19
www.monitorproducts.com
MAINTENANCE CONSIDERATIONS
The MZ is an extraordinarily durable and well-designed heat
source. It is built in the same manner as a fine boat or airplane.
While there are parts of the MZ that will eventually wear out,
they are easily replaced. The heart of the MZ, the heat
exchanger, is made of high-grade stainless steel and will last
for many, many years of normal service. Premature failure of
the MZ’s heat exchanger can be caused by the ingestion of
contaminant’s in the combustion air, the use of very hard, very
acidic or very basic water in the MZ, or continuous addition of
water to the system.
In order to minimize no-heat calls other than those that are the
unavoidable result of rare events such as a lightning strike or the
failure of one of the mechanical or electrical components of the
MZ, we recommend that the MZ be given an annual clean-and-
check. The few drops of water that will normally leak out of a
system over time can easily be replenished during maintenance.
If the MZ is not cleaned and checked regularly, there will
eventually be an interruption in the function of the MZ due to
one of the following, easily remedied events:
1) The air-pressure switch will not open due to a reduction in
airflow through the MZ due to an accumulation of dirt on the
inlet side of the combustion-air fan, the accumulation of dirt
in the burner, the accumulation of ash on the heat-
exchanger’s fin tube or the accumulation of ash in the
condensate trap.
2) The interference with ignition due to flame erosion of the
igniter rods.
Annual service will bring the chance of nuisance no-heat calls
to near zero.
MAINTENANCE PROCEDURES
(Approximate time, 15 minutes.)
1) Disconnect plastic tube at top of fan. Grasp plastic nozzle
that connects fan to the burner with right hand. Rest left
hand on combustion chamber and pull fan to right. Fan will
slip off of burner. Disconnect fan wiring connector and set
fan aside.
2) Disconnect plastic hose, igniter wire, flame-proving wire
and ground wire from burner top. Open union in gas line at
burner top. Four bolts secure clips that hold burner to
combustion chamber. Remove front clips. Loosen bolts and
rear spin clips so that burner can be removed and remove
burner.
3) Using plain water, wash heat exchanger fin-tubes. Water
will run out through condensate trap. Unscrew bottom half
of condensate trap. Check trap for accumulation of ash/
mud and clean if necessary. Fill the trap with water and
replace it.
4) Inspect flame proving rod and igniters. Replace if worn. Re-
gap igniter according to specifications in the Technical
Instruction packed with heating system. (2.25 mm, 0.09
inches.) Brush or vacuum burner face. If vacuum is at hand,
vacuum burner outlet. Check fan inlet for dirt on blades and
clean if necessary. Re-connect burner, hoses, wiring, and
fan.
5) Fire MZ, check safety limits and CO and/or CO2 according
to values in installation instructions.
QUICK TROUBLE-SHOOTING GUIDE FOR MZ
HEATING SYSTEMS:
!WARNING!
Only trained HVAC service people should do MZ
troubleshooting. The MZ is fed by an electrical current
source that could electrocute. Take care to avoid shock.
Wear safety glasses!
Make sure that the MZ has power, gas, that there is water in
the heating system and that there is a call for heat. Check all
visible hoses and wiring inside the MZ for integrity and good
connection.
Is pump running?
Toggle on-off switch. Water pressure will change when pump
starts. If no change, remove cap from pump end. Rotate shaft
with screwdriver. If shaft rotates freely, check power to pump
(CAUTION, 110 VOL TS). If no power to pump, check pump
relay and associated wiring.
Fan runs but MZ doesn’t try to fire?
Check for air-pressure-switch operation with voltmeter. If
switch does not close, check for blocked flue, blocked
condensate trap or drain. If MZ has been in service for a long
time, make sure that heat exchanger is not dirty. Inspect
venting to insure compliance with installation instructions.
Is water-flow switch closing?
Disconnect flow-switch wiring-harness. Jump connections
back to MZ. If fan runs with connections jumped, most likely
cause is low system water flow. Check for stuck valve,
obstruction in piping, strainer or pump vanes clogged, etc.
Use ohmmeter to check for flow-switch operation. Switch
closes at 3.52 GPM for the MZ25 and 4.4 GPM for the
MZ20-40.
Does the MZ try to fire?
Gas valve and spark normally act simultaneously about 20
seconds after air pressure switch closes. If attempt to light
occurs, but no flame results, (flame failure), the ignition module
will lock out, the fan runs continuously, and power has to be
interrupted before another attempt to light will occur.
Is combustion-air fan running?
If pump runs and flow switch closes, combustion air fan should
run. If not, verify call for heat, check that operating limit is not
satisfied and that manual reset fixed high-Iimit switches are
not open. If fan does not run, check fan power (CAUTION,
110 V.). If no power, check fan relay and associated wiring.
MAINTENANCE - TROUBLESHOOTING
I V . MAINTENANCE
V . TROUBLESHOOTING
To Next Page
Loading...