Compact Unit / Utility Heater
13
Operating Instructions and Owner’s Manual
HIGH ALTITUDE
Units may be fired at full input up to 2000 ft. (610m) above sea level.
Above 2000 ft. (610m), manifold pressure must be adjusted on some
units. Adjust pressure regulator to pressure shown in
table 4
for
natural gas and
table 5
for LP/propane gas.
Table 4
NATURAL GAS MANIFOLD PRESSURES - IN. W.C.. (KPA)
MHU 50/80/125
ALTITUDE FT. (M)
0-2000 (0-610)
2000-4500 (610-1370)
MHU 50/80/125
4.0”WC (0.99 KPA)*
3.6”WC (0.89 KPA)
*NO ADJUSTMENT REQUIRED
Table 5
LP/PROPANE GAS MANIFOLD PRESSURES - IN.W.C.. (KPA)
MHU 50/80/125
ALTITUDE FT. (M)
0-2000 (0-610)
2000-4500 (610-1370)
MHU 50/80/125
10”WC (2.62 KPA)*
8.5”WC (2.12KPA)
*NO ADJUSTMENT REQUIRED
GAS FLOW
To check for proper gas flow to the combustion chamber, determine
the Btu input from the appliance rating plate. Divide this input rating
by the Btu per cubic feet of available gas. Result is the required
number of cubic feet per hour. Determine the flow of gas through the
gas meter for two minutes and multiply by 30 to get the hourly flow
of gas.
GAS PRESSURE
1. Check gas line pressure with unit firing at maximum rate. A
minimum of 5.0” w.c. for natural gas or 10.9” w.c. for LP/propane
gas should be maintained for proper unit operation.
2. After line pressure has been checked and adjusted, check manifold
pressure. Correct manifold pressure is shown on the unit rating
plate. See
figure 9
for gas pressure adjustment screw location. A
natural gas to LP/propane gas changeover kit is required to convert
unit. Refer to installation instructions provided with changeover kit
for conversion procedure.
SERVICE
CAUTION
Turn off gas and electrical power to unit before performing
any maintenance or service operations on this unit. Remember to
follow lighting instructions when putting unit back into operation after
service or maintenance.
If any of the original wire as supplied with the appliance must
be replaced, it must be replaced with wiring material having a
temperature rating of at least 105°C. Do not use this appliance if
any part has been under water. Immediately call a qualified service
technician to inspect the appliance and replace any gas control which
has been under water.
BURNERS
1. Periodically examine burner flames for proper appearance during
the heating season.
2. Before each heating season examine the burners for any deposits or
blockage that may have occurred.
3. Clean burners as follows:
•
Turn off both electrical and gas supplies to unit.
•
Disconnect gas supply piping, high tension and sensor leads.
Remove gas manifold. Remove burner tray.
•
Clean burners as necessary. Make sure that burner heads line up
properly to ensure flame crossover. Check spark gap on electrode
and adjust if required. The gap should be between 0.110 inch and
0.140 inch (2.79mm to 3.56mm). The gap may be checked with
appropriately sized twist drills or feeler gauges.
•
Reinstall burner tray, gas manifold, high tension and sensor leads.
Reconnect gas supply piping.
•
Restore electrical power and gas supply. Follow lighting instructions
to light unit. Check burner flame.
FLUE PASSAGEWAY AND FLUE BOX
The flue passages and flue box should be inspected and cleaned prior
to each heating season. The sequence of operation should be as
follows:
1. Turn off both electrical and gas supply to unit.
2. Disconnect combustion air blower wiring.
3. Remove screws securing flue box to unit. Remove flue box. If
necessary, remove blower assembly from flue box. Clean flue box
with wire brush.
4. Remove turbulator retention bracket and turbulators. Clean
turbulators with wire brush.
5.
Remove burners as described in section “BURNERS” section.
6. Clean tubes with a wire brush.
7. Reassemble unit. The combustion air and flue box gaskets should
also be replaced during reassembly.
8. Restore electrical power and gas supply. Follow lighting instructions
to light unit. Check operation of unit.
COMBUSTION AIR BLOWER
Under normal operating conditions, the combustion air blower should
be checked and cleaned prior to the heating season with the power
supply disconnected. Use a small brush to clean blower wheel.
ELECTRICAL
1. Check all wiring for loose connections.
2. Check for correct voltage at unit (unit operating).
3. Check amperage draw.
FLUE AND CHIMNEY
Check all vent and vent connector joints for tightness. Ensure that
connections are sealed and that there are no blockages.
FAILURE TO OPERATE
If unit fails to operate check the following:
1. Is thermostat calling for heat?
2. Is main disconnect closed?
3. Is there a breaker tripped or a fuse blown?
4. Is gas turned on at meter?
5. Is manual shutoff valve open?
6. Is unit ignition system in lock out? If unit locks out again, call service
technician to inspect unit.
7. Is pressure switch closed? Obstructed flue will cause unit to shut off
at pressure switch. Check flue passage and outlet.
