IM 738-2
117
Maintenance:
Refrigerant Leaks
Figure 119. 44" and 49" SWSI airfoil wheel-to-funnel
alignment
Refrigerant Leaks
R-407C is a zeotropic blend of three HFC refrigerants (R-32,
R-125, and R-134a). Zeotropic blends do not behave as one
substance. Therefore, a change of phase does not occur at a
fixed temperature. R-407C has a “glide” of 8°F because it
boils and evaporates over an 8°F change in temperature.
If an R-407C unit leaks refrigerant, there is no way to
determine how much of each of the three component
refrigerants leaked. However, experience in the field has
shown that
R-407C systems can be “topped off” after a leak
and will operate normally
. There is no need, except in the
case of critically charged systems, to replace the entire charge
after a leak.
Add charge per instructions on page 42.
Refrigerant Charge
The unit nameplate references proper charge for each RPS/
RDT refrigerant circuit in case a full charge must be added to
the unit. Verify these values using pages 39–41. Refer to pages
39–41 for RFS/RCS units.
Servicing Refrigerant Sensors or Switches
The
Daikin
Rooftop unit includes the following refrigerant
sensors or switches.
1
Low refrigerant pressure sensing, operating switch,
automatic reset
a
Disables their associated compressors on a drop in
suction pressure to approximately 35 psig.
b
Enables their associated compressors on a rise in suction
pressure to approximately 60 psig.
2
SpeedTrol™ high refrigerant pressure sensor (not available
on sizes 15 to 30). See page 90 for more information.
3
High refrigerant pressure, protective switch, manual reset,
reset by breaking control power to the S1 control switch.
a
All R-22 high pressure switches disable their associated
compressors on a rise in discharge pressure to 400 psig.
b
R-407C high pressure switches disable their associated
compressors on a rise to the following discharge
pressure:
– Scroll compressor units (sizes 015 to 105C) =
425 psig
– Reciprocating compressor units (sizes 15 to 135C)
= 400 psig
a
The switches have a differential of 100 psig.
4
High pressure relief, protective valve on sizes 115 to 135C
only and located on the condenser headers.
The low pressure and SpeedTrol sensors/ switches sense
refrigerant pressure through shrader fittings that contain cores.
The cores are stop valves that do not allow refrigerant to flow
through the shrader unless the device is in place. Therefore the
low pressure and SpeedTrol sensors/switches can be replaced
without reclaiming the refrigerant.
The Shrader that serves the high pressure switch does not
contain a core in order to maximize the functionality of the
safety. Therefore it cannot be replaced unless the
refrigerant has already been reclaimed.
Winterizing Water Coils
Coil freeze-up can be caused by such things as air stratification
and failure of outdoor dampers and/or preheat coils. Routine
draining of water cooling coils for winter shutdown cannot be
depended upon as insurance against freeze-up. Severe coil
damage may result. It is recommended that all coils be drained
as thoroughly as possible and then treated in the following
manner.
•
Fill each coil independently with an antifreeze solution
using a small circulating pump and again thoroughly drain.
•
Check freezing point of antifreeze before proceeding to next
coil. Due to a small amount of water always remaining in
each coil, there will be a diluting effect. The small amount of
antifreeze solution remaining in the coil must always be
concentrated enough to prevent freeze-up.
Note:
Carefully read instructions for mixing antifreeze
solution used. Some products have a higher freezing
point in their natural state than when mixed with water.
Table 31: 44" and 49" SWSI airfoil wheel-to-funnel
Relationship
Wheel-to-funnel relationship (in inches)
Wheel diameter
“A”
44
16.21
49
17.81
WARNING
Potential severe loss of charge may occur if the high refrigerant
pressure switch is replaced before reclaiming the refrigerant.
Replace switch after reclaiming refrigerant.
W h e e l
F u n n e l
A
