Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The Crest FBN2001 and FBN2501 are the boundary between the two halves of the FB line: the 2001 closes the 25:1-turndown band at 1999 MBH, while the 2501 opens the 20:1 band at 2500 MBH with a 2" gas inlet, a 9" vent and a jump to 157 gallons of water.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Lochinvar Crest FBN2001 | Lochinvar Crest FBN2501 |
|---|---|---|
| Heating input, minimum | 80 MBH | 125 MBH |
| Heating input, maximum | 1,999 MBH | 2,500 MBH |
| Gross output | 1,923 MBH | 2,400 MBH |
| Net AHRI water rating | 1,699 MBH | 2,087 MBH |
| Water content | 111 gal | 157 gal |
| Pipe outlet connection | 4" | 4" |
| Pipe inlet connection | 4" | 4" |
| Gas connection | 1-1/2" | 2" |
| Air size | 8" | 8" |
| Vent size | 8" | 9" |
| Weight with water | 2,570 lb | 3,600 lb |
The 2001 is the largest Crest with 25:1 turndown and the 2501 is the smallest with 20:1 per the I&O — a real part-load difference, not just a capacity step: minimum fire rises from 80 to 125 MBH between them.
Maximum input rises from 1999 to 2500 MBH with gross output from 1923 to 2400 MBH and the AHRI net rating from 1699 to 2087 MBH. Water content jumps from 111 to 157 gallons and weight with water from 2,570 to 3,600 lb.
The connections step at the 2501: the gas inlet grows from 1-1/2" to 2" and the ratings table prints an 8" air size with a 9" vent (the I&O notes 2501 models using the 10" vent option need increase adapters). The 2001 keeps the 8"/8" air and vent of the 1501-2001 family.
Lochinvar
The Crest FBN2001 fires 80 to 1999 MBH with 1923 MBH gross output and a 1699 MBH AHRI net rating at 25:1 turndown, closing the 25:1 band of the FB line.
Lochinvar
The Crest FBN2501 fires 125 to 2500 MBH with 2400 MBH gross output and a 2087 MBH AHRI net rating at 20:1 turndown, stepping the gas inlet to 2" with a 9" vent.
The I&O assigns 25:1 to the 2001 and 20:1 to the 2501, which is why the 2001's minimum fire is 80 MBH and the 2501's is 125 MBH despite the 2501 having only 501 MBH more ceiling.
The ratings table prints 8" air with a 9" vent (against 8"/8" on the 2001), and the I&O adds that 2501 models using the 10" vent diameter option require the appropriate increase adapters.
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 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.