RTHB150 Current overload

[darooo]

I have a Rthb150 that tripps on current overload only at night on ice making start up. Cts/Compressor mod, all ok per IOMs, just replaced load/unload sol valves as appears pistion press/amp was increasing on a manual hold. Seems to have corrected the problem for a week an reoccured, this problem has been around since start up 10 years agoand has been limited at 80%. Any help or direction would be great( I did attend RTHB training)

[Doesn'tPhaseMe]

just replaced load/unload sol valves as appears pistion press/amp was increasing on a manual hold.

So the compressor is loading up by itself right?

Is it fully unloading and amps going all the way down prior to shut down so your'e not getting a loaded start up next time?

[darooo]

There doenst seem to be a problem during normal run, Only in ice making mode at night, goes into current limit, observed pistion cavity pressure increasing, so suspected load sol valve leaking, did not correct problem. Possibly pistin leaking?

[Doesn'tPhaseMe]

Does the comp cycle at all during the day or once it goes occupied it runs all day? The slide valve pressure should not change by itself, possible internal problems like a lip seal.

[darooo]

Runs in ice burn mode til about 1000 am then cycles normally, until 400 pm, although there is not much load on the bldg since our temps here in fl have been so low. At 1100 pm goes into ice making mode, starts, loads 100% goes into current limit, as should, seems to try to unload but its like it doesnt fast enough, tripps. I have been able to force it in ice building during the day, to monitor, and same occurace happens. I guess I need to gather some more information.

[Doesn'tPhaseMe]

I think you are not fully unloading at shut down and getting a semi loaded start up. Are you getting any transistion failures too? I think the ice is keeping your load down on the chiller at 10 am and just may be enough to keep it from tripping. At 11 pm your ice is gone and cw temp maybe 15 - 20f warmer putting more load on chiller at start up then.

Put your gauges on so you can externally operate the slide valve. Put the slide vale in hold, Unload the chiller externaly and see what your amps are. Put slide valve back in auto and let it load up then put the slide valve in unload and see how low your amps go. If everything is working properly your amp readings on both tests should be the same.

Edit - If you can fully unload it manually do it then shut it down and restart in ice mode

[darooo]

Thanks I ll try that as soon as possible

[bobby m]

I would look into inverted starts,compressor taking back liquid,any type of tuning that may alter loading / unloading between comfort cooling and it's ice making pid's,and i would recommend installing amperage recording equip. to pinpoint issue.may not all apply but somethings to ponder.

[darooo]

Although we have very dirty power here our local utility comp has monitored incoming power, no problems found. Have put on voltage amd current monitors, problem only occurs when starting to full load during the ice making. Since there is not much load right now a full load of ice will last about 3-4 days. I can manually unload to around 40% capasity. But any ideas at this point are of great help. Thanks everyone, its getting old with the 1100 wake up from the summit. Customer is very understanding. (thank goodnesss) but its not 100 degrees yet

[duke of earl]

Is there a Trane factory startup form on site? I would check the original configuration and setpoints against the current setup and see if someone has changed something. You say this has been an issue for 10 years? I'm surprised the customer has allowed this for so long.

[jayguy]

...At 1100 pm goes into ice making mode, starts, loads 100% goes into current limit, as should, seems to try to unload but its like it doesnt fast enough, tripps...

how long does this take? 2 hours? 2 minutes? need lots more info...ent/lvg evap AND cond temps. water flows would be nice. first check is whether the settings (like current limit) are correct for this machine.

[darooo]

I kind of inherited the problam after two previous tech passed away, unit had been set to limit at 80% capasity, all setting are correct. RLA is 313 and set for 313. Trip occurs on start up at 1100 pm I get notified by 1115. Ice usually at 75% full on start up each night, CWT is usaually ambient at time as is a tower on roof. I will be back to log chiller at start up. Thanks

[triggerhappy]

I kind of inherited the problam after two previous tech passed away, unit had been set to limit at 80% capasity, all setting are correct. RLA is 313 and set for 313. Trip occurs on start up at 1100 pm I get notified by 1115. Ice usually at 75% full on start up each night, CWT is usaually ambient at time as is a tower on roof. I will be back to log chiller at start up. Thanks

I am not talking from actual experience on these machines but have heard the recip. guys around the shop talking.

Does this machine have a CH530 on it and if so do you have the latest version of the software?

From what I remember hearing the current limit setpoint is ignored in ice making and is at 100% in earlier versions of software, and this was addressed along with some other issues in the loading pertaining to the situation that you describe.

Like I said this may be wrong as it is second hand but it might jog some of the Trane guys that work on these into remembering something.

[Doesn'tPhaseMe]

At 11 pm your ice is gone and cw temp maybe 15 - 20f warmer putting more load on chiller at start up then.

I meant chilled water not cond water.

[jemawalton]

If you have a piston pressure increase while holding and you have already changed the load and unload solenoid valves, you might have an issue with the copper line that runs to the piston. The actual line itself runs inside the oil seperator enclosure so it is exposed to discharge pressure. It has flare fittings that connect it to the piston housing and to the internal line leading to the load and unload solenoids. If one of those is leaking, it will allow discharge pressure in and thus pressurize the load piston causing it to want to move toward the load position. If the leak is small enough, the unload solenoid may be able to bleed pressure fast enough so that it can unload but at a slower rate.

[Doesn'tPhaseMe]

If you have a piston pressure increase while holding and you have already changed the load and unload solenoid valves, you might have an issue with the copper line that runs to the piston. The actual line itself runs inside the oil seperator enclosure so it is exposed to discharge pressure. It has flare fittings that connect it to the piston housing and to the internal line leading to the load and unload solenoids. If one of those is leaking, it will allow discharge pressure in and thus pressurize the load piston causing it to want to move toward the load position. If the leak is small enough, the unload solenoid may be able to bleed pressure fast enough so that it can unload but at a slower rate.

I had 2 smaller 60hp screws on an RTWA (I think, I am bad with Tranes screw #'s) that both were doing the same thing. I actually had discharge pressure downstream of the unload solenoid. So they would actually load up when the unload solenoid was pulsed. Called Pueblo they had me put some other press taps to confirm what I was seeing. They had a aluminum manifold that gets bolted between the unloader solenoids and the compressor. No change to the load side but the unload side had a flare fitting now that gets piped into the suction line and the old port on the compressor is no longer used. It worked great.

[Healey Nut]

The parts that dont phase me is referring to is called a lip seal bypass kit . If the lip seal is leaking it allows discharge pressure to get behind the piston and cause the compressor to load without signals from the UCM. The kit re-routes this wayward gas directly back to suction faster than the lip seal can leak ,correcting the problem .
Its a popular fix for the larger RTAA compressors .

[Doesn'tPhaseMe]

The parts that dont phase me is referring to is called a lip seal bypass kit . If the lip seal is leaking it allows discharge pressure to get behind the piston and cause the compressor to load without signals from the UCM. The kit re-routes this wayward gas directly back to suction faster than the lip seal can leak ,correcting the problem .
Its a popular fix for the larger RTAA compressors .

Matter of fact it was made for a different compressor, they had me cut it in half because the bolt pattern was not the same so the pieces could be rotated into the proper position. I was the guniea pig for this according to Larry Volk in Pueblo.

[Dan Espy]

I am working on a rthb150 it does not appear to be unloading and has 22 starts in 4 hours

[stickerhead]

This is a different problem but related to RTHB on ice storage. I had two RTHB300 on ice storage with UCP 2 on them. I had one hell of a time controlling the discharge gas superheat because it would load up so fast it drop the discharge superheat, close the EXV and cause it to go off on low evap because the ice building mode causes the slide valve go to 100% period. The way I fixed it was not to command the ice mode contact closure but tell the leaving chilled water sensor to make 15 degrees. This left all the slide valve pulsing in the equation but still made the left the safeties in because it would control off the low evap staging which would unload the slide. This way the exv had time to respond to the discharge gas temp. FYI, the chiller was not overcharged.
Sorry for the rambling sentence...............