Enerco MHU 75, MHU 45 owner manual Service

minimum of 5.0" w.c. for natural gas or 10.4" 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.

LIMIT CONTROL

The limit control switch is factory set and not field adjustable.

TABLE 4

NATURAL GAS MANIFOLD PRESSURES - IN.WC. (KPA)

	ALTITUDE FT. (M)
MHU45/75 HSU45/75	0-2000	2 000-4500
	(0-610)	(610-1370)
45/75	4.0 (0.99)*	3.6 (0.89)

*No adjustment required.

TABLE 5

LP/PROPANE GAS MANIFOLD PRESSURES - IN.WC. (KPA)

	ALTITUDE FT. (M)
MHU45/75 HSU45/75	0-2000	2 000-4500
	(0-610)	(610-1370)
45/75	10 (2.49)*	8.0 (1.99)

*No adjustment required.

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.

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.

Enerco Compact Unit Heater 12 Operating Instructions and Owner’s Manual