Condensing Gas Boilers

TJ’s offers installation and service on a wide variety of condensing gas boilers, including:

Be sure to read our blog on Flue Gas Temperatures and PVC Venting.

Bosch Greenstar™ Series Boilers Set New Standard in Ultra Efficient Home Comfort

Bosch has announced the addition of six new ultra efficient wall mounted condensing boilers to its Thermotechnology line of products. Bosch Greenstar gas-fired condensing boilers can offer efficiency levels of up to 98.7 percent, turning 98.7 percent of the fuel used into heat – a significant upgrade compared to traditional or non-condensing boilers.

The Bosch Greenstar™ series, available in configurations ranging from 57.2 to 151.6 MBH, utilize condensing technology – an invention where the latent heat in the unit’s exhaust gases is extracted and re-used – a highly efficient use of energy which also significantly reduces carbon dioxide emissions into the atmosphere.

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Buderus Logamax Plus GB142

Thanks to the prefabricated manifold, the GB142 has the fastest installation in the industry. Specially designed with an appropriately sized circulator, this manifold ensures proper flow rate through the boiler.

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Offering well developed and energy-saving condensing technology, the entire Logamax plus GB142 series is the best. The Logamax plus GB142 can supply any type of home with heating.

Advantages at a Glance:

  • Efficient energy utilization – AFUE’s of 96%
  • Clean combustion
  • May be connected to many different flue systems, even without availability of a chimney
  • Space-saving installation of the Logamax allows minimal space used with direct wall mounting
  • Flexible selection of the installation location
  • Low power consumption
  • Quiet operation


  • Modulating operation, i.e. matched to the actual heat demand
  • Available as boiler with integral Logamatic EMS control unit; easy to add an optional Buderus hot water tank or RC35 Control
  • Integral aluminum heat exchanger with a large surface area for condensing operation all year round
  • Optimum energy utilization and minimized operating costs through ETA plus system
  • Output modulates between 30% and 100%
  • Selectable flue gas routing: open flue version may be connected to an existing chimney; alternatively balanced flue connection with a system-certified balanced flue system (room sealed balanced flue)
  • Outputs of 75, 95, 142, 199 MBH



Condensing Technology

Condensing technology maximizes fuel utilization and reduces your heating bills. By capturing the portion of latent heat, which in conventional heating boilers is lost through the chimney, condensing boilers, like the Vitocrossal 300, use as much as 98% of the original energy input to heat your building.

Viessmann Vitocrossal 300, CU3A

Viessmann’s latest gas-fired condensing boiler is unlike any other condensing boiler system.   TJ’s has seen, first hand, just how this boiler operates, and what makes it so special.

With its combination of high temperature capability, high mass (water volume), floor standing design, condensing stainless steel construction and modulating gas burner, the Vitocrossal 300, CU3A is the ideal choice for boiler retrofits or new construction. From homes equipped with high mass cast iron radiators, to homes with multi-zone high temperature fin tube radiators, and new installations with high DHW requirements – the Vitocrossal 300, CU3A is the best choice on the market today.


Features and Benefits

  • Compact, floor-standing gas condensing boiler from 19-199 MBH.
  • Multi-boiler installation with 8 boilers up to 1592 MBH.
  • High efficiency of 95% AFUE on all models.
  • High temperature operation of up to 90°C (194°F).
  • Inox-Crossal heat transfer surface – 316Ti stainless steel heat exchanger for efficient utilization of condensing technology – self-cleaning effect via smooth stainless steel surfaces.
  • Vitocrossal Pocket Design with wide water passage ways allow for system/full flow applications. No dedicated boiler pump required and eliminates primary/secondary piping.
  • MatriX dome gas burner with 5:1 turndown ratio to ensure high efficiency and extremely clean combustion.
  • High water volume extends burner run time and reduces cycling.
  • A self-calibrating Lambda Pro combustion management system ensures optimal combustion efficiency at all times regardless of gas/air quality. Simple commissioning with no field adjustments and adjusts to all fuel types (NG and LPG).
  • Durable, reliable, and long service life with Inox-Crossal stainless steel heat exchanger and high mass design.
  • Multi-venting options and configurations with vent lengths up to 198 ft.
A Peek Inside the Viessmann Vitocrossal 300

A Peek Inside the Viessmann Vitocrossal 300

Vitodens 100

The perfect mix of performance, quality and value, the Vitodens 100-W gas-fired wall-mount condensing boiler is ideal for any home and any budget. With added product features, the new generation of this popular boiler now offers even greater versatility and choice.

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Some benefits of the Viessmann Vitodens 100:

  • Fits Any Home and Budget with high performance at an attractive price.
  • Outstanding Efficiency of 95.2% A.F.U.E. on all models.
  • Lasting Performance with industry-leading Viessmann made SA240 316 Ti stainless steel Inox-Radial heat exchanger constructed to CSA B51 and ASME Section IV.
  • Low-Emission Combustion with Viessmann made stainless steel MatriX cylinder burner for natural gas or propane. Factory calibrated.
  • Versatile On-Board Boiler Control interfaces with most external controls. Now with integrated 0-10V and OpenTherm® communication ability. Outdoor temperature sensor standard.
  • Greater Venting Flexibility with increased vent length (up to 200’) and multiple venting options
– Horizontal or vertical sealed combustion coaxial venting (factory supplied).
– Horizontal, vertical or hybrid sealed combustion double-pipe venting (field supplied).
– Horizontal or vertical single-wall venting (field supplied).
  • Suitable for Altitude Levels of up to 10,000 ft. / 3000 m.
  • Easy Installation, Service and Maintenance with all pipe connections located at the bottom and serviceable components easily accessible from the front.
  • Extremely Quiet Operation; quieter than most refrigerators.
  • Compact, Lightweight Design and zero clearance to combustibles.
  • Built-in Automatic Frost Protection prevents freeze-up during long shut-off periods.
  • Limited Lifetime Warranty in residential applications

NEW! On-demand DHW with Vitodens 100 CombiPLUS Package

With the new Vitodens 100 CombiPLUS Package add on-demand domestic hot water (DHW) to your new Vitodens 100 space heating boiler and say goodbye to your DHW tank. Enjoy DHW at the snap of your fingers all day long with an outstanding flow rate of up to 3.6 GPM†, plus added cost savings with the energy-efficient on-demand indirect-fired design. Slightly bigger than a large shoe box, the CombiPLUS Kit installs underneath or beside the boiler and requires only minimal piping and electrical connections. Equipped with a stainless steel heat exchanger, built-in pressure bypass, DHW temperature and fl ow sensors, 3-speed pump and 3-way diverting valve, get nothing but reliable, high-quality DHW day after day.

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Benefits of the Vitodens 100-W CombiPLUS Package:

  • All the benefits of a Vitodens 100 boiler, plus on-demand domestic hot water (DHW) with CombiPLUS Kit.
  • DHW at the snap of your fingers all day long! Up to 3.6 GPM.
  • Energy-efficient and low-cost due to on-demand indirect-fired DHW production.
  • Reduced energy waste with fully-modulating input from boiler.
  • Space-saving and lightweight wall-mount design. More compact than any other hot water heater.
  • Virtually silent DHW production.
  • Easy installation with all piping and electrical connections included.
  • Quality you can count on! Stainless steel heat exchanger, built-in pressure bypass and 150 psig working pressure rating.
  • Reliable and even DHW supply with built-in DHW temperature and flow sensors.
  • Complete space / DHW heating management by boiler control, powerful built-in 3-speed pump and diverting valve.
  • Great fit for apartments, condos, cottages, single-family homes, or installs where space is at a premium.

Vitodens 200

Equipped with the industry’s first intelligent combustion management system and powerful control technology, the new generation Vitodens 200-W gas-fired wall-mount condensing boiler delivers unparalleled performance, reliability and comfort.

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Some benefits of the Viessmann Vitodens 200:

  • Best Value in its Class with new industry-leading technology and the most standard features.
  • Highest Efficiency of up to 98% at full modulation and up to 96.1% A.F.U.E. CSA thermal efficiency to ANSI Z.21.13/CSA 4.9 of 94.5% (for model WB2B 105 only).
  • Lasting Performance with industry-leading Viessmann made SA240 316 Ti stainless steel Inox-Radial heat exchanger constructed to CSA B51 and ASME Section IV.
  • Low-Emission Combustion with Viessmann made stainless steel MatriX cylinder burner for natural gas or propane. Factory calibrated.
  • Fast Installation and Reduced Maintenance with Lambda Pro, industry-first intelligent combustion management system. Adjusts automatically to gas type and quality. No fuel conversion kit required.
  • Powerful and User-Friendly Viessmann Vitotronic on-board multifunction outdoor reset boiler and system control for multi-temperature space and DHW heating.
  • Expanded Application Range with increased capacity up to 370 MBH. Multi-boiler installation up to 1480 MBH with up to 4 boilers (models WB2B 45 and up).
  • Greater Venting Flexibility with increased vent length (up to 180’) and multiple venting options.
– Horizontal or vertical sealed combustion coaxial venting (factory supplied).
– Horizontal, vertical or hybrid sealed combustion double-pipe venting (field supplied).
– Horizontal or vertical single-wall venting (field supplied).
  • Compact, Lightweight Design and zero clearance to combustibles.
  • Extremely Quiet Operation; quieter than most refrigerators.
  • True High-Altitude Operation up to 10,000 ft / 3,000 m with simple electronic adjustment.
  • Limited Lifetime Warranty in residential applications.

Lochinvar Knight Condensing Gas Boiler

The KNIGHT’s high-tech design and high-efficiency performance make it the smartest way to heat your home. There’s a new champion in home heating — the KNIGHT high-efficiency condensing boiler from Lochinvar. With a 93% Annual Fuel Utilization Efficiency (AFUE) rating, you can rest assured that 93¢ out of every energy dollar goes directly into heating your home. That’s well above ENERGY STAR® standards, and its efficiency goes up to an astounding 98.6% in low-temperature radiant applications, saving you hundreds of dollars each heating season!

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The KNIGHT’s burner and combustion system features the industry’s most advanced modulation for unsurpassed comfort. Ordinary boilers turn on at full power and run for a few minutes, then shut completely off – repeating this many times throughout the day. In contrast, the KNIGHT boiler will modulate from 20% to maximum input in steady increments so that you always get the comfort level you desire. It’s like having the efficiency advantage of multiple boilers in one compact, space-saving unit. The burner/combustion system also provides environmentally friendly operation (either natural gas or LP), with air quality emissions so low that they exceed the toughest environmental standards.

Comfort Control At Your Fingertips
The KNIGHT’s unique SMART SYSTEM™ Control includes an energy-saving setback function that lets you custom-tailor the boiler’s performance to your comfort needs. It also features a 2-line LCD display that alerts you when servicing is required. And as the outside t e m p e r a t u r e changes, the automatic energy monitor adjusts the KNIGHT’s output for maximum comfort and energy savings.

Weil-McLain Ultra Series 3-UE Gas Boiler

Weil-McLain’s Ultra Series 3-UE delivers peace of mind, unmatched comfort and immediate payback in energy savings.

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Key Features

  • Gas fired water boiler with cast aluminum heat exchanger
  • Venturi mixing body mixes air and gas providing higher efficiency
  • Designed to operate in low temperature condensing applications
  • Outdoor reset and domestic hot water priority standard
  • Negative regulated gas valve precisely delivers gas to the boiler
  • U-Control gives you the power for easy set-up and maintenance
  • Modulates with 5 to 1 turn-down ratio capability
  • Variable speed motor matches combustion output to heating needs
  • High grade stainless steel burner features quiet operation, high efficiency, and cleaner combustion for low NOx applications

Laars Mascot

Mascot is a high-efficiency, wall-mounted boiler available in three BTU sizes –126, 167, and 242 MBTU. The two 126 MBTU boilers are considered residential and they are available both as “heating only” boilers (model HT 1.330) and as “combi” boilers with both hydronic heating and domestic hot water (model HT 330). The Mascot 167 & 242 MBTU boilers (HT 1.450 & HT 1.650) are packaged differently for potential commercial applications using either single or multiple boiler installations. This means that customers may order single or multiple piping assemblies, and single or multiple venting systems with the HT 1.450 & HT 1.650.

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Both residential models (HT 330 & HT 1.330) are loaded with features that most other boilers don’t include, making Mascot boilers faster, easier and less expensive to install. Mascot residential boiler features that are standard with every 330 and 1.330 boiler include:

  • Energy Star Rated Gas Boiler
  • Sleek, appliance-grade cabinet that looks great in any location
  • Up to 96% efficiency, condensing operation
  • 2-year parts warranty, 10-year heat exchanger warranty
  • Sealed combustion
  • Direct spark ignition for reliability and smooth starts
  • Three venting options to meet the needs of almost any installation
  • Modulating gas valve that varies from 30% to 100% input
  • Variable speed quiet blower
  • Boilers are set up for natural gas, no parts necessary for conversion to LP gas
  • Built in expansion tank that will handle 26.4 gallons of system water (enough to cover 1,800’ feet of ½” PEX tubing)
  • Built-in water fill valve
  • Water flow sensor for hydronic system
  • Grundfos circulator with air vent and “quickremove” mounting system
  • Automatic 3-way valve for DHW priority (both combi and heating only)
  • Back-flow preventer
  • Mounting kit with template and wall bracket for fast and easy installation
  • Light-weight (100 lbs.) makes handling easy
  • Stainless steel A.S.M.E. primary heat exchanger with externally welded manifolds for better flow rates and prevention of leaks
  • Stainless steel brazed plane DHW heat exchanger (combi models) with advanced hall sensor flow switch that detects .5 gpm DHW flow rates
  • Built-in reverse-pressure by-pass to prevent short cycling
  • Advanced Siemens control system with temperature control, diagnostics, outdoor reset capability, and easy access for field wiring
  • Complete piping kit with isolation valves, gas cock, domestic water connection adapters withunions, hydronic connectors with unions
  • Condensate trap that is easy to inspect & remove from outside the boiler

Munchkin Boiler

The Munchkin Boiler is one of the most compact and efficient residential boiler available on the market today. Each Munchkin Boiler will modulate its firing rate to match the energy needs of the living space. This feature provides additional savings versus traditional single firing heaters. With stainless steel construction, you can be assured that you are buying the highest quality appliance. Proven European technology, manufactured in the United States. A quiet operational appliance is just another benefit that comes with the Munchkin boiler.

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  • Fully modulating for ultra high efficiency 95.1%
  • Consists of stainless steel construction 316L
  • ASME And Vision One Control Now Standard
  • Direct vent with standard schedule 40 PVC    plastic pipe
  • Quiet operation
  • State-of-the-art control
  • Reliable field-proven spark ignition
  • Each unit is inspected for 100% quality satisfaction
  • Sealed combustion
  • Environmentally friendly
  • Modular component construction
  • 12 year limited warranty
  • Operates at low supply temperature