Laarsen Associates IW Maintenance, 3D. To Turn Off Heater, 3E. To Shut Down System, Indoor Models

Mighty Therm Volume Water Heater Page 19

depressed for one minute then release. Once the pilot is lit, the power is supplied through the aquastat to the main gas valve.

2. To set the temperature and high-limit controls:

When using a tank aquastat:

Set the tank aquastat to the desired tank temperature. Set the heater temperature control 20°F higher than tank aquastat. Set the manual reset high limit 50°F higher than tank aquastat. Example: If desired temperature is 140°F, set the tank aquastat at 140°F, set the heater temperature control at 160°F, and set the manual reset high limit at 190°F. If the heater is equipped with a pump time delay, the three-position switch on the side of the heater can be put into the “Auto Pump” pposition, so that the pump will only run when the tank aquastat calls for heat. then, when the call for heat is satisfied, the heater will turn off, but the pump will run for the set amount of delay time (adjustable between 0.1 and 10 minutes).

When a tank aquastat is not used:

The pump on the heater must run continuously, so the heater's temperature control will sense the tank's water temperature. Set the heater temperature control to the desired tank temperature. Set the manual reset high limit 50°F higher than the heater temperature control. Example: If desired temperature is 140°F, set the heater temperature control at 140°F, and set the manual reset high limit at 190°F.

3D. To Turn Off Heater:

1.Turn off main electric switch.

2.Close all manual gas valves.

3E. To Shut Down System:

To shut down heater, turn off all manual gas valves and electrical disconnect switches. Whenever danger of freezing exists, shut off water supply and remove drain plug in the bottom of front header cover. Drain every part of system subject to freezing temperature.

SECTION 4.

Maintenance

1.Lubricate the water circulating pump (see instructions found on the pump).

2.If a strainer is employed in a pressure reducing valve or in piping, clean it every six (6) months.

3.At start-up and every six (6) months thereafter, the pilot and main burner flame should be observed for proper performance (see Figure 21). See attached lighting and shut-down instructions for proper pilot flame pattern). If flame has the

Figure 21. Main Burner Flame Pattern.

appearance of “sooting” tips, check for debris near orifices. Call serviceman.

4.Inspect the venting system for obstruction, leakage and corrosion at least once each year.

5.Keep heater area clear and free from combustible material, gasoline and other flammable vapors and liquids (see Table 1 for minimum clearances).

6.Be certain all combustion air and ventilation openings are unobstructed.

7.Check for fouling on the external surfaces of the heat exchanger every six months. (NOTE: After installation and first start-up, check the heat exchanger for fouling after the following periods of operation: 24 hours, 7 days, 30 days, 90 days, and once every six months thereafter).

Fouling on the external surfaces of the heat exchanger is caused by incomplete combustion and is a sign of combustion air and/or venting problems. As soon as any fouling is observed, the cause of the fouling should be corrected (see Section 5, Troubleshooting Guide). The heat exchanger can be checked by locating a mirror under the burners with a flashlight. An alternate method is to remove the venting and top panel as necessary to inspect from above. Also check the vent system for defects at this time.

a.If cleaning is required, shut off all electrical and gas supply to the heater.

b.To expose the heat exchanger:

Indoor Models:

Remove flue pipe, top of unit, rear upper jacket, flue collector rear panel and heat exchanger baffles.

Outdoor Models:

Remove vent top assembly, rear upper jacket, flue collector rear panel and heat exchanger baffles.

c.Remove all burners:

It is usually more convenient to remove the burner tray assembly. Disconnect sensor wire, ignition cable (or thermocouple generator) and pilot gas line. Disconnect manifold inlet union(s). Remove the four (4) retaining screws. Grasp burner/pilot assembly firmly at the front. Push it back, disengaging it from the gas orifice.