Cambridge Air Solutions.
32
M-Series Technical Manual
c.2. To change the profile plate pressure drop on
model M118 - M140 heaters with a Manual
Profile Adjust mechanism, locate the adjusting
mechanism in the gas train enclosure, loosen
the jam nut, and rotate the adjusting nut to
increase or decrease the pressure drops, as
required. Hold the adjusting nut and retighten
the jam nut to secure the mechanism.
c.3. For make-up air heaters with an Automatic
Profile Adjust system, check the Differential
Pressure Switch/Gauge and verify that the
left orange needle is set to the Minimum
setting and the right orange needle is set to the
Maximum setting as defined in the the column
labeled "Automatic Adjust" in the table on
page 31.
IMPORTANT
Call the Cambridge Air Solutions Customer Service
Group at 800-473-4569 if unable to obtain the required
pressure drop across the burner profile plate.
6. MOTOR AMP DRAW CHECK
IMPORTANT
The heater access doors must be closed for this test.
a. Check the motor current at the overload relay
on all three legs.
b. Turn the blower service switch to the “OFF”
position.
IMPORTANT
The average amps must not exceed the motor nameplate
FLA. High amperage may indicate excessive blower
RPM. Call the Cambridge Air Solutions Customer
Service Group at 800-473-4569 if unable to obtain
acceptable amperage readings.
7. CALCULATING AND ADJUSTING BURNER
MANIFOLD PRESSURE
a. Turn the disconnect switch off.
b.1. For units with an A1014 or an A1044 amplifier:
Disconnect #3 wire from the amplifier to drive the
modulating valve to full open and keep the heater in
continuous high fire.
b.2. For units with a signal conditioner (SC25S):
• Check control signal (4-20 mA, 0-10 VDC).
• Disconnect push ons at Sensor terminals T1 & T2 of the
SC25S. This will take the discharge temperature sensor
TS194(Q) out of the circuit.
• Place an 1100 Ohm resistor across T1 & T2. This will mimic
the sensing of ambient air. Since the TS194(Q) can no longer
sense temperature, it cannot override the control signal,
reduce the DC voltage and maintain discharge limits between
the set limits.
• Note polarity of the terminals: #5 is negative, #6 is positive.
