Lochinvar · Crest (FB / Hellcat FCB)
Lochinvar Crest FBN4001
The Crest FBN4001 fires 333.3 to 3999 MBH with 3843 MBH gross output and a 3342 MBH AHRI net rating at 12:1 turndown, stepping air and vent to 12" with a 2-1/2" gas inlet.
Key figures
- Max input
- 3,999 MBH
- Max CSA output
- —
- AFUE
- —
- Min input
- 333.3 MBH
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Lochinvar Crest FBN4001 in practice
The FBN4001 is the first Crest FB size whose turndown tightens to 12:1 per the I&O: the ratings table lists 333.3 to 3999 MBH input with 3843 MBH gross output and a 3342 MBH AHRI net water rating. Water content is 201 gallons on the 4" pipe outlet and inlet, with the gas inlet stepping to 2-1/2" and air and vent both growing to 12".
The wave fire-tube boiler carries the SMART TOUCH control with CON·X·US and vents in stainless steel, polypropylene, PVC or CPVC to 100 equivalent feet per the page feature list. Weight with water reaches 5,200 lb per the ratings table — the first size past the 2-tonne mark — and the family page prints the 10-year heat exchanger warranty.
Best suited to
- Central plants whose load approaches 4.0 million BTU/hr
- Projects planned around 12" air and vent openings
- Designs that accept the 333.3 MBH minimum fire at 12:1 turndown
Applicability and support
- Model number
- FBN4001
- 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 | 333.3 MBH | Per the I&O ratings table. |
| Heating input, maximum | 3,999 MBH | Per the I&O ratings table. |
| Output | ||
| Gross output | 3,843 MBH | Per the I&O ratings table. |
| Net AHRI water rating | 3,342 MBH | Per the I&O ratings table. |
| Venting and air | ||
| Air size | 12" | Per the I&O ratings table. |
| Vent size | 12" | Per the I&O ratings table. |
| Venting | Category IV sealed combustion; stainless steel, polypropylene, PVC or CPVC venting | Up to 100 equivalent feet per the Crest product-page feature list. |
| Physical and connections | ||
| Water content | 201 gal | Per the I&O ratings table. |
| Pipe outlet connection | 4" | Per the I&O ratings table. |
| Pipe inlet connection | 4" | Per the I&O ratings table. |
| Gas connection | 2-1/2" | Per the I&O ratings table. |
| Weight with water | 5,200 lb | Per the I&O ratings table. |
Manuals
Alerts documented for this model
- Gas Pressure SW Open
- Low Water Cutoff Open
- Blocked Drain SW Open
- APS Open
- Anti-cycling
- Flame Failure
- Flame Fail Running
- Gas Valve / Relay Failure
- Auto Reset High Limit
- Manual Reset High Limit Open
- Fan Speed Low
- Fan Speed High
- Louver Proving Sw Open
- Flue Temp High
- Delta T High
- Outlet Temp High
- Parameter Programming Complete
- Sensor Open
- Sensor Shorted
- Flue Sensor Open
- Flue Sensor Shorted
- Too Many Resets - Try Later
- Internal Fault
- Flue Temp Shutdown
- Delta T Shutdown
- Outlet Temp Shutdown
- Writing/Programming EEProm Error
- CRC Parameter Error
- Wrong Error Code
- Flame Sense Out of Sequence 1
- Flame Sense Out of Sequence 2
- Flue Damper Switch Open
- IO Expander Out Error
- Failure ADC Controller
- Outlet Sensor Differential
- Flue Sensor Differential
Frequently asked questions
What are the FBN4001's ratings?
333.3 to 3999 MBH of input with 3843 MBH gross output and a 3342 MBH AHRI net water rating per the I&O ratings table, at 12:1 turndown.
How does turndown change at the FBN4001?
The I&O assigns 12:1 turndown to the 4001 (against 20:1 on the 2501-3501), which matches the 333.3 MBH minimum input against the 3999 MBH maximum.
Questions about the Lochinvar Crest FBN4001?
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
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- Crest (FB / Hellcat FCB) series hub
- Buying guide
Sources and verification
- Lochinvar — Crest Condensing Boiler (FBN1001) model page · accessed September 9, 2026
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.