U.S. Boiler Company K2WT-120B
The U.S. Boiler Company K2WT-120B is the last size in the compact 16-3/16-inch-wide cabinet: 12–120 MBH input with 112 MBH DOE heating capacity and a 97 MBH net AHRI water rating at 95% AFUE on the K2 condensing platform.
Key figures
- Max input
- 120 MBH
- Max CSA output
- —
- AFUE
- 95 %
- Min input
- 12 MBH
Input is gas energy consumed; output is heat delivered. Never size from input alone.
U.S. Boiler Company K2WT-120B in practice
The K2WT-120B is a K2 watertube condensing gas boiler rated at 12–120 MBH input. Its row in the K2 Product Data Sheet (Form USBL14061) prints 112 MBH DOE heating capacity, a 97 MBH net AHRI water rating and 95% AFUE.
The boiler weighs about 105 lb, vents in 3" with horizontal and vertical configurations up to 135 equivalent feet per side, and connects on 1" NPT supply and return with a 1/2" gas line. Standard equipment includes the Sage2.3 control with touch screen, a pre-installed boiler-loop circulator, a universal vent connection for CPVC/PVC, polypropylene and stainless steel, a flow switch, supply/return/high-limit water sensors and a pre-installed hanging bracket and wall-mount kit.
Boilers.ca documents this size at model level from the K2 Product Data Sheet for identification and service planning; the K2 Firetube and K2 Combi siblings are covered on the K2 series page because no printed rating table is published for them. Gas, venting and electrical work belongs with a licensed contractor. No official Canadian-sales statement was found, so canadianStatus stays 'unknown'.
Best suited to
- 12-to-120 MBH residential heat-loss loads
- Homes needing the wider K2 cabinet and 3-inch venting
- Buyers comparing K2 watertube sizes against the K2 Firetube line
Applicability and support
- Model number
- K2WT-120B
- Canadian availability
- unknown
- Production status
- current
- ROMA supplies
- Confirmed at consultation
- ROMA services
- Confirmed at consultation
- Warranty
- Series terms
Where ROMA provides on-site service
On-site service is currently offered in Greater Vancouver, BC, including Vancouver, Burnaby, Richmond, Surrey, Coquitlam, North Vancouver, West Vancouver, New Westminster, Port Coquitlam, Port Moody, Delta, Langley, Maple Ridge, Abbotsford, Chilliwack, White Rock, Pitt Meadows, Tsawwassen, Anmore, Lions Bay, Belcarra, Bowen Island, Mission. Everything else on this site is reference information you can use anywhere in Canada.
Specifications
Published specifications
Values as published by U.S. Boiler Company. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| Input, minimum | 12 MBH | Minimum input per the K2 Product Data Sheet ratings table. |
| Input, maximum | 120 MBH | Maximum input per the K2 Product Data Sheet ratings table (performance shown for elevations to 2,000 ft). |
| Output | ||
| DOE heating capacity | 112 MBH | DOE heating capacity per the K2 Product Data Sheet ratings table. |
| Net AHRI water rating | 97 MBH | Net AHRI water rating per the K2 Product Data Sheet ratings table. |
| Efficiency | ||
| Efficiency (AFUE) | 95 % | 95.0% AFUE per the K2 Product Data Sheet ratings table; the page headline is 95% AFUE with 10:1 turndown. |
| Domestic hot water | ||
| Domestic hot water | Heating-only boiler — domestic hot water comes from a separate indirect tank or water heater | |
| Venting and air | ||
| Vent size | 3" | Vent size per the K2 Product Data Sheet: 3". Typical venting configurations are horizontal and vertical up to 135 equivalent feet each. |
| Venting | Direct vent, sealed combustion; universal connection for CPVC/PVC, polypropylene and stainless steel | Universal exhaust vent connection per the Product Data Sheet; horizontal and vertical two-pipe, concentric, low-profile and hybrid configurations illustrated, plus polypropylene and stainless chimney-chase options. |
| Physical and connections | ||
| Approx. net weight | 105 lb | Net weight per the K2 Product Data Sheet ratings table. |
| Dimensions (A × B × C) | 16-3/16" × 3" × 7-7/16" (A × B × C) | K2 dimension table values; the open control door extends dimension A by 15 inches. |
| Supply/return connections | 1" NPT supply and 1" NPT return | Water connection sizes per the K2 Product Data Sheet dimension drawing. |
| Gas connection | 1/2" gas line per the dimension drawing | Gas connection per the K2 Product Data Sheet dimension drawing; LP conversion kits are sold separately by size. |
| Operating limits and other | ||
| Control | Sage2.3 Control System with LCD touch screen | Sage2.3 control with self-guided menus, built-in diagnostics, two additional circulator outputs, eight-boiler sequencer, outdoor reset, DHW priority and warm-weather shutdown per the Product Data Sheet. |
| Fuel | Natural gas (LP conversion kit sold separately) | Boilers shipped set for natural gas; LP conversion kits are listed by size (080B–100B P/N 107873-01, 120B–150B P/N 107874-01, 180B P/N 107875-01, 180M P/N 108101-01). |
Frequently asked questions
What are the K2WT-120B's ratings?
12–120 MBH input, 112 MBH DOE heating capacity, a 97 MBH net AHRI water rating and 95% AFUE per the K2 Product Data Sheet.
What venting does the K2WT-120B use?
3" venting per the K2 Product Data Sheet, with typical horizontal and vertical configurations up to 135 equivalent feet per side and a universal connection accepting CPVC/PVC, polypropylene and stainless steel.
Questions about the U.S. Boiler Company K2WT-120B?
Describe what the boiler is doing and get a straight answer about the next step.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Compare and explore
- U.S. Boiler Company K2WT-100B vs K2WT-120BComparison
- U.S. Boiler Company K2WT-120B vs K2WT-150BComparison
- U.S. Boiler Company K2WT-080BSame series
- U.S. Boiler Company K2WT-100BSame series
- U.S. Boiler Company K2WT-150BSame series
- U.S. Boiler Company K2WT-180BSame series
- U.S. Boiler Company K2WT-180MSame series
- K2 series hub
- Buying guide
Sources and verification
- U.S. Boiler Company — K2 High-Efficiency Condensing Boiler product page · accessed September 9, 2026
- K2 Product Data Sheet, Form USBL14061 (PDF) · USBL14061 · accessed September 9, 2026
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.