Laars MINI-THERM JX Series Installation And Operation Instructions Manual

Residential gas-fired hydronic boilers sizes 50-200 mbtu/h

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Installation and operation instructions manual (52 pages)

Installation and operation instruction manual (52 pages)

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Installation and Operation Instructions

FOR YOUR SAFETY: This product must be installed and serviced by a professional service technician,

qualified in hot water boiler and heater installation and maintenance. Improper installation and/or operation

could create carbon monoxide gas in flue gases which could cause serious injury, property damage, or

death. Improper installation and/or operation will void the warranty.

If the information in this manual is not followed

exactly, a fire or explosion may result causing

property damage, personal injury or loss of life.

Do not store or use gasoline or other flammable

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

fire department.

Installation and service must be performed by

a qualified installer, service agency, or gas supplier.

Installation and Operation Instructions for

WARNING

-T

INI

HERM

Residential

Gas-Fired

Hydronic Boilers

Sizes 50-200 MBTU/h

AVERTISSEMENT

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

Ne pas entreposer ni utiliser d'essence ni d'autres

vapeurs ou liquides inflammables 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 qualifié ou par le

fournisseur de gaz.

Document 1478A

ou la mort.

Table of Contents

Troubleshooting

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Do you have a question about the MINI-THERM JX Series and is the answer not in the manual?

Questions and answers

Steve price

April 18, 2025

Just installed a j X Mini boiler not getting any power 24 volts from 24 volt terminal to pv1 says in the instructions to replace control I did that still the same problem

1 comments:

Mr. Anderson

May 9, 2025

If there is no 24V power from the 24V terminal to PV1 after replacing the control on a Laars MINI-THERM JX Series boiler, possible causes include:

1. Incorrect wiring to the new control—verify all connections match the wiring diagram.
2. No power to the control—check that 120VAC is supplied to the boiler and the control is powered (TEMP ACTIVE LED should be on).
3. Safety or interlock circuits not closed—ensure all safety switches and interlocks are properly connected and closed.
4. Faulty replacement control—if wiring and power are correct, the new control may be defective.
5. Issue with field wiring—inspect field wiring for loose connections or damage.

Use the wiring diagram and logic diagram to trace the 24V path and confirm each component is functioning.

This answer is automatically generated

Summary of Contents for Laars MINI-THERM JX Series

Page 1 Installation and Operation Instructions Document 1478A Installation and Operation Instructions for HERM ® Residential Gas-Fired Hydronic Boilers Sizes 50-200 MBTU/h FOR YOUR SAFETY: This product must be installed and serviced by a professional service technician, qualified in hot water boiler and heater installation and maintenance. Improper installation and/or operation could create carbon monoxide gas in flue gases which could cause serious injury, property damage, or death.
Page 2: Table Of Contents
LAARS Heating Systems TABLE OF CONTENTS SECTION 1 GENERAL INFORMATION Field Connections ......24 Safety Warnings ........4 7.D.1 TB1 (Term Block 1 -TT, DHW, OAS) . 24 Introduction ..........6 7.D.1.a TT (Central Heat)........24 Warranty ..........6 7.D.1.b DHW............ 24 Model Number and Nomenclature ..
Page 3 JX Residential Boilers INI- HERM ® Advanced Programing ....... 32 8.B.1 Fahrenheit or Celsius ......32 8.B.2 Low Water Cut-Off ........ 32 8.B.2.a RESET, Manual or Automatic ....32 8.B.2.b Testing Low Water Cut OFF ....33 8.B.3 High Limit Differential ......33 Sensor Programming ......
Page 4: Section 1 General Information 1.A Safety Warnings
Page 4 LAARS Heating Systems SECTION 1 GENERAL INFORMATION 1.A Safety Warnings Safety Warnings are used throughout this manual to bring attention to the presence of hazards with various risk levels and to oﬀ er important information concerning the life of this product. There are 3 basic types.
Page 5 JX Residential Boilers Page 5 INI- HERM ® WARNING WARNING The Repair Parts list designates parts that contain Electrical Shock Hazard refractory ceramic ﬁ bers (RCF). RCF has been classiﬁ ed Electrical shock can cause severe injury, death or as a possible human carcinogen. When exposed to property damage.
Page 6: B Introduction
1.C Warranty (Low Loss Header & Pump Installed) P = 50-100 with Pump Kit The Laars Mini-Therm JX boilers are covered by a 8th Character (Altitude in Feet) limited warranty. The owner should complete the warranty registration online by going to www.Laars.
Page 7: E Model Overview
JX Residential Boilers Page 7 INI- HERM ® 1.E Model Overview Low Loss Header. Models 125 - 200 only 200 MBH Rating Plate with Model Number Figure 1. Largest and Smallest 50 MBH and Nomenclature Temperature and Pressure Gauge The Temperature and Pressure gauge is viewable just above the Digital Dashboard.
Page 8 Page 8 LAARS Heating Systems 1.E Model Overview (continued) Hydronic Return Hydronic Supply Low Loss Header (sizes 125 - 200) Vent Damper Temp and Pressure Gauges Panel Lock The Digital Dashboard See 8.A on page 30 Drain Rating Plate Pressure Relief Valve ‘Knock-outs’...
Page 9: G Dimensions
JX Residential Boilers Page 9 INI- HERM ® 1.G Dimensions IN (Return) Dimensional 1-1/4” NPT Male IN (Return) Data 1-1/4” NPT Male OUT (Supply) Out Supply 1-1/4” NPT Male 7" OUT (Supply) In Return 18cm Out Supply 1-1/4” NPT Male 7"...
Page 10: H The Installation Kit
Page 10 LAARS Heating Systems 1.H The Installation Kit Accessory Kits Available See Section 12.C on page 50 for part numbers. This residential unit is shipped in a single crate with a boxed installation kit that contains these components. •...
Page 11: Section 3 Air And Venting 3.A Safety Warnings
JX Residential Boilers Page 11 INI- HERM ® SECTION 3 Air and Venting 3.A Safety Warnings WARNING WARNING This boiler must be vented in accordance with Part For Category I, II and IV boilers, have horizontal runs sloping upwards not less than ¼ inch per foot (21 mm/m) 7, Venting of Equipment, of the latest edition of the from the boiler to the vent terminal.
Page 12: B Combustion Air Supply
Page 12 LAARS Heating Systems 3.B Combustion Air Supply Boiler Size Outside Air Area Inside Air Area The boiler location must provide sufficient air supply for sq. in sq. in. sq. cm sq. cm proper combustion, and ventilation of the surrounding area as outlined in the latest edition of U.S.
Page 13: C Venting
JX Residential Boilers Page 13 INI- HERM ® 10 (3.0) OR LESS MORE THAN 10 (3.0) 2 (0.6) MIN. 3 (0.9) 3 (0.9) MIN. MIN. WALL OR WALL OR PARAPET TERMINATION PARAPET CHIMNEY 10 FT. (3.0m) CHIMNEY OR LESS FROM RIDGE, NOTE: NO HEIGHT WALL OR PARAPET 10 (3.0)
Page 14: D Vertical Venting - Category I
Page 14 LAARS Heating Systems 3.D Vertical Venting - Category I WARNING All venting must comply with fuel gas code and be Do not store any chemical, cleaners, or other installed by a licensed installer. corrosive material near combustion air openings or in the room.
Page 15: E Locations For Vent Pipe Terminator
JX Residential Boilers Page 15 INI- HERM ® 3.E Locations for Vent Pipe Terminator Canadian Installations 1 U.S. Installations 2 A = Clearance above grade, veranda, porch, deck, or balcony B = Clearance to window or door that may be ●...
Page 16: F Venting With A Power Venter
Page 16 LAARS Heating Systems Venting with a Power Venter 3.G Évent Commun This boiler is certified for use with the manufacturer's suggested Power Venter, which is supplied in a kit that AVERTISSEMENT includes Installation Instructions. See the accessories Lorsqu'une chaudière existante est retirée d'un list in the Parts Section of this manual.
Page 17: Section 4 Gas Connections 4.A Gas Supply And Piping
JX Residential Boilers Page 17 INI- HERM ® SECTION 4 Gas Connections 4.A Gas Supply and Piping Follow this guideline checklist for the gas supply installation. CAUTION 1. Gas piping installation must be in accordance Permanent damage to the gas valve will occur if the with the latest edition of ANSI Z223.1 and all local following procedures are not followed.
Page 18: Blp Gas Conversion
Page 18 LAARS Heating Systems NOTE: The boiler and all other gas WARNING appliances sharing the boiler gas supply line must be firing at maximum capacity to The boiler is designed for use with either natural properly measure the inlet supply pressure.
Page 19: Section 5 Pump Requirements
1-1/4 29.3 24.9 36.6 31.1 1-1/4 1-1/4 44.0 37.2 JX Residential Boilers Page 19 INI- HERM ® 1-1/4 58.3 49.2 SECTION 5 PUMP REQUIREMENTS 5.A Pump Sizing Water Flow Requirements Temperature Rise 15°F 8°C 20°F 11°C 25°F 14°C Size Flow Rate Headloss Flow Rate Headloss...
Page 20: Section 6 Water Connections 6.A Water Piping
Page 20 LAARS Heating Systems SECTION 6 WATER CONNECTIONS 6.A Water Piping could benefit from its use. NOTE: This boiler must be installed in a closed pressure system with a minimum of 12 psi (82.7kPa) static pressure at the boiler.
Page 21: E Typical Plumbing Diagrams
JX Residential Boilers Page 21 INI- HERM ® 6.E Typical Plumbing Diagrams These diagrams are only meant as a guide. All components or piping required by local code must be installed. Check Check Valves Air Scoop Valves Air Scoop Air Scoop Check Valv Air Scoop...
Page 22 Page 22 LAARS Heating Systems Typical Plumbing Diagrams (continued) Check Air Scoop Valves Valves Zone Pumps (must be sized properly) Pump Valves Valves Check Valve Low Loss Header w/ Pump Indirect Tank Figure 14. Low Loss Header with Zone Pumps and DHW Low Loss Header is standard on models 125, 150, and 200 and Optional for models 50, 75, and 100.
Page 23: And Safety Warnings
Input Natural Gas Conn. Conn. Size MBTU/h MBTU/h JX Residential Boilers Page 23 1-1/4 INI- HERM 14.7 12.6 ® 1-1/4 22.0 18.8 1-1/4 29.3 24.9 SECTION 7 ELECTRICAL AND WIRING DIAGRAMS 1-1/4 36.6 31.1 7.A Safety Warnings 44.0 37.2 1-1/4 58.3 49.2 1-1/4...
Page 24: D Field Connections
Page 24 LAARS Heating Systems 7.D Field Connections This boiler has three Field Connection Terminals. TB1, TB2 and TB3 (TB3 is for optional equipment). Open TB2 - 120 VAC Outputs Closed TB3 -DHW Relay Connections (optional) TB1 -TT, DHW, OAS Figure 17.
Page 25: Tb2 (For Pumps And Aux Power)
JX Residential Boilers Page 25 INI- HERM ® 7.D.2 TB2 (for pumps and aux power) 7.D.2.a Boiler Pump This terminal and the 120V(N) terminal will provide power to the boiler pump whenever the boiler is running. Use this to power the Low Loss Header (LLH) pump or a boiler pump in a Primary/Secondary application.
Page 26: E Wiring Connects, Power Vent And Air
Figure 19. Combustion Air System wiring example Combus�on Air System Example: Laars Power Vent Kit and Fields Controls CAS-4 Wiring to JX Combustion Air System Example: Laars Power Vent Kit and Fields Controls CAS-4 Wiring to JX Example: Laars Power Vent Kit and Fields Controls CAS-4 Wiring to JX...
Page 27 JX Residential Boilers Page 27 INI- HERM ® Laars Power Vent Kit Example: Typical Zone Pump Control Wiring to JX for Anti-condensing protection Terminals 2 and 3 are both 120V Neutral NOTE: Must have a dedicated boiler pump (such as LLH) when using this method.
Page 28: F Wiring Diagram
Page 28 LAARS Heating Systems Wiring Diagram CUSTOMER POWER CONNECTION 120VAC TRANSFORMER 24VAC DAMPER CONNECTOR Boiler Controller BLOCKED VENT ROLL OUT SWITCH SWITCH PILOT VALVE 24V (L) GAS VALVE MAIN VALVE 24V (N) 24V (L) 120VAC FACTORY INSTALLED JUMPERS: 24VAC...
Page 29: G Logic Diagram
JX Residential Boilers Page 29 INI- HERM ® 7.G Logic Diagram 120VAC (1PH/60Hz) 10K OHM L1 N SENSOR INPUTS WWSD FIELD 24V (N) PV2 INPUTS Field AUX POWER TB2:5A TB2:3A Interlock 120VAC OPTIONAL P1:1 P1:2 HEAT DHW PUMP RELAY DEMANDS P1:3 BOILER/HEATER 120VAC CONTROL INPUT...
Page 30: Section 8 The Digital Dashboard 8.A Getting To Know The Digital Dashboard
Page 30 LAARS Heating Systems SECTION 8 THE DIGITAL DASHBOARD 8.A Getting to know the Digital Dashboard. The digital dashboard for the controller is protected by a removable clear plastic cover. See Figure 25. Under the removable clear cover, there are three (3) dials and one (1) button.
Page 31: The Lo Limit Dial (Advanced Programing)
JX Residential Boilers Page 31 INI- HERM ® 8.A.5 Control LEDs See Figure 26 8.A.1 The Lo Limit Dial 8.A.5.a TS ACTIVE (TEMP) (Advanced Programing) Indicates that the control is powered and that the This efficient hybrid copper/cast iron heat exchanger temperature function is active.
Page 32: Digital Leds
Page 32 LAARS Heating Systems 8.A.7.b V-PWR See Figure 26 8.A.6 Digital LEDs Indicates power has been sent to the vent damper. The The Digital Display is the numeric display in the middle damper will open causing it’s end switch to close.
Page 33: B.2.B Testing Low Water Cut Off
Dial Default Feature Options Description Setting Setting Degrees Fahrenheit Fahrenheit or Celsius JX Residential Boilers Page 33 OPTIONAL FEATURES continued INI- HERM ® Degrees Celsius LWCO Manual or Automatic Reset Automatic Reset Manual Reset Dial Default Feature Options Description Setting Setting Not available on this control...
Page 34: Adjusting Reset Ratio)
Page 34 LAARS Heating Systems adjust the ECONOMY dial to the desired setting. To turn the feature off - which will allow space heating Reset Ratio regardless of outdoor temperature - press and hold the Mode button and simultaneously turn the ECONOMY dial fully counter-clockwise.
Page 35: Restore Factory Default Settings
JX Residential Boilers Page 35 INI- HERM ® 8.D View Current Settings 8.C.4 Restore Factory Default Settings down. The boiler water will continue to circulate and heat the The Mode button has several functions when TEMP ACTIVE Indicates that the Fuel Smart To restore advanced settings, to factory default settings house as long as the thermostat call continues.
Page 36: Section 9 Initial Startup
Page 36 LAARS Heating Systems SECTION 9 INITIAL STARTUP WARNING Carbon monoxide hazard. The vent damper must be 9.A Filling the System fully open and the flue must be clear before the main burner fires. If the burner fires when the vent damper...
Page 37 JX Residential Boilers Page 37 INI- HERM ® 6. When pilot flame is sensed the green FLAME LED will turn on. If flame is not sensed in 75 seconds the pilot valve will de-energize, the spark will terminate, and the green FLAME LED will blink. After a 5 minute delay the sequence will retry at step 5.
Page 38: C Proper Pilot Flame
Page 38 LAARS Heating Systems 9.C Proper Pilot Flame To view the pilot flame, the cover must be unlocked Open and removed. A properly adjusted pilot should have a blue, steady flame with an inner cone that engulfs 3/8” - 1/2” of the pilot ignitor sensor. See Figure 39 The pilot ignitor sensor should glow bright orange from the heat and the flame current should be 1.0 μA to 1.8 μA.
Page 39: D Lighting Instructions Decal
JX Residential Boilers Page 39 INI- HERM ® FOR YOUR SAFETY READ BEFORE OPERATING 9.D Lighting Instructions WARNING: If you do not follow these instructions exactly, a fire or explosion Decal may result causing property damage, personal injury or loss of life. A.
Page 40: E System Shutdown
Page 40 LAARS Heating Systems 9.E System Shutdown Turn off the main electrical disconnect switch. Close all manual gas valves. These boilers are certified for indoor use only and should not be subjected to freezing temperatures. When shutdown or during and extended power outage, component failure or other issue when freezing is likely, the boiler and system must be drained.
Page 41: Side Panel Removal
JX Residential Boilers Page 41 INI- HERM ® 10.A.3 Side Panel Removal Remove the front access and the top as described previously. Drain the boiler and remove the drain valve and/or the PRV and associated fittings depending on the panel being removed.
Page 42: B Maintenance
Page 42 LAARS Heating Systems 10.B Maintenance to drain that side. BOTH SIDES MUST BE WARNING DRAINED. See Section 9.E on page 40 The Warranty does not cover damage caused by 10. The gas and electric controls on the boiler are...
Page 43: Operating Details And Troubleshooting
JX Residential Boilers Page 43 INI- HERM ® SECTION 11 Operating Details and Troubleshooting 11.A Operating Details CAUTION When power is turned on, the digital display will indicate Label all wires prior to disconnection when the boiler outlet temperature. If a demand for heat is servicing controls.
Page 44: C Troubleshooting Table
Page 44 LAARS Heating Systems 11.C Troubleshooting Table Symptom Cause Remedy Boiler Pump not No power. Check circuit breakers and power source. Replace. Recheck wiring Pump defective. diagrams (System pump will not work if below 160ºF or if DHW call) operating Incorrectly wired.
Page 45: D Troubleshooting Flow Charts
Troubleshooting Flow Chart 1 – Burner Will Not Fire JX Residential Boilers Page 45 INI- HERM ® 11.D Troubleshooting Is the Flow Charts The Temp Active LED will be on at all times when the control is powered. Green LED The Control is Check for 120 VAC on the control input.
Page 46: Troubleshtng Flow Chart 1 (Burners Off)
8 & 9 for external power vent kit or Replace Control combustion air end switches. Page 46 LAARS Heating Systems Is there spark at the pilot? Check gas pressure to the pilot. Troubleshooting Flow Is There Clean or replace pilot orifice.
Page 47: A Parts Illustrations
JX Residential Boilers Page 47 INI- HERM ® SECTION 12 REPLACEMENT PARTS 12.A Parts Illustrations Reference to 12.B Parts List starting on next page.
Page 48 F0024300 F2032800 1-106 E2403300 E2402100 F0035900 H2410700 H2410600 REVISIONS THIS DOCUMENT AND THE INFORMATION CONTAINED HEREIN ARE PROPRIETARY TO LAARS HEATING SYSTEMS REV. DRAFT CHECK E0101800 ENGR APP AND SHALL NOT BE REPRODUCED, TRANSFERED 20-026N-01 JM 6JUL20 CF 6JUL20 KAG 6JUL...
Page 49: B Parts List
Jacket Components Jacket Components Panel, Top, Front Panel, Top, Front R5X3032 R5X3032 R7X3032 R7X3032 R10X3032 R10X3032 R12X3032 R12X3032 R15X3032 R15X3032 R20X3032 R20X3032 Panel, Left Side Panel, Left Side JX Residential Boilers R5X3043 R5X3043 R5X3043 R5X3043 R5X3043 R5X3043 R5X3043 R5X3043 R5X3043 R5X3043 R5X3043 Page 49 R5X3043 INI- HERM ® Jacket Components Panel, Front 5X3038 7X3038 10X3038...
Page 50: C Accessories List
L0052500 Main Gas Orifice (not shown) Note: For complete conversion kits (LP or Nat all altitudes available) see accessory section. Main Gas Valves Air Shutter, Burner L0055900 L0055900 L0055900 L0055900 L0055900 L0055900 Natural Gas 0‐2000' L0032200 L0032200 L0032200 L0032200 L0032200 L0032200 Page 50 LAARS Heating Systems Gas Valve, (Natural) RV2030700 RV2030700 RV2030700 RV2030700 RV2030700 RV2030700 Main Gas Orifice (not shown) Note: For complete conversion kits (LP or Nat all altitudes available) see accessory section. 2001'‐5000' L0050700 L0050700 L0050700 L0050700 L0050700 L0050700 Gas Valve, Regulator Spring(LP) V2015100 V2015100...
Page 51: D Glossary Of Terms
JX Residential Boilers Page 51 INI- HERM ® 12.D Glossary of Terms Temperature Controllers Air Vent A device used to purge air from the circuit. It should be The primary temperature controller maintains all located at the highest point in the circuit. normal heating operations.
Page 52 Customer Service and Product Support: Industrial Way, Rochester, NH, USA 03867 • 603.335.6300 • Fax 603.335.3355 Headquarters: 9 Brigden Gate, Halton Hills, Ontario, Canada L7G 0A3 • 905.203.0600 • Fax 905.636.0666 www.Laars.com Litho in U.S.A. © Laars Heating Systems 21-02 Document 1478A...

Laars MINI-THERM JX Series Installation And Operation Instructions Manual

D Field Connections

TB1 (Term Block 1 -TT, DHW, OAS)

TB2 (for Pumps and Aux Power)

TB3 (for Optional Equipment)

SECTION 8 the DIGITAL DASHBOARD 8.A Getting to Know the Digital Dashboard

8 A Getting to Know the Digital Dashboard. 3 0

Advanced Programing

C Sensor Programming

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Troubleshooting

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Summary of Contents for Laars MINI-THERM JX Series

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