Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
Boilers.ca is a brand of ROMA Heating & Cooling · Licensed gas contractor LGA0202903
Comparison
Verdict in brief
The Knight WHB155 and WHB199 are the two mid-large wall-hung Knights and share 3"-only venting to 100 equivalent feet, but the 199 fires 44 MBH higher (199 versus 155) with 183 MBH of DOE capacity, steps up to 1-1/4" water connections and holds 5.2 gallons against 3.2.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Lochinvar Knight WHB155 | Lochinvar Knight WHB199 |
|---|---|---|
| Heating input, minimum | 15.5 MBH | 19.9 MBH |
| Heating input, maximum | 155 MBH | 199 MBH |
| DOE heating capacity | 144 MBH | 183 MBH |
| AHRI net water rating | 125 MBH | 159 MBH |
| Efficiency (AFUE) | 95 % | 95 % |
| Water content | 3.2 gal | 5.2 gal |
| Space-heating water connections | 1" | 1-1/4" |
| Gas connection | 1/2" | 1/2" |
| vent-max-2 | — | — |
| Max. equivalent vent/air length, 3" | 100 ft | 100 ft |
| vent-max-4 | — | — |
| Domestic hot water | Heating-only boiler | Heating-only boiler |
Both models are 95% AFUE heating-only Knights on the SMART SYSTEM, venting in 3" pipe to 100 equivalent feet with a 1/2" gas connection. Domestic hot water comes from an indirect tank such as Lochinvar's Squire on both.
The 199's ratings step up across the board: maximum input rises from 155 to 199 MBH, DOE capacity from 144 to 183 MBH and the AHRI net rating from 125 to 159 MBH. Minimum fire also rises, from 15.5 to 19.9 MBH.
The 199 is the first wall Knight to need 1-1/4" water connections, and its 5.2-gallon water content reflects the larger heat exchanger. Near-boiler piping must step up to match, which is a planning difference on site rather than a problem.
Lochinvar
The Knight WHB155 reaches 15.5 to 155 MBH input at 95% AFUE with 144 MBH DOE capacity, and from this size upward the Knight vents in 3" pipe only.
Lochinvar
The Knight WHB199 is the 199 MBH wall-hung Knight: 19.9 to 199 MBH input at 95% AFUE, stepping up to 1 1/4" water connections and 3" venting to 100 equivalent feet.
Yes — both are 3"-only to 100 equivalent feet per the I&O manual. The 2" option ended at the 110 size.
Water connections step from 1" to 1-1/4" and water content from 3.2 to 5.2 gallons; the gas connection stays 1/2". Near-boiler piping must be sized for the larger fittings.
A consultation includes a heat-loss review so the size is right the first time.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.