Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The NFB700-800C and NFB700-1000C are the two large-frame NFB700-C commercial boilers and are physically identical: 750 lb dry (1,059 lb with water), 37 gallons, 2 1/2" NPT water connections, 6" venting and a 66 MBH minimum fire at 97.5% thermal efficiency. The 1000C fires to 999 MBH against 799, with capacity rising from 779 to 974 MBH; note its product page prints a 974 MBH net AHRI rating equal to its capacity, which reads like a page error against the 800C's 677 MBH.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Navien NFB700-800C | Navien NFB700-1000C |
|---|---|---|
| Input, minimum | 66 MBH | 66 MBH |
| Input, maximum | 799 MBH | 999 MBH |
| Heating capacity | 779 MBH | 974 MBH |
| Net AHRI water rating | 677 MBH | 974 MBH |
| Thermal efficiency | 97.5 % | 97.5 % |
| Weight | 750 lb | 750 lb |
| Water content | 37 gal | 37 gal |
| Heating water connections | 2 1/2" NPT | 2 1/2" NPT |
| Gas connection | 1 1/4" NPT | 1 1/4" NPT |
| Venting | 6" PVC, CPVC, approved polypropylene or approved stainless steel, or 6" special gas vent Type BH (Class III A/B/C) | 6" PVC, CPVC, approved polypropylene or approved stainless steel, or 6" special gas vent Type BH (Class III A/B/C) |
The 800C and 1000C share the large NFB700-C frame outright: 750 lb dry and 1,059 lb with water at 23.8 x 73.3 x 33.0 in, holding 37 gallons of water with 2 1/2" NPT water and 1 1/4" NPT gas connections and 6" forced-draft direct venting. Both fire down to the same 66 MBH minimum and print 97.5% thermal efficiency with a 12–160 PSI water pressure range.
The 1000C adds 200 MBH at the top: 999 MBH of input against 799 MBH, with the heating capacity stepping from 779 to 974 MBH. Because the minimum fire is identical, the extra ceiling costs nothing in low-fire behaviour — the 1000C is the same boiler with a higher firing limit.
One caution on the ratings table: the 1000C product page prints its "Net AHRI Rating, Water" at 974 MBH, identical to its capacity. Net ratings sit below capacity on the other three NFB700-C models (about 14% lower), so the printed figure reads like a page error; Boilers.ca records it as printed and recommends re-verification with Navien before comparing the two models on a net-rating basis.
Navien
The Navien NFB700-800C is the third size of the floor-standing NFB700-C commercial boiler series: 66 to 799 MBH of input with a 779 MBH heating capacity and a 677 MBH net AHRI water rating at 97.5% thermal efficiency, in the larger 750 lb cabinet.
Navien
The Navien NFB700-1000C is the top model of the floor-standing NFB700-C commercial boiler series: 66 to 999 MBH of input with a 974 MBH heating capacity at 97.5% thermal efficiency, in the same 750 lb cabinet as the 800C.
Yes. Both weigh 750 lb dry (1,059 lb with water), measure 23.8 x 73.3 x 33.0 in and hold 37 gallons, with 2 1/2" NPT water connections and 6" venting; only the firing ceiling and capacity differ.
The 800C page prints 677 MBH. The 1000C page prints 974 MBH — the same figure as its capacity — which looks like a page error, so the 1000C's net figure should be re-verified with Navien before use.
When the heat-loss or plant calculation approaches or exceeds the 800C's 799 MBH ceiling. Below that load the two boilers behave identically at the same 66 MBH minimum fire.
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.