LAARS Mighty Therm LO-NOx VW (Sizes 250/400) - Installation, Operation and Maintenance Instructions - Manual (Page 22)

LAARS Heating Systems Page 22
Plug
Figure 34. Scale Inspection.
Figure 33. Flame Patterns.
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 Hi-Limit Switch Checkout
After running the heater for a long enough
period, bring the water temperature within the range of
the hi-limit switch and slowly back off the high limit
setting until the heater shuts off. The main burners
should reignite (following the normal ignition cycle)
when the hi-limit switch is reset and turned back up to
its original setting. The heater should now run until it
shuts off automatically on operating control.
Should overheating occur or the gas supply fail to
shut off, turn off the manual gas control valve to the
heater (refer to troubleshooting section).
3.4 Shut-Down Procedure
Shut down the heater following the instructions
in Figures 27 and 28.
Where there is a danger of freezing, shut off the
water supply and remove the drain plugs on both sides
of the heater jacket. Drain every part of the system
subject to damage from freezing temperatures.
SECTION 4.
Maintenance
4.1 General Instructions
1. Oil the water circulating pump in accordance
with the manufacturer's instructions.
2. If a strainer is used in a pressure reducing valve
or in the piping, clean it every 6 months in
accordance with the manufacturer's instructions.
3. At startup and every 6 months after, check the
main burner flame. If the flame has the
appearance of sooting tips, check for debris near
orifices. Call service technician (see Figure 32).
4. Inspect the venting system for blockage, leakage,
and corrosion at least once a year.
5. Keep the heater area clear of combustible
material, gasoline, and other flammable liquids
and vapors.
6. Be sure all combustion air and ventilation
openings are not blocked.
7. Check for black carbon soot buildup on the
external surfaces of the heat exchanger every 6
months.
8. Do not use the heater if any part has been under
water. Replace anypart of the control system and
any gas control which has been under water.
NOTE: After installation and first startup, check the
heat exchanger for black carbon soot buildup after the
following periods of operation: 24 hours, 7 days, 30
days, 90 days, and once every 6 months thereafter.
4.2 HEAT EXCHANGER
4.2.1 Inspecting the Heat Exchanger
To check the scale buildup, periodically inspect
the tube having the highest temperature as follows:
OUT OF
PRODUCTION