Viessmann · Vitodens 100-W (legacy B1HA / B1KA and earlier)
Viessmann Vitodens 100-W B1HA 35, 125
The Vitodens 100-W B1HA 35, 125 is the larger heating-only model of the B1HA generation: 21 to 125 MBH natural gas input at 95.0% AFUE in the 79.4 lb (36 kg) cabinet.
Key figures
- Max input
- 125 MBH
- Max CSA output
- —
- AFUE
- 95 %
- Min input
- 21 MBH
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Viessmann Vitodens 100-W B1HA 35, 125 in practice
The B1HA 35, 125 raises the B1HA range to 125 MBH: printed CSA input 21-125 MBH (6.2-36.6 kW) natural gas and 31-125 MBH (9.1-36.6 kW) propane, with 20-116 MBH (5.7-34.1 kW) output and a 101 MBH Net AHRI rating at 95.0% AFUE.
Weight, dimensions and water content match the B1HA 26, 94 — 79.4 lb (36 kg), 400 x 400 x 768 mm and 1.02 USG — as does the 45 psig maximum operating pressure. The boiler is heating-only, so domestic hot water comes from an indirect tank or from the combi model of the same generation, the B1KA 35, 125.
Best suited to
- Owners of existing B1HA 35/125 units looking up printed ratings
- Homes whose heat-loss calculation exceeds the B1HA 26, 94 ceiling
- Documentation for the larger heating-only B1HA size
Applicability and support
- Model number
- B1HA 35, 125
- 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, minimum (natural gas) | 21 MBH | 6.2 kW, per the technical data manual |
| CSA input, maximum (natural gas) | 125 MBH | 36.6 kW, per the technical data manual |
| CSA input (liquid propane) | 31-125 MBH | Printed LPG range from the same table. |
| Output | ||
| CSA output / DOE heating capacity (natural gas) | 20-116 MBH | 5.7-34.1 kW, based on 140°F / 120°F supply/return |
| Net AHRI rating | 101 MBH | Based on piping and pick-up allowance of 1.15. |
| Efficiency | ||
| Efficiency (AFUE) | 95 % | 95.0% AFUE on all B1HA/B1KA models per the technical data manual. |
| Physical and connections | ||
| Weight | 79.4 lb | 36 kg |
| Shipping weight | 88.2 lb | 40 kg |
| Overall width | 400 mm | 15¾ in |
| Overall depth | 400 mm | 15¾ in |
| Overall height | 768 mm | 30¼ in |
| Operating limits and other | ||
| Fuel | Natural gas or liquid propane | NG minimum supply pressure 4 in. w.c.; LPG 10 in. w.c. |
| Boiler water content | 1.02 USG | 3.88 L. |
| Maximum operating pressure | 45 psig | 3 bar at 210°F (99°C). |
| Boiler heating supply / return | ¾ in. NPTM | Pressure relief valve ¾ in. NPTF; flue gas connection 2⅜ in (60 mm). |
Manuals
- Technical Data Manual — Vitodens 100-W B1HA Series and B1KA Combi Boiler, doc 5784 566 - 125784 566 - 12 · 2025-04
- Installation and Service Instructions — Vitodens 100-W B1HA/B1KA, rev 2222 · 2025-08
- Technical Data Manual — Vitodens 100-W WB1A Series, doc 5347 963 v1.15347 963 v1.1 · 2007-10
- Technical Data Manual — Vitodens 100-W WB1B Series, doc 5369 277 v1.55369 277 v1.5 · 2010-01
Alerts documented for this model
None documented yet.
Frequently asked questions
What is the B1HA 35, 125 rated at?
21-125 MBH (6.2-36.6 kW) natural gas input, 31-125 MBH on propane, 20-116 MBH output, a 101 MBH Net AHRI rating and 95.0% AFUE.
How does the B1HA 35, 125 differ from the B1HA 26, 94?
Only the firing range: the 35, 125 tops out at 125 MBH against 94 MBH. Both weigh 79.4 lb with the same cabinet, water content and 95.0% AFUE.
Does the B1HA 35, 125 make domestic hot water?
No — it is a heating-only boiler. The B1KA 35, 125 combi of the same generation adds on-demand DHW through a plate heat exchanger.
Questions about the Viessmann Vitodens 100-W B1HA 35, 125?
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 Vitodens 100-W B1HA 26, 94 vs B1HA 35, 125Comparison
- Viessmann Vitodens 100-W B1HA 35, 125 vs B1KA 35, 125Comparison
- Viessmann Vitodens 100-W B1HA 26, 94Same series
- Viessmann Vitodens 100-W B1KA 35, 125Same series
- Viessmann Vitodens 100-W WB1A 8-24Same series
- Viessmann Vitodens 100-W WB1A 8-30Same series
- Viessmann Vitodens 100-W WB1B 26Same series
- Viessmann Vitodens 100-W WB1B 35Same series
- Vitodens 100-W (legacy B1HA / B1KA and earlier) series hub
- Buying guide
Sources and verification
- Technical Data Manual — Vitodens 100-W B1HA Series and B1KA Combi Boiler, doc 5784 566 - 12 · 5784 566 - 12 · 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.