LAARS SUMMIT SMW-250 - Install and Operating Manual - Manual (Page 32)

Page 32 LAARS Heating Systems
8.6.2 Gas Valve Regulation
Gas valve regulation problems can also cause
delayed ignitions. See Sections 7.2.2 and 7.2.2.1
8.6.3 Defective Burner - occurs on
startup or at burner shutdown
A defective burner can cause a delayed ignition
during operation or at shutdown. If the gas supply
pressure is proper, the gas valve is functioning
properly and the gas valve throttle and offset pressure
are set correctly, the burner should be inspected. For
inspection: remove the blower and blower mounting
piece as one unit. The burner is retained by the blower
mounting piece and may be lifted out of the top of the
chamber after the blower mounting piece and blower
have been removed. There should be no distortion or
perforations in the burner other than the punched
holes. Replace if indicated.
8.7 Short Cycling
SMB-200/250 Boiler
Because the Summit 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. If short cycling is frequently
experienced, regardless of the control’s attempt to
limit it, the heating load should be redistributed to
control it.
8.8 Short Cycling
SMW-200/250 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 Summit is a
modulating 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.
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.
8.9 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
) can not 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
). Check
gas valve/venturi setup (Throttle and Offset
Adjustment – Section 7.2.2.1) and adjust if indicated.
Do not attempt to correct combustion without an
O
2
or CO
2
kit and a Magnehelic® pressure gage.
SECTION 9.
Replacement Parts
Description Part Number
1. Thermostat Kit (140°F) 2400-130
2. Pump, Grundfos, UP26-99F - SMB 2400-090**
2. Pump, Grundfos, UP26-99BF - SMW 2400-388***
3. Venturi, Gaskets included 2400-131
4. Exhaust (Flue) Assembly 2400-402
5. Blower 2400-133
6. Gas Valve 2400-134
7. Burner (Flameholder) 2400-135
8. Economizer Coil *
9. Boiler Coil *
10. Combustion Chamber Ass’y 2400-136
Gasket Kit (Not Shown) 2400-137
11. Ignitor/Flame Sensor Ass’y 2400-138
12. Pressure Gauge (75 PSI) - SMB 2400-574**
Pressure Gauge (300 PSI) - SMW 2400-150***
Pressure Relief Valve (50 PSI) - SMB 2400-316**
Pressure Relief Valve (125 PSI) - SMB 2400-097**
Pressure Relief Valve (150 PSI) - SMW 2400-095***
Appliance Control (PCB) 2400-139
Differential Pressure Switch 2400-106
Flue Overheat T’stat (Limit) 2400-058
Sensor, Appliance Discharge 2400-556
Safety Limit 2400-055
Exhaust (flue) Terminal 2400-104
Intake Terminal 2400-102
Wall Flange 2400-100
Propane Conversion Kit 2400-140
* Not Sold Separately, Part of 2400-136
** SMB-200/250 Only
*** SMW-200/250 Only