Thermostat; Safety Valve; Thermocouple; Burner - Dometic RM2150 Series Service Manual

7.3 THERMOSTAT

On the LP gas mode, full line pressure is directed
through the thermostat to the burner until the thermostat
senses that the refrigerator cabinet has reached proper
cooling temperature. At that time an internal valve
closes and redirects the gas flow through the bypass
screw. This reduces the amount of LP gas going to the
burner assembly. The gas flow remains in this "bypass"
mode until the thermostat senses that the refrigerator
cabinet needs more cooling. Again, the thermostat
directs LP gas flow through the thermostat at full line
pressure until the cabinet temperature is sufficient. The
thermostat is calibrated by the manufacturer so that at
mid-range the cabinet temperature should be approxi-
mately 40 degrees Fahrenheit. To check the calibra-
tion of the thermostat, place a container of water in
the cabinet of the refrigerator and operate at mid-range
setting until the thermostat is satisfied. Then, check the
temperature of the water. It should be approximately 40
degrees. We do not recommend any calibration in the
field. If calibration is not correct, replace the thermostat.
To check the thermostat for proper gas flow, set the
thermostat to maximum and check the gas pressure at
the pressure test port. It should be line pressure,
between 11 to 12 inches water column. If you have less
than 11 inches of water column pressure, the next step
would be to shut off the gas supply and remove the
bypass screw. Then install a bypass screw that does
not have the small o-ring on it. Next, turn on the gas
supply and take a reading. If the manometer now reads
11 inches of water column, the thermostat is defective
and must be replaced. If the bypass screw test shows
no change in pressure, the problem lies in the filter (See
Sec. 7.2) the shut-off valve (See Sec. 7.1) or the gas
supply (See Sec. 6). Shut off the gas supply, remove
the bypass screw, replace it with the original one that
has an o-ring and turn the gas on.
NOTE: Check for leaks with an approved LP gas leak
solution whenever any part of the gas system has been
worked on or the system has been separated.

SAFETY VALVE

7.4
The safety valve is an assembly that shuts off the
supply of LP gas to the burner if the flame goes out for
any reason. This is to ensure that a concentration of
unburned gas does not accumulate in the refrigerator
vent area. To check the safety valve, use a known good
thermocouple (see SEC. 7.5) and install into the safety
valve. Next, supply flame to the tip of the thermocouple
for 2 to 3 minutes while holding in on the safety valve
stem. Next, remove flame from thermocouple tip and
release safety valve stem. The safety valve should hold
in for at least 30 seconds. If it releases earlier than 30
seconds, replace the safety valve.
8

7.5 THERMOCOUPLE

The thermocouple is a component extending above the
burner assembly so the tip is in the path of the flame. It
will produce 14 to 30 millivolts DC in normal operation.
To check the thermocouple, use a known good safety
valve (See Sec. 7.4) and attach to the thermocouple.
Next, supply flame to the tip of the thermocouple for 2
to 3 minutes while depressing the safety valve. Remove
the flame and release the safety valve. The valve
should hold for at least 30 seconds. If it does not hold
the safety valve open for 30 seconds, replace the
thermocouple. If it does hold for 30 seconds or more,
the thermocouple is good, do not replace it.
NOTE: Be sure the tip on the thermocouple is clean.

7.6 BURNER

The burner is a slotted metal tube located below the flue
tube on the cooling unit. It should be level and the slots,
in the burner, should be directly below the flue tube.
The burner should be cleaned periodically, at least once
a year. To clean the burner, remove from the refrigera-
tor and check for any foreign residue that could cause a
deflection of the gas flow or the flame. Next, soak the
burner in an alcohol based solvent and allow to air dry.
After cleaning, reinstall in the refrigerator.

7.7 FLUE BAFFLE

The flue baffle is designed to concentrate the heat from
the gas flame and direct it to a certain area of the flue
tube. It should be cleaned periodically, at least once a
year. To clean, remove from the flue tube and check for
any damage, then clean thoroughly.
The length of the flue baffle assembly (flue baffle
and wire) on the RM2150 and RM2190 is 13-1/8";
On the RM2201 it is 13-3/4". The flue baffle itself
should measure 3-15/16" long and 9/16" wide on
the RM2150, RM2190 and RM2201. The proper
position of the baffle above the burner is 3-1/2" on
RM2150 and RM2190; and 3-3/8" on the RM2201.