Product manual

IOMM ACR/AGR-1 43
DX Evaporator
The evaporator is of the direct expansion type with removable internally finned tubes. The copper
tubes are individually rolled into heavy duty steel tube sheets and sealed by a steel refrigerant head.
The water connection nozzles that enter and leave the shell are on the same side of the unit. The
water inlet is located on the end having the refrigerant connections. No special attention is required
for the cooler except that clean, filtered water should be supplied.
Sequence of Operation
AGR-AM, Remote Evaporator
Starting
With control power on, 115Vac power is applied through F1 to the compressor crankcase heaters and
control transformer T2. T2 supplies 24Vac to the Global UNT controller. The green light on the Global
UNT controller will begin to flash. The panel Alarm Light will illuminate. Put the System Switch S1
into the AUTO position. This applies power to the control circuit and a digital input to the Global
UNT controller. Control power is applied through the Mechanical High Pressure Control (MHP) to the
compressor inherent motor protectors (MP). After approximately a two (2) minute time delay, the MP’s
are energized and the panel Alarm Light will turn off. If this is a first start, depress the Freezestat Reset
Button for 1 seconds. There is a default time delay of 5 minutes on the Freezestat reset.
Start the chiller water pump and put the chiller into the run mode by closing the remote start / stop
input or time clock input. After the flow switch has made, the Global UNT controller will begin to ramp
up if the chilled water temperature is above the leaving water setpoint dial plus 1/2 the control band
dial. Internal timing functions will vary the stage up time.
The starting refrigerant circuit is switched every ten (10) starts. This maintains equal starts on the first
compressor of each refrigerant circuit. Refrigerant circuit #1 is assumed as the starting circuit for the
following.
When the first stage of cooling is required, relay BO1 will be energized and if the evaporator pressure
is above the LPSS (low pressure starting setpoint), relay BO7 will be energized starting Compressor #1
and energizing the liquid line solenoid valve (SV1) through control relay CCR1.
As additional cooling is required, relay BO2 will be energized and if the evaporator pressure is above
the LPSS (low pressure starting setpoint), relay BO8 will be energized starting Compressor #2 and
energizing the liquid line solenoid valve (SV2) through control relay CCR2.
As additional cooling is required, relays BO3 and BO6 will deenergize compressor unloaders.
The reverse will occur as the cooling requirement is reduced. Relays BO6 and BO3 will open
energizing the compressor unloaders. Relay BO2 will open closing the #2 refrigerant liquid line
solenoid valve. Compressor #2 will continue to operate until the LPLL (low pressure low limit) is
reached or the PDTD (pumpdown delay time period) timer times out. Relay BO8 will open stopping
compressor #2. Relay BO1 will open closing the #1 refrigerant liquid line solenoid valve. Compressor
#1 will continue to operate until the LPLL is reached or the PDTD timer times out. Relay BO7 will open
stopping compressor #1. The compressors will not cycle on if the evaporator pressure exceeds the
LPSS setpoint. The Global Reciprocating Chiller has a one-time pumpdown.