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MZ INSTALLATION & MAINTENANCE
for combustion is approved if National Fuel Gas Code
requirements are followed.
Utilizing indoor air can cause a decrease in the overall system
efficiency. The MZ should not be run where ambient
temperatures exceed 125° F.
MOUNTING THE MZ:
The MZ comes from the factory with a wall mount bracket,
gas and water pipes. With this method you must: Mount the
bracket securely, hang the MZ, attach the included turn-down
elbows and begin piping. Note that when the caps that cover
the nipples on the heating system are removed, it is normal to
find water left over from the test-run firing at the factory. Watch
out for black-water staining if you are working in a clean area.
Always flush the heating system with plenty of clean water
before commissioning.
There are times when the rough piping for the heating system
must be installed and pressure tested before the heating
system is actually needed. The pre-plumbed wall bracket was
designed for this scenario.
Note that the pre-plumbed brackets come with and domestic
cold water shut-off valves on the 25S.
The pre-plumbed bracket (part #9511 for MZ25C pictured at
right, #9512 - MZ40C and #9513 for MZ25S) allows
completion of the heating and domestic water piping without
the heating system present. NOTE: All MZ heating systems
are shipped with an offset “Z” bracket for flush mounting. The
#9515 Spacer Back Plate for MZ25C & the #9516 Spacer Back
Plate for MZ25S and MZ40C allow piping to be run up behind
the unit.
Pre-plumbed brackets can be a big help with radiant systems
on new construction or major remodel jobs. Fit the bracket,
pipe the gas and heat, use standard pipe plugs with the
supplied fiber gaskets to pressure test the entire system.
When the time comes for the heating system, simply
remove the plugs, hang the MZ, tighten the union nuts
that connect the MZ to the piping and fill the unit. Pre-
plumbing spares you the worry (and cash flow) of having
the heating system sit on the job site out of your control
while construction goes on. Thirty minutes should be all
you need from delivery to light off.
USING MZS TO PRODUCE DOMESTIC HOT WATER:
a 54º F temperature rise. That is a constant draw of 174
gallons per hour. That setting maximizes efficiency and DHW
production, and works fine for a one-shower application.
The tank on the right side of the MZ25S inside its cover holds
system water. A copper fin-tub coil inside the tank transfers
heat from system water to domestic water. The adjustable
aquastat just above and to the left of the tank sets the limit
for the DHW-water temperature. We recommend a setting of
no more than 120°. If the DHW aquastat is set above 145º F
the fixed, manual-reset high-Limit supply-water thermostat
on the MZ may trip, causing nuisance callbacks.
The temperature of DHW is independently controlled and
regulated by adjustable settings on the MZ25S. The MZ25S
also includes an adjustable flow setting device for DHW.
When there is a low DHW flow through the MZ25S, the system
water in the tank will give up heat to the DHW and its
temperature will fall until the aqustat closes. The MZ will add
heat to the tank at faster rate than it is being taken out, and
the temperature in the tank and in the DHW will rise until the
aquastat is satisfied. Then the temperature will start to fall
again until the aquastat calls for heat again. This situation
presents little or no problem for laundry, dishwashing, hand
washing or other common DHW uses.
SIZING:
As long as the BTU output of the MZ is greater than the design
heat loss of the structure, the DHW draw on the MZ does not
have to be taken into account because DHW run times are
very short. The only time that DHW loads affect sizing is when
they are unusually large.
INDIRECT:
Because of its very high efficiency and very quick response
time, the MZ series is especially well suited for high-volume
DHW water production through the use of water storage tanks
using the heat produced by the MZ. Our 25, 40, 50 and 80
gallon stainless tanks are designed with the contractor, the
end-user and the MZ in mind.
In mixed space-heat DHW applications, the DHW function is
given priority over space heat through the use of a three-way
valve or priority pump system controlled to direct 100% of
the MZ’s output to the heat exchanger in the DHW system.
DIRECT DOMESTIC HOT WATER, THE MZ 25S:
The MZ 25S provides space-heat and DHW at extremely high
levels of efficiency and low levels of pollution. It is especially
well suited for structures in which floor space is at a premium.
The MZ 25S will produce 2.9 GPM of domestic-hot-water at
INSTALLATION AND TECHNICAL
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