LAARS Mighty Therm HH (Sizes 2000-5000) - Installation, Operation and Maintenance Instructions - Manual (Page 11)

Mighty Therm Hydronic Boiler Page 11
3. Once the pilots are lit and have been established
for five minutes, the flame failure response time
should be checked as follows:
System 16: (Electronically supervised standing
pilot system standard on propane gas) Extinguish the
pilot flame by placing the manual pilot valve in the
closed position, and, at the same time, begin recording
the time it takes for the output signal from the
electronic ignition control to be interrupted. Refer to
the electrical drawing supplied with the boiler for
wiring details. The signal interruption can be detected
either with a test light or a voltmeter. Because the
ignition controls are in series, the control just
upstream of the gas valves should be tested first.
Under no circumstances should the response time
exceed 5 seconds.
System 18: (Intermittent ignition supplied only
for natural gas) With this system, pilots are
automatically lit when the thermostat calls for heat.
The pilots are permitted a trial period for ignition, then
the system is locked out if it fails to light. To retry
ignition, power to the boiler must be momentarily
interrupted. After the pilot is initially lit, the trial for
ignition time should be checked by turning off pilot
gas, and, at the same time, monitoring the time it takes
for the audible sparking at the pilot burner to stop.
Under no circumstances should the trial for ignition
exceed 15 seconds. Because the electronic ignition
controls are in series, the control just upstream of the
gas valves should be tested first (refer to the electrical
drawing supplied with the boiler).
Once the trial for ignition period has been
checked, the controls should be reset and the flame
failure response time checked by following the
procedure given for system 16.
4. With the pilots lit, initial activation of the main
burners can be achieved by slowly opening the
main manual valve. The result should be a
smooth lighting of the main burners.
Hi-Limit Checkout
After running the boiler for a long enough period
to bring the water temperature within the range of the
hi-limit, slowly back off the high limit setting until the
boiler shuts off. The main burners should reignite
when the hi-limit is turned back up to its original
setting.
The high limit should now be reset and the boiler
run until it shuts off automatically on high limit.
Now that all tests of the safety shutoff devices
have been completed, refer to Section 3B for the
proper settings of temperature controls.
3B. To Start Up System
(See Section 3A for Initial Startup)
1. Start up boiler:
a.
Be certain system pump is running.
b. Lighting instructions are provided on the
boiler rating plate and in the User’s Manual
and are as follows:
1. Turn off main electrical switch.
2. Turn off all manual gas valves and wait five
minutes.
3. Set aquastat or thermostat to lowest setting.
4. Slowly turn manual gas valve to ON.
5. Reset all safety valves (pressure switch and
manual reset high limit).
6. Open manual pilot valve. Turn on main electrical
switch.
7. Set temperature controller to desired
temperature. Pilot will light automatically to
ignite main burners whenever the thermostat
calls for heat.
8. The low firing rate setting must be equal to or
greater than the specified minimum input rating
as shown on the appliance rating plate. For
example, size 2450 has a specified minimum
input of 735,000 BTUs/hr. The unit's input rate
must not be below this value (refer to rating
plate). Laars boilers use gas valves which are
factory set to provide an input on low fire that
meet or exceed the specified minimum.
2. Set temperature controls:
Boilers on constant flow will have the
temperature controller bulb located in the boiler inlet
and the high limit sensing bulb in the boiler outlet.
Boilers on variable flow will have both the
temperature control sensing bulb and the high limit
sensing bulb located in the boiler outlet.
When boiler is installed on a constant water
flow system, set temperature controller at the designed
system supply temperature less the temperature drop
in the system. Set the high limit switch 30°F above the
supply temperature to the system.
When boiler is equipped with staged or
modulated
fire and installed on a variable flow system, set
temperature controller at the designated system
temperature. Set the high limit switch 30°F above the
supply temperature to the system.