A
HE, DE & RE MANUAL
IOM-26
25 of 33
Oct 12 R4
9.
Do not adjust the main pressure regulator (appliance regulator). The firing rate has been factory
set and should not require any adjustment. The air temperature rise should be as listed on the
nameplate. If not, the air volume through the unit should be adjusted. This may be accomplished
by adjusting the blower speed, by balancing dampers, or both. The air temperature rise and unit
inlet gas pressure should be measured when the modulating valve is wide open.
The modulating valve can be made to stay wide open by turning the modulating temperature control
up to its maximum setting and removing its sensing element from the air stream and exposing it to
a cool temperature. If unit inlet gas pressure is less than minimum inlet pressure on the unit label,
the unit may not have enough heat on the coldest (design ambient) days. With proper airflow the
flame should be approximately 16" long and tipped with a reddish orange flame. If the flame is
much longer and mostly yellow, or it the flame is much shorter and florescent blue only, check the
separate trouble shooting guide for the necessary adjustments.
10.
Confirm gas inlet pressure matches unit rating plate at high fire.
11.
Perform a flame supervision check as follows: With the burner firing, close the main manual firing
valve and the pilot firing valve. The automatic valves should close within 4 seconds and the flame
ignition control should lock out within 10 to 15 seconds. To return to normal operation, reset the
flame safeguard and open the manual valves.
12.
Check for leaks on unit piping with unit firing.
13.
Check the low limit (optional) by adjusting the setting above the discharge set point until the unit
shuts down. The low limit will not shut the units down until the bypass timer contact has opened.
14.
Return the low limit and temperature controller to their proper settings (see control settings).
15.
The blower motor and particularly the belt, should be checked after the previous tests and
adjustments have been completed. The belts have a tendency to stretch during the first few weeks
of operation and may need to be adjusted. The amperage draw of the motor should be checked
with an ammeter and should not exceed the rated amperage stated on the motor rating plate.
Otherwise, the motor overload will lockout the motor.
If the installation has an exhaust fan, adjust the exhaust air to match the supply air within ± 10%.
CONTROL SETTINGS
The following settings of the adjustable controls are acceptable for most applications. Refer to unit function
and wiring diagram for settings specific to your unit.
Single and two stage ductstat: 55
– 70°F (13 – 21°C).
Single, two stage and modulating space thermostat: 68
– 74°F (20 –23°C).
Remote temperature selector: 60
– 70°F (16 – 21°C).
