Laarsen Associates PW Manual Do Utilizador

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.

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.

1.

Turn off main electric switch.

2.

Close all manual gas valves.

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.

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

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:

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

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.