035-14511-000 REV B (1299)
Unitary Products Group
11
®
Two Stage Furnaces - The ideal fan setting is to set the high
speed (second stage) air flow at the fan motor high speed
and the low speed (first stage) airflow at the fan low speed. If
the low speed air flow is too high, unsatisfactory dehumidifac-
tion may occur on first stage operation. To correct for unsatis-
factory dehumidification, either add a dehumidistat per figure
10 or change the blower motor for better air flow perfor-
mance.
SYSTEM START-UP
ENERGIZE CRANKCASE HEATER
This unit is equipped with a crankcase heater for the compressor.
A warning label with an adhesive back is supplied in the unit
installation instruction packet. This label should be attached
to the field supplied disconnect switch where it will be easily
seen. See below.
In order to energize the crankcase heater:- Set indoor two
stage cooling thermostat to “OFF” position.- Close the line
power disconnect to the unit.
CHECKING SYSTEM CHARGE
The factory charge listed in the tabular data sheet and unit
nameplate data is for the smallest matching indoor coil and
15 feet of line set. The tabular data sheet also lists the addi-
tional charge for other matching indoor coils and the addi-
tional charge for longer line sets.
The H*TS condensing unit must only be used with the match-
ing thermostatic expansion valve kit listed in the tabular data
sheet. The best way to check the system charge is by checking
the system subcooling during the second stage of operation.
SERVICING AND VERIFY:
For 2nd stage (2 cylinder) operation, the recommended sub-
cooling for H*TS036 is 14°F and 20°F for all other models.
For 1st stage (1 cylinder) operation, the recommended sub-
cooling is 10F for all models.
1.
Set the system running in the second stage (2 cylinder
operation) by setting the thermostat at least 6°F below
the room temperature. Short the “TEST” pin to bypass
the 5 minute anti-short cycle timer if necessary.
2.
Operate the system for a minimum of 15 to 20 minutes.
3.
Refer to the tabular data sheet for the recommended air-
flow and verify this indoor air flow (it should be about 400
SCFM per ton)
4.
Measure the liquid refrigerant pressure P and tempera-
ture T at the service valve.
5.
Calculate the saturated liquid temperature ST from Table
1.
6.
Subcooling temperature TC = Saturated Temperature ST
- Liquid temp T
The recommended subcooling level should be about 14+/-3°F
for H*TS036 and 20+/-3°F for all other models. Add charge if
the calculated subcooling temperature TC in step 6 is lower
than the recommended level. Remove and recover the refrig-
erant if the subcooling TS are higher than the recommended
level.
IMPORTANT
An attempt to start the compressor without at least 8
hours of crankcase heat will damage the compressor.
It is unlawful to knowingly vent, release or discharge
refrigerant into the open air. It is necessary to recover
the refrigerant during any repair or installation of the
system.
WARNI
Refrigerant charging should only be carried out by a
qualified air conditioning contractor.
Example: The pressure P and temperature T measured at
the H*TS024 service port is 220 Psig and 95°F. From Table
1, page 12, the saturated temperature for 220 Psig is 108.
The subcooling temperature TC = 108 - 95 = 13°F.
CAUTIO
