Viessmann · Vitogas 100 (GS1 / GS10)
Viessmann Vitogas 100 GS1-29
The Vitogas 100 GS1-29 is the second GS1 size: 115 MBH input (34 kW), 98 MBH output and 85.5% AFUE with four burners and a 3.1 USG water content.
Key figures
- Max input
- —
- Max CSA output
- —
- AFUE
- 85.5 %
- Min input
- —
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Viessmann Vitogas 100 GS1-29 in practice
The GS1-29 steps the GS1 range to 115 MBH (34 kW) input, 98 MBH (29 kW) output and an 85 MBH (25 kW) Net I=B=R rating at 85.5% AFUE. It adds a third cast-iron section and a fourth burner over the GS1-22 while keeping the same 844 x 650 mm footprint.
Weight rises to 326 lb (148 kg) and boiler water content to 3.1 USG; maximum operating pressure stays 60 psig. The GS1 series is a fully assembled atmospheric boiler vented through a draft hood with a vent damper.
Best suited to
- Existing GS1-29 installations needing printed ratings
- Residential loads between the GS1-22 and GS1-35
- Comparing four-burner GS1 sizes
Applicability and support
- Model number
- GS1-29
- Canadian availability
- historical
- Production status
- discontinued
- ROMA supplies
- Confirmed at consultation
- ROMA services
- Confirmed at consultation
- Warranty
- Not verified
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 Viessmann. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| CSA input (natural gas) | 115 MBH | 34 kW, per the technical data manual |
| Output | ||
| CSA output / DOE heating capacity | 98 MBH | 29 kW |
| Net I=B=R rating | 85 MBH | 25 kW; based on piping and pick-up allowance of 1.15. |
| Efficiency | ||
| Efficiency (AFUE) | 85.5 % | With intermittent pilot electronic ignition and vent damper. |
| Venting and air | ||
| Vent pipe collar | Per model | 5 to 7 in. outside diameter per the technical data manual. |
| Physical and connections | ||
| Weight (boiler with insulation, burner and control) | 326 lb | 148 kg |
| Overall length | 844 mm | Printed as 33¼ in; heights 33¼ in (845 mm) with control in operating position. |
| Overall width | 650 mm | Printed as 25½ in |
| Overall height (operation) | 845 mm | 33¼ in; 955 mm with control in operation position, 1180 mm for servicing. |
| Operating limits and other | ||
| Fuel | Natural gas or propane | 5 in. w.c. minimum NG supply pressure; 11 in. w.c. for propane. |
| Cast iron sections | 3 | 4 burners. |
| Boiler water content | 3.1 USG | |
| Maximum operating pressure | 60 psig | |
| Boiler supply / return | 1½ in. male thread | Gas supply ½ in. NPT. |
Manuals
- Technical Data Manual — Vitogas 100 GS1 Series, doc 5167 462 v1.55167 462 v1.5 · 2011-02
- Installation Instructions — Vitogas 100 GS1, rev 1.31.3 · 2011-02
- Technical Data Manual — Vitogas 100 GS10 Series, doc 5167 466 v1.35167 466 v1.3 · 2011-02
- Service Instructions — Vitogas 100 GS10, rev 1.11.1 · 2007-11
Alerts documented for this model
None documented yet.
Frequently asked questions
What is the GS1-29 rated at?
115 MBH (34 kW) input, 98 MBH (29 kW) output, an 85 MBH (25 kW) Net I=B=R rating and 85.5% AFUE.
How does the GS1-29 differ from the GS1-22?
It adds a cast-iron section and a burner (3 sections / 4 burners vs 2 / 3), raising input from 90 to 115 MBH and weight from 273 to 326 lb, in the same footprint.
What fuel does the GS1-29 use?
Natural gas or propane; the technical data manual prints a 5 in. w.c. minimum natural-gas supply pressure and 11 in. w.c. for propane.
Questions about the Viessmann Vitogas 100 GS1-29?
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.
Compare and explore
- Viessmann Vitogas 100 GS1-22 vs GS1-29Comparison
- Viessmann Vitogas 100 GS1-22Same series
- Viessmann Vitogas 100 GS1-35Same series
- Viessmann Vitogas 100 GS1-42Same series
- Viessmann Vitogas 100 GS1-48Same series
- Viessmann Vitogas 100 GS1-60Same series
- Viessmann Vitogas 100 GS10-72Same series
- Viessmann Vitogas 100 GS10-84Same series
- Viessmann Vitogas 100 GS10-96Same series
- Vitogas 100 (GS1 / GS10) series hub
- Buying guide
Sources and verification
- Technical Data Manual — Vitogas 100 GS1 Series, doc 5167 462 v1.5 · 5167 462 v1.5 · accessed September 9, 2026
- Viessmann Canada — Historic manuals · accessed September 9, 2026
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.