Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The XTherm H7-4005 adds 500 MBTUH of input and 480 MBTUH of output over the XTherm H7-3505 on the same XTherm platform. The 4005 is the largest XTherm: 4,000 MBTUH input, a 12 in flue, 230 gpm maximum flow and 33.8 gal water content, but turndown returns to 7:1 from the 3505's 10:1.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Raypak XTherm H7-3505 | Raypak XTherm H7-4005 |
|---|---|---|
| Input | 3,500 MBH | 4,000 MBH |
| Output | 3,360 MBH | 3,840 MBH |
| AHRI thermal efficiency | 96 % | 96 % |
| Turndown | 10:1 | 7:1 |
| Flue outlet | 10 in | 12 in |
| Weight | 2,925 lb | 3,058 lb |
| Maximum water flow | 208 GPM | 230 GPM |
The H7-3505 is rated 3,500 MBTUH input and 3,360 MBTUH output with 10:1 turndown; the H7-4005 is rated 4,000 MBTUH input and 3,840 MBTUH output with 7:1 turndown. Both models carry the same published efficiency figure, so capacity is the variable rather than efficiency.
The 4005 is the largest XTherm: 4,000 MBTUH input, a 12 in flue, 230 gpm maximum flow and 33.8 gal water content, but turndown returns to 7:1 from the 3505's 10:1. Maximum water flow rises from 208 gpm to 230 gpm, which is the main plant-side difference between the two sizes. Shipping or operating weight moves from 2,925 lb to 3,058 lb, which matters for rigging and floor loading.
Both sizes are documented in the same official Raypak submittal for the XTherm family, so the decision is a heat-loss and plant-layout question rather than a documentation difference: size to the calculated design-day load, then check flow, connection and venting dimensions against the submittal for the exact model.
Raypak
The Raypak XTherm H7-3505 is a vertical modulating condensing commercial hydronic boiler rated 3,500 MBTUH input and 3,360 MBTUH output at 96% thermal efficiency, with 10:1 turndown, Category IV venting and a 10 in flue.
Raypak
The Raypak XTherm H7-4005 is a vertical modulating condensing commercial hydronic boiler rated 4,000 MBTUH input and 3,840 MBTUH output at 96% thermal efficiency, with 7:1 turndown, Category IV venting and a 12 in flue.
The H7-4005 at 4,000 MBTUH input and 3,840 MBTUH output, per submittal 241868 and the product page.
Both use a 10 in flue per the 241868 submittal, with combustion air stepping from 12 in on the 3505 to 12 in on the 4005 as well; both are Category IV.
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.