LAARS Pennant PNCV (Sizes 200, 300, 400) - Install and Operating Manual - Manual (Page 36)

LAARS Heating Systems
Page 34 Pennant 200, 300, 400 Page 35
3. Disconnect and remove the wires, conduit and
sensors from all components that are attached to
the inlet/outlet header.
4. Isolate the heat exchanger from the water supply.
5. Disconnect the header flanges from the inlet and
outlet.
6. Allow the heat exchanger to drain. Remove the
venting and remove the top, by removing the
screws that attach the top to the side panels.
Remove the side panels.
7. Remove the heat exchanger from the unit.
NOTE: Heat exchangers are heavy and may
require two people to remove to avoid personal
injury.
8. Clean the heat exchanger: A light accumulation
of soot or corrosion on the outside of the heat
exchanger can be easily removed. Use a wire
brush to remove loose soot and scale from the
heat exchanger.
9. NOTE: While the heat exchanger is out of the
unit, inspect the firewall refractory insulation.
Replace if necessary.
10. Inspect the inside of the copper tubes for scale
buildup. Scale can build up on the inner surface
of the heat exchanger tubes, which can restrict
water flow. If the tubes show signs of scaling,
clean the internal surface.
11. Reassemble in the reverse order, and check
appliance operation after start-up.
NOTE: The warranty does not cover damage
caused by lack of required maintenance, lack of
water flow, or improper operating practices.
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 40 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 in. w.c. (1.2 kPa)
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
Boiler short cycling is caused when the load
on the boiler system swings rapidly causing frequent
cycling between call for heat and satisfied conditions.
This condition is greatly reduced on two stage units
or stage controlled multiple boiler systems which can
change heat input to better match the load. If short
cycling is a problem, it may be due to an oversized
boiler, improper control strategy, incorrect set points
or a load distribution problem. The boiler controls
must be set such that the heating loop temperature
setpoint, SP2 (if used), does not interfere with the
setpoint of the boiler operating control, SP1. If the
set points are correct and the system design, controls
scheme, etc. are fixed, the temperature differentials
may be increased to reduce short cycling. If desired
temperature response is not achievable without short
cycling it may be necessary to install a buffer tank
in the system. 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. 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.