McQuay Centrifugal Oil pressure

[setrite]

Hi,

We have WSC100 McQuay centrifugal chillers. Have noticed that the Net Oil pressure drops while the chiller has just been started and stabilises later. It is set to maintain 110 psid, don't understand why the pressure drops to 60 psid at start-up.

We have six of them and all six have the same issue. They sometimes trip on Low Oil Delta Pressure. McQuay says there is no problem, but what about the future. Is anyone out there facing the same problem.

McQuay. I don't understand why they need 110 psid, the YORK I used earlier required just 35 psid.

[sedgy]

hi setrite, not sure about Mc quay oil pressure , but all chentriffs are a copy of the old westinghouse water cooled water chillers, with the famous impella, there where no bearings on the compressor even on the highspeed shaft that the impella ran on at 27000rpm no bearings just aluminium sleave which with 40psi oil pressure over suction pressure lifted the shaft off the aluminium sleave to let it run friction free of cource a blip in the oil psi and the steel shaft touched the sleave and it would melt instantly,

[MQFS Mo]

We use a hydrostatic bearing design, thus the need for higher oil pressures. High speed, Low mass.
Never encountered one yet where the oil pressure dropped that low when starting. The only thing I can think of is that there is excessive bearing wear that is causing the pressure drop up until the point that the thrust pump in the compressor overcomes it.
Typically, with that kind of bearing wear, you'd see low oil pressure even during pre-lube though.

What vintage are we talking here? Got the first few digits of the serial number?

[setrite]

MQFS Mo,

I suspect two things:
1. The Oil pressure regulating valve.
2. The compressor bearings.

However, this is happening on most of the chillers at the site.

Compressor Model is SE100MBA71HBXM
First few digits of the Serial is:506L01

[setrite]

MQFS Mo,

One more observation, Oil level in Oil sump rises about an Inch and half as the Net Oil pressure lowers.

[MQFS OZ]

Setrite,

Check your oil feed temp.The synthectic lubricant we use these days is very thin(viscosity) any extra heat means a loss of oil pressure, hence your oil pressure rises after the oil cooler solenoid opens. During pre-lube the oil cooler solenoid is not open, it opens after condenser pump/compressor start. Typically in warmer ambient locations we remove the oil cooler solenoid wire from the compressor controller output and wire it to the oil pump output on the Microtech compressor controller so that the oil cooler solenoid is open during pre lube. After the system stabilizes set your oil feed temp to 95 degrees f

[setrite]

MQFS OZ,

Thanks! What we found was that the gear case heater were rasing the temp of the gear case to 185 F. We wired the gear case heaters through a relay that controls the Oil sump temp.

Problem solved.

[DAC josep]

Hi,
McQuay WDC 100 oil level losing in the oil tank ( External) and the pump gets starving.Oil is not return to the external oil pump while on running.But it reaching when the compressor off.pls help what may be the reason.

[ptsac]

Hi,
McQuay WDC 100 oil level losing in the oil tank ( External) and the pump gets starving.Oil is not return to the external oil pump while on running.But it reaching when the compressor off.pls help what may be the reason.

http://hvac-talk.com/vbb/attachment....2&d=1274236727
Try this link for pdf oil loss guide

[DAC josep]

Hi
Any one can advise about the Mcquay impeller pull out method.Is it required any special specified tools or equipment ? please advise.

[binti]

Hi
Any one can advise about the Mcquay impeller pull out method.Is it required any special specified tools or equipment ? please advise.

The ones i have pulled out have a allan key high tensile bolt. access is under the nose cone. I had to weld a hex key onto a long tee bar to reach the bolt. I think it is a left hand thread too (from memory) to prevent it from undoing itself.