U.S. Boiler Company SERIES 3 Service manual

103796-04 - 3/13
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
30__B Boiler Serial Number Installation Date
Heating Contractor Phone Number
Address
INSTALLATION, OPERATING AND
SERVICE INSTRUCTIONS FOR
SERIES 3™
Gas - Fired Boiler

2
FOLLOW ALL INSTRUCTIONS and warnings
printed in this manual and posted on the boiler.
INSPECT THE BOILER ANNUALLY. To keep your
boiler safe and efcient, have a service technician
follow the Service checklist near the end of this
manual.
IF YOU ARE NOT QUALIFIED to install or service
boilers, do not install or service this one.
THE BOILER MAY LEAK WATER at the end of
its useful life. Be sure to protect walls, carpets,
and valuables from water that could leak from the
boiler.
PROTECT YOUR HOME IN FREEZING
WEATHER. A power outage, safety lockout, or
component failure will prevent your boiler from
lighting. In winter, your pipes may freeze and cause
extensive property damage. If you must leave
your home unattended for an extended time when
outdoor temperatures are below 32°F, rst turn off
your home’s main water supply and drain the water
from all pipes.
DO NOT BLOCK AIR FLOW into or around the
boiler. Insufcient air may cause the boiler to
produce carbon monoxide or start a re.
KEEP FLAMMABLE LIQUIDS AWAY from the
boiler, including paint, solvents, and gasoline.
The boiler may ignite the vapors from the liquids
causing explosion or re.
KEEP CHILDREN AND PETS away from hot
surfaces of the boiler, boiler piping, and vent pipe.
CARBON MONOXIDE (CO) is an odorless, deadly
gas that may be introduced into your home by
any malfunctioning fuel-burning product or vent
system failure. Consider installing CO alarms near
bedrooms in all levels of the building to warn you
and your family of potential CO exposure.
WARNINGS FOR THE HOMEOWNER
READ THIS ENTIRE MANUAL before attempting
installation, start-up, or service. Improper
installation, adjustment, alteration, service, or
maintenance may cause serious property damage,
personal injury, or death.
DO NOT DISCONNECT PIPE FITTINGS on the
boiler or in the heating system without rst verifying
that the system is cool and free of pressure and
that your clothing will protect you from a release
of hot water or steam. Do not rely solely on the
boiler’s temperature and pressure gage when
making this judgment.
USE PROPER PERSONAL PROTECTION
EQUIPMENT when servicing or working near the
boiler. Materials of construction, ue products, and
fuel contain alumina, silica, heavy metals, carbon
monoxide, nitrogen oxides, and/or other toxic or
harmful substances that can are hazardous to
health and life and that are known to the State of
California to cause cancer, birth defects, and other
reproductive harm.
INSTALL ALL GUARDS, cover plates, and
enclosures before operating the boiler.
THIS INSTALLATION IS NOT COMPLETE until
the front air dam is installed (See Figure 2-a).
Product performance will be negatively affected if
the front air dam is not installed which can cause
serious property damage, personal injury or death.
SIZE THE BOILER PROPERLY relative to the
design heat load or, if using domestic hot water
priority, the peak hot water load, whichever
is larger. A grossly oversized boiler will cycle
excessively and this will lead to premature failure
of the boiler and its components. Our warranty
does not apply to damage from excessive cycling.
ADHERE TO ALL LOCAL CODE
REQUIREMENTS. Contact your local code
inspector prior to installation. In the absence of
a local code, adhere to the National Fuel Gas
Code ANSI Z223.1/NFPA 54 or CAN/CSA B149.1,
Natural Gas and Propane Installation Code.
ALL WIRING must comply with the National
Electrical Code ANSI/NFPA 70 (in the USA) or the
Canadian Electrical Code CSA C22.1 (in Canada)
and any local regulations.
IT IS THE RESPONSIBILITY OF THE INSTALLING
CONTRACTOR to see that all controls are correctly
installedandareoperatingproperlywheninstallation
is complete including verifying that the limit sensor
is fully installed.
Failure to properly install Limit Sensor may result in
property damage, personal injury or loss of life due to
elevated operating temperatures and/or pressures.
WARNINGS FOR THE INSTALLER

3
Congratulations on your purchase of a new Series 3™ boiler—designed and constructed to provide you
with years of reliable service.
• ENERGY STAR™ efficiency – friendly on the environment and your wallet.
• Cast iron heat exchanger – for reliability and durability, nothing beats a cast iron heat exchanger.
• IQ Control™ – the most advanced and easiest to use control available.
 • System-friendly – built-in protection from condensation and thermal shock.
1. q Series 3™Boiler
2. q Vent Damper w/ Carton
 4” Damper  303B (102284-01)
5” Damper  304B (102284-02)
6” Damper  305B & 306B (102284-03)
7” Damper  307B & 308B (102284-04)
8” Damper  309B (102284-05)
3. q Circulator & Gasket Kit
 Taco 007-2 (8056170)
 Grundfos UP-15 (102805-02)
 B & G NRF-22 (8056174)
4. q Miscellaneous Parts Bag (102627-01)
q Temperature/Pressure Gage; ¼” NPT
(100282-01)
q Circulator Mounting Hardware Kit,
1-1/4” NPT (6056007)
q Drain Valve; ¾” NPT (102802-01)
q Pressure Relief Valve; 30 psi
(81660363)
q Water Manifold for Pressure Relief/
Temp. Gage (80607001)
What's in the crate? 5. q Instruction Envelope (103795-01)
q Instruction & Operation Manual
(103796-04)
q Boiler Warranty Sheet (103203-01)
q Boiler Warranty Card (103204-02)
*IQ Control System Overview
Series 3 Boiler uses a microprocessor based control system called the "IQ Control System". This "IQ
Control System" consists of an Intelligent Hydronic Control (Control) and an IQ Option Panel (Option
Panel) with optional "plug-in" IQ Option Cards (Option Card). The IQ Control System fully integrates both
factory and eld installed components, simplifying installation and troubleshooting. The IQ Control System
is designed to efciently operate the entire boiler system to save energy, installation and setup time while
ensuring adequate supply of heat and domestic hot water.

4
Series 3
Boiler Model Input (MBH) DOE Heating Capacity (MBH) Net AHRI Rating (MBH) AFUE (%)
303B 70 59 51 84
304B 105 88 77 84
305B 140 117 102 84
306B 175 146 127 84
307B 210 176 153 84
308B 245 205 178 84
309B 280 234 203 84
Ratings
SPECIFICATIONS
Boiler
Model Depth Width Height Supply NPT (inch) Return NPT (inch) Vent (inch) Gas NPT (inch) Relief Valve NPT (inch) Drain NPT (inch)
303B 33 12¾ 41 1¼ 1¼ 4 ½ ¾ ¾
304B 33 15½ 41 1¼ 1¼ 5 ½ ¾ ¾
305B 33 18½ 41 1¼ 1¼ 6 ½ ¾ ¾
306B 33 21½ 41 1¼ 1¼ 6 ½ ¾ ¾
307B 33 24¾ 41 1¼ 1¼ 7 ¾ ¾ ¾
308B 33 27¾ 41 1¼ 1¼ 7 ¾ ¾ ¾
309B 33 30¾ 41 1¼ 1¼ 8 ¾ ¾ ¾
Dimensions and Connections
Electrical Requirements: 120VAC, 60 Hz, 1-ph, 15A
Maximum Allowable Working Pressure - 50 psi. Boiler shipped from factory with a 30 psi relief valved.
Boiler Model Allowable Supply Water Temperature
(°F)
Minimum Return
Water Temperature
(°F)
Minimum Flow
(GPM)
Waterside Pressure Drop
at 20°F DT
(Ft. of Head)
303B 130-220 110 None <1
304B 130-220 110 None <1
305B 130-220 110 None <1
306B 130-220 110 None <1
307B 130-220 110 None <1
308B 130-220 110 None <1
309B 130-220 110 None <1
Water Temperatures and Flows
Boiler
Model Shipping Weight (lbs) Empty Weight (lbs) Water Content (gal)
303B 254 180 2
304B 304 231 3
305B 357 284 4
306B 405 332 5
307B 462 382 5
308B 518 438 6
309B 564 484 7
Weights and Volume

5
Figure S-1: Minimum Clearances to Combustibles and Alcove Dimensions
SPECIFICATIONS (continued)

6
Installation:
1. Unpack the crate ............................................................................................. 7
2. Position the boiler............................................................................................ 8
3. Provide combustion air .................................................................................... 9
4. Connect venting............................................................................................... 9
5. Connect gas piping........................................................................................ 10
6. Connect boiler water piping ........................................................................... 10
7. Connect electrical wiring................................................................................ 12
8. Program the controls ..................................................................................... 13
9. Check for gas and water leaks ...................................................................... 16
10. Perform startup checks and adjustments ...................................................... 17
Annual Maintenance Checklist............................................................................ 18
Troubleshooting.................................................................................................... 19
Repair Parts List................................................................................................... 25
InternalWiring....................................................................................................... 31
Appendices:
A – Combustion Air..................................................................................................35
B – Venting..............................................................................................................36
C – Gas Piping ........................................................................................................40
D – System Piping...................................................................................................41
E – Filling the System and Checking for Leaks.......................................................45
F – Adjusting Gas Input Rate ..................................................................................46
G – Checking Draft and Combustion.......................................................................47
H – Operation..........................................................................................................48
I – IQ Control System..............................................................................................49
BOILER QUICK-START

7
THE BOILER IS TOP-HEAVY. Do not
allow it to tip over.
1. Remove the sleeve.
2. Remove the contents from the skid, except
the boiler.
3. Remove the four (4) hex-drive lag screws
holding the boiler to the skid (Figure 1-a).
DO NOT DAMAGE front air dam. It is
required for proper operation of the boiler.
1. UNPACK THE CRATE
4. Tip the boiler and shimmy it off the skid
(Figure 1-b).
1-a 1-b

8
2. POSITION THE BOILER
WARNINGS
1. Slide the boiler into desired location.
2. Meet the minimum clearances to
combustible construction per the
Specification Section of this manual.
3. Allow 24" service clearance in front and on
the left side of the boiler.
OBSERVE MINIMUM CLEARANCES to
combustible walls and ceilings to avoid potential
re hazard.
DO NOT INSTALL ON CARPET. This may cause
a re.
INSTALLING THE BOILER NEAR A SOURCE OF
FLAMMABLE LIQUIDS or gases may cause re or
explosion.
CLEAN BURNERS DAILY if operating the boiler in
a dusty environment.
PROTECT IGNITION SYSTEM COMPONENTS
from sources of water that may spray, drip, or rain
on them during installation or service.
4. Level the boiler, using shims as necessary.
5. Assure that the front air dam (applicable to
5-section thru 9-section boilers only) is in
place and undamaged. See Figure 2-a.
2-a
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.
Note: Front Air Dam applicable
to Models 305B thru
309B only

9
3. PROVIDE COMBUSTION AIR
INSUFFICIENT COMBUSTION AIR
SUPPLY may result in the production and
release of deadly carbon monoxide (CO) into the
home which can cause severe personal injury or
death.
4. CONNECT VENTING
DAMPER MUST BE OPEN when the main burner is ring.
Like all fuel-burning appliances, boilers need air to
operate reliably and safely.
Provide combustion air using the instructions in
Appendix A—Combustion Air.
4-a
IMPROPERVENTINGmayresultinproperty
damage and the release of ue gases which
contain deadly carbon monoxide (CO) into the home,
which can cause severe personal injury, death or
substantial property damage.
INSPECT EXISTING CHIMNEY before
installing boiler. Failure to clean or replace
perforated pipe or tile lining will cause severe injury
or death.
The vent system shall be designed and constructed
in accordance with NFPA 54 and applicable local
codes to develop a positive ow adequate to convey
ue or vent gases to the outdoors, while ensuring
that ue gases do not cool prematurely.
Observe all general venting guidelines provided in
Appendix B—Venting. Additionally:
1. This appliance shall be vented into a listed
gas vent, masonry, metal, or factory-built
chimney as required by NFPA 54 and
applicable local codes for Category I
appliances. If venting this appliance into
a masonry chimney, the chimney must be
lined with approved clay ue lining, a listed
chimney lining system, or other approved
material as required by NFPA 54 and
applicable local codes.
2. Attach the vent damper with three sheetmetal
screws around the perimeter of the ue collar
(Figure 4-a), oriented so that the position
indicator is visible. The vent damper may
also be mounted anywhere between the ue
outlet and the chimney within reach of the
electrical harness.
3. Vent connector shall meet the requirements
of NFPA 54 and applicable local codes.
Using sheetmetal screws, attach the vent
connector between the vent damper and the
vertical chimney (Figure 4-b).
4-b

10
2. Screw the water supply manifold into the
boiler outlet tapping “O.”
3. Orient the manifold with the relief valve on
top.
4. Screw the relief valve into manifold tapping
“RV”.
i This installation is not complete until the
relief valve is installed.
PIPE THE RELIEF VALVE DISCHARGE
to a location where it will not harm
people or damage property. The relief valve may
discharge scalding hot water or steam.
BLOCKING THE RELIEF VALVE may
result in boiler explosion.
5. Screw the temperature-pressure gage into
manifold tapping “G”.
6. Connect the system supply to the open end
of the manifold "S" using a 1¼” male NPT
tting.
5. CONNECT GAS PIPING
Size gas piping according to Appendix C – Gas
Piping SHUT OFF GAS SUPPLY before
servicing the boiler.
ALL GAS PIPING MUST BE GAS
TIGHT. Use gas rated thread compound
on all threaded joints to avoid leaks, which may
result in re or explosion.
SIZE GAS PIPING, regulators, valves,
and meters so as to provide an adequate
gas ow and pressure to the boiler during
operation. Failure to do so may cause poor
combustion, noise, injury, or death.
1. Remove boiler door, locate gas valve and
remove plastic shipping plug.
2. Thread a ¾" x 1½" nipple, a 90° street
elbow, or a Honeywell ange onto the gas
valve and pipe through the slot in the left
jacket panel (Figure 5-a). In Canada, close
nipples and street ells are not approved for
use as gas piping.
3. Pipe through the left jacket panel, and
complete drip leg as shown (Figure 5-a).
6. CONNECT BOILER WATER PIPING
General system piping guidelines are included in
Appendix D—System Piping.
Additionally, for this particular boiler install piping
shown below (Figure 6-a).
6-a
1. Apply sealant to all threads.
RV
S
R
O
G
D
5-a

11
7. Screw an installer-supplied 1¼” pipe or
nipple into the water return tapping “R”.
8. Screw the supplied drain valve into tapping
“D”.
6. CONNECT BOILER WATER PIPING (continued)
9. See Figure 6b for suggested near boiler
piping of IQ Options.
6-b
Item Description Part Number
1 1¼ x 1¼ x ½ Tee 806601021
2 Immersion Well, ½ NPT 80160456
3 1¼ x 6 Nipple 806600029
41¼ Tee 806601030
5 1¼ x ¾ Bushing 806600504
6 LWCO Sensor, ¾ NPT 102305-01
7 1¼ x 3 Nipple 806600005
8 1¼ Elbow 806601528

12
DISCONNECT ELECTRICAL POWER
to the boiler and heating system before
servicing. Positively assure that no voltage is
present. Lock electrical boxes to prevent someone
from inadvertently restoring power before the
heating system is safe to operate.
NEVER DEFEAT OR JUMP OUT safety
devices.
PROTECT EACH BOILER circuit with a
properly sized over-current protection
device.
MAKE ELECTRICAL CONNECTIONS
CAREFULLY according to the boiler’s
wiring diagram and instructions
Refer to the Internal Wiring diagrams later in this
manual.
1. Locate the wiring box on the left side of the
boiler and open the cover (Figure 7-a).
2. Install a 120V disconnect near the boiler.
3. Connect the 120V wiring from the disconnect
to the boiler's white (neutral), black (hot),
and green (ground) labeled "120VAC Power
supply". Do not reverse polarity.
4. Connect the 120V wiring from the circulator
to the white (neutral) yellow (hot) wires
marked "circulator".
WIRE AN ADDITIONAL SAFETY LIMIT
such as a low water cutoff or temperature
limit device, other than an IQ™ Control device,
in series with the 120V circuit used to power the
boiler. Do not alter the boiler’s factory wiring when
adding an additional limit.
7. CONNECT ELECTRICAL WIRING
5. Connect the 24V wiring from the thermostat
to the "T-T" terminals on the Option Control
Panel.
6. To connect other external devices, refer to
the instructions included with these devices.
7-a
1

123 T T
7-b
THE MAXIMUM ALLOWABLE
CURRENT for each circulator is 5 amps at
120V AC. For circulators with higher amp ratings,
you must install a circulator relay or starter coil to
provide line voltage to the circulator and connect
only the relay or starter coil to boiler terminals.
The combined boiler and circulator amperage must
not exceed 15 amps.
Install over-current protection in accordance with
authority having jurisdiction or, in the absence of
such requirements, follow the National Electric
Code, NFPA 70, and/or CSA C22.1 Electrical
Code. Do not provide over-current protection
greater than 15 amperes.

13
8. PROGRAM THE CONTROLS
Intelligent Hydronic Control
8-b
IQ Option Panel
8-a
Using Intelligent Hydronic Control Display
The Intelligent Hydronic Control (control) is located
inside the boiler front door, just above the IQ
Option Panel (Figure 8-a).
Intelligent
Hydronic Control
The control display, along with Up ñ, Down ò,
and “I” keys may be used to view boiler operating
status (Figure 8-b). Please note that these keys
look similar to the keys on the IQ Option Panel
but are in a different orientation, and they perform
different functions.
Viewing the Operating Mode Options
In operating mode the user may view (but not
change) boiler operating status, settings and
troubleshooting information. To view control
display information:
Unit Display
OR
Sample
Display
1 sec
1 sec
1 sec
1. Press and release the “I” key on the
control to change from one parameter to
the next. Each setting will alternately ash
between the relevant display code and its
corresponding value.
Operating Mode Options
StA Status
bt Boiler Temperature
SP Operating Setpoint (Outdoor Reset)
HL High Limit Setting
HdF High Limit Differential
tt Heat Request Status
dh DHW Heat Request Status
FLA Flame Current
rUn Run Time Hours
CYC Boiler Cycles
Err Error (see Error Numbers)
The STA (status) display code has the below listed
values. This list is also available on the control
cover.
Status Code Displayed in STA Mode
1 Standby
4 Prepurge
6 Spark
7 Flame Proving
8 Running
10 Retry/Recycle Delay
13 Soft Lockout
14 Hard Lockout
15 Waiting for Limit to Close
16 Flame Present Out of Sequence
17 Self Test
18 Waiting for Damper to Open
20 Damper Failure to Open
For example, when the “I” key is pressed on the
control until “bt” is displayed, it will then ash a
three digit number (such as “180”) followed by
either “F” (or “C”). This indicates that the boiler
water temperature is 180°F. Other operating
parameters display the information in a similar
fashion.

14
8. PROGRAM THE CONTROLS (continued)
Please note that in operating mode to hold the
display on the value the user can press and hold
either the Up ñor Down ò keys and the value
will be continuously shown. This may be helpful in
watching a value “live”.
Changing the Adjustable Parameters
To adjust the Parameters such as High Limit
Setpoint and High Limit Differential:
1. Access the adjustment mode by pressing
and holding the Up ñ, Down ò, and “I”
keys simultaneously for three (3) seconds.
This procedure is intended to discourage
unauthorized changes or accidental changes
to limit settings.
2. Press the "I" key to display available
Adjustment Mode options. Select an option.
Adjustment Mode Options
HL_ 140-220°F Adjust High Limit Setting
dF_ 10-30°F Adjust High Limit Differential
Or_ 0-10 minutes Circulator Overrun Time
PP_ 2-20 minutes Circulator Pre-purge Time
St_ 140-180°F Start Temperature
Pt_ On or off Priority time
dh_ dh or tt2 DH Terminal Function
rst Reset Lockout
f-C For C Select degrees F or C Mode
bac Back to Operating Mode
3. Press the Up ñand Down ò keys to adjust
the displayed item to the desired value.
4. To return to the normal operating mode from
the Adjustment Mode, when the "bAc” option
is displayed, press either the Up ñor Down
ò key. If no keys are pressed, after ve (5)
minutes the control will automatically return
to the Operating Mode.
More Information about Adjustable Parameters
1. High Limit (HL_)
The control is factory programmed with a
High Limit Setpoint of 180°F. The burner
turns "off" when the boiler temperature (bt)
is above Operating Setpoint. The Operating
Setpoint (SP) will equal the High Limit
Setpoint unless an IQ Outdoor Reset IQ
Option Card is installed.
The Outdoor Reset IQ Option Card reduces
the Operating Setpoint to regulate heat
delivery, increase home comfort and
save energy. Refer to the Appendix I for
additional information. The High Limit
Setpoint is adjustable between 140° and
220°F.
2. Differential (df_)
The control is factory programmed with a
Differential of 15°F. The Differential is the
number of degrees the boiler temperature
must decrease below the Operating Setpoint
before the boiler can restart. The differential
is adjustable between 10° through 30°F.
3. Circulator Overrun Time (OR_)
The control is factory programmed with
a Circulator Overrun Time of 0 minutes.
Circulator Overrun Time (also called
“circulator off delay” or “circulator post
purge”) continues circulator operation after
a call for heat has ended, sending excess
heat from the boiler into the system. Ensure
system piping and zone panel settings allow
water ow to the priority zone after the call
for heat ends. The Circulator Overrun Time
is adjustable between 0 through 10 minutes.
4. Circulator Pre-purge Time (PP_)
When the boiler is warm (boiler water
temperature higher than 140°F (adjustable
using Start Temperature parameter)) and
there is a thermostat call for heat, the
system circulator is started and boiler ring
is delayed Circulator Pre-purge minutes. If
the temperature drops below 140°F or there
is a DHW call for heat the boiler is started
without delay. Additionally, the boiler is
started without delay if the thermostat call
for heat is initiated when the boiler water
temperature is less than 140°F. This
feature helps save energy by satisfying
home heating needs with residual boiler
heat rather than cycling the boiler. The
Circulator Pre-purge time has a factory
setting of 2 minutes and is eld adjustable
between 2 and 20 minutes. When reset card
is installed, pre-purge time may be adjusted
down to zero (0) minutes. Refer to Table 8a.

15
8. PROGRAM THE CONTROLS (continued)
Table 8a: Circulator Pre-purge Time example,
(PP_ = 2 minutes)
Call for
Heat
Source
DHW
Terminal
Selection
Boiler
Temperature Burner Status
TT = on - <140 Start with no delay
TT = on - >140 Start after 2 minute delay
DHW = on tt2 <140 Start with no delay
DHW = on tt2 >140 Start after 2 minute delay
DHW = on dh <140 Start with no delay
DHW = on dh >140 Start with no delay
5. Start Temperature (St_)
Amount of “Heat available” is calculated
by taking the difference between measured
boiler water temperature and the Start
Temperature setting. Useful “Heat
Available” is dependent on the type of
heating emitter installed in the home.
Heat emitters require a certain minimum
temperature to operate effectively. Our
default settings reect cast iron radiators.
Fan Coils may require a start temperature
setting of 180°F or 160°F before providing
heat to the home. The Start Temperature
has a factory setting of 140°F and is eld
adjustable between 140°F and 180°F.
6. Priority Time (Pt_)
When the Priority Time parameter is set
to “on” and Domestic Hot Water (DHW)
call for heat is “on” the DHW demand will
take “Priority” over home heating demand.
During Priority Time the system circulator
will be forced “off”. Priority Time ends and
the system circulator is released to service
home heating demand when Domestic Hot
Water call for heat is over. When Priority
Time parameter is set to “Off” the DHW
call for heat does not force “off” the system
circulator. The Priority Time has a factory
setting of “On” and is eld adjustable
between “On” and “Off” Refer to Table 8b.
7. Domestic Hot Water (DHW) Terminal
Function (dh_)
The control allows conguration of the
DHW Circulator output functionality to help
the Boiler integrate into each installation
more effectively. The DHW Circulator
output can be connected to a domestic hot
water circulator or a second heating zone
circulator. These applications are selected
as follows:
a. When dh_ is set equal to Domestic Hot
Water Demand (h)
When there is an Indirect Water Heater
(IWH) the control provides “DHW” input
terminals for the IWH Aquastat and “DHW
Circulator” output terminals for the DHW
Circulator. When there is a DHW call for
heat, the System Circulator is “forced off”,
the DHW Circulator terminal is energized
and the circulator pre-purge time delay
control logic is bypassed to allow the
boiler to re without delay. When DHW
demand ends the System Circulator
“force off” is removed, the circulator
can respond normally, and the DHW
Circulator is de-energized. The DHW
call for heat is detected by a voltage on
to the "DHW" terminal. When the Priority
Time parameter is set to “off” the System
Circulator is not forced off for a DHW call
for heat. Refer to Table 8b.
Table 8b: DHW Terminal Function (dh_)
Selection = Domestic Hot Water Demand,
(Parameter dh_ = dh)
Call for Heat Circulator Status
T-T
Input DHW Input
Priority
Time
(Pt_)
System
Circulator
Output
DHW
Circulator
Output
on off On on off
on on On off on
off on On off on
on off OFF on off
on on OFF on on
off on OFF off on

16
b. When dh_ is set equal to Second Heating
Zone (tt2)
When there is no IWH the “DHW
Circulator” output may be congured to
control a second heating zone. This is
particularly helpful when the home uses
only two heating zones. The control
replaces the need for a two circulator
zone panel. When DHW Terminal
Function (dh_) is set to “tt2" the control’s
two circulator outputs are used to control
two independent heating zones. Refer
to Table 8c. A “TT” input causes a call
for heat and energizes the “System
Circulator” output to service heating zone
1 and a second zone's thermostat wired
to the “DHW” input causes a call for heat
and energizes heating zone 2 circulator
wired to the "DHW Circulator" output.
When there is a Second Heating Zone
(call for heat) the boiler is started and the
DHW Circulator terminal is energized.
When Second Heating Zone is de-
energized the call for heat is ended and
the Second Heating Zone Circulator is
de-energized. A Second Heating Zone
is detected by sensing a voltage on the
DHW terminal.
8. PROGRAM THE CONTROLS (continued)
Using the IQ Option Panel
IQ Option Cards are available from U.S. Boiler
Company distributors and are the simplest way
to add functionality, safety and efciency to your
heating system. The IQ Option Panel provides
an easy and convenient means to "plug-in" an
Auxiliary High Limit, Low Water Cut-off and/or
Outdoor Reset function.
For installation, programming, and troubleshooting
instructions, refer to the instructions supplied with
those cards.
Using the Optional LCD Display Kit
The LCD Display is an easy to use touch screen
type display that allows a technician to monitor and
adjust the control and connected IQ Option Cards.
All boiler settings, status and error codes are
displayed in full text. All Outdoor Reset IQ Option
Card parameters are adjustable with graphic and
help information screens. The LCD Display Kit
includes a mounting bracket and wiring harness
to allow mounting in the boiler plastic hood above
the front door. For installation, programming,
and troubleshooting instructions, refer to the
instructions supplied with the display.
Call for Heat Circulator Status
T-T
Input DHW Input
System
Circulator
Output
(Zone 1)
DHW
Circulator
Output
(Zone 2)
off off off off
on off on off
on on on on
off on off on
Table 8c: DHW Terminal Function (dh_)
Selection = Second Heating Zone,
(Parameter dh_ = tt2)
9. CHECK FOR GAS AND WATER LEAKS
GAS LEAKS may result in re or
explosion.
WATER LEAKS may cause extensive
property damage.
Refer to Appendix E – Filling the System and
Checking for Leaks

17
10-b
10. PERFORM STARTUP CHECKS AND ADJUSTMENTS
FAILURE TO PERFORM THESE
CHECKS of the boiler's combustion and
safety systems may result in serious property
damage, injury, or death.
IF YOU SMELL GAS, STOP and repair
the leak. Lighting the boiler when gas is
leaking may cause explosion or re.
Follow the checklist below:
1. Verify that the venting, water piping, gas
piping, and electrical systems are properly
installed and checked.
2. Apply power to the boiler.
3. Adjust zone thermostat to maximum setting.
4. Allow gas line to purge of air.
qBoiler lights cleanly within 60 seconds.
5. Adjust gas input rate. See Appendix F
– Adjusting Gas Input Rate
10-a
qPilot and main burner flames appear
clean and blue.
6. Disconnect pilot lead wires from gas valve
(Figure 10-b).
qBoiler shuts off.
7. Reconnect pilot lead wires to gas valve.
qBoiler restarts.
8. Adjust zone thermostat to minimum setting.
qBoiler shuts off.
9. Adjust zone thermostat to maximum setting.
10. Observe temperature gage as boiler heats.
11. Adjust the high limit setting to its minimum
level (see "Programming High Limit" in
Section 8).
qBoiler shuts off when temperature gage
reads within 15°F of high limit setting.
12. Return high limit to the desired setting (see
"Programming High Limit" in Section 8).
13. Check draft. See Appendix G
– Checking Draft and Combustion.
qNo spillage observed.
14. Check combustion in the vent stack and
record results in the spaces provided below.
_____ CO2(less than 7%)
_____ O2(more than 9%)
_____ CO (less than 50 ppm, air free)
ANY FAILED STARTUP CHECK
Must be corrected before placing the boiler
in service.

18
ANNUAL MAINTENANCE CHECKLIST
WARNINGS
THE BOILER CONTAINS REFRACTORY
CERAMIC FIBER, a possible human carcinogen
Use a NIOSH approved respirator when servicing
high-temperature insulation and gasket materials.
Wash exposed skin gently with soap and water
after contact Wash exposed clothing separate
from normal laundry.
LABEL ALL WIRES prior to disconnection when
servicing controls. Wiring errors can cause
improper and dangerous operation
FAILURE TO MAINTAIN THE BOILER in proper
working condition may lead to re, explosion,
personal injury or death, and extensive property
damage.
TURN OFF ALL GAS AND ELECTRIC power
supplies to the boiler before servicing. Contact with
or release of dangerous ammable gas, electrical
voltage, moving parts, and very hot water under
pressure may cause serious personal injury,
property damage, or death.
LOCK ELECTRICAL BOXES AND GAS VALVES
CLOSED to prevent someone from inadvertently
restoring power or gas before the heating system is
safe to operate.
Equipment you will need:
qSoft bristle brush
q Bristle ue brush
q Vacuum with brush attachment
Perform these tasks each year:
1. Clean low water cutoff probe (if applicable).
2. Inspect vent for obstruction and signs of
condensation, distortion, overheating or gas
leakage.
3. Clean vent terminal and air intake screens.
4. Inspect boiler ue passages:
(1) Remove vent pipe, damper.
(2) Remove top panel and hood.
(3) Remove blocked vent switch and
canopy.
(4) Examine all ue passageways. Using
bristle ue brush and vacuum,
remove any soot or obstructions.
5. Remove and clean main burners:
(1) Remove jacket front panel.
(2) Disconnect pilot tubing at gas valve.
(3) Disconnect pilot lead wires at gas valve.
(4) Remove wires from ame roll-out switch.
(5) Remove burner access panel.
(6) Mark location of the pilot main burner on
the manifold if the marking on manifold
is missing or obliterated. AM-1
(7) Hold burner at throat. Lift front of burner
to clear orice (Figure AM-1). The
burner that holds the pilot can only be
removed by rst lifting the burner
adjacent to its right.
6. Perform Startup Checks and Adjustments
described earlier in this manual.
7. Check operation of airow sensing switches.
8. Check for water leaks on the boiler or water
pooling around boiler.
9. Manually operate the relief valve. If the
water is grey or black, there is excessive
oxygen in the system. Oxygen is corrosive
to boilers. Eliminate any source of oxygen.
10. Verify proper operation after servicing.

19
Before troubleshooting
The following pages contain trouble shooting
tables for use in diagnosing control problems.
When using these tables the following should
be kept in mind:
1. This information is only meant to be used by
a professional heating technician as an aid
in diagnosing boiler problems.
2. Where applicable, follow all precautions
outlined in Section 10, 'Perform Startup
Checks and Adjustments' on page 17.
3. In general, these tables assume that
there are no loose or miswired electrical
connections. Before using these tables
inspect all electrical connections on the
boiler to make sure that they are tight. Also,
check the wiring on the boiler against the
wiring diagram in Figures IW-1 and IW-2.
Ensure that incoming 120 Vac power polarity
is correct and that the boiler is properly
grounded. Further, ensure that the control
power supply is 24 VAC (minimum 18 VAC
to maximum 30 VAC) and polarity is correct.
4. All controls on the boiler are tested at least
once in the manufacturing process and a
defective control or component is generally
the least likely cause. Before replacing a
component, try to rule out all other possible
causes.
5. When checking voltage across wiring
harness pins be careful not to insert
the meter probes into the pins. Doing
so may damage the pin, resulting in a
loose connection when the harness is
reconnected.
TROUBLESHOOTING
Press “I” key on the control to change
from one parameter to the next. Each
setting will alternate between display
code (for example STA) and value.
When Err (error) is shown:
Value Description
4 Flame current lower than threshold
6 Flame Out of Normal Sequence
18 Electronics Failure
23 Flame Sensed During Pre-purge
32 Temperature Sensor Failure
55 Damper Failed to Open
57 Flame Rod Shorted to Ground
58 AC Line Frequency
59 Line Voltage Error
60 Thermostat input higher than threshold
61 Line Voltage Unstable
63 Soft Lockout – Recycles Exceeded
64 Soft Lockout – Internal Failure
Possible STA (status) values:
Value Description
1 Standby
4 Pre-purge
6 Spark
7 Flame Proving
8 Running
10 Retry/Recycle Delay
13 Soft Lockout
14 Hard Lockout
15 Waiting for Limit to Close
16 Flame Present Out of Sequence
17 Self Test
18 Waiting for Damper to Open
20 Damper Failure to Open

20
TROUBLESHOOTING (continued)
Use Control Display ERR (error) NumberTo DirectTroubleshooting Efforts
If the control detects an error it will ash “Err” (error) followed by a number. Use this number to identify
the boiler problem and corrective action in the table below. If there is no Err display proceed to next
Section:
Display Status Recommended Corrective Action
Blank Boiler or Control is not powered No 120 Vac Power at boiler, check breaker and wiring between breaker
panel and boiler
Err 4 Flame Current Lower than Threshold Check pilot assembly. Refer to Troubleshooting Section, 6.
Err 6 Flame Sensed Out of Normal Sequence Flame sensed out of normal sequence (before opening gas valve or after
closing gas valve). Check gas valve for proper operation.
Err 18 Electronics Failure Cycle power to control. Replace control if problem persists.
Err 23 Flame Sensed During Pre-purge Flame sensed during post-purge (before gas valve signaled open). Check
the gas valve for proper operation. Replace gas valve if problem persists.
Err 32 Temperature Sensor Failure
Temperature sensor or interface failure (open or short connection, increased
connection resistance, dual sensor mismatch) or control hardware failure.
- Check sensor is securely attached to control P7 connector.
- If secure, replace sensor.
- If problem persists, replace control.
eRR 35 Duplicate Zone Alarm Refer to IQ Zone Panel Instructions.
Err 55 Damper Failed to Open Atmospheric Damper End Switch failed to close (end switch contacts stuck
open). Refer to Troubleshooting Section, 5.
Err 57 Flame Rod Shorted to Burner Ground
Flame Rod shorted to burner ground, this can result from excessive ue gas
condensation.
- Check for excessive condensate. Dry pilot. Adjust setpoint higher.
- Check for loose or damaged ignition wire.
Err 58 AC Line Frequency Error AC Signal is too noisy or frequency is incorrect. Check supply voltage.
Err 59 Line Voltage Error AC voltage out of specication high or low. Check supply voltage.
Err 60 Thermostat Input Higher than Threshold Check thermostat wiring.
Err 61 Line Voltage Unstable Possibly too many heavy loads switching on and off cause erratic supply
voltage. Check supply voltage.
Err 63 Soft Lockout – Maximum Recycles
Exceeded Maximum number of recycles exceeded. Refer to Troubleshooting Section, 6.
Err 64 Soft Lockout – Internal Failure
The electronics has detected an error. This can be caused by an actual
controller internal fault or wiring fault:
- Check vent damper, cycle power with vent damper disconnected. If error
is cleared, reconnect the vent damper and refer to Recommended
Corrective Action listed under stA 20, damper failed to open.
- Check pilot assembly,
- If problem persists, replace the control.
Err 89 Communication Lost Check wiring between control and IQ Zone Panel or IQ Reset Card.