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

[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.

[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.

[Dan Espy]

THIS IS HOW IT LOOKS RIGHT BEFORE SHUT DOWN
EWT 52, EVAP LWT 46, COND EWT 80, COND LWT 87, SAT EVAP RFGT TEMP 42, EVAP RFGT PRESS 75, SAT COND TEMP 87, COND REF PRESS 160, COMP DISC TEMP 122 DISCH SUPERHEAT 34, DISCH SUPERHEAT CONTROL POINT 34, EXV POSITION 45.6%, EVAP APPRCH 2.4, COND APPRCH 0.0
SERVICE SETTINGS ARE PRETTY CLOSE TO FACTORY SETTINGS THROUGHOUT
ILL SEND OVER SETTINGS TOMORROW

[jayguy]

THIS IS HOW IT LOOKS RIGHT BEFORE SHUT DOWN
EWT 52, EVAP LWT 46, COND EWT 80, COND LWT 87, SAT EVAP RFGT TEMP 42, EVAP RFGT PRESS 75, SAT COND TEMP 87, COND REF PRESS 160, COMP DISC TEMP 122 DISCH SUPERHEAT 34, DISCH SUPERHEAT CONTROL POINT 34, EXV POSITION 45.6%, EVAP APPRCH 2.4, COND APPRCH 0.0
SERVICE SETTINGS ARE PRETTY CLOSE TO FACTORY SETTINGS THROUGHOUT
ILL SEND OVER SETTINGS TOMORROW

without any other info, this chiller looks ok...the exv position might be a little far open...what was the %rla? got both gpm's? or at least ACCURATE pressure drops?

[darooo]

Thanks I ll try that as soon as possible