LAARS Mighty Therm VW (Sizes 2000-5000) - Installation, Operation and Maintenance Instructions - Manual (Page 13)

Page 13 Mighty Therm Volume Water Heaters
Caution
If the tank temperature control is set too high, a
potential for hot water scalding may exist.
After a setting has been chosen for the tank
temperature control, set the heater temperature control
10°F (6°C) higher. The heater’s temperature control
senses the inlet water temperature to the heater. The
heater’s manual reset high limit (and automatic reset
high limit, if applicable) senses heater outlet
temperature.
If the unit is equipped with an automatic reset
high limit, set the automatic reset high limit 20°F
(11°C) above the outlet temperature to avoid nuisance
lockouts. Set the manual reset high limit 5°F (3°C)
above the automatic reset high limit.
For units that only have a manual reset high limit
(no automatic reset high limit), set the manual reset
high limit 20°F (11°C) above the outlet temperature to
avoid nuisance lockouts.
Example, Imperial units: If the tank temperature
is set to 140°F, set the heater’s temperature control to
150°F (140°F + 10°F). Further, if the temperature rise
through the heater is 25°F, the outlet temperature will
be 175°F (150°F + 25°F). Therefore, set the
automatic reset high limit to 195°F (170°F + 20°F),
and the manual reset high limit to 200°F (195°F + 5°F).
Example, Metric units: If the tank temperature
is set to 60°C, set the heater’s temperature control to
66°C (60°C + 6°C). Further, if the temperature rise
through the heater is 15°C, the outlet temperature will
be 81°C (66°C + 15°C). Therefore, set the automatic
reset high limit to 92°C (81°C + 11°C), and the
manual reset high limit to 95°C (92°C + 3°C).
b. Internal Water Heater Temperature Control:
When an external control is not used, the
circulator between the heater and the storage tank
must run continuously, so that the heater’s
temperature control can detect and control the water
temperature in the storage tank. The water heater’s
temperature control is adjusted to its lowest
temperature position when shipped from the factory.
This is the preferred starting point for setting the
temperature control.
If the unit is equipped with an automatic reset
high limit, set the automatic reset high limit 20°F
(11°C) above the outlet temperature to avoid nuisance
lockouts. Set the manual reset high limit 5°F (3°C)
above the automatic reset high limit.
For units that only have a manual reset high limit
(no automatic reset high limit), set the manual reset
high limit 20°F (11°C) above the outlet temperature to
avoid nuisance lockouts.
Example, Imperial units: If the heater’s
temperature control is set to 130°F, and the
temperature rise through the heater is 25°F, the outlet
temperature will be 155°F (130°F + 25°F). Set the
automatic reset high limit to 175°F (155°F + 20°F)
and set the manual reset high limit to 180°F (175°F +
5°F).
Example, Metric units: If the heater’s
temperature control is set to 55°C, and the
temperature rise through the heater is 14°C, the outlet
temperature will be 69°C (55°C + 14°C). Set the
automatic reset high limit to 80°C (69°C + 11°C) and
set the manual reset high limit to 83°C (80°C + 3°C).
3.3 To Turn Off Heater
1. Turn off main electrical switch.
2. Close all manual gas valves.
3.4 To Shut Down System
To shut down heater, turn off all manual gas
valves and electrical disconnect switch. Whenever
danger of freezing exists, shut off water supply and
remove drain plug in bottom of front header cover and
drain every part of system subject to freezing
temperatures.
SECTION 4.
Maintenance
1. If a strainer is employed in a pressure reducing
valve or in the piping, clean it every six (6)
months.
2. At start-up and every six (6) months thereafter,
the pilot and main burner flame should be
observed for proper performance (see Figures 15
and 16; see attached lighting and shutdown
Figure 14. Pilot Location.
Figure 15. Periodic Flame Observation.