U.S. Boiler Company X-203 Service manual

106636-01 - 10/15
9700609
Price - $5.00
For service or repairs to boiler, call your heating contractor. When seeking information on boiler,
provide Boiler Model Number and Serial Number as shown on Rating Label.
Boiler Model Number
X-20
Boiler Serial Number Installation Date
Heating Contractor Phone Number
Address
INSTALLATION, OPERATING AND
SERVICE INSTRUCTIONS FOR
X-2™ Series
Cast Iron Gas - Fired Boiler

2
The following terms are used throughout this manual to bring attention to the presence of hazards of various
risk levels, or to important information concerning product life.
DANGER
Indicates an imminently hazardous situation
which, if not avoided, will result in death, serious
injury or substantial property damage.
CAUTION
Indicates a potentially hazardous situation which,
if not avoided, may result in moderate or minor
injury or property damage.
WARNING
Indicates a potentially hazardous situation which,
if not avoided, could result in death, serious injury
or substantial property damage.
NOTICE
Indicates special instructions on installation,
operation, or maintenance which are important
but not related to personal injury hazards.
The City of New York requires a Licensed Master Plumber supervise the installation of this product.
The Massachusetts Board of Plumbers and Gas Fitters has approved the X-2™ Series Boiler. See the Massachusetts Board of
Plumbers and Gas Fitters website, http://license.reg.state.ma.us/pubLic/pl_products/pb_pre_form.asp for the latest Approval
Code or ask your local Sales Representative.
The Commonwealth of Massachusetts requires this product to be installed by a licensed Plumber or Gas tter.
Table of Contents
I. Pre-Installation....................................5
II. Unpack Boiler .....................................5
III. Water Piping and Trim ........................6
IV. Venting ................................................9
V. Gas Piping.........................................11
VI. Electrical............................................12
VII. System Start-up and Checkout ..........16
VIII. Operation..........................................20
IX. Service and Maintenance ...................24
X. Troubleshooting ................................27
XI. Repair Parts.......................................32

3
Table 1A: Dimensions and Connections
Boiler
Model Depth Width Height Supply NPT (inch)
Return NPT
(inch)
Vent
(inch)
Gas NPT
(inch)
Relief Valve
NPT (inch)
Drain
NPT (inch)
X-203 32 14 40 1¼ 1¼ 4 ½ ¾ ¾
X-204 32 16 40 1¼ 1¼ 5 ½ ¾ ¾
X-205 32 19 40 1¼ 1¼ 6 ½ ¾ ¾
X-206 32 22 40 1¼ 1¼ 6 ½ ¾ ¾
X-207 32 25 40 1¼ 1¼ 7 ¾ ¾ ¾
X-208 32 28 40 1¼ 1¼ 7 ¾ ¾ ¾
X-209 32 31 40 1¼ 1¼ 8 ¾ ¾ ¾
Electrical Requirements: 120VAC, 60 Hz, 1-ph, Less than 12A
Maximum Allowable Working Pressure - 50 psi. Boiler shipped from factory with a 30 psi relief valve.
(1) Input ratings can be used for elevations up to 2000 ft. Refer to System Start-up and Checkout Sections for elevations 2000 ft.
or higher.
Boiler
Model Input (MBH) (1) Shipping Weight (lbs)
Empty Weight
(lbs)
Water Content
(gal)
X-203 70 254 180 2
X-204 105 304 231 3
X-205 140 357 284 4
X-206 175 405 332 5
X-207 210 462 382 6
X-208 245 518 438 7
X-209 280 564 484 8
Table 1B: Weights and Volume

4
Figure 1: Minimum Clearance to Combustible Materials and Alcove Dimensions

5
I. Pre-Installation
WARNING
Carefully read all instructions before installing
boiler. Failure to follow all instructions in proper
order can cause personal injury or death.
A. Inspect shipment carefully for any signs of damage.
All equipment is carefully manufactured, inspected
and packed. Our responsibility ceases upon delivery
of boiler to carrier in good condition. Any claim
for damage or shortage in shipment must be led
immediately against carrier by consignee. No claims
for variances or shortages will be allowed by Boiler
Manufacturer, unless presented within sixty (60) days
after receipt of equipment.
B. Installation must conform to the requirements of the
authority having jurisdiction. In the absence of such
requirements, installation must conform to National
Fuel Gas Code, ANSI Z223.1/NFPA 54.
C. Appliance is design certied for installation on
combustible ooring. The boiler must not be installed
on carpeting.
D. Provide clearance between boiler jacket and
combustible material in accordance with local re
ordinance. Refer to Figure 1 for minimum clearance
from combustible material for alcove installation.
Provide 1/2" clearance from water piping to
combustible materials.
E. Provide practical service clearances. A minimum
of 24" from the left side and front jacket panels is
recommended for servicing but may be reduced to
minimums shown in Figure 1.
F. Install on level oor. For basement installation provide
concrete base if oor is not level or if water may be
encountered on oor around boiler.
CAUTION
ASSURE THAT THE FRONT AIR DAM is in place
and undamaged. A damaged front air dam will
negatively affect the performance of this boiler,
which can cause serious property damage,
personal injury or death.
G. Protect gas ignition system components from water
(dripping, spraying, rain, etc.) during boiler operation
and service (circulator replacement, condensate trap,
control replacement, etc.).
H. Provide combustion and ventilation air in accordance
with the section "Air for Combustion and Ventilation,"
of the National Fuel Gas Code, ANSI Z223.1/NFPA 54,
or applicable provisions of local building codes.
WARNING
Adequate combustion and ventilation air must be
provided to assure proper combustion.
I.Do not install boiler where gasoline or other
ammable vapors or liquids, or sources of
hydrocarbons (i.e. bleaches, cleaners, chemicals, sprays,
paint removers, fabric softeners, etc.) are used or stored.
II. Unpack Boiler
CAUTION
Do not drop boiler. Do not bump boiler jacket
against oor.
A. Move boiler to approximate installed position.
B. Remove all crate fasteners.
C. Lift outside container and remove with all other
inside protective spacers and bracing. Save two of the
wooden slats from the container sleeve for use in Steps
E and F.
D. Remove all boiler hold-down fasteners.
E. Tilt the boiler to one side and slide a wooden slat under
the two raised feet.
F. Tilt the boiler to the other side and slide another
wooden slat under the two raised feet.
G. Slide the boiler forward or backward off the skid using
the two wooden slats as runners.
H. Move boiler to its permanent location.

6
III. Water Piping and Trim
WARNING
Failure to properly pipe boiler may result in
improper operation and damage to boiler or
building.
A. Design and install boiler and system piping to
prevent oxygen contamination of boiler water.
Oxygen contamination sources are system leaks
requiring addition of makeup water, ttings, and
oxygen permeable materials in distribution system.
Eliminate oxygen contamination by repairing system
leaks, repairing ttings, and using non-permeable
materials in distribution system.
B. Install circulator with anges, gaskets and bolts
provided.
C. Install Safety Relief Valve. See Figure 2. Safety Relief
Valve must be installed with spindle in vertical position.
WARNING
Safety relief valve discharge piping must be piped
near oor to eliminate potential of severe burns.
Do not pipe in any area where freezing could
occur. Do not install any shut-off valves.
D. Connect system supply and return piping to boiler.
Refer to Figures 2, 4 and 5. Also consult Residential
Hydronic Heating Installation and Design I=B=R
Guide. Maintain minimum ½ inch clearance from hot
water piping to combustible materials.
E. If boiler is used in connection with refrigeration
systems, boiler must be installed with chilled medium
piped in parallel with the heating boiler using
appropriate valves to prevent chilled medium from
entering boiler. See Figure 3. Also consult Residential
Hydronic Heating Installation and Design I=B=R
Guide.
F. If boiler is connected to heating coils located in
air handling units where they may be exposed to
refrigerated air, boiler piping must be equipped with
ow control valves or other automatic means to prevent
gravity circulation of boiler water during operation of
cooling system.
G. Use a boiler bypass if the boiler is to be operated
in a system which has a large volume or excessive
radiation where low boiler water temperatures may be
encountered (i.e. converted gravity circulation system,
etc.).
Remove circulator and install pipe tee between
circulator and boiler return along with second tee in
supply piping as shown in Figures 4 and 5. Bypass
should be same size as the supply and return lines with
valves located in bypass and supply outlet as illustrated
in Figures 4 and 5 in order to regulate water ow to
maintain higher boiler water temperatures.
Set by-pass and boiler supply valves to half throttle
position to start. Operate boiler until system water
temperature reaches normal operating range.
Adjust valves to provide 180° to 200°F supply water
temperature. Opening the boiler supply valve will raise
system temperature, while opening by-pass valve will
lower system supply temperature.
H. If it is required to perform a long term pressure
test of the hydronic system, the boiler should rst be
isolated to avoid a pressure loss due to the escape of air
trapped in the boiler.
To perform a long term pressure test including the
boiler, ALL trapped air must rst be removed from the
boiler.
A loss of pressure during such a test, with no visible
water leakage, is an indication that the boiler contained
trapped air.
Figure 2: Near Boiler Piping
Figure 3: Recommended Piping for Combination
Heating & Cooling (Refrigeration) Systems

7
Figure 4: Recommended Water Piping for Zone Valve Zoned Heating Systems
III. Water Piping and Trim (continued)

8
Figure 5: Recommended Water Piping for Circulator Zoned Heating Systems
III. Water Piping and Trim (continued)

9
IV. Venting
A. Install Vent Damper
OPEN THE VENT DAMPER CARTON and remove the
Installation Instructions. READ THE INSTALLATION
INSTRUCTIONS THOROUGHLY before proceeding.
The automatic gas control valve supplied on each X-2
Series boiler provides the redundancy referenced in the
vent damper Installation Instructions.
CAUTION
Do not use one vent damper to control two heating
appliances.
1. The vent damper must be the same size as the outlet
of the Draft Hood supplied with the boiler (see
Table 1A). Unpack the damper carefully - DO NOT
FORCE IT CLOSED! Forcing the damper may
damage the gear train and void the warranty.
2. Mount the vent damper assembly onto the canopy/
diverter. (Refer to Figure 6 and to instructions
packed with the vent damper for specic
instructions). Do not modify either the draft hood or
vent damper.
NOTICE
Provide adequate clearance for servicing.
3. Locate vent damper position indicating means to be
visible following installation.
WARNING
Provide 6" minimum clearance between damper
and combustible construction.
4. Plug the factory harness vent damper connector into
damper motor polarized receptacle.
DANGER
Inspect existing chimney before installing boiler.
Failure to clean or replace perforated pipe or tile
lining will cause severe injury or death.
B. Inspect chimney and remove any obstructions or
restrictions. Clean chimney if previously used for solid
or liquid fuel-burning appliances or replaces.
C. Install vent system in accordance with "Venting of
Equipment" of the National Fuel Gas Code, ANSI
Z223.1/NFPA 54, or applicable provisions of local
building codes. The X-2 Series boiler is a Category I,
draft hood equipped appliance.
WARNING
D. If an Existing Boiler is Removed:
When an existing boiler is removed from a common
venting system, the common venting system is likely
to be too large for proper venting of the appliances
remaining connected to it.
At the time of removal of an existing boiler, the
following steps shall be followed with each appliance
remaining connected to the common venting system
placed in operation, while the other appliances
remaining connected to the common venting system are
not in operation:
a. Seal any unused openings in the common venting
system.
b. Visually inspect the venting system for proper
size and horizontal pitch and determine there is no
blockage or restriction, leakage, corrosion, and other
deciencies which could cause an unsafe condition.
c. Insofar as is practical, close all building doors and
windows and all doors between the space in which
the appliances remaining connected to the common
venting system are located and other spaces of the
Figure 6: Vent Damper Installation

10
building. Turn on clothes dryers and any appliance
not connected to the common venting system.
Turn on any exhaust fans, such as range hoods and
bathroom exhausts, so they will operate at maximum
speed. Do not operate a summer exhaust fan. Close
replace dampers.
d. Place in operation the appliance being inspected.
Follow the Lighting (or Operating) Instructions.
Adjust thermostat so appliance will operate
continuously.
e. Test for spillage at the draft hood relief opening after
5 minutes of main burner operation. Use the ame
of a match or candle, or smoke from a cigarette,
cigar or pipe.
IV. Venting (continued)
f. After it has been determined that each appliance
remaining connected to the common venting system
properly vents when tested as outlined above, return
doors, win dows, exhaust fans, replace dampers and
any other gas-burning appliance to their previous
condition of use.
g. Any improper operation of the common venting
system should be corrected so the installation
conforms with the National Fuel Gas Code, ANSI
Z223.1/NFPA 54. When resizing any portion of
the common venting system, the common venting
system should be resized to approach the minimum
size as determined using the appropriate tables in
Chapter 13 of the National Fuel Gas Code, ANSI
Z223.1/NFPA 54.

11
A. Size gas piping. Design system to provide adequate gas
supply to boiler. Consider these factors:
1. Allowable pressure drop from point of delivery to
boiler. Maximum allowable system pressure is ½
psig. Actual point of delivery pressure may be less;
contact gas supplier for additional information.
Minimum gas valve inlet pressure is listed on rating
label.
2. Maximum gas demand. Consider existing and
expected future gas utilization equipment (i.e. water
heater, cooking equipment).
B. Connect boiler gas valve to gas supply system.
1. Use methods and materials in accordance with local
plumbing codes and requirements of gas supplier. In
absence of such requirements, follow National Fuel
Gas Code, ANSI Z223.1/NFPA 54.
2. Use thread (joint) compounds (pipe dope) resistant
to action of liqueed petroleum gas.
3. Install sediment trap, ground-joint union and manual
shut-off valve upstream of boiler gas control valve.
See Figure 7.
V. Gas Piping
Figure 7: Pilot and Gas Piping
4. All above ground gas piping upstream from manual
shut-off valve must be electrically continuous and
bonded to a grounding electrode. Do not use gas
piping as grounding electrode. Refer to National
Electrical Code, ANSI/NFPA 70.
C. Pressure test. The boiler and its gas connection must
be leak tested before placing boiler in operation.
1. Protect boiler gas control valve. For all testing over
½ psig, boiler and its individual shutoff valve must
be disconnected from gas supply piping. For testing
at ½ psig or less, isolate boiler from gas supply
piping by closing boiler's individual manual shutoff
valve.
2. Locate leaks using approved combustible gas
detector, soap and water, or similar nonammable
solution. Do not use matches, candles, open ames,
or other ignition source.

12
VI. Electrical
A. General. Install wiring and electrically bond boiler to
ground in accordance with requirements of authority
having jurisdiction, or in absence of such requirements,
with the National Electrical Code, ANSI/NFPA 70.
B. Install thermostat. Locate on inside wall
approximately 4 feet above oor. Do not install on
outside wall, near replace, or where inuenced by
drafts or restricted air ow, hot or cold water pipes,
lighting xtures, television, or sunlight. Allow free air
movement by avoiding placement of furniture near
thermostat.
C. Wire boiler. Boiler is rated for 120 VAC, 60 hertz,
less than 12 amperes. A separate electrical circuit
must be run from the main electrical service with an
over-current device/disconnect in the circuit. A service
switch is recommended and may be required by some
local jurisdictions. Connect to black and white wires
and green ground screw. See Figures 8 and 9.
D. For installations using zone valves provide separate
transformer for zone valve wiring. Consult zone valve
manufacturer for assistance. See Figure 10.
CAUTION
This boiler contains controls which may cause
the boiler to shut down and not restart without
service. If damage due to frozen pipes is a
possibility, the heating system should not be
left unattended in cold weather; or appropriate
safeguards and alarms should be installed on the
heating system to prevent damage if the boiler is
inoperative.

13
Figure 8: Wiring Connection Diagram
VI. Electrical (continued)

14
Figure 9: Schematic Ladder Diagram
VI. Electrical (continued)

15
VI. Electrical (continued)
Figure 10: Wiring Schematic, Zone Valves
Figure 11: Wiring Schematic, Zone Circulators

16
VII. System Start-up and Checkout
A.Main Burner Check - Check main burners to see
that they were not dislodged during shipment. Rear
of burners should be in the vertical slots in the rear of
burner tray and the front of the burners should be seated
completely on the orices.
B. Initial start -
For models equipped with IDL 1200 LWCO follow
these steps:
1. Before lling the boiler with water, turn on power
to the boiler and set the thermostat to call for heat.
Both the green "POWER" LED and amber "LOW
WATER" LED should illuminate (see Figure 12).
The burner should not re. WARNING: If the
burner res with no water at the probe, immediately
shut down power to the boiler and contact the
factory for assistance.
2. Proceed to ll the boiler with water. When water
reaches the IDL 1200 Sensor, the "LOW WATER"
LED will turn off and the burner will re.
3. Turn off the power to the boiler and nish lling the
system.
4. Before leaving the job, set the thermostat to call for
heat and push the "TEST" button on the Model IDL
1200 to simulate a low water condition. The amber
"LOW WATER" LED will illuminate and the burner
will shut down.
5. Release the "TEST" button and the burner will light
off.
For models equipped with zone valves follow the
these steps.
1. Fill entire heating system with water and vent air
from system.
a. Close isolation valve in boiler supply piping.
b. Isolate all circuits by closing zone valves or
balancing valves.
c. Attach a hose to hose bib located just below
isolation valve in boiler supply piping. (Note
- Terminate hose in ve gallon bucket, at a
suitable oor drain, or outdoor area).
d. Starting with one circuit, open zone valve.
e. Open hose bib.
f. Open ll valve (Make-up water line should be
located directly above isolation valve in boiler
supply piping).
g. Allow water to overow from bucket until
discharge from hose is bubble free for 30
seconds.
h. Open zone valve to the second zone to be
purged, then close the rst. Repeat this step until
all zones have been purged, but always have one
zone open. At completion, open all zone valves.
i. Close hose bib, continue lling the system
until the pressure gauge reads 12 psi. Close ll
valve. (Note - If make-up water line is equipped
with pressure reducing valve, system will
automatically ll to 12 psi. Leave globe valve
open).
j. Open isolation valve in boiler supply piping.
k. Remove hose from hose bib.
2. Turn ROOM THERMOSTAT to lowest setting.
3. Be sure that gas to pilot and main burners has been
off for at least ve minutes and vent damper has
been in the open position.
4. Turn "OFF" the electric switch serving boiler.
5. Open valve on main gas line at meter.
6. PURGE AIR FROM GAS PIPING. Adequate
ventilation must be provided and no smoking or
open ame permitted.
7. Turn "ON" electric switch serving boiler.
8. Open Manual Shut-off Valve upstream of
Combination Gas Valve.
9. Loosen or remove Inlet Pressure Tap Plug in
Combination Gas Valve and when purging is
complete, tighten or replace plug. (See Figure 13).
10. Check pipe and ttings from meter to Combination
Gas Valve using soap solution or other approved
methods.
Figure 13: Top View of Honeywell Gas Valves
Figure 12: IDL 1200 Low Water Cut-Off

17
Figure 14: Operating Instructions
VII. System Start-up and Checkout (continued)

18
VII. System Start-up and Checkout (continued)
CAUTION
11. Test gas piping and connections between
Combination Gas Valve and manifold, orices, and
pilot piping for leaks after boiler is operating. Use
soap solution or other approved method.
C. Check Gas Input to Boiler
1. Input Rate and Maximum Inlet Pressure shown on
Rating Label must not be exceeded. Inlet pressure
must not be lower than minimum inlet pressure
shown on Rating Label.
2. Input ratings shown on boiler rating label can be
used for elevations up to 2000 ft. For elevations
2000 ft or higher, reduce input rate 4 percent per
1000 ft above sea level. Do not install at elevations
above 12,000 ft. See Table below.
Boiler
Model
Input [Mbh]
Rating
Label
5000 ft.
(1525 m)
7,000 ft.
(2130 m)
10,000 ft.
(3050 m)
X-203 70.0 56.0 49.0 42.0
X-204 105.0 84.0 73.5 63.0
X-205 140.0 112.0 98.0 84.0
X-206 175.0 140.0 122.5 105.0
X-207 210.0 168.0 147.0 126.0
X-208 245.0 196.0 171.5 147.0
X-209 280.0 224.0 196.0 168.0
3. All Rate checks and all adjustments are to be made
while boiler is ring - all other appliances connected
to the same meter as the boiler must be off.
4. With boiler off, water Manometer or water column
gauge should be connected to a shut-off valve
installed in the 1/8" outlet pressure tap in the gas
valve (see Figure 13). By installing gas valve
upstream of manometer, gas pressure can be
introduced gradually - without shut-off valve; surge
of pressure when boiler is turned on, could blow
liquid out of manometer. Replace plug in gas valve
when rate check is nished.
5. Lp Gas Input:
Adjust Regulator on Gas Valve so that manifold
pressure is 10 inches water column. Turning
Regulator Adjusting Screw Clockwise increases
pressure. Counterclockwise rotation decreases
pressure.
6. Natural Gas Input:
Adjust regulator on Gas Valve so that manifold
pressure is 3½ inches water column. Turning
Regulator Adjusting Screw Clockwise increases
pressure. Counter-clockwise rotation decreases
pressure.
D. Check Main Burner Flame. See Figure 15. Flame
should have a clearly dened inner cone with no yellow
tipping. Orange-yellow streaks caused by dust should
not be confused with true yellow tipping.
Figure 15: Main Burner Flame
E. Check Pilot Burner Flame.
1. See Figure 16. The pilot burner should be lit only
if thermostat is calling for heat. The pilot burner
produces three (3) ames. The center ame should
be steady, medium hard blue enveloping 3/8 to 1/2
inch of sensing probe.
F. Check Ignition System Safety Shut-off Device.
Remove 3-wire plug from gas valve.
If burners do not shut down determine cause of
malfunction. Replace necessary items and check
operation.
G. Check Vent Damper Operation. Vent Damper must
be in open position when main burners are operating.
H. Check High Limit Control.
Jumper Thermostat connections in boiler wiring
harness. Allow burners to operate until shutdown by
limit. REMOVE JUMPER.
I. Check Thermostat Operation. Raise and lower
temperature setting to start and stop boiler operation.
Adjust thermostat to normal setting.
CAUTION
Avoid operating this boiler in an environment
where saw dust, loose insulation bers, dry wall
dust, etc. are present. If boiler is operated under
these conditions, the burner interior and ports
must be cleaned and inspected daily to insure
proper operation.

19
VII. System Start-up and Checkout (continued)
Figure 16: Pilot Burner Flame
J.Combustion Chamber Burn-off
1. The mineral wool combustion chamber panels
may contain a cornstarch based binder that must be
burned out at installation to prevent odors during
subsequent boiler operation.
2. Ventilate the boiler room, set the high limit to its
maximum setting, set the thermostat to call for heat.
Allow the boiler to re for at least an hour or until
the odor from the cornstarch has dissipated.
3. Return the high limit and thermostat to their desired
settings.
K. Review User's Information Manual and system
operation with owner or operator.
L. Post instructions near boiler for reference by owner
and service personnel.

20
VIII. Operation
Status Codes displayed in STA Mode
Status STA Description
Standby
(Burner off
Circulator off)
1No call for heat detected
Circulator
Pre-purge
(burner off
circulator on)
1
Either condition is true:
a. Call for heat detected and boiler
temperature higher than operating
setpoint.
b. Call for heat detected and boiler
temperature higher than Start
Temperature (140°F default) and
Circulator Pre-purge Time has not
expired.
Self Test 17 Control internal checking
Drive Damper
Open 18
The damper is energized. The
control is waiting for the damper
switch to close. If the damper
end switch doesn't close within 60
seconds, the control goes to STA 20
Pre-purge 4Damper is open for a 2 second delay
Spark 6The pilot fuel valve is open and
sparking is started.
Flame
Proving 7The main fuel valve is open and ame is being proven.
Running 8
The burner runs until the call for heat
is satised or the operating setpoint is
reached.
Table 2: Sequence of Operation
Status Codes displayed in STA Mode
Status STA Description
Retry /
Recycle
Delay
10
If the burner fails to light off (no ame
signal), it waits 5 minutes and retries
or if the control loses ame signal
during running, it will wait 10 seconds
and then recycle.
Soft Lockout 13 System is shutdown and will restart
following a one hour enforced delay.
Hard Lockout 14
System is locked out. A manual or
power reset is required to be able to
light off again.
Limit Open 15 There is a call for heat from the
thermostat, but a Safety Limit is open.
Flame
Present Out
of Sequence
16 Flame signal is still present when
expected to be 0 (no ame).
Damper
Failed to
Open
20
The damper is still energized and the
damper end switch has not closed.
Table 3: Sequence Fault
A. BOILER SEQUENCE OF OPERATION
NORMAL OPERATION
1. The X-2 Series Boilers are equipped with an
Intelligent Hydronic Control (control). This control
replaces the traditional separate ignition control,
high limit switch and circulator relay and adds
energy saving thermal purge features. Energy is
saved by starting the circulator and delaying the
burner start when there is residual heat available in
the boiler.
2. The boiler’s sequence of operation is shown in
Table 2.
3. When the thermostat calls for heat the control
starts the system circulator and the thermal purge
(circulator Pre-purge time) begins. If the time is
completed or boiler temperature is less than the
Start Temperature (140°F default) the start sequence
continues by energizing the vent damper. Once the
vent damper is fully open the ignition sequence is
started allowing gas ow and ignition of the burners.
Damper must be in open position when appliance
main burners are operating.
4. If the thermostat is not satised and the operating
setpoint is reached the system circulator will
continue to operate and the burners will stop.
When the boiler water temperature drops below the
setpoint less the differential setting the burners will
restart.
5. After the thermostat is satised the burners and
circulator are stopped and vent damper is closed.
6. When an indirect water heater aquastat call for heat
is wired to the DHW input, the control starts the
Domestic Hot Water circulator and, if the boiler
temperature is less than the operating setpoint less
differential, the vent damper is energized without
delay. Once the vent damper is fully open, the
ignition sequence is started allowing gas ow and
ignition of the burners.
7. Models equipped with IDL 1200 LWCO:
The IDL 1200 Low Water Cut-Off is designed
to protect from potentially damaging low water
conditions in the boiler. In the event of a low water
condition, the "LOW WATER" LED will turn on
and the control will shutdown the burner.
WARNING
A low water condition is a serious and potentially
dangerous condition. In the event the IDL 1200
detects a low water condition, the system must be
inspected by a qualied service technician before
the boiler is returned to service. Do not attempt to
add water to a hot boiler. Allow the boiler to fully
cool before adding water.
B. BOILER FAULT
In the event the boiler fails to start, the control provides
status information to help determine the cause of the
problem. Table 3 provides a list of boiler status codes
that are reported. Refer to the Troubleshooting Section
for more information.