Munchkin HIGH EFFICIENCY HEATER with the "925" Controller - Manual (Page 22)

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PIPING
PART 5. PIPING
A. HYDRONIC PIPING WITH CIRCULATORS OR ZONE VALVES
The Munchkin is designed to function in a closed loop 15 PSI System. To assure you that you have
adequate pressure in the system, we have installed in the outlet manifold, a pressure switch that will
not let the Munchkin operate without a minimum of 10 PSI water pressure. This assures you that if the
system does have leak, the Munchkin will lock out (PRO on the display) before it damages the Stainless
Steel Heat Exchanger. We have also included a Temperature and Pressure gauge which should be
located on the Munchkin outlet to monitor the system pressure and outlet temperature from the
Munchkin. It is important to note that the Munchkin has a minimal amount of pressure drop and must
be figured in when sizing the circulators. Each Munchkin installation must have an Air Elimination
device which will remove air from the system. Install the Munchkin so the gas ignition system
components are protected from water (dripping, spraying, etc.) during appliance operation for basic
service of circulator replacement, valves and other. Observe minimum 1” clearance around all un-
insulated hot water pipes when openings around pipes are not protected by non-combustible
materials. On a Munchkin installed above radiation level, some states and local codes require a low
water cut off device at the time of installation. If the Munchkin supplies hot water to heating coils in air
handler units, flow control valves or other devices must be installed to prevent gravity circulation of
heater water in the coils during the cooling cycle. Chilled Water Medium must be piped in parallel with
the heater. Freeze Protection for new or existing systems must use glycol that is specially formulated
for this purpose. It includes inhibitors, which prevent the glycol from attacking the metallic system
components. Make certain that the system fluid is checked for the correct glycol concentration and
inhibitor level. The system should be tested at least once a year and as recommend by the producer
of the glycol solution. Allowance should be made for the expansion of the glycol solution in the system
piping. Example 50% by volume solution expands 4.8% in volume for the temperature increase from
32 F to 180 F, while water expands 3% with the same temperature rise.
Basic steps are listed below, with Illustration, which will guide you through the installation of the
Munchkin.
1. Connect the system return marked “Heater In”, make sure to install with pipe sealant com-
pound. Threaded connections are 1 ¼” NPT Brass nipples located on the left hand side of
unit.
2. Connect the system supply marked “Heater Out”, make sure to install with pipe sealant com-
pound. Threaded connections are 1 ¼” NPT Brass nipples located on the left hand side of the
unit.
3. Install Purge and Balance Valve or shut off valve and drain on system return to purge air out
of each zone.
4. Install a Back Flow preventor on the Cold Feed Make-Up Water line.
5. Install a Pressure Reducing Valve on the Cold Feed Make-Up Water line, (15 PSI nominal on
the system return). Check Temperature and Pressure Gauge which should read minimum
pressure of 12 PSI.
6. Install a circulator on system supply. Make sure the circulator is properly sized for the system
and friction loss.
7. Install an Expansion Tank on the system supply. Consult the tank manufacturer’s instruction
for specific information relating to tank installation. Size the expansion tank for the required
system volume and capacity.
CAUTION
The Munchkin should not be operated as a potable Hot Water Heater. It should not be
used as a direct Hot Water Heating Device.