Lochinvar · Crest (FB / Hellcat FCB)
Lochinvar Crest FBN3501
The Crest FBN3501 fires 175 to 3500 MBH with 3364 MBH gross output and a 2925 MBH AHRI net rating at 20:1 turndown, with a 202-gallon water content on 4" pipe.
Key figures
- Max input
- 3,500 MBH
- Max CSA output
- —
- AFUE
- —
- Min input
- 175 MBH
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Lochinvar Crest FBN3501 in practice
The FBN3501 carries the Crest FB line to 3.5 million BTU/hr of input: the I&O ratings table lists 175 to 3500 MBH with 3364 MBH gross output and a 2925 MBH AHRI net water rating, at 20:1 turndown per the manual. Water content grows to 202 gallons and weight with water to 4,600 lb, while the 4" pipe outlet and inlet, 2" gas inlet and 10" air and vent sizes carry over from the 3001.
Venting is in stainless steel, polypropylene, PVC or CPVC to 100 equivalent feet per the page feature list, on the wave fire-tube platform with the 8" LCD touchscreen SMART TOUCH control and CON·X·US. The family page prints the 10-year heat exchanger warranty.
Best suited to
- Large plant rooms with design-day loads between 3.0 and 3.5 million BTU/hr
- Projects keeping 4" boiler piping at a 3.5 million BTU/hr ceiling
- Systems that want 20:1 turndown with the 175 MBH minimum fire
Applicability and support
- Model number
- FBN3501
- 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 | 175 MBH | Per the I&O ratings table. |
| Heating input, maximum | 3,500 MBH | Per the I&O ratings table. |
| Output | ||
| Gross output | 3,364 MBH | Per the I&O ratings table. |
| Net AHRI water rating | 2,925 MBH | Per the I&O ratings table. |
| Venting and air | ||
| Air size | 10" | Per the I&O ratings table. |
| Vent size | 10" | 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 | 202 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" | Per the I&O ratings table. |
| Weight with water | 4,600 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 FBN3501's ratings?
175 to 3500 MBH of input with 3364 MBH gross output and a 2925 MBH AHRI net water rating per the I&O ratings table, at 20:1 turndown.
What connections does the FBN3501 use?
4" pipe outlet and inlet, a 2" gas inlet and 10" air and vent sizes, with a 202-gallon water content and 4,600 lb weight with water per the ratings table.
Questions about the Lochinvar Crest FBN3501?
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
- Lochinvar Crest FBN0751Same series
- Lochinvar Crest FBN1001Same series
- Lochinvar Crest FBN1251Same series
- Lochinvar Crest FBN1501Same series
- Lochinvar Crest FBN1751Same series
- Lochinvar Crest FBN2001Same series
- Lochinvar Crest FBN2501Same series
- Lochinvar Crest FBN3001Same series
- Lochinvar Crest FBN4001Same series
- Lochinvar Crest FBN5001Same series
- Lochinvar Crest FBN6001Same series
- Lochinvar Crest FCB1000Same series
- Lochinvar Crest FCB1500Same series
- Lochinvar Crest FCB2000Same series
- Lochinvar Crest FCB2500Same series
- Lochinvar Crest FCB3000Same series
- Lochinvar Crest FCB4000Same series
- Lochinvar Crest FCB5000Same series
- Lochinvar Crest FCB6000Same series
- 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.