Lochinvar · Knight XL Commercial (KBX)
Lochinvar Knight XL KBX0650
The Knight XL KBX0650 reaches 65 to 650 MBH input with 631 MBH gross output and a 549 MBH AHRI net rating at 97% thermal efficiency, stepping the gas connection to 1-1/4" and the vent to 6".
Key figures
- Max input
- 650 MBH
- Max CSA output
- —
- AFUE
- —
- Min input
- 65 MBH
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Lochinvar Knight XL KBX0650 in practice
The KBX0650 is the first Knight XL size to step the venting: the I&O ratings table (Series 110-111 for this size) lists 65 to 650 MBH input with 631 MBH gross output and a 549 MBH AHRI net water rating at 97% thermal efficiency, with a 6.2-gallon water content. Water connections stay at 2", the gas connection grows to 1-1/4", and the air intake remains 4" while the vent steps to 6".
It shares the family platform — floor-mounted stainless steel water-tube condensing boiler, SMART TOUCH control with CON·X·US, ENERGY STAR and ASME H — and vents in PVC, CPVC, polypropylene, ABS or stainless steel to 150 equivalent feet per the submittal. The submittal prints a 456 lb shipping weight, and the concentric vent kit covers the KBX0400-KBX650 sizes while the common vent kit serves KBX0500-KBX1000.
Best suited to
- Commercial buildings whose design-day load crosses 500 MBH
- Mechanical rooms laid out for a 6" vent with a 4" air intake
- Projects stepping up to a 1-1/4" gas connection at the boiler
Applicability and support
- Model number
- KBX0650
- Canadian availability
- available
- 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 Lochinvar. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| Heating input, minimum | 65 MBH | Per the I&O ratings table. |
| Heating input, maximum | 650 MBH | Per the I&O ratings table. |
| Output | ||
| Gross output | 631 MBH | Per the I&O ratings table. |
| Net AHRI water rating | 549 MBH | Net AHRI rating based on a piping and pickup allowance of 1.15, per the I&O rating notes. |
| Efficiency | ||
| Efficiency (thermal) | 97 % | 97% thermal efficiency per the product-page spec block; the KBX submittal prints 97.0%. |
| Venting and air | ||
| Air inlet size | 4" | Per the I&O ratings table. |
| Vent size | 6" | Per the I&O ratings table. |
| Venting | Category IV sealed combustion; room air/direct vent in PVC, CPVC, polypropylene, ABS or stainless steel | Direct-vent vertical or horizontal up to 150 equivalent feet per the KBX submittal; concentric vent kit KBX0400-KBX650 and common vent kit KBX0500-KBX1000 listed among the submittal venting options. |
| Physical and connections | ||
| Water content | 6.2 gal | Per the I&O ratings table. |
| Space-heating water connections | 2" | Per the I&O ratings table. |
| Gas connection | 1-1/4" | Per the I&O ratings table. |
| Shipping weight | 456 lb | Shipping weight per the KBX submittal. |
Manuals
Alerts documented for this model
- Gas Pressure SW
- Flow Switch/LWCO
- Blocked Drain SW/HEX O-Temp SW
- APS Open
- Anti-cycling
- Flame Fail Ign
- Flame Sequence
- Outlet ARHL
- Outlet MRHL
- Fan Low/High OR Fan Speed Low/High
- Sensor Open
- Sensor Shorted
- Louver Proving Sw
- Inlet Sensor Fault
- Outlet Sensor Fault
- Outlet Temp Diff
- Flue Sensor Fault
- Flue Temp Diff
- Flue Temp Limit
- Fatal Error
- Memory Error
- Flue Temp High
- Delta T High
- Outlet Temp High
- Rem Ctrl Flt
- Parameters Progr
- Service Blk
- Low 24 vac
- Watch Dog Error
- Write EEProm
- CRC Parameters
- No Error Stored
Frequently asked questions
What are the KBX0650's ratings?
65 to 650 MBH of input with 631 MBH gross output and a 549 MBH AHRI net water rating at 97% thermal efficiency, per the I&O ratings table.
What changes in the connections at the KBX0650?
The gas connection grows from 1" to 1-1/4" and the vent from 4" to 6"; the 2" water connection and 4" air intake are unchanged from the smaller sizes.
Questions about the Lochinvar Knight XL KBX0650?
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
Sources and verification
- Lochinvar — Knight XL Commercial Boiler (KBX0400N) model page · accessed September 9, 2026
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.