Specifications

Open the high side valve on the manifold only and allow the refrigerant to ﬂ ow until the system

pressure equalizes. At this point the system will have 78-85% of the total refrigerant charge.

Start the (evaporator) motor(s). Start the compressor(s) and check the operating pressures and

temperatures.

A quick and easy way to run the blower and compressor is using the manual switches on the

unit’s microprocessor. Switch the blower and compressor manual switches to the ON position. All

automatic control is disabled but safety switches will remain functional.

Before starting a compressor, the crankcase heaters should be energized for a minimum of 12

hours to reduce the possibility of liquid slugging on start-up. Failure to energize crankcase heaters

could result in compressor damage.

Start the evaporator fan and verify the fan rotation. From a vacuum, add liquid refrigerant to the

high side of the system until the pressures equalize. Start the compressor. Check the liquid line

sight glass to get a feel for the approximate charge. Bubbles in the sight glass are not unusual at

this point and be caused by ﬂ ashing from liquid pressure drop, low sub-cooling or low charge. It is

likely that more refrigerant will be required to complete the charging procedure.

If the receiver (head) pressure is below 350 PSIG for R-410A, block part of the condenser coil

surface until the pressure rises to 350 PSIG or higher. If the receiver (head) pressure is below 230

PSIG with R-407C, block part of the condenser coil surface until the pressure rises to 230 PSIG or

higher. During extremely cold weather all the condenser fans have to be de-energized to maintain

head pressure. Add refrigerant to the system until the ball in the sight-glass is at the 1/3 level.

After the system is allowed to stabilize, the superheat at the compressor suction line (reading from

at least 6 inches from the sight glass) should be 8 – 15°F. Remove any blocks that may have been

used on the condenser coil. If the ambient temperature is below 60°F, some of the refrigerant will

be backed up in the condenser coil causing the liquid level in the receiver to drop (this is normal).

Note: Charging to a full liquid line sight glass should never be the sole means of determining the

correct refrigerant charge. Other parameters such as superheat, suction pressure, head pressure,

sub-cooling and ambient temperature are also important. A system charged to a clear sight glass

is often overcharged.

5.4 Water/Glycol Cooled Systems

5.4.1 Water/Glycol Cooled Systems Charging

All water/glycol cooled units are factory charged with refrigerant. The water regulating valve

should be adjusted to maintain a discharge pressure between 340–390 PSIG for R-410A and 230-

260 for R-410A. Saturated suction pressure should be 100 PSIG or higher with R-410A and 58 PSIG

or greater with R-407C. The superheat at the compressor suction line at least 6 inches away from

compressor should be between 8-15°F.

Field charging water/glycol system should be done by referring to the unit electrical nameplate

for factory charge. Although this ﬁ gure represents the original factory charge, it is still necessary

to measure and note proper unit operation including superheat, head and suction pressure. Some

adjustment to charge may be required.