe 5-10 minutes is just out of sight. It does come back into sight, but doesn't raise up any higher than just visible. Throughout all this "oil level watching", the pressure never rises higher than 4 psi. However, it did rise to 12 psi for maybe a day after first changing the oil pump. Don't know why. As for high superheat on both circuits, tried opening txv's, no help. Maybe they are getting oil logged? The liquid line sight glass is full, overcharging will bring down superheat but compressor cant handle overcharge on startup, it trips Comp. lockout relay. Yeah, flipping the pig to open and look at oil screen doesn't sound fun, my book says it weighs 350. Maxpower, can you explain how it is pumping itself out of oil with worn rings/cylinder? Just curious. wouldn't the suction pressure be higher? I'm not attacking you, just want to sound smart. this post is long, like me. Thanks dad.

[Randy S.]

TXV power head?

[Jarredsdad]

copper filings, bad very bad. THink of it like an engine. Just no combustion. Cylinder walls should have a pattern but no straight up and down marks. Comps will blow oil by just like a car with bad rings.

Second compressor makes me think the original problem is still there.

Any oil traps on this system?

[rtu]

Did you try reversing rotation? If affects oil pump.
Like Jarredsdad's post filings not good.

[pop]

I assume your air handler is a 40RMQ dual circuit, if the oil leaves on start up and then returns when the unit shuts down, one of the check valves is open in one of the evaporator circuits. It is hard to find and figure out.

[chillersandcontrols]

There is a small check valve between the sump and the suction inlet section under the motor that may be stuck. Also, I cured this issue on a large Carrier RTU by adding a 1/4 copper tube from the lowest point on the evaporator header directly back to the suction inlet of the compressor. Put a sight glass near the compressor and watch that oil suck back where it belongs! Cheers

[JRINJAX]

There is a small check valve between the sump and the suction inlet section under the motor that may be stuck. Also, I cured this issue on a large Carrier RTU by adding a 1/4 copper tube from the lowest point on the evaporator header directly back to the suction inlet of the compressor. Put a sight glass near the compressor and watch that oil suck back where it belongs! Cheers
This is a good idea and used to be incorporated into the larger Carrier 39 series coils as an oil return line.

[Coolmaniac]

Did you try reversing rotation? If affects oil pump.
Like Jarredsdad's post filings not good.

If it does make a difference there's really something weird going on, as the pumps are designed to work in either direction. But the compressor has worn in, in only one. If you try it, don't leave it that way, or you'll definitely have to get a new one soon.

[maxpower]

Comps will blow oil by just like a car with bad rings.

Kraeusen, I guess I should said it like this.

[maxpower]

:confused: how did my first reply get posted twice? :confused: