ignition control board emits radio noise as the sparking process
WARNING
is underway. The level of energy may be sufficient to disturb a logic circuit in a microprocessorElectric shock hazardcontrolled. Canthermostatcause injury. Itoris
death. Do not use this heater if any part has recommended that an isolation relay be used when connecting
been under water. Immediately call a qualified the unit heaters to aservicemicroprocessortechnician ctontrolledinspect thermostatfurnace.and Install the thermostatto replaceaccordinganytopartinstructionsof the controlprovidedsystem. Selectand
any gas control which has been under water. circuit protection and wire size according to the unit rating plate.
InstallWARNINGa separate disconnect switch (protected by either fuse or circuit breaker) near the unit so that power can be turned off for servicing. ConnectDangerwiringof throughexplosionknockout. Can causeoninjurythe junctionor
product or property damage. If
occurs or if gas supply fails to shut off, shut diagram for connectionoff theinformationmanual gas. Usevalve18 togaugethe appliancewire or larger
for thermostat connectionsbefore shutting. off electrical supply.
ElectricallyWARNINGground unit in accordance with local codes or, in the absence of local codes, in accordance with the current National
Electric shock hazard. Can cause injury or Electrical Code (ANSI/NFPA No. 70) in the U.S.A., and in Canada
death. Before attempting to perform any with the current Canadianservice orElectrmaicalntenance,Code, Paturnt 1theCSAelectricalC22.1.
power to unit OFF at disconnect switch(es). NOTE
tape to avoid damage to the electrical system.
Make line voltage connections as shown in . Connect field
WARNINGfigure 7
wiring as shown on wiring diagram on unit. Also refer to typical diagram in this manualDanger. An additionalof explosionthermostatand fire. Canwirecausemust be
injury or product or property damage. You run to terminal “G” on heater when continuous blower is desired.
must follow these instructions exactly.
GAS CONNECTION
GASWhen connectingCONNECTIONgas supply lines, the length of the piping run
from the meter to must be considered in determining the pipe size When connecting gas supply, the length of the run from the
to avoid excessive pressure drop. A line pressure of 7” WC (178mm meter must be considered in determining the pipe size to avoid WC) for natural gas should be maintained when sizing the piping. excessive pressure drop. A line pressure of 7” w.c. (178mm w.c.) A line pressure of 13” WC (330mm WC) should be maintained
for natural gas should be maintained when sizing piping. A line for propane (LP) gas. For correct sizing of piping, refer to the pressure of 13” w.c. (330mm w.c.) should be maintained for (American) National Fuel Gas Code ANSI Z223.1, or (Canada) CSA liquefied petroleum (LP) gas. For correct sizing of piping, refer to B149.1, National Gas and Propane Installation Code or consult the the (American) National Fuel Gas Code ANSI Z223.1 or (Canada) utility having jurisdiction.
CSA B149.1, Natural Gas and Propane Installation Code or consult the utilityWARNING:having jurisdictionTO PREVENT. HEATER DAMAGE.
WHEN USING A PROPANE TANK TO SUPPLY
A drip leg should be installed in the vertical pipe run to the unit.
HEATER, A MINIMUM 11”W.C. LOW PRESSURE
In some localities, codes may require that a manual main shutoff
REGULATOR TO A MAXIMUM 14”W.C. LOW PRESSURE valve and union (furnished by installer) be installed external to the
REGULATOR IS REQUIRED. THIS REGULATOR MUST BE unit. Union must be of the ground joint type. A drip leg should be
INSTALLED BETWEEN THE TANK AND THE HEATER.
readily accessible to permit cleaning and emptying. See figure 8.
Regulator not supplied with heater.
NOTE If a switch box is mounted over electrical knockouts on A drip leg should be installed in the vertical pipe run to the unit. back of unit, leave a minimum of 4” (102mm) clearance between In some localities, codes may require that a manual main shutoff switch box and drip leg.
valve and union (furnished by installer) be installed external to the
unit. Union must be of the ground joint type. A drip leg should be A 1/8” NPT plugged tap shall be installed immediately upstream readily accessible to permit cleaning and empting. See figure 8. of the gas supply connection to the heater.
NOTE If a switch box is mounted over electrical knockouts on back NOTE Compounds used on threaded joints of gas piping must be of unit, leave a minimum of 4” (102mm) clearance between switch resistant to the actions of liquefied petroleum gases.
box and drip leg.
A 1/8” NPT plugged tap shall be installed immediately upstream of the gas supply connection to the heater.
NOTE Compounds used on threaded joints or gas piping must be resistant to the actions of Liquefied petroleum gasses.
LEAK CHECK
After gas piping is completed, carefully check all piping connections, (field and factory), for gas leaks. Use a soap solution or other preferred means.
Due to the natural heating cycles and vibration of this unit it is recommended, as part of its annual maintenance, to check these
connections for proper tightness and
CAUTION DO NOT use matches, candles, flame or other sources of ignition to check for gas leaks.
IMPORTANT The heater and its individual shut off valve must be disconnected from the gas supply piping system during any pressure testing of that system at test pressures in excess of 1/2 psig (3.45kPa).
The appliance must be isolated from the gas supply piping system by closing its individual manual gas shutoff valve during any pressure testing of the gas supply system at test pressures equal to or less than 1/2 psig (3.45kPa). See figure 9.
NOTE In case emergency shutdown is required, shut down main gas valve and disconnect main power to unit. These devices should be properly labeled by the installer.
START – UP AND OPERATION
UNIT START–UP
FOR YOUR SAFETY READ BEFORE LIGHTING
BEFORE LIGHTING smell all around the appliance area for gas. Be sure to smell next to the floor because some gas is heavier than air and will settle on the floor.
Use only your hand to move the gas control switch to the on position. Never use tools. Do not use excessive force to switch valve from off to on position. Force or attempted repair may result in a fire or explosion.
MHU 50/80 unit heaters are equipped with an automatic spark ignition system. There is no pilot. In case of a safety shutdown, move thermostat switch to OFF, then return the thermostat switch to HEAT position.
Should overheating occur, or the gas supply fail to shut off, shut off the manual gas valve to the appliance before shutting off the electrical supply.
GAS VALVE OPERATION FOR HONEYWELL VR8205M SERIES VALVE (FIGURE 10)
1.STOP! Read the safety information at the beginning of this section.
2.Set the thermostat to lowest setting.
3.Turn off all electrical power to appliance.
4.This appliance is equipped with an ignition device which automatically lights burner. DO NOT attempt to light the burners manually.
5.There is a black rotary switch knob that can be moved between the on and off position. Rotate the switch knob to the off position. (See Figure 10)
6.Wait five minutes to clear out any gas. If you then smell gas, STOP! Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s instructions. If you do not smell gas go to next step.
7.Rotate the black switch knob to ON.
8.Turn on electrical power to unit.
9.Set the thermostat to desired setting.
10.The combustion air blower will start. The burners will light within 40 seconds.
Compact Unit / Utility Heater
