HTP · Mod Con Double Stack Commercial Gas Boiler
HTP Mod Con 1700 Double 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.
Key figures
- Max input
- 1,700.005 MBH
- Max CSA output
- —
- AFUE
- —
- Min input
- 170 MBH
Input is gas energy consumed; output is heat delivered. Never size from input alone.
HTP Mod Con 1700 Double Stack in practice
The Mod Con 1700 Double Stack is documented on HTP's retired page as a modulating condensing commercial boiler operating at up to a 94% thermal efficiency rating with a 10 to 1 turndown. The printed page table lists the Mod Con 1700 at 170–1,700.005 Btu/hr and 94.1% thermal efficiency; the page describes two independent boilers working together as one unit and concentric venting with one exhaust connection and up to 150 ft of vent.
The lp-428-r1 installation manual (boilers manufactured after August 13, 2013) supplies the rating rows used here: 1600 MBH heating capacity, a 1160 lb shipping weight, 11.6 gal of boiler water content, a 109 GPM minimum flow rate at a 30 °F ΔT, 3" NPT supply/return, a 2-1/2" NPTF gas inlet, the 8" (150 ft) max combined, 16 ft minimum vent allowance and 120 V / 60 Hz / 6.3 A power. LP-426 prints two 316L stainless steel heat exchangers with ASME 75 PSI relief valves, gasketless design, built-in low-water cut-offs, blocked vent pressure switches and 926 digital controls with outdoor reset and cascade wiring for up to eight boilers.
The Mod Con Double Stack is retired: 'Mod Con Double Stack' is listed on HTP's official discontinued-products index. Boilers.ca records the model with productStatus 'discontinued' and canadianStatus 'unknown'; owners should have an installed unit serviced by a licensed contractor against lp-428-r1.
Best suited to
- Existing Mod Con 1700 Double Stack installations needing identification and service planning
- Plants comparing a two-boiler stack with built-in redundancy against separate commercial boilers
- Spaces where the stacked footprint and concentric venting suit the mechanical room
Applicability and support
- Model number
- Mod Con 1700
- Canadian availability
- unknown
- Production status
- discontinued
- 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 HTP. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| Input rate, minimum | 170 MBH | 170,000 Btu/hr, as printed on the official page table and lp-428-r1 Table 2. |
| Input rate, maximum | 1,700.005 MBH | 1,700,005 Btu/hr, as printed on the official page table and lp-428-r1 Table 2. |
| Output | ||
| Heating capacity | 1,600 MBH | As printed in lp-428-r1 Table 2. |
| Efficiency | ||
| Thermal efficiency | 94.1 % | The printed page table gives 94.1% for both models; LP-426 prints '94.1% thermal efficiency (All Models)'. |
| Venting and air | ||
| Vent size and maximum combined run | 8" (150 ft) max combined, 16 ft minimum | 16 ft minimum combined run as printed in lp-428-r1 Table 2. |
| Venting | Category IV sealed-combustion direct vent / power vent; concentric venting with one exhaust connection up to 150 ft | Page copy states the DS uses concentric venting with one exhaust connection and up to 150 ft of vent; LP-426 permits stainless steel or PVC/CPVC with the optional adapter. |
| Physical and connections | ||
| Shipping weight | 1,160 lb | As printed in lp-428-r1 Table 2. |
| Boiler water content | 11.6 gal | As printed in lp-428-r1 Table 2. |
| Supply / return connection | 3" NPT | As printed in lp-428-r1 Table 2. |
| Gas inlet | 2-1/2" NPTF | As printed in lp-428-r1 Table 2. |
| Dimensions (W x H x D) | 42" W x 72.5" H x 88.5" D | As printed in lp-428-r1 Table 2. |
| Heat exchangers | Two 316L stainless steel water-tube heat exchangers, 160 PSI ASME stamped, National Board listed, gasketless | LP-426 prints all-stainless construction with gasketless design and ASME 75 PSI relief valves (two kits where required). |
| Water pressure | Heat exchanger MAWP 160 psi; ASME 75 psi relief valves | As printed in LP-426 and lp-428-r1 Table 2. |
| Electrical | ||
| Power supply | 120 V / 60 Hz, 6.3 A | As printed in lp-428-r1 Table 2; ambient temperature range 33–104 °F. |
| Operating limits and other | ||
| Minimum flow rate at 30 °F ΔT | 109 GPM | As printed in lp-428-r1 Table 2. |
| Turndown | 10:1 | Page copy and LP-426 print a 10 to 1 turndown; each stack contains two independent modulating boilers working as one unit. |
| Control | 926 SIT digital controls with LCD and LED indicators | LP-426 prints one 926 control per boiler with outdoor reset with indirect priority, 0-10 VDC BMS input, dry alarm contacts (top boiler) and cascade up to 8 boilers. |
| Warranty | 10-year limited warranty, no registration required | Page copy and LP-426 print a 10-year limited warranty. |
Manuals
- HTP Mod Con Double Stack Installation Manual (boilers manufactured after August 13, 2013) — lp-428-r1 Rev. 008 Rel. 012 Date 7.21.20lp-428-r1 Rev. 008 (7.21.20) · 2020-07-21
- HTP Mod Con Commercial Condensing Heating Boiler Submittal (1,000,000 / 1,700,005 BTU Models) — lp-426 Rev. 7.30.20lp-426 (7.30.20)
- HTP Mod Con Double Stack Specification — lp-427lp-427
Alerts documented for this model
None documented yet.
Frequently asked questions
What is the input range of the Mod Con 1700 Double Stack?
The official page table and lp-428-r1 Table 2 print 170 to 1,700.005 Btu/hr with 1600 MBH heating capacity.
What does 'double stack' mean?
The page describes two independent boilers working together as one unit with built-in redundancy; the DS uses concentric venting with a single exhaust connection.
Is the Mod Con Double Stack still sold?
No — HTP's discontinued-products index lists 'Mod Con Double Stack'; the product page and manuals remain for support.
Questions about the HTP Mod Con 1700 Double Stack?
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.
Sources and verification
- HTP — The Mod Con Double Stack Commercial Gas Boiler (printed model table) · accessed September 9, 2026
- HTP — Mod Con Double Stack Documents · accessed September 9, 2026
- Mod Con Double Stack Installation Manual (boilers manufactured after August 13, 2013), lp-428-r1 · accessed September 9, 2026
- Mod Con Double Stack Submittal, lp-426 (7.30.20) · accessed September 9, 2026
- HTP — Discontinued Products index · accessed September 9, 2026
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.