LAARS HEATING SYSTEMS
Page 20
3E. 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 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.
3F. Shut-Down Procedure
Shut down the heater following the instructions
found on the inside of the heater.
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
4A. 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, look at the
pilot and main burner flame (see Figure 29). If
the flame has the appearance of sooting tips,
check for debris near orifices. Call service
technician.
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.
Figure 28. Temperature controls.
Manual Reset Temp. Control
Temperature Controller
Heaters on constant flow have the temperature
control sensor bulb in the heater inlet and the manual
reset hi-limit sensing bulb located in the heater outlet.
Set the temperature control dial (see Figure 28) at the
designed system temperature. Set the hi-limit switch
40 to 50°F (4 to 10°C) above the supply temperature to
the system.
Heaters on intermittent flow have the temperature
control sensing bulb in the storage tank and the manual
reset hi-limit sensing bulb located in the heater outlet.
Set the hi-limit switch 40 to 50°F (4 to 10°C) above
the supply temperature to the system.
3D. Adjustment for Minimum Input Rate
(models with modulating gas valve)
Adjust the red knob on the modulating gas valve
to the dial number for the desired water temperature
(see Table 7). Adjusting the red knob to number "1"
sets the gas flow rate to minimum. The control is
factory set at "5" which is satisfactory for most
installations.
Temp.
Dial No.
°F
°C
1
120
49
2
127
53
3
135
57
4
142
61
5
150
66
6
157
69
7
165
74
8
172
78
9
180
82
Table 7. Water Temperature Setting.
