66
SERVICING
Total External Static
2. Measure the static pressure of the supply duct,
(Positive Pressure).
3. Add the two readings together.
NOTE: Both readings may be taken simultaneously and
read directly on the manometer if so desired.
4. Consult proper table for quantity of air.
If the external static pressure exceeds the minimum or
maximum allowable statics, check for closed dampers,
dirty filters, undersized or poorly laid out ductwork.
S-201 Checking Temperature Rise
Temperature rise is related to the BTUH output of the
unit and the amount of air (CFM) circulated over the heat
exchanger.
All units are designed for a given range of temperature
increase. This is the temperature of the air leaving the unit
minus the temperature of the air entering the unit.
The more air (CFM) being delivered through a given
unit the less the rise will be; so the less air (CFM)
being delivered, the greater the rise. The temperature
rise should be adjusted in accordance to a given unit
specifications and its external static pressure.
1. Check BTUH input to unit do not exceed input rating
stamped on rating plate.
2. Take entering and leaving air temperatures.
3. Select the proper speed tap or dip switch setting for
direct drive units.
4. For gas heat units, the airflow must be adjusted so
that the air temperature rise falls within the ranges
given stated on Data Plate by adjusting the variable
pitch sheave on the motor (see Blower Performance
section in appropriate Spec Sheet Manual for correct
pulley adjustment).
5. Take motor amperage draw to determine that the
motor is not overloaded during adjustments.
RISE = SUPPLY -
T
T
T
T
SUPPLY
RETURN
Checking Temperature Rise
S-206 Indoor Fan Rotation Check
Evaporator Fan Rotation Check (Three Phase Models
Only)
Check that fan rotates counter-clockwise when viewed
from the drive side of unit and in
accordance with rotation
arrow shown on blower housing. If it does not, reverse any
two incoming power cables at Single Point Power Block. In
this case, repeat bearing check.
Do not attempt to change load side wiring. Internal wiring
assures all motors and compressors will rotate in correct
direction once evaporator fan motor rotation check has
been made.
S-300 Testing Primary Limit Control
DRG units use a snap-disk type primary limit device.
Sometimes referred to as “stat on a stick”. The limit setting
is fixed and must not be readjusted in the field.
Содержание DRG0361DL00001S
Страница 20: ...20 SYSTEM OPERATION...