Compact Unit / Utility Heater
10
Operating Instructions and Owner’s Manual
5. Test for spillage at the draft hood relief opening after five minutes
of main burner operation. Use the flame of a match or candle, or
smoke from a cigarette, cigar, or pipe.
6. After it has been determined that each appliance remaining
connected to the common venting system properly vents when
tested as outlined above, return doors, windows, exhaust fans,
fireplace dampers and any other gas-burning appliance to their
previous condition of use.
7. If improper venting is observed during any of the above tests,
the common venting system must be corrected. The common
venting system should be re-sized to approach the minimum size as
determined by using the appropriate tables
ELECTRICAL CONNECTIONS
NOTE:
The MHU series unit/utility heaters use a direct spark ignition
system. There is no pilot necessary as the spark lights the main burner
as the gas valve is turned on. The direct spark ignition control board
emits radio noise during burner ignition. The level of energy may
be enough to disturb a logic circuit in a microprocessor controlled
thermostat. It is recommended that an isolation relay be used when
connecting the unit heater to a microprocessor controlled thermostat.
Select circuit protection and wire size according to the unit rating
plate. Install a separate disconnect switch (protected by either fuse
or circuit breaker) near the unit so that power can be turned off for
servicing. Remove electrical junction box cover and connect wiring
through knockout on the junction box located on the side of the
heater. Refer to heater wiring diagram for connection information.
Use 18 gauge wire or larger for line power connections. Make sure to
connect line power to wires located in the external electrical junction
box behind junction box cover.
DO NOT CONNECT LINE POWER TO
THERMOSTAT TERMINAL STRIP ON OUTSIDE OF HEATER.
Electrically ground the unit in accordance with local codes or in the ab-
sence of local codes, in accordance with the current National Electrical
Code (ANSI/NFPA No. 70) in the USA, and in Canada with the current
Canadian Electrical Code, Part 1 CSA C22.1
NOTE:
Un-insulated ground wire must be wrapped in electrical tape to
avoid damage to the electrical system.
Make line voltage connections as shown in figure 6. Connect field
wiring as shown on wiring diagram on unit. Also, refer to typical
diagram in this manual.
To use the blower for air circulation only, your thermostat must have
a “fan only” or fan selection setting. In case your thermostat has this
option. an additional wire should be run to the “G” terminal on the
thermostat connection block. See wiring schematic on page 13.
UNIT
LINE VOLTAGE FIELD WIRING
L1
N
BLACK
BLACK
WHITE
WHITE
EQUIPMENT
GROUND
BLACK WIRE WITH WHITE TAPE
OR WHITE WIRE WITHOUT TAPE
FIGURE 6
DRIP LEG
GROUNDED
JOINT UNION
MANUAL
MAIN SHUT-OFF VALVE
(FURNISHED BY INSTALLER)
GAS FLOW
GAS SUPPLY CONNECTION
FIGURE 7
UNIT HEATER
CAP
ISOLATE GAS
VALVE
MANUAL MAIN SHUT-OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
GAS SUPPLY TO UNIT HEATER
FIGURE 8
