Bosch Thermotechnology · Greenstar Wall (ZBR/ZWB)
Bosch Greenstar ZWB 35-3A
The Greenstar ZWB 35-3A is the mid-size wall-hung Greenstar combi — 36,000 to 131,900 BTU/hr natural-gas heating input with DHW output to 118,700 BTU/hr at a 140 °F outlet and 3.17 GPM maximum DHW flow — documented in the Greenstar Wall I&O manual because the Combi 100P/151P manual does not cover the 35-3A size.
Key figures
- Max input
- 131.9 MBH
- Max CSA output
- 122.8 MBH
- AFUE
- —
- Min input
- 36 MBH
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Bosch Greenstar ZWB 35-3A in practice
The ZWB 35-3A is the wall-hung combi of the 35 kW class: it heats space from 36,000 to 131,900 BTU/hr input and produces domestic hot water on demand through its built-in DHW plate heat exchanger and three-way valve. Bosch's Canada documentation situation is unusual for this size: the 'Greenstar Combi 100P and 151P' I&O manual covers only the ZWB 28-3A and ZWB 42-3A, so the 35-3A's technical data and fault tables live in the Greenstar Wall I&O manual (6721853955, 11.2025), which is the manual cited here.
On the DHW side the manual prints output of 120,500 BTU/hr at a 113 °F outlet and 118,700 BTU/hr at 140 °F, with a maximum DHW flow rate of 3.17 GPM and nominal flow of 2.6 GPM at a 140 °F outlet. The combi hardware adds the expansion vessel (3.17 gal total contents, 10.9 psi pre-charge) and raises the cabinet weight to 110.2 lb against 103.6 lb for the heat-only ZBR models.
The ZWB 35-3A is a combi: no separate tank is required for typical domestic hot water. It runs the same Heatronic control with two-character fault codes as the rest of the wall line, and its vent tables place it in the 35/42 class with the shorter runs documented in the manual.
Best suited to
- Homes needing the 35-class heating input with on-demand hot water in one wall appliance
- Households whose hot-water draws fall between the 100p (28-3A) and 151p (42-3A) combi ratings
- Wall-hung installations where a combi's 110.2 lb cabinet suits the mounting wall
Applicability and support
- Model number
- ZWB 35-3A
- Canadian availability
- available
- Production status
- current
- 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 Bosch Thermotechnology. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| Input rate, minimum | 36 MBH | 36,000 BTU/hr at 180/79 °F (82/26 °C), natural gas. |
| Input rate, maximum | 131.9 MBH | 131,900 BTU/hr at 180/79 °F (82/26 °C), natural gas; altitude tables in the manual reduce the maximum above 2,000 ft. |
| Output | ||
| Output rate, maximum (104/86 °F) | 122.8 MBH | 122,800 BTU/hr at 104/86 °F water temperatures per the manual technical table. |
| Domestic hot water | ||
| DHW output rate (113 °F (45 °C) outlet) | 120.5 MBH | 120,500 BTU/hr per the manual technical table. |
| DHW output rate (140 °F (60 °C) outlet) | 118.7 MBH | 118,700 BTU/hr per the manual technical table. |
| Maximum DHW flow rate | 3.17 gpm | Maximum domestic hot water flow rate per the manual technical table. |
| Nominal DHW flow rate (140 °F outlet) | 2.6 gpm | Nominal domestic hot water flow at a 140 °F (60 °C) outlet temperature. |
| Maximum approved DHW pressure | 150 psi | 150 psi (10.3 bar); minimum water pressure 4.35 psi (0.3 bar). |
| Venting and air | ||
| Venting | 2" NG only; 3" or 3"/5" (80/125 mm) concentric for LPG | Per the manual: the 35/42 model class is limited to 25 ft of straight 2" concentric pipe with 2 elbows (NG), or 44 ft of 3"/5" concentric pipe with 1 elbow. Termination type changes the tables. |
| Physical and connections | ||
| Weight (without packaging) | 110.2 lb | 110.2 lb (50 kg) without packaging per the manual. |
| Dimensions (W x H x D) | 17-21/64" × 33-15/32" × 13-57/64" (440 × 850 × 353 mm) | Per the manual technical data table. |
| Sound pressure level | ≤ 44 dB(A) | Per the manual technical data table. |
| Maximum supply temperature | 187 °F | 187 °F (86 °C). |
| Maximum permissible operating pressure (PMS), heating | 30 psi | 30 psi (2.07 bar). |
| Expansion vessel total contents | 3.17 gal | 3.17 gal (12 l); pre-charge pressure 10.9 psi (0.75 bar). |
| Permissible inlet gas pressure | NG 3.5–10.5 in. W.C.; LPG 8–13 in. W.C. | NG is the factory default; LPG only after successful gas conversion with the included conversion kit. |
| Operating limits and other | ||
| Fuel | Natural gas or propane | Separate NG and LPG ratings in the manual; LPG requires the gas conversion kit included with the appliance. |
Frequently asked questions
Why is the ZWB 35-3A documented under the Greenstar Wall series?
Because Bosch's Combi 100P/151P I&O manual covers only the ZWB 28-3A and ZWB 42-3A. The ZWB 35-3A's technical data and fault-code tables appear only in the Greenstar Wall I&O manual (6721853955), which Boilers.ca follows for this record.
How much hot water does the ZWB 35-3A produce?
The manual prints a 3.17 GPM maximum DHW flow rate and 2.6 GPM nominal flow at a 140 °F outlet, with DHW output of 118,700 BTU/hr at 140 °F outlet temperature.
What is the difference between the ZWB and ZBR codes?
ZBR codes are the heating-only wall models; ZWB codes are the wall-hung combis with built-in domestic hot water. Both share the -3A generation and the same 440 x 850 x 353 mm cabinet.
Questions about the Bosch Greenstar ZWB 35-3A?
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
- Bosch Home Comfort Canada — Greenstar Boilers · accessed September 7, 2026
- Greenstar Wall Boilers Installation and Service Manual (6721853955) · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.