M-Series Technical Manual
31
Cambridge Air Solutions
CAUTION:
Do not proceed with start-up unless the supply
voltage agrees with the nameplate voltage. If the
supply voltage does not agree with the nameplate
voltage, check with your local Cambridge Air
Solutions representative or Cambridge Air
Solutions’s Customer Service Group at 800-473-
4569 to determine what changes are required.
3. GAS SUPPLY PRESSURE VERIFICATION
Verify that the gas supply pressure complies with the
heater nameplate.
CAUTION:
Do not proceed with start-up unless the gas supply
pressure agrees with the nameplate pressure
requirements. If the gas supply pressure is in
excess of the maximum pressure indicated, a
separate positive shut-off high pressure regulator
must be added upstream of the heater’s low
pressure manual shut-off valve. If a high pressure
regulator is needed and has not been installed,
check with your local Cambridge Air Solutions
representative or Cambridge Air Solutions’
Customer Service Group at 800-473-4569 to
determine the size and capacity requirements that
are required.
4. BLOWER ROTATION CHECK
a. Open the access door on the electrical control enclosure
side and turn the disconnect switch on.
WARNING:
When the disconnect switch is activated with
the enclosure open, live power is present. Only
experienced technicians with knowledge and
respect for live power should proceed beyond this
point.
b. Turn the blower service switch to the
“
LOCAL
”
position. The blower motor will start after the
motorized damper opens. Then turn the blower service
switch to the
“
OFF
”
position and verify the blower is
rotating in the proper direction. (See the directional arrow on
the blower housing.)
IMPORTANT
On a three phase system, the rotation direction of the
blower may be reversed by switching any two wires
located on the downstream side of the service disconnect.
The electrical supply to the heater must be turned off
prior to switching the wiring.
IMPORTANT
Indications of loose belts include barking or squealing
when the blower starts. If these symptoms occur,
please refer to the BELT TENSIONING section of the
MAINTENANCE INSTRUCTIONS (page 60). Periodic
belt adjustments may be required.
5. BURNER PROFILE DAMPER PRESSURE
DROP CHECK
IMPORTANT
The blower access doors must be in place when adjusting
the profile plate.
IMPORTANT
Verify that the inclined manometer, if applicable, is level
and zeroed for proper readings to be obtained.
a. Turn the blower service switch to the “LOCAL”
position. (Note: The burner service switch must
remain in the “OFF” position)
b. Check the pressure drop across the burner profile
plate to ensure that it complies with the table
below:
Profile Plate Pressure Drop -
Blower Only
(inches WC)
Gas
Type
Models
Filters Manual
Adjust
Automatic
Adjust
Min. Max.
Natural
M110-M140
No
0.68
0.62 0.72
M110-M136
Yes
0.72
M140
Yes
0.75
LP
M110-M140
No
0.90
0.84 0.94
M110-M136
Yes
0.94
M140
Yes
0.97
c.1. To change the profile plate pressure drop on
model M110 - M115 heaters with a Manual
Profile Adjust mechanism, locate the adjusting
mechanism in the electrical control enclosure,
loosen the lock-down bolt, and rotate the
adjuster to increase or decrease the pressure
as required. Retighten the lock-down bolt to
secure the mechanism.
