LAARS Pennant PNCV (Sizes 500-2000) - Install and Operating Manual - 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