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Do not short thermostat wires since this will damage the
control transformer. The total resistance of these low
voltage wires must not exceed one (1) ohm. Any
resistance in excess of 1 ohm may cause the control to
malfunction because of the excessive voltage drop.
Thermostat Heat Anticipator
The thermostat heat anticipators should be set to .4 amps
on single or two stage thermostats.
IMPORTANT: Upon completion of wiring check all electrical
connections, including factory wiring within the unit, make
sure all connections are tight. Replace and secure all
electrical box covers and access doors before leaving the
unit or turning on the power to the unit.
Thermostat
The room thermostat should be located on an inside wall
approximately 56" above the floor where it will not be
subject to drafts, sun exposure or heat from electrical
fixtures or appliances. Follow manufacturer's instructions
enclosed with the thermostat for general installation
procedure. Four color coded insulated wires (minimum #18
AWG) should be used to connect thermostat to unit.
Power and Control Wiring
Field wiring to the unit must conform to provisions of the
current NEC ANSI/MFPA No. 70 or CEC and/or local
ordinances. The unit must be electrically grounded in
accordance with local codes or in their absence with the
NEC/CEC voltage tolerances which must be maintained at
the compressor terminals during starting and running
conditions as indicated on the unit rating plate.
The wiring entering the cabinet must be provided with
mechanical strain relief.
A fused disconnect switch should be field supplied
REFRIGERATION SYSTEM
R-410a Refrigerant Precautions
WARNING
DO NOT USE R-22 SERVICE EQUIPMENT OR
COMPONENTS ON 410-A REFRIGERANT EQUIPMENT.
FAILURE TO FOLLOW THIS WARNING COULD RESULT
IN PERSONAL INJURY OR EQUIPMENT DAMAGE.
• R-410A refrigerant operates at much higher pressure
than R-22 refrigerant
• Only use service equipment and replacement components
designed to operate with R-410A refrigerant
• Recovery cylinder service pressure rating must be 400
psig, DOT4BA400 or DOT BW400
• Hose pressure rating must be 700 psig
• Manifold set ratings should be 700 psig high side and
180 psig low side
• Leak detectors should be designed to detect R-410A
refrigerant
• R-410A refrigerant systems should be charged ONLY with
liquid refrigerant
• Only use liquid line filter driers with rated working
pressures above 600 psig
• Do not expose oil to atmosphere.
• Use only TXV rated for use with R-410A refrigerant
Subcooling Charging
The unit comes from the factory charged with refrigerant.
If the unit needs additional refrigerant follow standard
procedures for charging systems that use R-410A
refrigerant.
Coils with TXVs should be charged 15-17 degrees F (+ or –
one degree) of sub-cooling. For proper sub-cooling
readings, a standard high side gauge is required for pressure
readings.
Use the chart below to determine the required sub-cooling
value.
Instructions
1. Measure the outdoor air temperature. (T1)
2. Measure the discharge pressure at the service port
provided and determine the liquid refrigerant
temperature by the scale on the high side pressure
gauge. (T2) In cooling mode take reading at the
indoor coil before TXV.
3. Measure the liquid line temperature on the liquid line.
(T3) In cooling mode take reading at the indoor coil
before TXV.
4. Subtract T3 from T2. (T2 - T3) This is the subcooling
value. Compare this value and the outdoor temperature
(T1), to the chart below. If the value is below the line,
add refrigerant. If the value is above the line, remove
refrigerant charge. When removing refrigerant, always
use standard reclaim procedures.
NOTE: For the majority of installations no adjustment to
the TXV setting is required. However, if the measured
superheat at the evaporator is less than 4° or greater
than 8° an adjustment is required. The adjustment stem
is at the base of the valve under the flare nut. To increase
superheat tighten the stem clockwise and to decrease
superheat back-out the stem counter-clockwise. Use a
1/4" refrigeration service wrench for this function.
NOTE: When removing refrigerant, always use standard
reclaim procedures.
SUBCOOLING CHART
17.5
17
16.5
16
15.5
55
OUTDOOR TEMPERATURE (°F)
10
65
75
85
95
105
115
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