Cambridge Air Solutions.
38
M-Series Technical Manual
4. BLOWER ROTATION CHECK
a. Open / remove the blower access door(s)
on the electrical control enclosure side of
the heater and verify the disconnect switch
is in the “ON” position.
WARNING:
When the disconnect switch is activated with
the electrical control enclosure door open, live
power is present. Only experienced technicians
with knowledge and respect for live power should
proceed beyond this point.
b. Place the blower service switch in the
“LOCAL” position. Once the damper
(inlet / discharge) opens and makes the
end switch (if applicable), press the
“HAND” button on the VFD keypad.
The VFD will energize the blower motor.
Allow the blower to run for a few seconds
then turn the blower service switch to
the “OFF” position. Verify the blower is
rotating in the proper direction. (See the
directional arrow on the blower housing.)
Once the blower rotation is verified, re-
install the blower access door(s) and latch.
5. BURNER PROFILE DAMPER PRESSURE
DROP CHECK
IMPORTANT
The blower access doors must be in place when verifying
the profile static on the photohelic gauge. Verify the
photohelic gauge is zeroed with the blower in the
“OFF” position.
a. Place the blower service switch in the
“LOCAL” position and verify the VFD
display is still in the “HAND” mode.
(Note: The burner service switch must
remain in the “OFF” position)
b. Once the Hz on the VFD display stop
climbing, verify the VFD is showing 60
Hz on the display. If the Hz are not at 60,
press the “UP” arrow on the VFD keypad
until the Hz reach 60. Verify the pressure
reading on the photohelic gauge (black
needle) is between the two orange needles.
Verify the photohelic settings (orange
needles) comply with the settings below:
Profile Plate Pressure Drop -
Blower Only (inches WC)
Natural Gas
The left orange needle on the photohelic should be set to
.62” and the right orange needle should be set to .72”. Be
sure right needle does not exceed .72”.
LP Gas
The left orange needle should be set to .84” and the right
orange needle should be set to .94”. Be sure the right
needle does not exceed .94”.
NOTE: The unit is equipped with a low temperature
cutout (LTC) relay; it is a 3 1/2 minute time delay relay
that is part of the freeze protection circuit. The LTC
monitors the incoming air temperature and cycles the
unit off in 3 1/2 minutes if the incoming air temperature
is 45°F or below and the burner is not energized. If the
outdoor temperature is 45°F or below and the blower
shuts down, place the blower service switch in the
“OFF” position for 2-seconds. Then place the blower
service switch back to the local position. This may have
to be done several times.
If the pressure measured on the photohelic gauge does
not settle between the two orange needles, please contact
Cambridge Air Solutions’s Customer Service Group at
800-473-4569.
6. MOTOR AMP DRAW CHECK – HIGH SPEED
IMPORTANT
The blower access doors must be closed for the duration
of the start-up procedure.
-Note: The burner service switch must remain in the
“OFF” position.
-Note: The VFD should still be in “HAND” mode and
the Hz at 60.
