05G Carrier Compressor

[rmw]

Can anyone tell me if the suction manifold to the second stage cylinders (top head) on the input shaft side of this compressor comes from a particular side of the compressor, left bank or right bank, again referenced to the input shaft, or if the discharge manifolds from both of the two first stage heads combine internally inside the pump casting?

I have a situation where the top head is cold to the touch on the input shaft side (opposite the discharge connection.) I have never encountered this before. The suction manifold side of the first stage heads are both cold (cool), but the discharge manifold while not cold, is touchable.

I have enough parts to do one first stage valve deck, so I don't want to pull the wrong head off, and if you note, this is a holiday weekend and I am stuck for parts until Tuesday.

This is on a bus A/C system, and we need the bus for hurricane Katrina relief work, so I need to cobble something together if I can.

What say you?

rmw

 

[MintJulep]

05G is a single stage compressor best I know.

All three heads are connected, but suction and discharge side by passages inside the casting.

The heads are split left/right high/low, not front/back.

Sounds to me like a stuck intake valve on the rear (nearest the shaft connection) piston of the middle bank.

This may help:

http://www.xpedio.carrier.com/idc/groups/public/documents/techlit/62-02756.pdf

 

[rmw]

The two pistons of the top head take their suction from the discharge of the left and right heads. I just don't know if the ports that feed the top head suction area from which the reed valves admit the gas to the cylinder is common to both the left/right heads, or if each is channeled from a respective side.

Thanks for the site; I already had it bookmarked.

Even in the past when I have had broken valves in either or both the left/right banks, but in only one cylinder of the bank, I still had some discharge from the cylinder not affected in that head, and therefore had a hot head on all sides of the top head.

In that I have a cold side of the top head, it is saying to me that I must have both valves broken in both the left/right heads, because that is the only way I could be getting crankcase temperature gas to the suction of the top head.

Where am I wrong?

rmw

 

[imok2]

RMW Quote"I just don't know if the ports that feed the top head suction area from which the reed valves admit the gas to the cylinder is common to both the left/right heads, or if each is channeled from a respective side"
The book I have shows that all 5 line compressors have a common discharge to the top head. So I believe you have defective suction valves on the left and right side heads.
(slugging)?

 

[rmw]

Thanks imok2,

That is what I reason. For the gas to be that temperature at that point, it has to be bypassing both the right and left banks so that suction pressure gas is reaching all the way to the top head. I have never seen condensation on the top head.

I customarily pat down the left and right heads opposite the unloaders, but don't generally dare touch the top head, normally.

The bus, while it didn't perform in a stellar fashion during the 95F ambient conditions, it did cool somewhat, and while parked for supper after sundown (80F ambient) it frosted the windows. I am pretty impressed at what the top head can do.

One other observation: the system works such that a pneumatic pressure sensor in the HP line engages the variable speed fan clutch for the condenser. A mental check is to listen for this fan to engage and come to high speed shortly after the A/C system is started (on high idle, of course-in cold weather, one can hear the fan modulating) So, one indication I had was that I could hear the high pitched whine of the fan as I drove through underpasses, etc at least during the earlier part of the trip. It is one of those things that one listens for subconsciously, but not so that I can remember where I ceased hearing it.

So, with the trip being fairly unremarkable, I don't know how I got into a slugging situation, whice I suspect, too. Other than the fact that the bus hasn't run a lot this summer, and has basically sat idle since April.

Any thoughts would be appreciated. I am danged tired of putting valve decks in this compressor.

rmw

 

[imok2]

Here are reasons why a compressor’s valves may become inefficient:

Slugging of refrigerant and/or oil.

Refrigerant migration problems.

Refrigerant flooding problems

Flooded starts.

Overheating the compressor.

Acids and/or sludge in the system deteriorating parts.

TEV set wrong resulting in too little superheat.

Too low on oil.

Loss of lubrication.

 

[rmw]

MintJulep,

Please accept my profound apoligies. It is single stage as you state. What I stated above was based on what I had been told once by a Carrier rebuilder. Now I have seen it with my own eyes. I hope the other stuff he told me (about unloader settings, etc.) weren't bogus as well.

The compressor had a broken diacharge reed in the right bank, and a hole in a suction reed in the left bank.

Top head was OK, but I put a new valve plate in it too just for good measure (and since I had to remove the head to inspect it). I put one new unloader on the left bank.

I changed the oil in the sump while I was in there.

I think I have refrigerant flooding problems, but I can't figure out why. It may be associated with the fact that with the problems that the compressor had, I couldn't pull the low side down low enough to move the refrigerant that condensed there during the winter (which was inactive for the bus) I'll take her out tomorrow, and see if my repair job makes the trip. I've enjoyed about all I can stand with working on this thing.

I have noted one thing. The chapter in the Eagle Bus Maintenance manual that pertains to A/C (out of some 23-24 is #13. I wonder if that is prophetic.

rmw