Installation / Operation Instruction Manual

Page 36
Bradford White Corp
SECTION 8 Trouble Shooting
8.A 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 shuto 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 Natural gas
pressure to the appliance must be above 4 in. w.c.
(1.0 kPa) throughout the entire start-up cycle. See
Table 11. 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 ue gas odor. The
odor may result from an improper gas/air ratio
(high or low O
2
or CO
2
). Brute Deluxe 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.B 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.C 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 satised conditions.
This condition is greatly reduced on two stage
units. If short cycling is a problem, it may be due
to an oversized boiler, incorrect set points or a load
distribution problem. If desired temperature response
is not achievable without short cycling it may be
necessary to install a buer tank in the system. Contact
your Bradford White representative to discuss possible
remedies.
8.D 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.
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
ow through the water heater. The cause should be
determined and corrected.
8.E High Gas Consumption
Appliances operating with an improper air/fuel
ratio are very inecient and consequently, have very
high gas consumption. Because eciency 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
eciency. 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. The
CO
2
should be 8% at high re for natural gas and 9.2%
at high re for LP. To check the CO
2
, rst verify that
the supply gas pressure is within 4.0 to 13 in. w.c. (1.0
to 3.2 kPa). See Table 11
With the Brute Deluxe running with all stages
ring, set the air box pressure to 1.8 in. w.c. (0.42 kPa)
(as a starting point), by adjusting the air shutter(s) at
the intake of the fan(s). Check the CO
2
, and adjust the
air shutters if further adjustment to the CO
2
is needed.