Laars NeoTherm NTH Installation And Operation Instructions Manual - page 34
LAARS Heating Systems
Page 34
the burner door blower arm. If the fan is determined to
be defective replace the existing fan with a new one
reversing the steps above. Make sure to install all of the
required O-rings and gaskets between the blower arm
and the blower and blower face and venturi flange.
7.2.8 Heat Exchanger Coils
Black carbon soot buildup on the external surfaces
of the heat exchanger is caused by one or more of the
following; incomplete combustion, combustion air
problems, venting problems and heater short cycling.
Soot buildup or other debris on the heat exchanger may
restrict the flue passages.
If black carbon soot buildup on the heat exchanger
is suspected, disconnect electrical supply to the unit,
and turn off the gas supply by closing the manual gas
valve on the unit. Access the heat exchanger through the
burner door at the front of the boiler, and inspect the
tubing using a flashlight. If there is a buildup of black
carbon soot or other debris on the heat exchanger, clean
per the following:
Caution
Black carbon soot buildup on a dirty heat exchanger
can be ignited by a random spark or flame. To
prevent this from happening, dampen the soot
deposits with a wet brush or fine water spray before
servicing the heat exchanger.
1.
Shut off the 120 Volt power supply to the boiler
2.
Turn off all manual gas valves connecting the
boiler to the main gas supply line.
3.
For NT 600 models only
(all other sizes please
skip to step four)
. NT 600 models will require the
gas valve to be removed in order to remove the
burner door. To do this, remove the wire
connections from the gas valve. Remove the flange
bolts from the gas supply pipe connected to the gas
valve (1B). Remove the flange bolts connecting
the gas train to the venturi (1A). Remove the gas
train assembly keeping gaskets and o-rings.
4.
Remove the four bolts connecting the blower
flange to the burner door arm.
5.
Remove the nuts located on the outside diameter
of the burner door to the heat exchanger.
6.
Remove the burner door/burner assembly from the
heat exchanger.
7.
Disconnect the condensate drain line.
8.
Attach a longer hose to drain and run to a bucket.
9.
Clean the heat exchanger by brushing light
accumulations of soot and debris. Use a brush with
soft bristle (non metal) to avoid damaging the
surface of the heat exchanger tubes.
10.
Once the tubes have been brushed clean rinse the
tubes and combustion chamber with a small
amount of water to rinse all of the debris out of the
bottom of the flue collector and into the longer
condensate trap line, which is being diverted into a
separate container.
NOTE: The Warranty does not cover damage caused
by lack of required maintenance, lack of water flow,
or improper operating practices.
WARNING
Failure to rinse the debris from the heat exchanger
and temporary drain line may lead to clogged
condensate lines, traps and neutralizers. Condensate
pumps (if used) may also be damaged from the
debris left behind, possibly causing property damage.
11.
Install all components removed in the reverse
order to place the appliance back in operation.
Make sure all gaskets are in place as components
are installed. Replace any damaged gaskets. Do
NOT reuse damaged gaskets.
12.
Place the appliance in operation according to
Section 6.2
checking all gas connections for leaks.
Confirm all fasteners are tight.
7.2.9 Gas Pressure Switches
(optional)
The high and low gas pressure switches are 24V
manual reset switches that act to cut power to the gas
valves if the gas pressure is too low or too high for
proper operation. The gas pressure switches used are
integrally vent limited, and do not require venting to
atmosphere. To remove a switch, remove the screw on
the plastic housing and pull the clear cover off.
Disconnect the two wires from the screw terminals.
Twist the switch off the pipe nipple. Reassemble in
reverse order. For natural gas, set the low gas pressure
switch to 3" w.c. For propane, set the low gas pressure
switch to 5" w.c. For natural and propane, set the high
gas pressure switch to 14".
SECTION 8.
Trouble Shooting
8.1 Sequence of Operation
NeoTherm is a cold start appliance that should
start only on a call for heat from a tank aquastat, room
thermostat, zone valve end switch or other space
temperature control device.
1.
Upon a call for heat: (a) the internal pump and
system pump will start; (b) the blower will begin a
30 second pre-purge.
2.
Following the prepurge cycle the direct spark
ignition will spark and will begin a 4 second trial
for ignition. The unit is allowed one or three
ignition retries.
3.
The gas valve will then be energized and a reduced
rate ignition will occur. The unit will remain in a
reduced rate start-up period for several seconds.
4.
After the reduced rate start time is over, the unit
will be in normal operation. Firing rate will
modulate based on the heating load via the