HVAC chiller help

T77911S · 03-26-2015, 08:51 AM

our chiller at work is freezing up from the TXV valve all the way back an into the compressor. R22 system. pressures are 41 lo and 155 hi, outside temp is 70.
site glass before TXV valve has lots of bubbles.
i am expecting 70 lo and about 200 hi for normal operation.

i was thinking it was just low because both hi and lo sides are low. if there was a blockage or the TXV valve was not openinig then my hi side should be really hi with my low side really low correct???? i removed the bulb from the lo side pipe to see if that made a differemce but it did not.

i put some R22 to it and no change. i dont want to put any more in yet.

billybek · billybek's Garage

Don't add any refrigerant.

It sounds like the expansion valve may be hung up open.
41 PSI saturated evaporator temperature is the same as 18 Deg F. Its going to freeze! When it does freeze it will let the snakes out of the system....SSSSSSSSSSSSSSSSSS!

Shut it down for now and look at water flow.
What does this chiller supply to?
There sounds like there is more going on than just refrigerant although that may be part of your problem.

What is the make and model? Anyone been working on it lately?

billybek · billybek's Garage

Removed the bulb from the lo side pipe to see if that made a differemce but it did not.

Missed this part. The bulb or element is the opening force for the TXV. At room temp it will allow all the refrigerant it possibly can in the evap.

Make sure that the bulb is re-attached well and insulated well.

T77911S · 03-26-2015, 09:51 AM

it was well attatched and insulated when all this started.

its a carrier. not real big, maybe 15-20 ton. never checked.

if the TXV does not open or is clogged, wouldnt the hi side be much higher than 150?
plus i would not see all the bubbles in the site glass.

i am goint to let it sit over night just to make sure there is nothing else frozen. the pipes i can see no longer have ice on them but within a few minutes of turning it back on they start to freeze.
the bottom half of the TXV all to the comp freezes at the same time. also the bottom half of the comp is freezeing.

we had 2 water lines freeze and bust several weeks ago when the outside temps dropped. nothing major but water sprayed all over the controls. one board did fry but it was something i added sevreal years ago that just monitored the low side temp and shut the system off if it got too cold. i think this was added because some pipes froze before in the winter.
this is a very old system and a lot of crap has been added over the years.
we are in the procsess of putting in a new chiller and i am just trying to make this one hang on a little longer.

T77911S · 03-26-2015, 09:52 AM

is there a way to check the bulb to make sure that it has not lost its charge?

billybek · billybek's Garage

Quote:

is there a way to check the bulb to make sure that it has not lost its charge?

Yes put the bulb in ice water and it should throttle back.

billybek · billybek's Garage

I would ensure that you have good water flow before doing much more.

BK911 · BK911's Garage

Bubbles usually means low on refrigerant.
Low high side pressure means low on refrigerant or bad compressor.
Ice usually means low refrigerant or low airflow. Dirty coil?
So my guess is low on refrigerant.

rick-l · 03-26-2015, 03:15 PM

Quote:

Originally Posted by T77911S

our chiller at work is freezing up from the TXV valve all the way back an into the compressor.

doesn't this mean there is a restriction back there (in the high side line)?

T77911S · 03-26-2015, 05:43 PM

I thought the low charge would also cause it to freeze.

Yes good water flow but we have reduced the load. But we usually do that in the summer.

Everything tells me low charge but I was not seeing pressures go up after putting in r22. Just wanted some other opinions.

I will look at the water again. I saw the hi pressure side was good. It is also suppose to be setup to auto fill if water gets low.

I am not chiller trained but have pretty much been the one to work on it for quite a while.

rc 82nd · rc 82nd's Garage

Not sure but,the head pressure seems a little low for 70°osa.
41#s of suction is about 18°evap temp. That will freeze.
Maybe low on refrigent. When the charge is closer,and the liquid line becomes more liquid and less bubbles,the head pressure will rise quicker. Those chiller units take alot of refrigent.

T77911S · 03-27-2015, 04:05 AM

i was just getting worried because it seemded like i put in a good bit and nothing got better.
i may not get back to it until monday. man the crap hit the fan yesterday.

had the chillar go bad, got another roof top 10 ton unit that froze and was pouring water in the womans bathroom

a module in the UPS that powers some of the radar stuff here craped out

another part for the radar system craped out

a display for one of the radar systems died at another airport. thank goodness someone else took care of that.

my wife had a flat.

this morning was not good either. tried to fix the UPS and made things worse on the radar system. i barely got the system working before we opened.
dont ever work on anything on a friday.

billybek · billybek's Garage

The fact that you have had some piping problems in the last while may indicate that there could be flow problems or air in the system.

What is the temperature of the water entering and leaving the evaporator when it is running?
Are there gauges to read the pressure drop of the water through the evaporator?

It may very well be just short of gas. The question that needs to be answered is where did the refrigerant go?

billybek · billybek's Garage

Man, that sounds like you are having a day!

Hope Friday gets better for you....

T77911S · 03-27-2015, 06:14 AM

it appears to be fixed....for now.

i think it was low and the coil (we could not see) was still frozen yesterday.

lo side is 60 but the hi side is a tad higher than what i would like . it was 250. (70 outside but a hi heat load cooling the building down). when the second condensor fan kicked on, has not done that in quite awhile, the l side got lo again, i think 40 and the hi side was down to 150.
superheat for the one fan running was 30 and for both fans it was 16.
site glass is clear. (super heat looks ok but still a little worried it may have too much).

gotta go work on something else. its a friday.

rc 82nd · rc 82nd's Garage

Looks like your chasing it down pretty good.Super heat on an adjustable TXV is important. Mount the buld in the original location,10:00 or 2:00. sub cooled liquid has to be looked at also.If you can get it close to operational pressures and temperatures,you'll just have to monitor it closer.as you know ,low ambient temps makes a little harder to charge properly. Got an economizer on that system?cooling tower or air dx.