Replacing The Gas Valve Unit; Frequency Of Operator Checks - Mr. Heater MH40NG Operating Instructions And Owner's Manual

refer to Figure 7.
a. Remove pilot adjustment cover screw. Refer to Figure 8.
b. Turn inner adjustment screw clockwise to decrease or counter-
clockwise to increase pilot flame.
c. Always replace cover screw after adjustment and tighten firmly
to ensure proper operation.
Pressure regulator
adjustment (beneath
Manual gas
cover screw)
control knob
Wrench
boss
Gas
inlet
Pilotstat Pilot flow adjusting screw
power unit (beneath cover screw)
Figure 8. Top view of standard capacity gas control.
TABLE 4. TROUBLESHOOTING CHART
Below in chart form are various symptoms of a malfunctioning
system, possible defects that will cause there symptoms and
suggested corrective measure. The chart assumes that the proper
SYMPTOMS
Burner light off very slow
Burner light off very slowly
Color stays dull
Burner flashback
(roaring noise during operation
and ceramic grid surface will be dark)
Ceramic grid or burner sooting up
(when new or after cleaning)
Pilot cannot be ignited
Pilot lights but goes out
Pilot stays lit but main burner will not light
Failure to ignite
Install long
screw in
outside corner
Standard
pressure
regulator
("A" model)
Step
opening
Pilot gas
regulator
outlet
("C" model)
(pressure
tapping
directly
beneath)
CAUSES
Partially blocked pilot orifice
Pilot out of adjustment
Partially blocked burner orifice
Low gas pressure
Damaged burner
First check for damaged
burner orifice
If burner orifice is not damaged
then check for damaged manifold.
Blocked pilot orifice
Gas cock not in position
Pilot gas flow adjustment screw may be closed
Defective thermocouple
Defective control
Loose wire or improperly wired
Defective control
Blocked burner orifice
Main gas off
Air in gas line
Loose wire connections
Dirty wire connections
E6
Model # MH40NG/LP

13. REPLACING THE GAS VALVE UNIT

a. Remove the two gas valve unit wires at the gas control valve
labeled "PP."
b. Unscrew gas valve from gas piping.
c. Reconnect gas valve and unit wires to terminals "PP." Be sure
to leave thermostat wire on one terminal.

14. FREQUENCY OF OPERATOR CHECKS

Intermittent Use
Appliances that are used seasonally should be checked before
shutdown and again before the next use.
Dusty, wet or corrosive environments can cause the gas control
to deteriorate more rapidly, the system should be checked more
often.
The gas control should be replaced if:
a. It does not perform properly on checkout or troubleshooting.
b. The gas control knob is hard to turn or push down, or it fails
to pop back up when released.
gas pressure is available to the heater and that the lighting
procedure is as stated on the plate attached to the heater.
SOLUTIONS
Re-adjust pilot
Replace
Replace
Correct line pressure or call your gas
supplier
Replace
Replace if damaged
Replace
Replace
Gas control knob must be turned to pilot
and held depressed
open and adjust (see Figure 8)
Replace
Replace
Tighten connections, check wiring
diagram
Replace
Clean orifice or replace
open manual valves
Bleed gas line
Tighten wire connections
Clean terminals and secure terminals
Installation Instructions and owner's Manual