Dometic MPD 93756 Mode D'emploi page 5

PREVENTATIVE MAINTENANCE
Spiders, mud wasps, and other insects can build nests in burner tube.
This causes poor combustion, delayed ignition or ignition outside
combustion tube. Listen for a change in burner sounds or in flame
appearance from a hard blue flame to a soft lazy flame or one that is
very yellow. These are indications of an obstruction in burner tube
( 9-C). Inspect and clean on a regular basis.
FIG
a. Remove air shutter screw (
down burner tube.
b. Run a flexible wire brush down burner tube (
visible at end of burner tube.
c. Vacuum burner where it enters combustion tube.
d. Return air shutter to original position and replace screw.
e. The orifice, burner tube and shutter must be aligned so that the shutter is not
binding on the air tube.
HOW TO CLEAN PILOT MODELS
1. Check main burner orifice and pilot assembly for contamination
(dirt, spider webs, etc.).
2. Clean main burner tube with small brush.
3. Main burner adjustment - open air shutter 1/4 way.
4. Low pilot flame. Check for contamination - if clean have the pilot
orifice replaced.
HOW TO CLEAN ELECTRONIC IGNITION MODEL
1. Check main burner orifice.
2. Clean and adjust main burner.
3. Main burner and valve manifold must align with each other
4. Check electrode for cracked porcelain.
5. Check electrode for proper gap - 1/8" between electrode and
ground.
6. If module board functions intermittently, remove board and clean
terminal block with pencil eraser.
WATER HEATER TANK CARE
SCALDING INJURY
Turn off water heater and allow time for water to cool before
•
removing drain plug to flush tank.
WINTERIZING (FLUSHING) INSTRUCTIONS
To insure the best performance of your water heater and add to the life
of the tank, periodically drain and flush the water heater tank. Before
long term storage or freezing weather drain and flush the tank.
1. Turn off main water supply (the pump or water supply (the pump or
water hook up source).
2. Drain Water Heater Tank by removing the drain plug. If the water
flows sporadically or trickles instead of a steady stream of water, we
recommend the following action; first open the Pressure
Temperature Relief Valve to allow air into the tank and secondly,
take a small gauge wire or coat hanger and poke through the drain
opening to eliminate any obstructions.
3. After draining the tank, because of the placement of the Drain Plug,
approximately two quarts of water will remain in the tank. This water
contains most of the harmful corrosive particles. To remove these
harmful corrosive particles flush the tank with either air or water.
Whether using air or water pressure, it may be applied through the
inlet or outlet on the rear of the tank or the Pressure Temperature
Relief Valve. (If using the Pressure Temperature Relief Valve the
Support Flange must be removed). The pressure will force out the
remaining water and the corrosive particles.
If you use water pressure, pump fresh water into the tank with the
assistance of the on-board pump or use external water for 90
seconds to allow the fresh water to agitate the stagnant water on
the bottom of the tank and force deposits through the drain
opening. Continue repeating adding water and draining until the
particles have been cleared from the water remaining in the tank.
4. Replace the Drain Plug and close the Pressure Temperature Relieve
Valve. The approximately two quarts of water remining in the tank
after draining will not cause damage to the tank should freezing occur.
9-A) and slide air shutter (
FIG FIG
9-C) until it is
FIG
WARNING
PRESSURE-TEMPERATURE RELIEF VALVE
Do not place a valve, plug or reducing coupling on outlet part of
•
pressure-temperature relief valve.
9-B)
A Pressure Temperature Relief Valve, dripping while the water heater is
running, DOES NOT mean it is defective. During normal expansion of
water, as it is heated in the closed water system of a recreation vehicle,
the Pressure Temperature Relief Valve will sometimes drip. The
Dometic water heater tank is designed with an internal air gap at the
top of the tank to reduce the possibility of dripping. In time, the
expanding water will absorb this air and it must be restored.
Turn off water heater before opening pressure-temperature relief
•
valve to establish air space. Storage water must be cool.
TO REPLACE THE AIR GAP FOLLOW THESE STEPS:
1. Turn off main water supply (the pump or water hook up source).
2. Let water cool or let run until cool.
3. Open the hot water faucet closest to the water heater.
4. Pull handle of pressure temperature relief valve straight out and
allow water to flow until it stops.
5. Allow pressure temperature relief valve to snap shut; close faucet;
turn on water supply.
6. Turn on water heater and test.
• At least once a year manually operate pressure-temperature relief
10 ).
valve (
FIG
When pressure-temperature relief valve discharges again, repeat above
procedure. For a permanent solution, we recommend one of the following:
• Install a pressure relief valve in cold water inlet line to water heater
and attach a drain line from valve to outside of coach. Set to relieve
at 100-125 PSI.
• Install a diaphragm-type expansion tank in cold water inlet line.
Tank should be sized to allow for expansion of approximately 15 oz.
of water and pre-charged to a pressure equal to water supply
pressure. These devices can be obtained from a plumbing
contractor or service center.
FLUSHING TO REMOVE UNPLEASANT ODOR
A rotten egg odor (hydrogen sulfide) may be produced when the electro
galvanic action of the cladding material releases hydrogen from the
water. if sulfur is present in the water supply the two will combine and
produce an unpleasant smell.
1. Turn off main water supply. Drain the water heater tank and reinstall
drain plug. Remove the pressure-temperature relief valve. Mix
solution of 4 parts white vinegar to two parts water. With a funnel,
carefully pour solution into tank.
2. Cycle water heater with the above solution, letting it run under
normal operation 4-5 times.
3. Remove the drain plug and thoroughly drain all water from the tank.
Flush the water heater to remove any sediment. You may flush the tank
with air pressure or fresh water. pressure may be applied through either
the inlet or outlet valves on the rear of the tank or through the pressure-
temperature relief valve coupling located on the front of the unit.
TO FLUSH TANK WITH AIR PRESSURE
Insert your air pressure through the pressure-temperature relief valve
coupling. With the drain valve open, the air pressure will force the
remaining water out of the unit.
To flush tank with water pressure:
Fresh water should be pumped into the tank with either the onboard
pump or external water pressure. Continue this flushing process for
approximately 5 minutes, allowing the fresh water to agitate the
stagnant water on the bottom of the tank and forcing the deposits
through the drain opening.
4. Replace drain plug and pressure-temperature relief valve.
5. Refill tank with fresh water that contains no sulphur.
The Dometic water heater is designed for use in a recreation vehicle. If
you use your vehicle frequently or for long periods of time, flushing the
water heater several times a year will prolong the life of the storage tank.
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WARNING
EXPLOSION
WARNING
SCALDING INJURY
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