McQuay MHC Series, Installation & Maintenance Data, Page: 31 / 36

IM 985-1 / Page 31 of 36
Troubleshooting
The in and outs of R-410A
R-410A­is­a­non-ozone­depleting­blend­of­two­
refrigerants - HFC-125 and HFC-32 in a fifty percent
mixture .­R-410A­exhibits­higher­operating­pressure­and­
refrigeration­capacity­than­R-22 .­R-410A­is­intended­
for­use­in­new­air­conditioning­applications­that­have­
traditionally­used­HCFC-22­(R-22) .­Due­to­higher­
capacity­and­pressure­of­R-410A,­it­must­not­be­used­in­
existing­R-22­systems .
Although R-410A is non-flammable at ambient
temperature­and­atmospheric­pressure,­it­can­become­
combustible­under­pressure­when­mixed­with­air .
Note: R-410A should not be mixed with air under
pressure for leak testing. Pressure mixtures of dry
nitrogen and R-410A can be used for leak testing.
Lubrication
R-410A­should­be­used­only­with­polyester­(POE)­
oil .­The­HFC­refrigerant­components­in­R-410A­will­
not­be­compatible­with­mineral­oil­or­alkylbenzene­
lubricants .­R-410A­systems­will­be­charged­with­the­
OEM­recommended­lubricant,­ready­for­use­with­R-
410A .
Charging
Due­to­the­zeotropic­nature­of­R-410A,­it­should­
be­charged­as­a­liquid .­In­situations­where­vapor­is­
normally­charged­into­a­system,­a­valve­should­be­
installed in the charging line to flash the liquid to vapor
while­charging .
­Make­certain­that­the­recycle­or­recovery­equipment­
used­is­designed­for­R-410A .­The­pressure­of­R-410A­
refrigerant­is­approximately­60­percent­greater­than­
that­of­R-22 .­Pressure­gauges­require­a­range­up­to­
800­PSIG­high­side­and­250­PSIG­low­side .­Recovery­
cylinders­require­a­400­PSIG­rating­–­do­not­put­R-
410A­in­a­300­PSIG­rated­cylinder .
Note: Because a water source heat pump operates
under a wide range of water and air temperatures, the
values printed below are to be taken as suggested
pressure and temperatures. All McQuay water
source heat pumps are designed for commercial
use. The units are designed for the cooling
mode of operation and fail safe to cooling. The
reversing valve is energized for the heating mode of
operation
.
Superheat Head Pressure Water Delta T
8 to 14 degrees 335-355 PSIG 10° to 14°
All information above is based on ISO standard
13256-1 and tested at these conditions.
General Maintenance
1 .­ Normal­maintenance­on­all­units­is­generally­
limited to filter changes. Units are provided with
permanently­lubricated­motors­and­require­no­oiling­
even­though­oil­caps­may­be­provided .
2 .­ Filter­changes­are­required­at­regular­intervals .­The­
time­period­between­changes­will­depend­upon­
the­project­requirements .­Some­applications­such­
as­motels­produce­a­lot­of­lint­from­carpeting­and­
linen changes, and will require more frequent filter
changes. Check filters at 60-day intervals for the
first year until experience is acquired. If light cannot
be seen through the filter when held up to sunlight
or­a­bright­light,­it­should­be­changed .­A­more­
critical­standard­may­be­desirable .
3 .­ The­condensate­drain­pan­should­be­checked­
annually and cleaned and flushed as required.
4 .­ Record­performance­measurements­of­volts,­amps,­
and­water­temperature­differences­(both­heating­and­
cooling) .­A­comparison­of­logged­data­with­start-up­
and­other­annual­data­is­useful­as­an­indicator­of­
general­equipment­condition .
5 .­ Periodic­lockouts­almost­always­are­caused­by­air­or­
water­problems .­The­lockout­(shutdown)­of­the­unit­
is­a­normal­protective­result .­Check­for­dirt­in­the­
water system, water flow rates, water temperatures,
airflow rates (may be a dirty filter), and air
temperatures .­If­the­lockout­occurs­in­the­morning­
following­a­return­from­night­setback,­entering­air­
below­machine­limits­may­be­the­cause .
Recycle/recovery equipment must be designated for R-
410A. R-410A pressure is greater than R-22. Improper
equipment can cause severe injury or death.
WARNING