FIGURE 36
STATIC PRESSURE
TEST
MANOMETER
OIL UNIT
Page 26
VI−TYPICAL OPERATING CHARACTERISTICS
A−Blower Operation and Adjustment
NOTE− The following is a generalized procedure and
does not apply to all thermostat controls.
1− Blower operation is dependent on thermostat con
trol system.
2− Generally, blower operation is set at thermostat sub
base fan switch. With fan switch in ON position, blower
operates continuously. With fan switch in AUTO position,
blower cycles with demand.
3− In all cases, blower and entire unit will be off when line
voltage is disconnected.
B−Temperature Rise
Temperature rise for O23, OHR23, and OF23 units depends
on unit input, blower speed, blower horsepower and static
pressure. The blower speed must be set for unit operation
within the range of AIR TEMP. RISE
°
F" listed on the unit rat
ing plate.
To Measure Temperature Rise:
1.
Place plenum thermometers in the supply and return air
plenums. Locate supply air thermometer in the first hori
zontal run of the plenum where it will not pick up radiant
heat from the heat exchanger.
2.
Set thermostat to highest setting.
3. After plenum thermometers have reached their
highest and steadiest readings, subtract the two
readings. The difference should be in the range
listed on the unit rating plate. If the temperature is too low,
decrease blower speed. If temperature is too high in
crease blower speed to reduce temperature. To change
blower speed see Blower Speed section.
C−Blower Speed
Blower speed selection is accomplished by changing the
wires at the blower motor spade connector.
To Change Blower Speed
1− Turn off electric power to furnace.
2− Remove blower access door.
3−
Remove two screws located in the front blower rails.
4−
Pull blower assembly forward enough to disconnect the
motor leads.
5− Disconnect heating (red) and / or Cooling (black)
wire(s) from the motor. The common (white) wire al
ways remains on C = common.
6− Select the desired speed for heating and cooling
(H = high, M = medium, L = Low). Table 9 lists the
factory connections.
7− If cooling and heating speeds are to be the same
speed, disconnect and discard the cooling wire.
Jumper the A and H spade terminals on the BCC2 and
BCC3 board and jumper COOL to HEAT on the
ST9103A board. Run the heating terminal wire from
the BCC2, BCC3 and ST9103A board to the correct
spade connection on the blower motor.
8− To achieve low speed on continuous blower on the
ST9103A board, run a FIELD supplied wire (16 AWG
or larger) from blower motor low speed terminal to the
ST9103A CONT terminal.
TABLE 9
BLOWER SPEED SELECTION
Unit
Factory Connected
Speed Taps
Speeds
Unit
Cool
(Black)
Heat
(Red)
Speeds
Available
Q270
M
L
3
Q3105/120
H
M
3
Q5140/154
H
M
3
D−External Static Pressure
1.
Measure tap locations as shown in figure 36.
2. Punch a 1/4" (6 mm) diam
eter hole in supply and re
turn air plenums. Insert
manometer hose flush with
inside edge of hole or in
sulation. Seal around the
hose with permagum. Con
nect the zero end of the ma
nometer to the discharge (supply) side of the sys
tem. On ducted systems, connect the other end of
manometer to the return duct as above. For systems
with non−ducted returns, leave the other end of the
manometer open to the atmosphere.
3. With only the blower motor running and the evapo
rator coil dry, observe the manometer reading. Ad
just blower motor speed to deliver the air desired
according to the job requirements.
4.
Pressure drop must not exceed 0.5" W.C. (124.3 Pa).
5.
Seal around the hole when the check is complete.
