12 Product Manual PM WSC/WDC
Heat Exchangers
High Performance Shell-and-Tube Flooded Evaporators
McQuay packaged centrifugal chillers are equipped with new high performance heat exchangers. The unique
design greatly increases heat transfer and reduces unit footprint and refrigerant charge compared to previous
designs. In many cases vessel length has been reduced by 40 percent. Chillers are designed, constructed and
tested in accordance with ASME Section VIII, ASHRAE Standard 15 requirements and TEMA recommendations.
The replaceable water tubes are integral internally and externally enhanced copper and are mechanically bonded
to steel tube sheets. Standard tubes are 0.025 inch wall copper in the evaporator and 0.028 inch wall copper in
the condenser. Optional tubes include 0.028 inch evaporator and 0.035 inch on either vessels and 90/10 cupro-
nickel, 304 stainless steel or titanium material. Clad tube sheets and epoxy coated heads are included when
other than copper tubes are specified.
Vessels are available for 1, 2 or 3 pass water flow. A 3/4" thick vinyl/nitrate polymer evaporator insulation is
standard. All seams are glued to form an effective vapor barrier. The entire chiller barrel including non-
connection heads and tube sheets are factory insulated. Detailed information on the insulation can be found
under “Physical Data” in this catalog.
Lubrication System
A separately driven electric oil pump assembly supplies
lubrication at controlled temperature and pressure to all
bearing surfaces and is the source of hydraulic pressure
for the capacity control system.
The control system will not allow the compressor to start
until oil pressure at the proper temperature is established,
and also allows the oil pump to operate after compressor
shutdown to assure lubrication during coast down.
Lubricant from the pump is supplied to the compressor
through an external brazed-plate heat exchanger and
internal single or dual 5 micron oil filter. All bearing
surfaces are pressure lubricated. Drive gears are operated
in a controlled lubricated mist atmosphere that efficiently
cools and lubricates them.
Lubricant is made available under pressure from the
compressor oil filter to the unit capacity control system and
is used to position the inlet guide vanes in response to
changes in leaving chiller water temperature.
Should a power failure occur an emergency oil reservoir
guarantees adequate lubrication flow under pressure and
prevents damage that could occur during the spin down
period with the oil pump stopped.
Since the McQuay chillers are positive pressure there is no need to change lubricant or filter on a regular basis.
An annual oil check is recommended to evaluate the lubricant condition.
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