LAARS Mighty Therm VW (Sizes 2000-5000) - Installation, Operation and Maintenance Instructions - Manual (Page 12)

LAARS Heating Systems
Page 12
SECTION 3.
Operation
3.1 Initial Start Up
Lighting: Safe lighting and other performance
criteria were met with the gas manifold and control
assembly provided on the heater when it underwent
tests specified in the ANSI Z21.13 standard.
Before placing the heater in operation, the
automatic safety shutoff devices must be checked.
Once the heater is connected to the gas piping and
after all of the requirements in Section 2 have been
met, follow this procedure:
1.
Before beginning the tests, make sure the main
manual gas valve, and any other heater firing
valves, are in the OFF position.
2. Make sure the power switch on the heater is in
the “ON” position. After placing the manual
pilot valves in the open position, and resetting all
safety devices (high limit, pressure switch, low-
water-cutoff, etc.), pilots can be lit following the
procedure located on the heater rating plate.
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). 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 heater 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). 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 heater
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 heater).
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 heater 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 heater shuts off. The main burners should re-
ignite when the hi-limit is turned back up to its
original setting.
The high limit should now be reset and the
heater run until it shuts off automatically on high
limit.
3.2 To Start Up System
1. Start up heater.
Be certain system pump is running.
2. Lighting instructions are provided on the heater
rating plate and in the User’s Manual and are as
follows:
a. Turn off main electrical switch.
b. Turn off all manual gas valves and wait
five minutes.
c. Set aquastat or thermostat to lowest setting.
d. Slowly turn manual gas valve to ON.
e. Reset all safety valves (pressure switch,
manual reset high limit, and ignition
control, if applicable).
f. Open manual pilot valve. Turn on main
electrical switch.
g. Set temperature controller to desired
temperature. Pilot will light automatically
to ignite main burners whenever the
thermostat calls for heat.
h. 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 BTU/
hr. The unit's input rate must not be below
this value (refer to rating plate. Laars's
boilers/heaters use gas valves which are
factory set to provide an input on low fire
that meet or exceed the specified minimum.
3. To set temperature controls:
a. Remote Water Heater Temperature Control:
The water heater can be used with a field-
supplied tank aquastat, sequencing control, or other
temperature control device, which will call the unit for
heat when the temperature goes below the controller’s
setpoint. For the most efficient setting, set the tank
temperature at the lowest possible setting for adequate
hot water in the application.