GSX14 Service Manual

SERVICING
113
C IRCULATOR B LOWER
This air handler is equipped with a multi-speed circulator
blower. This blower provides ease in adjusting blower
speeds. The Specification Sheet applicable to your model
provides an airflow table, showing the relationship between
airflow (CFM) and external static pressure (E.S.P.), for the
proper selection of heating and cooling speeds. The heating
blower speed is shipped set at 21kW or 25kW, and the
cooling blower speed is set at “D”. These blower speeds
should be adjusted by the installer to match the installation
requirements so as to provide the correct electric heating
CFM and correct cooling CFM.
Use the CFM LED (green) to obtain an approximate airflow
quantity. The green CFM LED blinks once for each 100 CFM
of airflow.
1. Determine the tonnage of the cooling system installed
with the air handler. If the cooling capacity is in BTU/hr
divide it by 12,000 to convert capacity to TONs.
Example: Cooling Capacity of 30,000 BTU/hr.
30,000/12,000 = 2.5 Tons
COM
TH
TR
DE
CAS
HUM
O
R
2
1
C
2
1
ST4
ST3
ST2
ST1
3A
C
Y2
24VAC
FUSE
W1W2
R
C
G
W1
W2
Y1
3
2
Dip Switches
Green CFM LED
Seven Segment
LED
Auxiliary
A
larms
2. Determine the proper air flow for the cooling system.
Most cooling systems are designed to work with air flows
between 350 and 450 CFM per ton. Most manufacturers
recommend an air flow of about 400 CFM per ton.
Example: 2.5 tons X 400 CFM per ton = 1000 CFM
The cooling system manufacturer’s instructions must be
checked for required air flow. Any electronic air cleaners or
other devices may require a specific airflow; consult instal-
lation instructions of those devices for requirements.
3. Knowing the air handler model, locate the high stage
cooling air flow charts in the Specification Sheet appli-
cable to your model. Look up the cooling air flow
determined in step 2 and find the required cooling speed
and adjustment setting.
Example: An AVPTC30C14 air handler installed with
a 2.5 ton air conditioning system. The air flow needed
is 1000 CFM. Looking at the cooling speed chart for
AVPTC30C14, find the air flow closest to 1000 CFM. A
cooling airflow of 1000 CFM can be attained by setting
the cooling speed to “C” and the adjustment to “0” (no
adjustment).
Communicating Board