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 10 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.
TABLE 4
NATURAL GAS MANIFOLD PRESSURES - IN.WG. (KPA)
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| ALTITUDE FT. (M) | |
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MHU 50/80 |
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50/80 |
| 4.0”WC (0.99 kPa)* | 3.6”WC (0.89 kPa) |
|
|
|
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*No adjustment required.
TABLE 5
LP/PROPANE GAS MANIFOLD PRESSURES - IN.WG. (KPA)
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| ALTITUDE FT. (M) | |
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|
|
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MHU 50/80 |
| ||
|
| ||
|
|
|
|
|
|
|
|
50/80 |
| 10.5”WC (2.62 kPa)* | 8.5”WC (2.12 kPa) |
|
|
|
|
*No adjustment required.
LIMIT CONTROL
The limit control switch is factory set and not field adjustable.
LOUVER VANE ADJUSTMENTS
Rotate louver vanes to direct airflow upward, downward, straight, or any combination of these directions. When unit is installed
in an inverted position, louvers may be positioned in the same
manner.
COMBUSTION AIR PRESSURE SWITCH
This pressure switch checks for proper combustion air blower operation before allowing an ignition trial. The switch is factory set
and no field adjustment is necessary.
FLAME ROLLOUT SWITCH
The flame rollout switch(es) are located on the burner box top, behind the ignition control board. This normally closed switch opens on a temperature rise. Check for adequate combustion air
before manually resetting switch.
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.
4.Clean burner filter screen as follows:
•Turn off both electrical and gas supply to unit.
•Remove the filter screen from the inlet to the burner housing by squeezing and pulling out.
•With screen out of the heater, clean with light soap and water or blow out with compressed air (blowing away from you).
•Dry screen thoroughly with air and make sure all air passages in the screen are fully opened.
•Replace screen into burner housing opening.
•Restore electrical and gas supply.
•Follow lighting instructions to light the heater. 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.
Compact Unit / Utility Heater |