Need Divine Intervention - plugged drier or expansion valve?

It's not really all that bad having all the tenants glare at me while the mercury soars. I just wanted to have a catchy title and "Need Help "seems to be a little overused, with no disrespect to those who really need it.

got an early 90s trane R-22 hydronic chiller (CGAC157HBN) two 7.5 ton circuits, drier/expansion valve design.

One compressor blew at the close of last season. Had it on the list for replacement next week, but we got our first heat wave a week early (why didn't we do it in the off season you ask, too busy keeping the heat going) and no 'tween season. We were heating through Friday and on Saturday they want air-con, so no set-up for test running water through without shutting off the heating and shunting the water through the chiller. We could have picked a day and done it and then gone back to heat, but we usually count on having a couple down weeks. So much for the excuses.

Anyhow, because of heat wave we decide to start the remaining circuit that was running fine last year. Unit is big enough that one circuit can just about handle the load anyway.

Murphy strikes.

Cleaned condensor. fill and bleed water circuit and insure flow through evaporator. Start unit, compressor kicks in fine, get brief, i.e. 5 second, flash of heat off high side right at the compressor and then nothing. Compressor running to beat band ultimately kicks off, I'm assuming one of the pressure actuated safeties after maybe a futile minute more of running. I didn't have any meters on it at the time and this is pre digital so I'm not getting any fault readouts, but the compressor is cool as a cucumber so I'm not betting on the thermal overload.

I go for the gauges and get back an hour later and it is still showing 7 inches of vaccum on the return and almost a buck-50 on the high side.

So, I'm assuming I have been graced with a plugged drier or expansion valve, but that doesn't make as much sense to me because it was working fine when we turned it off last fall.

So after another couple of hours the vaccum in the return drops maybe halfway down to 3 or 4 inches and I brave a restart to see if I get any different information from actually running it. Vacuum pops right up over 10 inches on the suction but the high side needle doesn't even budge. Now I'm thinking maybe I got a stuck valve in the compressor or???

This might be the most obvious symptom in the world, but I've never encountered it before and haven't managed to get Brian-UK to forward me (Brian-US) his troubleshooting guide so I'm going to the boards here, just like the Celtics later today, but I digress, for any thoughts on whats up or what else to test.

Also printing the 300 plus page manual on compressor selection from the book section, but open to any recommendations for replacement of the bad compressor (and maybe the 'good' compressor as well). These are Trane "model H" hermetic 7.5 ton reciprocals as far as I know. The counter that I use is recommending scroll replacements as low as 5 ton since I have almost double capacity for the load (I didn't do the load calcs, but this is my emperical experience from running this unit and its predecessor for 35 years) and energy savings is more important consideration now than redundant capacity. (esp. unless somebody can point me to a better staging contoller and water temp management controller. On the heat side we use a TACO-PC 702 -- sorry don't have privileges to post a link to the specs for this control,it's a relabeled Tekmar proportional reset and two stage boiler controller -- but I have been unable to find an analogous device for cooling control)

I assume that between the expansion valve adjustment and the fact that these would be undersized for the evaporator I wouldn't have a problem with liquid return and would get reasonable performance, but I concede immodestly here to being a whiz on the electric side while modestly to being just a straight OEM guy on the frig side to date.

So I have no fear whatsoever of reworking the harness, for instance added thermal overloads for the condensor fans that drop out individual fans generally before a bad motor takes down the entire unit, but I have not had as much creativity in approaching the frig circuit.

Given parts life, should I replace the expansion valves while changing the driers at this point or am I opening a can of worms. I have yet to remove the insulation to see how the capillary signal from the evaporator is installed. On the one hand, if I can test and confirm proper operation of these units in any way, it might be simpler to leave 'em alone, but given the price of a charge, if I'm going to end up doing it all over next season anyway, i might bite the bullet at this point.

Thanks,

[I'm] Brian [and so's me wife]

i think you gave the answer to your question yourself, but its nice to read your analyses.:)

keep us updated,

Ice

Early -90's...

Has this baby got a solenoid valve or is it relying on an electronic expansion valve?

Quote:

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Originally Posted by archibaldtuttle

got an early 90s trane R-22 hydronic chiller (CGAC157HBN) two 7.5 ton circuits, drier/expansion valve design.

Anyhow, because of heat wave we decide to start the remaining circuit that was running fine last year. Unit is big enough that one circuit can just about handle the load anyway.

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So don't use a smaller compressor, if you end up replacing it.

Quote:

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Originally Posted by archibaldtuttle

I go for the gauges and get back an hour later and it is still showing 7 inches of vaccum on the return and almost a buck-50 on the high side.

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Both too low for R22

My SWAG theory is, as simple as it sounds, that the system leaked some refrigerant during the off time. Have you tried adding some refrigerant to get the pressures up?

Quote:

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Originally Posted by powell

Both too low for R22

My SWAG theory is, as simple as it sounds, that the system leaked some refrigerant during the off time. Have you tried adding some refrigerant to get the pressures up?

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That was my first intutition of what happened and I grabbed gauges leak detector, etc. but those readings are not running readings, those are static ambients after sitting for an hour.

I don't see how the system hasn't equalized by then unless I've got some kind of a blockage somewhere.

Then I turned on the compressor and the suction went into deeper vacuum but I got no movement whatsoever, not even a flicker on the high side which totally surprised me, so I abated my plan to bleed in a little more refrigerant and headed for the web.

Has anyone experienced a no pressure gain on the high side even while showing obvious draw on the suction side and it was something besides the compressor? These taps are just on either side of the compressor, so I feel like there is nothing else to blame but internal compressor parts themselves which is why I'm guessing a stuck valve but...

I just like to think I know what the problem is as it seems almost inevitable given the age of the compressor and the fact that I'm already replacing it's twin, that I will just replace both, but I'm glad to know somebody, i.e. icecube51, thinks I have the answer. all I have to do is figure out which of my instincts is right.

So my proposals for action are take out the dryer, blow some nitrogren through the expansion valve trying to note if it seems blocked and then blows open or anything, then run the compressor a burst on the nitrogen and see if it is putting out to the high side. Then decide based on that result whether to replace the compressor or put it all together and try and run as is.

The Viking asks:

Quote:

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Both too low for R22

Has this baby got a solenoid valve or is it relying on an electronic expansion valve?

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The expansion valve appears to be adjusted by a direct pressure sensing capillary. No electrics.

Lastly,

Powell advises against smaller compressor. Is this to maintain redundancy factor or likelihood of some other failure or inadequacy. I was bit taken aback by the recommendation at my refrigeration counter for a 33% reduction, but on principle should the idea be rejected, or should I choose a slightly closer match if available?

Anyone with experience of putting a 33% reduced scroll or something like that onto a an existing evap condesor setup theoretically sized larger -- say you had a 5 ton in the truck and you gave it a try to get the thing up and running while your ordered the right size, or deliberate downsize for efficiency or???

thanks for the international symposium on these burning, or should I say freezing, question of refrig.

[I'm] Brian [and so's me wife]

Brian