Laars Pennant PNCH Installation And Operation Instructions Manual - page 51
Pennant
(500-2000)
Page 51
controller setup. Contact your Laars representative to
discuss possible remedies.
8.4 Short Cycling — Water Heater
Short cycling will generally occur only in
combination space heating and water heating
applications when the water heater is operating in the
space-heating mode. Because the Pennant is a stage-
fired water heater and its input will reduce when there
is a reduction in heating load, short cycling is greatly
reduced. If the heating load drops below the minimum
input of the water heater for an extended period, the
water heater will have a tendency to short cycle. If
short cycling is frequently experienced, regardless of
the control’s attempt to limit it, the heating load should
be redistributed to control it. See Section 6.3 regarding
controller setup.
If short cycling occurs in a water heater
application, it is probably caused by undersized piping
between the water heater and the storage tank or by
some other factor that restricts proper water flow
through the water heater. The cause should be
determined and corrected.
8.5 High Gas Consumption
Appliances operating with an improper air/fuel
ratio are very inefficient and consequently, have very
high gas consumption. Because efficiency is high when
the CO
2
is high (or O
2
is low), appliances operating
with low CO
2
or high O
2
(especially LP appliances)
consume more gas. Adjust the CO
2
or O
2
for optimum
efficiency. If no combustion analyzing equipment (CO
2
or O
2
) is available then a proper adjustment of the air/
fuel ratio (CO
2
or O
2
) cannot be accomplished.
However, by briefly sniffing the flue gases it is
possible to determine if the CO
2
or O
2
is within the
proper range. No significant flue gas odor should be
detected when combustion is proper. A strong piercing
smell indicates poor combustion and generally a lean
mixture - low CO
2
or high O
2
. The CO
2
should be 8%
at high fire. To check the CO
2
, first verify that the
supply gas pressure is within 5" to 13" w.c. (1.2 to 3.2
kPa) With the Pennant running with all stages firing,
set the air box pressure to 1.5" w.c. (0.37 kPa) (as a
starting point), by adjusting the air shutter(s) at the
bottom of the fan(s). Check the CO
2
, and adjust the air
shutters if further adjustment to the CO
2
is needed.
Sizes 1250 to 2000 have two blowers and two air
chambers (boxes). The pressure of each air box must
be equal when the final adjustment is made.
8.6 Troubleshooting the Temperature
Control
See Table 12.
8.7 Troubleshooting Pennant Controls
The Pennant series consists of two 2-stage
SECTION 8.
Trouble Shooting
8.1 Resolving Lockouts
There are many causes of lockouts. The three
most common causes are: (1) inadequate gas supply,
(2) poor combustion, (3) ignitor failure.
1.
Inadequate gas supply: Before proceeding, ensure
that the gas supply has not been shutoff or the LP
tank (LP boilers) is not empty. Then, restart the
boiler and observe the operational cycle. After a
15-second fan pre-purge, the ignitor will heat up
for 20 seconds, and then the unit will light. If it
does not, check the gas supply pressure to the
appliance, after resetting the appliance and
attempting another start-up. The gas pressure to
the appliance must be above 5" w.c. (1.2kPa)
throughout the entire start-up cycle. If it is not,
correct the supply problem (check gas valves or
supply piping). If the supply pressure is
adequate, consult the factory for assistance.
2.
Poor Combustion: Poor combustion should be
suspected if there is a strong flue gas odor. The
odor may result from an improper gas/air ratio
(high or low O
2
or CO
2
). Pennant appliances
operate best with 45% excess air (8% CO
2
on
natural gas, 9.2% CO
2
on LP). Check the CO
2
of
the appliance and adjust if necessary.
3.
Ignitor failure: If the boiler goes through a normal
start cycle but combustion does not occur, ignitor
failure should be suspected. Check the ignitor by
unplugging the ignitor plug and measuring the
ignitor resistance. It should be 50-80 ohms. If the
resistance is not 50-80 ohms, replace the ignitor.
If the resistance is correct, reset the boiler and
check for 120 VAC at the ignitor plug during the
start cycle. If there is no voltage, replace the
faulty ignitor wire harness or the ignition control.
8.2 Delayed Ignition — Possible Causes
A defective burner can cause a delayed ignition.
If the gas supply pressure is proper and the gas valves
are functioning properly, then burners should be
inspected. There should be no distortion or
perforations in the burners outside of the active burner
port area. Replace if indicated.
8.3 Short Cycling — Boiler
Because the Pennant is a stage-fired 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. See Section 6.3 regarding