2000 HP Chiller
2000 HP Chiller
(OP)
Gents,
I have an issue w/ a 2000HP chiller, and wondered if I could get some insight. Originally, the chiller was fed by a 2000kVA, 4160V substation, that was about 30 yrs. old. We then replaced the substation transformer with a new one (I think the only change may have been the new one had a slightly larger Z). The chiller has a primary-reactor starter (fed directly from the sub via bus) which has a GE 369 motor management relay. Now, before the sub xfmr was replaced, we had no issues. What is happening now is the chiller sometimes will drop off (the 369 takes it out on UV from voltage dips on our grid) if running, and sometimes if it is not running and the operators want to start it, it will not start (once again, they are telling me the 369 takes it out on startup on a UV condition). An operator called me yesterday, and said they couldn't get this chiller to start. He said it had been sitting for 3 or 4 days. I asked him just for grins, to try starting it again (I'm not aware of how long it was between starts). The chiller started with no problems. Any ideas or insight is appreciated.
Mike
I have an issue w/ a 2000HP chiller, and wondered if I could get some insight. Originally, the chiller was fed by a 2000kVA, 4160V substation, that was about 30 yrs. old. We then replaced the substation transformer with a new one (I think the only change may have been the new one had a slightly larger Z). The chiller has a primary-reactor starter (fed directly from the sub via bus) which has a GE 369 motor management relay. Now, before the sub xfmr was replaced, we had no issues. What is happening now is the chiller sometimes will drop off (the 369 takes it out on UV from voltage dips on our grid) if running, and sometimes if it is not running and the operators want to start it, it will not start (once again, they are telling me the 369 takes it out on startup on a UV condition). An operator called me yesterday, and said they couldn't get this chiller to start. He said it had been sitting for 3 or 4 days. I asked him just for grins, to try starting it again (I'm not aware of how long it was between starts). The chiller started with no problems. Any ideas or insight is appreciated.
Mike





RE: 2000 HP Chiller
"Venditori de oleum-vipera non vigere excordis populi"
RE: 2000 HP Chiller
What is the UV setting, btw? A larger Z could cause some greater voltage drop during a momentory dip, but it the motor is not tripping on overload, UV trip is most likeky a nuisance trip..
RE: 2000 HP Chiller
"Venditori de oleum-vipera non vigere excordis populi"
RE: 2000 HP Chiller
Aside — The relay might also be tested to assure its time-voltage characteristic has not drifted.
RE: 2000 HP Chiller
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: 2000 HP Chiller
Definitely change in Z, but the xfmr ratio is the same as before.
Mike
RE: 2000 HP Chiller
V2=aV1-I2/Zt
a= transformer ratio
V1= phase primary voltage
I2= secondary load current
Zt= transformer impedance
You need to match the UV setup to the new expected voltage drop.
RE: 2000 HP Chiller
I have some new data now that suggests the grid is "sagging" quite a bit longer than the delay we have programmed in, and the RUNNING UV setting that we currently have. I'm going to change the setting from 8 to 10% and see how that works. I'm also going to try to contact the chiller manufacturer to see if the chiller can tolerate that low of a voltage for the low voltage period.
Mike
RE: 2000 HP Chiller
Mike Cole, mc5w@earthlink.net
RE: 2000 HP Chiller
RE: 2000 HP Chiller
When you say 'the grid' is sagging, do you mean the HV side of the transformer is seeing a sag, or the LV side? If your motor is causing a noticeable sag on the HV side, then expect the utility to come calling once they realise where the sag originates, because it will quite possibly affect other customers fed from the same HV source.
----------------------------------
If we learn from our mistakes,
I'm getting a great education!
RE: 2000 HP Chiller
The time delay I believe is set for 4 or 5 seconds. The UV relay is seeing the sag of the LV side. The odd thing is that I would expect the same response from our other chillers as well, but they remained in operation during the event. It's quite strange to me,...maybe something else is going on.
Mike
RE: 2000 HP Chiller
The same concept is used in small control transformers that are say 130 volts open circuit to compensate for voltage drop during the inrush period of contactor and relays coils.
Mike Cole, mc5w@earthlink.net