Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The Mod Con 1000 and 1700 Double Stack are the two stacked models: both print 94.1% thermal efficiency and a 10:1 turndown, with two independent boilers per unit. The 1700 lifts the ceiling from 1,000,000 to 1,700,005 Btu/hr and heating capacity from 940 to 1,600 MBH, moving from a 6 in to an 8 in vent, a 2 in to a 2-1/2 in NPTF gas inlet and 1,010 to 1,160 lb shipping.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | HTP Mod Con 1000 Double Stack | HTP Mod Con 1700 Double Stack |
|---|---|---|
| Input rate, minimum | 100 MBH | 170 MBH |
| Input rate, maximum | 1,000 MBH | 1,700.005 MBH |
| Heating capacity | 940 MBH | 1,600 MBH |
| Thermal efficiency | 94.1 % | 94.1 % |
| Turndown | 10:1 | 10:1 |
| Shipping weight | 1,010 lb | 1,160 lb |
| Boiler water content | 8.4 gal | 11.6 gal |
| Minimum flow rate at 30 °F ΔT | 66 GPM | 109 GPM |
| Vent size and maximum combined run | 6" (150 ft) max combined, 16 ft minimum | 8" (150 ft) max combined, 16 ft minimum |
| Supply / return connection | 3" NPT | 3" NPT |
| Gas inlet | 2" NPTF | 2-1/2" NPTF |
Both Double Stack models are floor-standing units that combine two independent 316L stainless steel water-tube boilers behind 926 controls, sharing the 42 in width, 72.5 in height, 16 ft minimum vent run, 3 in NPT supply/return, 160 PSI MAWP with 75 PSI relief valves and the 10-year limited warranty. The 1000 fires 100,000–1,000,000 Btu/hr to 940 MBH; the 1700 fires 170,000–1,700,005 Btu/hr to 1,600 MBH.
The packaging grows with capacity: depth from 66.75 to 88.5 in, shipping weight from 1,010 to 1,160 lb, water content from 8.4 to 11.6 gal, minimum flow at a 30 °F ΔT from 66 to 109 GPM, and the vent adapter from 6 in to 8 in (both 150 ft maximum combined).
Both print the same 94.1% thermal efficiency and 10:1 turndown, so the choice between them is a capacity decision — the 1700's higher 170,000 Btu/hr minimum fire versus the 1000's 100,000 Btu/hr low end. Both are retired and documented for service planning.
The HTP Mod Con 1000 Double Stack is the 1000 MBH class model of HTP's discontinued stacked commercial condensing boiler: 100 to 1,000 Btu/hr input, 940 MBH heating capacity, 94.1% thermal efficiency and two independent boilers working as one unit in a 1010 lb stack.
The HTP Mod Con 1700 Double Stack is the 1700 MBH class model of HTP's discontinued stacked commercial condensing boiler: 170 to 1,700.005 Btu/hr input, 1600 MBH heating capacity, 94.1% thermal efficiency and two independent boilers working as one unit in a 1160 lb stack.
Both the Mod Con 1000 and 1700 Double Stack print 94.1% thermal efficiency in the official table and LP-426.
660 MBH: 1,600 MBH heating capacity against the 1000's 940 MBH, with input up to 1,700,005 Btu/hr.
The 1700 uses an 8 in vent adapter and a 2-1/2 in NPTF gas inlet; the 1000 uses 6 in and 2 in NPTF. Both allow 150 ft maximum combined vent.
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.