LAARS Mighty Therm2 MT2V (Sizes 500–2000 MBTU/h) - Install and Operating Manual - Manual (Page 28)

LAARS Heating Systems Page 28
as long as the unit is being called for heat. The
blower and pump come on for pre-purge, then
the ignitor warm-up sequence starts and after the
ignitor warm-up is complete and all safety devices
are verified, the gas valves open. If ignition doesn’t
occur, check that there is proper gas supply. Wait
5 minutes and start the unit again. During initial
start up, air in the gas line may cause the Mighty
Therm2 to "lock out" during the first few trials
for ignition. Depending on the ignition modules
installed, the manual reset button on the ignition
modules may need to be depressed to restart the
Mighty Therm2.
6. When the unit is running, the supply gas pressure
must be checked. Inlet gas pressure must not
exceed 13" W.C. (3.2kPa). The minimum inlet gas
pressure is 5" W.C. (1.2kPa).
7. Once the inlet gas pressure is verified, the
outlet gas pressure from each valve (manifold
gas pressure) must be checked, and adjusted, if
necessary. The manifold gas pressure must be 2.5"
W.C. (0.62kPa).
8. Complete the setup by checking the CO
2
at the
outlet of the unit. The CO
2
should be 8% for natural
gas, or 9.2% for propane.
9. After placing the appliance in operation, the
Burner Safety Shutoff Device must be tested.
(a) Close gas shutoff valve with burner operating.
(b) The flame will go out and blower will
continue to run for the post purge cycle.
One additional attempt to light will follow.
Ignition will not occur as the gas is off. The
ignition control will lockout, and will have to
be reset before the unit will operate.
(c) Open gas shutoff valve. Restart the appliance.
The ignition sequence will start again and the
burner will start. The appliance will return to
its previous mode of operation.
NOTE: Unit sizes 1000–2000 have two ignition controls
and two ignitors, which work independently of one
another. If the ignition control for stage 1 fails to properly
light the main burners for that stage, the second ignition
control will still be active, and will be able to energize
stage 2. This, of course, will only occur upon call for
stage 2 and if all other safety devices confirm that the
unit will run in a safe condition.
6.6.2 High Altitude Adjustment and Set Up
Mighty Therm2 appliances may be operated at
high altitude (7700 ft., 2347 m) with a reduction in
output of approximately 10%. At altitudes of less than or
more than 7700 ft. (2347 m) the appliance will perform
equally as well, but with differing reductions in output.
At elevations higher than 7700 ft. (2347 m) the reduction
in output will exceed 10% and at elevations below 7700
ft. (2347 m) it will be less than 10%. High altitude
adjustment must not be made on appliances operating at
elevations below 2500 ft. (762 m).
and to replace any part of the control system and any
gas control that may have been
under water.
6.3 Operating Temperature Control
All Mighty Therm2's are equipped with a two-stage
aquastat. To utilize this mounted controller be sure to
have the "Local/Remote" selector switch to "Local".
Set the controller to the desired operating set point.
The controller has an interstage differential that can be
adjusted from 3°F to 10°F. This allows the user to have
some control over how stage 2 and stage 1 call for heat
( see Figure 22 ).
Because the Mighty Therm2 controller senses inlet
water and the manual reset high limit senses outlet water,
the high limit should be set 40-50°F higher than the
controller, to avoid nuisance lockout of the manual reset
high limit.
6.4 External Boiler Operations
If controlling the stages of the MT2 from an
external source (multiple boiler control, BAS, etc) the
"Local/Remote" selector switch above the terminal strip
must be placed in the "Remote" position. In this mode,
the controller that is mounted on the MT2 will no longer
have control of the unit. The 24V from the unit waits at
the input terminal, and the external control switches this
24V from the input terminal to the stage terminal.
6.5 Limit Controls
The manual reset high limit control is provided
as standard equipment on all heaters. An additional
automatic reset switch is optional.A high limit
temperature-sensing bulb is always located in the heater
outlet. Burners will automatically shut down whenever
overheating occurs.
6.6 Operating the Burner and Set Up
6.6.1 Set Up for 0 to 2500 Feet Altitude
The Mighty Therm2 appliance utilizes a modular
design to achieve its stage-firing. The setup must be
checked before the unit is put in operation. Problems
such as failure to start, rough ignition, strong exhaust
odors, etc. can be due to improper setup. Damage to the
Mighty Therm2 resulting from improper setup is not
covered by the limited warranty.
1. Using this manual, make sure the installation
is complete and fully in compliance with the
instructions.
2. Determine that the appliance and system are filled
with water and all air has been bled from both.
Open all valves.
3. Observe all warnings on the Operating Instructions
label and turn on gas and electrical power to
appliance.
4. Switch on the appliance power switch located on
the right side of the unit.
5. The Mighty Therm2 will enter the start sequence,