Scotsman MDT6N90 - Manual (Page 28)

MDT6N90
May 2001
Page 28
REFRIGERATION SERVICE
General: This ice machine uses R-404A refrigerant
and polyolester oil. Do NOT use mineral oil in this
refrigeration system.
· When the system is serviced, a special liquid
line drier is required. It is included with
replacement compressors.
· R-404A is not compatible with mineral oil so
these ice machines use Polyolester oil.
Polyolester oil absorbs water very easily. A
system opened for service must be re-sealed as
soon as possible (15 minutes maximum).
· Special leak detection equipment is required to
locate small refrigerant leaks. Usually a leak
detector capable of detecting a Halongenated
refrigerant or HFC-134a will work. Check with
the leak detector manufacturer if in doubt.
· Evacuate to 300 microns.
· Liquid charge the system
Access Valves: To use the
access valves:
· Remove the cap from the
stem, use a 3/16" allen
wrench to check that the
valve is CLOSED. The
remove the core cap.
· Close the valve and
replace the caps when done. The valve must be
closed and the caps must be on or the valve will
leak.
Instructions for Liquid Charging R-404A
In preparation for charging, the low side hose
should have a sight glass, and/or a restricting
device (such as a “Charge Faster”) installed in it for
metering liquid into the low side of the system.
1. After a thorough evacuation shut off the manifold
valves and switch off the vacuum pump.
2. Place a drum of R-404A onto an electronic
scale.
3. Attach the charging hose to the drum.
4. Open the valve on the drum and purge the
charging hose.
5. Zero out the scale.
6. Shut the low side access valve at the ice
machine.
7. Open the discharge manifold valve full open.
8. Watch the scale, when the correct charge is
shown, shut the manifold valve.
Note: If all of the charge will not “go in” the
discharge side:
A. Shut the discharge access valve at the ice
machine.
B. Switch the machine on.
C. Open the low side access valve at the ice
machine.
D. Open the low side manifold valve and observe
the sight glass to be certain that only gas is flowing
into the system.
E. When the proper charge is indicated on the
scale, shut off the manifold valve(s).
9. Shut off the valve on the refrigerant drum.
10. Re-open the manifold valves until all liquid has
flowed out of the hoses.
11. Shut the low side access valve on the ice
machine.
12. Remove hoses from ice machine and replace
all caps.
SCALE
Hose Connection Schematic for Liquid Charging
Sight Glass
R-404A
Tank Must
Be in Liquid
Dispensing
Position -
Check Tank!
Torque stem
to 6-8 ft.-lb.,
caps to 7-12
ft.-lb.