LAARS U.H.E. User Manual
Service Manual Document 11019A
Service Manual for
U.H.E.
Ultra High Efciency
Water Heaters
UHE60T125E*(NA,XA)(2)
UHE60T150E*(NA,XA)(2)
UHE60T199E*(NA,XA)(2)
UHE100T150E*(NA,XA)(2)
UHE100T199E*(NA,XA)(2)
UHE100T250E*(NA,XA)(2)
UHE100T300E*(NA,XA)(2)
UHE100T399E*(NA,XA)(2)
(*) Denotes Warranty Years
Troubleshooting Guide and Instructions for Service
These instructions are to be stored next to the boiler for reference purposes.
FOR YOUR SAFETY: This product must be installed and serviced by a professional service technician,
qualied in hot water boiler installation and maintenance. Improper installation and/or operation could
create carbon monoxide gas in ue gases which could cause serious injury, property damage, or death.
Improper installation and/or operation will void the warranty.
WARNING
If the information in this manual is not followed
exactly, a re or explosion may result causing
property damage, personal injury or loss of life.
Do not store or use gasoline or other ammable
vapors and liquids in the vicinity of this or any
other appliance.
WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use
any phone in your building.
• Immediately call your gas supplier from a
nearby phone. Follow the gas supplier's
instructions.
• If you cannot reach your gas supplier, call the
re department.
Installation and service must be performed by
a qualied installer, service agency, or gas
supplier.
Assurez-vous de bien suivres les instructions
données dans cette notice pour réduire au
minimum le risque d’incendie ou d’explosion
ou pour éviter tout dommage matériel, toute
blessure ou la mort.
Ne pas entreposer ni utiliser d’essence ni
d’autres vapeurs ou liquides inammables dans
le voisinage de cet appareil ou de tout autre
appareil.
QUE FAIRE SI VOUS SENTEZ UNE ODEUR DE GAZ:
• Ne pas tenter d’allumer d’appareils.
• Ne touchez à aucun interrupteur. Ne pas
vous servir des téléphones dansle bâtiment
où vous êtes.
• Appelez immédiatement votre fournisseur de
gaz depuis un voisin. Suivez les instructions
du fournisseur.
• Si vous ne pouvez rejoindre le fournisseur
de gaz, appelez le sservice des incendies.
L’installation et l’entretien doivent être assurés
par un installateur ou un service d’entretien
qualié ou par le fournisseur de gaz.
AVERTISSEMENT
Page 2
LAARS Heating Systems
U.H.E. Series Commercial Gas
Ultra High Efciency Water Heaters
Table of Contents
Page U.H.E.
Service Procedure
Introduction 3 - - -
How to use this manual 4 - - -
Tool required for service 4 - - -
Specifications 5 - - -
Sequence of Operation 8 - - -
Troubleshooting 10 - - -
Thermostat Circuit, Testing & Replacement 12 I
Combustion System Testing and Replacement 18 II
Burner Tube Inspection & Replacement 22 III
Gas Valve Replacement 24 IV
Blower Testing and Replacement 25 V
Exhaust Pressure Switch Testing and Replacement 27 VI
Hot Surface Igniter Testing and Replacement 30 VII
Flame Sensor Testing and Replacement 32 VIII
TM
Ignition Module/Control Board Replacement 34 IX
Transformer Replacement 35 X
Vent Safety Switch Testing and Replacement 36 XI
Anode & Flue Baffle Inspection and Replacement 38 XII
Installation Check List 43 - - -
Heater Service Report 44 - - -
Parts List 45 - - -
Glossary of Terms 48 - - -
2
U.H.E Service Manual
U.H.E. Series Commercial Gas
Ultra High Efciency Water Heaters
Introduction
The LAARS heating system Ultra High Efficiency Water Heater is designed to
deliver a remarkable thermal efficiency rating in a quiet running unit with venting
options that allow for installation flexibility. Several technologically advanced
design features are incorporated in the design that will require additional
knowledge on the part of the qualified service provider. The information in this
manual will instruct service and maintenance professionals on the function, proper
diagnosis and repair of LAARS Heating System Ultra High Efficiency Water
Heater.
Page 3
The LAARS heating system Ultra High Efficiency Water Heater uses a low Nox
premix power burner located at the top of the water heater to direct a turbulent
flame down into a submerged combustion chamber. This turbulence causes a
thorough mixing of gas and air for optimum combustion. The combustion gases
then travel through a three pass flue system keeping the gases moving at a high
velocity. The combination of high turbulence and velocity results in an optimum
transfer of heat from the flue gases into the water.
Burner operation is controlled using an electronic ignition module. The module
monitors the status of the electronic thermostat, vent temperature limit switch, vent
system pressure switches and a flame sensor to control output voltage to blower
motor, hot surface igniter and gas valve. The module contains programming which
determines the sequence of operation and timings for purge periods, trial for
ignition, flame sensing and lockout. The module will also provide diagnostic
information to help in determining the cause of system lockouts.
The contents in this manual are detailed informational tools to assist in the proper
diagnosis of the Ultra High Efficiency Water Heater operational faults. Please read
this service manual completely and provide as much information regarding the
Ultra High Efficiency Water Heater operation and installation specific concerns.
Page 4
It is intended for this manual to be used by qualified service personal for the primary purpose
of troubleshooting analysis and repair of the LAARS heating system Ultra High Efficiency
Water Heater. Understanding the sequence of operation section of this manual will contribute
greatly to troubleshooting this product.
An “Installation Check List” is shown on page 43. Compare the installation against the
installation check list to confirm all requirements are met.
An “UHE Service Report” is shown on page 44. Completing this form will assist in the
troubleshooting efforts. Should you need to call for technical support, Please provide the
information shown on this form to the support technician to insure accurate troubleshooting.
Troubleshooting begins with “System Observation” to determine failure mode as indicated by
the LED status of the ignition module. Troubleshooting continues with “Failure Modes and
Probable cause” listed on page 10 directing the service provider to a series of test
procedures to determine root cause of failure. Component replacement procedures directly
follow the test procedures for a given component.
LAARS Heating Systems
In some difficult to diagnose conditions, it may be necessary to isolate the heater from the
vent system to determine root cause.
Contact Technical support immediately if diagnosis is not determined using the methods
described in this service manual.
Tools Required for Service
Manometer: Two types available, a liquid “U” tube type or a digital (magna-helic)
type. This device is used to measure gas and/or air pressures and
vacuum.
Multi-Meter: A digital type is strongly recommended. This device is used to measure
electrical values. The meter you select must have the capability to
measure volts AC, volts DC, Amps, micro-amps and ohms.
Thermometer: Used to measure water temperature. An accurate thermometer is
recommended.
Water Pressure Gage: Used to measure water supply pressure. Also used to determine tank
pressure by adapting to the drain valve of the heater.
Jumper Leads: A length of wire (12" min.) with alligator clip at both ends.
Various Hand Tools: Pipe wrench, channel locks, open end wrench set, 12" crescent wrench,
Allen wrench set, torx bit set, screw drivers (common & phillips), long
reach (12") magnetic tip phillips head screw driver #2 tip, ¼" nut driver,
pliers (common & needle nose), socket set including a 1-1/16 deep well
socket, wire cutters, wire strippers, wire crimpers, torpedo level, small
shop vac, step ladder, and flashlight.
4
U.H.E Service Manual
Page 5
Model No
UHE60T125
UHE60T150
UHE60T199
UHE100T150
UHE100T199
UHE100T250
UHE100T300
UHE100T399
Input
Rate
BTU/h
125,000
150,000
199,999
150,000
199,999
250,000
300,000
399,999
1stHr
Del
Gal
@
100°F
Rise
187
211
265
250
309
364
405
521
363.6
422.7
557.6
450.5
597
734.8
836.4
1,127
Recovery GPH
at Degree Rise
145.5
169.1
223
180.2
238.8
293.9
334.5
451
140°F100°F40°F
103.9
120.8
158
129
171
210
239
322
Stg
Cap
U.S.
Gal
60
60
60
100
100
100
100
100
Therm
Eff
%
96.0
93.0
92.0
99.1
98.5
97.0
92.0
93.0
A
Ht
57
57
57
77 5/8
77 5/8
77 5/8
77 5/8
77 5/8
B
Dia
28 ¼
28 ¼
28 ¼
28 ¼
28 ¼
28 ¼
28 ¼
28 ¼
C
Flr
to
Vent
Outlet
5
5
5
5
5
5
5
5
D
Flr to
Inlet
Wtr
Conn
13
13
13
13
13
13
13
13
DIMENSIONS (INCHES)
F
E
Flr To
Flr to
Outlet
T&P
Wtr
Valve
Conn
Conn
40
42 ¼
40
42 ¼
40
42 ¼
60
62 ¼
60
62 ¼
60
62 ¼
60
62 ¼
¼
60
62
G
Flr. To
Air
Intake
52 ½
52 ½
52 ½
73 1/8
73 1/8
73 1/8
73 1/8
73 1/8
H
Flr to
Gas
Conn
53 ½
53 ½
53 ½
74 ¾
74 ¾
74 ¾
74 ¾
73 ¼
Front
Wtr
Conn
Dia
1 ½
1 ½
1 ½
1 ½
1 ½
1 ½
1 ½
1 ½
Space
Heating
Conn
Dia
1
1
1
1
1
1
1
1
Gas
Conn
Dia
(NPT)
¾
¾
¾
¾
¾
¾
¾
1
T&P
Valve
Open
(NPT)
5
Shpg
Wt
(lbs)
¾
570
¾
570
¾
570
¾
900
¾
900
¾
900
¾
900
1
950
Page 6
Power supply Dedicated 120 VAC, 60 Hz, 15A, GFI
Gas Supply
Approved Gas Type Natural or Propane. Unit must match gas type supplied.
Gas Pressure (Nat & L.P.) 14.0" W.C. maximum static, 4.5" W.C. minimum running (recommend 7.0" W.C. min running)
Venting System Power vent, balanced direct vent or unbalanced direct vent. See vent tables on page 7
Approved Vent Materials PVC, CPVC or ABS
Minimum Clearance
for Servicing
Maximum Water Supply
Pressure
Thermostat Sensor 11,900 Ohms @ 70°F, ECO opens @ 201°F Max., ECO close @ 100°F Min.
Temperature Dial Min. set point 5400-6600 ohms, Max set point 0-50 ohms.
Thermostat Board Max temp 180°F, Min temp 91°F, 24VAC, 60Hz max.
Ignition Module See page 9
Transformer 120VAC primary, 24VAC secondary, 40VA.
Hot Surface Igniter 120VAC, 30-120 ohms @ room temperature.
Flame Sensor Output Minimum 1 micro amp, Typical range 4 to 7 micro amps.
Gas Valve Negative regulation, 24 VAC, ½" PSI max., 4.5" W.C. Minimum running inlet.
Minimum 1" NPT for UHE100T399, all others ¾" NPT
(schedule 40 black iron pipe recommended)
18" from top, 24" from front, 4" sides and rear.
150 PSI
LAARS Heating Systems
Vent Safety Switch Normally closed, opens @ 350°F, manual reset.
Blocked Vent Pressure
Switch
Blower 120VAC, 60Hz, .6-1 amps, 6400 RPM.
Combustion Levels CO2: 10-11%, CO: less then 0.04 percent (400 PPM) air free
24VAC, normally closed, opens when pressure increases to +2.70 W.C.
6
U.H.E Service Manual
Page 7
Vent Tables
Balanced Direct Vent Systems
PVC, CPVC
Total length of intake piping and exhaust piping
added together must not exceed “Maximum
Combined Length”
Shown below
Maximum Combined Length (feet)
Model Number 3"
UHE60T125, UHE100T150 120'
UHE60T150, UHE100T199
UHE60T199 80' 130'
UHE100T250
UHE100T300
UHE100T399 50' 100'
Unbalanced Direct Vent Systems
Air intake CAN NOT exceed exhaust
by more than 30 feet
100'
80'
60'
4"
170'
150'
130'
110'
Power Vented Systems
PVC, CPVC
Total length of exhaust piping must not exceed
“Maximum Vent Length”
Shown below
Maximum Vent Length (feet)
Model Number 3"
UHE60T125, UHE100T150 120'
UHE60T150, UHE100T199
UHE60T199
UHE100T250 80' 130'
UHE100T300
UHE100T399 50' 100'
100'
80'
60'
4"
170'
150'
130'
110'
Notes:
1) Multiply the total number of 90° elbows (intake and exhaust) by 5 feet. Do not include the
termination fittings or 3" condensate elbow.
2) Multiply the total number of 45° elbows (intake and exhaust) by 2 ½ feet.
3) Add this to the total length of straight pipe - intake and exhaust.
4) The sum total of all elbows and straight pipe - intake and exhaust must not exceed maximum
lengths from tables above.
Example: UHE100T199
A 3" Balanced Direct vent system has 30 feet of straight exhaust pipe and 30 feet of straight intake pipe.
It has 3- 90° elbows in the exhaust and 3- 90° elbows in the intake. It has 1- 45° elbow in the exhaust and
1- 45° elbow in the intake.
Therefore:
6- 90° elbows x 5 feet = 30 feet.
2- 45° elbows x 2½ feet = 5 feet.
60 feet of straight pipe + 30 feet + 5 feet = 95 feet.
System is within “Maximum Combined Length” from table above.
7
Page 8
1
Thermostat calls for heat.
LAARS Heating Systems
Prior to energizing blower, ignition module checks to make sure the vent temperature switch is in the normally closed
position. If the vent temperature switch is open, the control waits indefinitely for the temperature switch to close.
2
Blower energizes, pressure switch contacts are normally closed. If the pressure switch contacts are open, blower operates for up to
5 minutes waiting for contacts to close, then blower stops and flashes red PURGE LED indicating lock-out condition.
3
Blower pre-purge period (5 seconds) indicated by PURGE LED on the module
4
Igniter warm up (18 seconds), indicated by the IGNITER LED on the module. Note: The blocked vent pressure switch
must be in the normally closed position for the ignition cycle to start.
5
Trial for Ignition (4 seconds, 3 trials).
a) Flame establishing period (2.5 seconds), gas valve and igniter on, indicated by the IGNITER and VALVE LED on the
module.
b) Burner on, flame proving period (1.5 seconds, looking for minimum of 1 micro amps), indicated by the FLAME &
VALVE LED on the module.
Steady state operation.
6
Ignition module monitors:
- Thermostat circuit.
- When thermostat opens, gas valve is shut down and post purge begins.
- Safety circuit.
- If vent temperature switch opens, gas valve is shut down, system will post purge and wait for switch to close
before attempting re-ignition.
- If the blocked vent pressure switch opens, indicating a blocked exhaust vent condition, the gas valve is shut
down, blower shuts down for 30 seconds and is re-energized and system attempts re-ignition if the pressure
switch is closed. Blower operates for 5 minutes to wait for pressure switch to close, then shuts off with purge
light flashing (lock-out). Will restart in 1 hour to attempt to close the switch and restart ignition sequence.
- Flame sensor circuit.
- If flame is lost, gas valve is shut down, system will post purge and system attempts re-ignition.
7
Thermostat satisfied.
8
Burner off.
9
Blower post purge (15 seconds).
8
U.H.E Service Manual
Lockout Conditions
Lockout conditions:
The system will go into lock out mode for the following reasons:
Blocked vent pressure switch contacts open:
Check for obstruction in exhaust pipe and vent terminal.
Check for blocked condensate trap or drain line. In cold climates, make sure drain is not frozen.
No ignition after 3 attempts:
a) Check inlet and outlet gas pressures (pressure taps located on top of gas valve).
b) Igniter resistance too high (lower resistance preferred < 150 ohms).
c) Misadjusted veturi screw (should be 6.5 turns out from bottom).
d) Flame sense microamp not present (1.0 microamps minimum, should be 5 microamps or more). If burner lit,
check flame rod for deposits.
e) Check burner tube condition. Refer to section UHE-III for Burner Tube Inspection and Replacement.
Ignition Module Specifications
Control Functions:
- Ignition & heating functions in response to thermostat.
- Hot surface ignition using a microprocessor to control timing, flame sensing using flame rectification & ignition
retries.
- Monitoring of system pressure switches and limit switches.
- Control of gas valve, inducer motor, and hot surface igniter element based on thermostat demand and status of
safety inputs.
- Diagnostic indicators to provide information on power to control and control status.
- Non-interchangeable polarized plug-in connectors for all interconnections.
Page 9
Control Inputs:
- Thermostat call for heat.
- Blocked vent pressure switch
(normally closed)
- Flame sensing.
- Low voltage supply.
- Line voltage supply.
IGNITION MODULE
Control Outputs:
- Inducer motor
- Hot surface igniter
- Gas valve
- Status indicator LEDs
Power - Green
Purge - Red
Igniter - Red
Valve - Red
Flame - Red
WIRING DIAGRAM
9
Page 10
LAARS Heating Systems
System Observation
Is front panel power
switch light on,
indicating power?
Y
Is ignition module
power light on?
Y
Position front panel
N
N
power switch to
“ON” position.
Is there 120VAC
across switch?
(see photo at right)
N
Is there 120VAC
across terminal block?
(see photo at right)
N
Determine power source
problem and correct.
Refer to ignition module
illustration, is there 120VAC
going to module at locations
P7(1) and P7(3)?
Replace ignition module.
(see page 24)
WARNING
120 volt potential exposure. Use caution
making voltage checks to avoid personal injury.
Power Switch
Light burned out,
Y
replace switch.
Terminal Block
Repair/replace wire
Y
harness to switch.
Y
N
Refer to ignition module
illustration, is there 120VAC
between P1(1) and P1(3)?
N
Replace ignition module.
(see page 24)
Y
Refer to ignition module
illustration, is there 24VAC
going to module at locations
P2(1) and P2(2)?
N
Replace transformer.
(see page 35)
Is ignition module
power and flame light
flashing?
N
Reset heater by
interrupting power.
IGNITION MODULE
Supply voltage polarity is
Y
incorrect.
Reestablish power and
Adjust thermostat to
call for heat,
tank must be cold.
Allow heater to run
through heating cycle.
Did heater complete
heating cycle and did
blower post purge?
Y
System is OK.
N
See next page
10
U.H.E Service Manual
Determine failure mode by observing flashing LED status on ignition module.
* Denotes conditions that may require the water heater to be isolated from the vent
LED STATUS
Only power light
is on and water heater
will not function.
Page 11
LED status & probable cause
For models with Hot Surface Ignition
LED status and probable cause shown below.
system to determine root cause.
Probable Cause*
Exhaust pressure
switch. (see page 27)
LED STATUS
Purge light flashing.
Probable Cause*
Exhaust pressure
switch. (see page 27)
LED STATUS
Valve light flashing.
Probable Cause
Hot surface igniter.
(see page 30)
Probable Cause
Thermostat circuit.
(see page 12)
Probable Cause
Blower.
(see page 25)
Probable Cause*
Combustion system.
(see page 18)
Probable Cause
Vent safety switch.
(see page 36)
Probable Cause
Flame sensor.
(see page 32)
LED STATUS
Power & flame
light flashing.
Probable Cause
Supply voltage
polarity.
11
Page 12
LAARS Heating Systems
IMPORTANT NOTE: This procedure assumes a cool tank
WARNING
Rotate temperature
dial to highest setting.
120 volt potential exposure. Use
caution making voltage checks
to avoid personal injury.
Refer to ignition module
illustration, Is there 24VAC
between P3(7) and P3(8)?
N
Thermostat
not calling
Y
OK, thermostat is
calling for heat.
Red Wire
(N.O.)
IGNITION MODULE
Yellow Wire
(COM)
Disconnect YELLOW and RED wires from the
thermostat board at location N.O. and COM shown in
photo at right. Use a jumper to connect these two
Turn off power to heater.
wires together as shown in photo at right.
Restore power to heater.
Did heater cycle on?
Y
Check thermostat sensor
for proper resistance
(OHMS) across blue wires.
(See page 13)
Are readings correct?
(see photo at right)
Y
Check sensor harness
continuity.
Is there continuity?
Y
Check temperature dial for
proper resistance (OHMS)
(See Appendix B,
temperature dial resistance)
Are readings correct?
(see photo at right)
Y
N
N
N
N
Replace
thermostat sensor.
(see page 12)
Replace harness.
Replace temperature dial
(potentiometer).
(see page 16)
See page 14
Yellow & Red
wires shown
jumpered
Thermostat
Sensor
Temperature Dial
Check temperature dial
harness continuity.
Is there continuity?
Y
Replace thermostat
circuit board.
(see page 15)
N
Replace harness.
12
U.H.E Service Manual
°F012345678 9
Example: If temperature of sensor is 84°F, then the resistance through the sensor would be 8449 (see shaded area).
Page 13
APPENDIX - A
Sensor Resistance at Various Temperatures
Be Careful When Making Voltage Measurements or Jumping Terminals
Not to Damage or Deform Connectors or Connector Pins.
Draw Water From The T&P Valve. Compare Temperature With
Temperature Ohms Chart Below.
NOTE: Sensor resistance increases as the temperature falls.
In Degrees F
40 26109 25400 24712 24045 23399 22771 22163 21573 21000 20445
50 19906 19383 18876 18383 17905 17440 16990 16553 16128 15715
60 15314 14925 14548 14180 13823 13477 13140 12812 12494 12185
70 11884 11592 11308 11032 10763 10502 10248 10000 9760 9526
80 9299 9078 8862 8653 8449 8250 8057 7869 7685 7507
90 7333 7165 7000 6839 6683 6531 6383 6238 6098 5961
100 5827 5697 5570 5446 5326 5208 5094 4982 4873 4767
110 4663 4562 4464 4368 4274 4183 4094 4006 3922 3839
120 3758 3679 3602 3527 3453 3382 3312 3244 3177 3112
130 3048 2986 2925 2866 2808 2752 2697 2643 2590 2538
140 2488 2439 2391 2344 2298 2253 2209 2166 2124 2083
150 2043 2004 1966 1928 1891 1856 1820 1786 1753 1720
160 1688 1656 1625 1595 1566 1537 1509 1481 1454 1427
170 1402 1376 1351 1327 1303 1280 1257 1235 1213 1191
180 1170 1150 1129 1110 1090 1071 1053 1035 1017 999
190 982 965 949 933 917 901 886 871 857 842
200 828 814 801 788 775 762 749 737 725 713
APPENDIX - B
Temperature Dial Resistance
Proper Readings Should Be 5400-6600 Ohms at Minimum Setting
And 0-50 Ohms at Maximum.
Be Careful When Making Voltage Measurements or Jumping Terminals
Not to Damage or Deform Connectors or Connector Pins.
13
Page 14
LAARS Heating Systems
Thermostat circuit.
(continued from page 12)
Refer to ignition module
illustration, Is there 120VAC
between P1(1) and P1(3)?
Y
Refer to ignition module
illustration, Is there
22 - 27VAC between
P2(1) and P2(2)?
Y
Check AC source to
determine why there is no
N
illustration, Is there 120VAC
between P7(3) and P7(1)?
N
power.
Replace
ignition module.
(see page 34)
Y
Refer to ignition module
Replace transformer.
(see page 35)
WARNING
120 volt potential exposure. Use caution
making voltage checks to avoid personal injury.
N
IGNITION MODULE
Red Wires
(Temperature Sensor)
Refer to ignition module
illustration, Is there 24VAC
between P3(9) and P2(1).
N
Replace ignition module.
(see page 34)
Check continuity through
ECO, red wires of
Y
thermostat sensor.
Check at temperature
less than 160°F
Is there continuity?
(see photo at right)
Check wire harness
continuity. Replace
thermostat sensor or wire
harness as necessary.
(see page 17)
Replace thermostat
circuit board.
(see page 15)
Y
N
14
U.H.E Service Manual
Thermostat Board Replacement Procedure
Page 15
Step 1. Position main power switch to “OFF”
Step 2. Disconnect (unplug) water heater from 120
volt power source.
Step 3. Un-latch and remove top surround cover
from top of heater.
Step 4. Locate thermostat board on control panel.
(see photo at right)
Thermostat
Board
Step 5. Carefully disconnect all wires from thermostat
board.
Note: it may be necessary to identify wires
for proper re-connection.
Step 6. Remove the two screws (Phillips head screw
driver) that secure thermostat board to
control panel.
Step 7. Install new thermostat board to control panel using
screws from step 6.
WARNING
120 volt potential exposure. Isolate the
appliance and reconfirm power is
disconnected using a multi-meter.
Mounting
screw locations
Step 8. Carefully reconnect wiring per the wire
diagram below. Reconfirm wire
connections are correct prior to putting
heater back in service
Step 9. Restore 120 volt power supply to water
heater and confirm proper operation following
the lighting instructions on the lighting
instruction label or the lighting instruction
located in the installation and operating
instruction manual.
Step 10. Replace surround cover on top of heater.
WIRING DIAGRAM
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