CVHF mystery

[mikeacman]

I have been working on a cvhf490 today and am a little baffled.

It was shutting down and restarting every 1/2 hour or so with no diagnostics.

I logged it out at various times and observed the following abnormalities.

set point is 42

fluid is water

#1 LCW sensor appeared to be off 7 degrees .

It appeared to have high approach and the sat suc was falling below 34 with a leaving water of 48 .

After measuring the actual LCW a foot down stream of the sensor I actually had a leaving water of 37.

I changed the sensor and restarted the chiller and had the same problem , sensor appeared off and approach was high .

measured the voltage at the power supply and sensor , 24 VDC , all other sensors OK.

#2 I have always complained to the BLDG owner about the current ,
at one point I read 213A , 257A , and 314A from the CH530 as well as the display on the starter .

I also caught it in phase imbalance limiting mode a couple of times .

#3 the condenser side looks good, 79 water in , 89 out, 0.5 approach

# 4 after the sun went down it all started acting better and stayed online but still surged at times ( mildly)

the LCW sensor started reading properly

the current is still off but not as bad .

The evap approach is still a little high compared to previous logs , now 4.5 but was 0.9 this morning

ECW 53 , LC2 42,

I am starting to feel it was shutting down on phase imbalance as I raised the setpoint to keep the sat suc above 37.

Why don't I get any kind of message as to why it shut down every 1/2 hour for 5 + hours,

#1 I never made setpoint or diff to stop

#2 I never witnessed a sat suc lower than 36 ( after raising SP early on )

#3 approach always appeared to be in excess of 10 at shutdown

#4 witnessed it in current limit a few times and phase imbalance but never caught it in these modes at shut down.

#5 IGV was always above 60% when it shutdown , it would rapidly unload then stop.

I am baffled

[kcwong]

How about your water system? The chiller seems stoped by no load, then no diagnostic appeared. Did you reset the chiller after it down?

[mikeacman]

I never had a diagnostic to reset and the chiller always came right back up withtin min of stopping.

I failed to mention that it was doing just fine until I shut it down for a half hour to do some work on the tower.

the load on the bldg came up if anything,

My entering water was always 5+ above LCW.

I never met the diff to stop or got below SP by more than a degree.

flow is appox 800+ GPM through chiller.

assuming high evap approach and the fact the LCW sensor is mounted on the top of the outlet nozzle i wondered about low charge or a leaking head gasket .

my alarm never reads any PPM and the purge hasn't pumped out in forever
( like a year)


It seemed to clear up about 20 min after the sun went down and the condenser loop dropped 3 or so degrees from where it was hanging out at.

I work on a lot of carrier stuff and trane is a little foreign to me but I assume if it was serious I would alarm out or at least get a reason for stoppage , again as said I do not believe I am meeting shutdown criteria such as diff to stop , I never made SP! or diff to stop .

[kcwong]

There are not so many nonlatching fault for CH530 e.g. no load, no flow, power loss/momentary power loss etc...

The water flow seemd too low. CVHF490 should be around 500 ton. Flow should be 1200gpm.

CVHF is using low pressure refrigerant R11/123, air leak in rather than refrigerant leak out. The unit will run noisey if air in.

I guess you need some help from local Trane office. In fact, we cannot solve the problem without touching the unit.

[chiller mekanik]

Your problem could be intermittent, possibly in the start stop path. Is this machine on an energy management system?

If there isn't someone in your organization thats a little more faniliar with centrifugal chillers, you may want to contact your service provider, doesn't have to be Trane if they are competent. I checked the roster at chillergroup website but I don't see anyone very close to you.

The readings you posted are all over the board as they contradict each other in more ways than one.

You may want to start proving what the problem is not as opposed to trying to prove what it is at this point.

Good luck!!

[Healey Nut]

Its clear from your posts that you are not fully familiar with centravacs you need to contact a reputable chiller service contractor who understands not only the chiller but the CH530 control platform and is able to diagnose your problem and hopefully guide you in how to log and understand the log readings you take .An accurate log is valuble to you but also to a service tech to check proper chiller performance. Graham Trane Tech

[jayguy]

wow.

It was shutting down and restarting every 1/2 hour or so with no diagnostics.

most likely, BAS or some other item (chilled water reset?) shut the unit off. i had a Johnson tech swear that they were saving the company money by starting the unit every 1/2 hour after running it for only 10-15 minutes.

#1 LCW sensor appeared to be off 7 degrees .

make sure that the chilled water sensor is all the way in the well.

It appeared to have high approach and the sat suc was falling below 34 with a leaving water of 48.

starting and stopping a chiller does affect the approach. true approach problems should still be there after the unit has a chance to settle down...you may not have enough time.

#2 I have always complained to the BLDG owner about the current ,
at one point I read 213A , 257A , and 314A from the CH530 as well as the display on the starter .

verify with a good known meter. you are running 20% phase "amperage" imbalance. typically a 1% "voltage" imbalance can cause a 10-15% amperage imbalance. i suspect that a larger voltage imbalance is the cause of your amperage imbalance. check your voltages.

# 4 after the sun went down it all started acting better and stayed online but still surged at times ( mildly)

if you have a low evap temp, the chiller still has to work real hard to lift the refrigerant to a "normal" head pressure. lift is lift.

The evap approach is still a little high compared to previous logs , now 4.5 but was 0.9 this morning

lower evap approach is good. with the chiller acting up like you say, 4.5 is ok until you can get things under control.

kinda sounds like you have some flow issues. i would keep an eye on your evap and cond water flows. what is the full model number? depending on which tubes you have and how much inhancement, passes, etc. will determine what your min/max pressure drops are. do you have variable primary flow?

good luck.

[jimbob73]

Jayguy, You need to send out a bill for them services

[jayguy]

Jayguy, You need to send out a bill for them services

i have a customer that has a whole boat load of RTU's that i am doing inspections on...feels good to do some "chiller work" again. hot and high humidity here. can not wait to get back into a nice cool mechanical room.

good luck.

[M100 Tech]

In the setup there is something called "Free Starts". A CTV will actually shut down and restart before the wheel has stopped if the number of free starts has not been exceeded! The problem you are experiencing is most likely the chilled water flow switch. It will cycle the unit! Peple use to use the flow switch to cycle the chiller. It is a bad idea to stop the pump and cycle the chiller based on the flow switch, what if the switch fails closed?

Just my 3 cents!

Dewey

[bertoh]

all that and check for air in water side of both evap and cond. 2 sensors and it is still off by 7 deg?? purge hasnt ran in a year?? not sure on the ch530 platform but the UCP2 would lock out purge if excess mins excedded in 24 hours, the chiller on the other hand would dance alll nite.
jump out the start contacts, clip a volt meter on the pair of wires (removed from term. strip) set up min/max on volt meter and see what is going on with the signal. or is machine vibrating so bad a relay is bouncing??
800 GPM?? is that a 3 pass or 2 pass evap? 800 too low for 2 pass