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
Stepping from the Knight WHB110 to the WHB155 raises input from 110 to 155 MBH and DOE capacity from 102 to 144 MBH at 95% AFUE, but the 155 loses the 2" venting option entirely (3" only, 100 feet), raises the minimum fire from 11 to 15.5 MBH and holds 3.2 gallons against 2.3.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Lochinvar Knight WHB110 | Lochinvar Knight WHB155 |
|---|---|---|
| Heating input, minimum | 11 MBH | 15.5 MBH |
| Heating input, maximum | 110 MBH | 155 MBH |
| DOE heating capacity | 102 MBH | 144 MBH |
| AHRI net water rating | 89 MBH | 125 MBH |
| Efficiency (AFUE) | 95 % | 95 % |
| Water content | 2.3 gal | 3.2 gal |
| Space-heating water connections | 1" | 1" |
| Gas connection | 1/2" | 1/2" |
| Max. equivalent vent/air length, 2" | 40 ft | — |
| Max. equivalent vent/air length, 3" | 100 ft | 100 ft |
| vent-max-4 | — | — |
| Domestic hot water | Heating-only boiler | Heating-only boiler |
Both are wall-hung, heating-only Knights rated 95% AFUE with 1" water connections and a 1/2" gas connection, driving an indirect tank for domestic hot water. The 155 exists for homes whose design-day load exceeds what 110 MBH of input can deliver.
The ratings table shows the step: minimum fire rises from 11 to 15.5 MBH and water content from 2.3 to 3.2 gallons. In a home whose load hovers near 100 MBH, the 110 tracks shoulder-season demand more closely than the 155.
Venting is the structural change: the I&O table lists 2" pipe for the 110 (to 40 feet) but the 155 and up are 3" only, to 100 equivalent feet. A retrofit with an existing 2" vent run therefore stops at the WHB110.
Lochinvar
The Knight WHB110 is the mid-size wall-hung Knight: 11 to 110 MBH input at 95% AFUE with 102 MBH DOE heating capacity, and 2" venting limited to 40 equivalent feet.
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.
No. From the 155 size upward the I&O ratings and Table 3D list 3" venting only, to a maximum of 100 equivalent feet. The 110 is the largest Knight that allows 2" pipe.
When the heat-loss calculation plus any indirect-tank recovery load exceeds the 110's capacity on a design day, and the mechanical room can route 3" venting.
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.