LAARS NeoTherm NTV600 - Install and Operating Manual - Manual (Page 51)

NeoTherm Boilers and Water Heaters
Page 49
SECTION 12.
Trouble Shooting
12.1 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
temperature controller settings and readings.
5. When the call for heat is complete, or the unit reaches
its setpoint temperature, the gas valve will close, and
the fan will continue to run for its 20 second post-
purge. If a pump delay time is used, the pump will
continue to run for the specified amount of time
(adjustable from 0.1 to 10 minutes).
12.2 Short Cycling
Because NeoTherm is a modulating boiler, and its
input will decrease when there is a reduction in heating
load, short cycling is greatly reduced. If the heating load
drops below the minimum input of the boiler for an
extended period, the boiler will have a tendency to short
cycle. This can be a symptom of improper control
strategy or setpoints, or a load distribution problem.
NeoTherm has a built-in anti-short cycle (ASC) feature.
ASC is a timed setting that will delay the boiler start for
a specified time after one call for heat is completed.
ASC time may be adjusted as desired (see
Section 8 for
more information).
12.3 Error Codes - See Table 18 .
NT SIZE (MBTU) KIT NUMBER
80 CA006201
105 CA006202
150 CA006203
199 CA006204
210 CA006204
285 CA006205
399 CA006207
500 CA006207
600 CA006207
750 CA006207
850 CA006207
Table 17. Propane Gas Conversion Kits.
11.2.9 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".
11.2.10 Gas Conversion
NeoTherm units can be converted from natural to
propane gas or from propane to natural gas easily in the
field. Some units require the addition of a gas orifice
along with proper gas valve adjustment. Other units
require no additional parts, only proper gas valve
adjustment. Please contact the Laars factory for specific
information regarding the gas conversion of an
appliance. If a gas conversion is performed, the unit
must be identified with the appropriate gas labels and a
conversion sticker to allow technicians performing
maintenance in the future to properly identify the gas
type of the appliance.