KeepRite K40-CU-IM-13, Installation And Maintenance Instructions Manual

Page: 27 / 36

27
Low Temperature Room Pull-Down
It can take up to two weeks to properly start-up and pull-down a large freezer. Large freezers should be pull-
down to temperature in stages. Too fast a pull-down can cause structural problems in pre-fabricated rooms and
will damage (crack) concrete floors. Reduce room temperature by 10 to 15
o
F (5.6 to 8.4
o
C) per day. Hold this
temperature for 24 to 48 hours at 35
o
F (1.7
o
C) and again at 25
o
F (-3.9
o
C). Monitor the amount of defrost water
during this pull down stage.
Once the room is pulled down to temperature, expect frost on the compressor end bell and any exposed suction
line. A lack of frost in these areas probably indicates too high of suction superheat. Reduce defrost frequency to
30 minutes every 6 hours if possible. Adjust the defrost termination (and time clock) so that the coil and drain
pan are
COMPLETELY free of frost / ice at termination. Too short of a defrost cycle will allow residual ice to
grow. Too long of a defrost will allow the coil(s) to steam at the end of the cycle. The steam will condense and
freeze fans, fan guards and create frosting on the ceiling of the room. The evaporator fan delay must allow any
condensate left on the coil surface to refreeze before the fans start.
Cut-in
(PSIG)
Cut-out
(PSIG)
Cut-in
(PSIG)
Cut-out
(PSIG)
Cut-in
(PSIG)
Cut-out
(PSIG)
50 35 5 70 20 85 30
40 25 5 55 20 70 30
30 17 5 40 20 50 30
20 12 0 30 10 40 20
10 7 5" Hg 20 0 30 10
0 5 5" Hg 15 0 20 5
-10 - - 15 0 15 0
-20 - - 10 0 10 0
-30 - - 10 0 6 3" Hg
* The coldest Temperature of either the fixture or outdoor ambient.
R-22 R-404A, R-507
Minimum
Temperature
o
F *
Pressure Control Settings
R-134a
Air-Cooled Units Water Cooled Units
R-134a 250 200
R-22 370 315
R-404A 400 315
Maximum Cut-out (PSIG)
High Pressure Control Settings
Refrigerant