ETL MUA Controls, Installation, Operation And Maintenance Manual

Page: 60 / 84

60
Figure 27 - High Fire/Low Fire Bypass Screw Setting
Figure 28 - Pressure vs. Firing Rate
Final Start-up Procedure
1. With the air and burner systems in full operation and all ducts attached, measure the system airflow.
The motor sheave (pulley) is variable pitch and allows for an increase or decrease of the fan RPM. If
an adjustment is needed, refer to
“Pulley Adjustment” on page 54
. Reference
Table 10 on page 54
and
“Pulley Combination Chart” on page 56
for adjustment specifications.
2. Once the proper airflow is achieved, measure and record the fan speed with a reliable tachometer.
Caution - Excessive speed will result in motor overloading or bearing failure. Do not set fan
RPMs higher than specified in the maximum RPM chart.
See the troubleshooting guide for more
information.
3. Measure and record the
voltage
and
amperage
to the motor and compare with the motor nameplate
to determine if the motor is operating under safe load condition.
4. Once the rpm of the wheel has been properly set, disconnect power and recheck belt tension and
pulley alignment, refer to
Figure 23 on page 55
.
12
Modulating Valve
Adjustment Screw Location #1
Firing Mode
Low Fire = 0-5V DC
Modulation = 5-15V DC
High Fire = 15-24V DC
Regulator
Vent
Primary
Outlet
Inlet
Regulator
Adjusting Screw
Gas
Dial
Pilot
Outlet
Pilot Adjustment
Key (Under Cap)
Combination Gas Valve
Regulator
Adjusting Screw
(High Fire)
Bypass Adjustment
(Low Fire)
Modulating Valve
Adjustment Screw Location #2
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0 100000 200000 300000 400000 500000 600000
Firing Rate (BTU/Hr/Ft. of Burner)
Manifold Pressure - Inches
W
ater Column (wc)
Average Manifold Pressure vs. Firing Rate/Ft. of Burner
Natural
Gas
Propane
Gas