88
Direct-Fired Make-up Air •
MUA-SVX01A-EN
Trouble Shooting
Excessive negative
burner pressure.
Close main gas supply,
and measure manifold
pressure with blower
operating. Reading should
be less than 1.5" w.c.
negative pressure.
a. If reading is
greater than
1.5" negative
pressure,
check for
clogged filters
or other inlet
air restrictions.
Consult factory
for other
solutions.
5. Continuous high fire
(electronics ok).
Foreign object holding
valve open.
Remove bottom plate and
inspect valve and seat.
a. Clean seat.
Clean valve or
replace if
necessary.
Plunger jammed.
Inspect. Plunger should
be smooth and clean and
operate freely in solenoid
sleeve.
a. Clean or
replace
plunger.
6. Incorrect high fire.
Inlet pressure too low.
Read pressure at inlet to
modulating valve using a
manometer with unit
operating at full fire.
Pressure should be equal
to the sum of outlet
pressure setting plus
pressure drop of the valve
plus 1.0" w.c.
a. Increase
inlet pressure
if possible or
change to
larger valve.
Consult factory
about
possibility of
using special
spring to
reduce
pressure drop
on selected
installations
Incorrect outlet
pressure adjustment of
pressure regulator.
Read outlet pressure
using manometer and
compare with the
pressure stated on the
specification plate.
a. See valve
adjustments
on page 37.
7. Continuous minimum
discharge air
temperature.
Faulty amplifier.
Follow procedures
outlined in
a. If amplifier
is proven at
fault, install
replacement
amplifier.
Incorrect space
temperature calibration.
Follow procedures
outlined in
a. If proper
action is
obtained, first
check room
sensor/
selector.
Table 18.
Trouble shooting guide for Modulationg Room Temperature (MRT)
controls
Symptom
Probable Cause
Field Test
Solution
*
Control circuits external to MRT controls can cause burner malfunction. Always check manual valve
to be certain gas is on, and check limit controls for normal operation.
