Skip to content
Boilers.caby ROMA Heating & Cooling

Weil-McLain · SVF (Stainless Vertical Firetube)

Weil-McLain SVF 850

The Weil-McLain SVF 850 is a current commercial stainless-steel vertical fire-tube condensing boiler: 850 MBH maximum input, 829 MBH gross output and a 721 MBH net AHRI rating at 97.5% thermal efficiency, with a 12:1 turn-down, 2-1/2" NPT supply/return, 1-1/4" NPT gas and a 6" vent connection.

CurrentCanadian status unknown
Service this modelEstimate a replacement

Key figures

Max input
850 MBH
Max CSA output
—
AFUE
—
Min input
—
Natural gasHeating-onlycommercial

Input is gas energy consumed; output is heat delivered. Never size from input alone.

Weil-McLain SVF 850 in practice

The SVF 850 is one of the current SVF (Stainless Vertical Firetube) commercial sizes documented on Weil-McLain's official product pages. Its Technical Specs row prints 850 MBH maximum input, 829 MBH gross output, a 721 MBH net AHRI rating and 97.5% thermal efficiency at a 160 psi maximum working pressure with a 12:1 turn-down ratio.

The unit connects on 2-1/2" NPT supply/return with a 1-1/4" NPT gas line and a 6" air-intake/exhaust vent, measures 42.2" long x 24.9" wide x 49.8" high and ships at about 675 lb with integrated roller casters and a shipping ramp; a 3-in-1 vent adapter is supplied for quick installation. Control is the Unity 2.0 color touchscreen Nuro platform with enhanced diagnostics, troubleshooting and remote monitoring, and the pages position the line as certified ENERGY STAR and heat-pump ready.

Boilers.ca records the printed spec row for the SVF 850 for commercial service planning. No official Canadian-sales statement was found on the US product pages reviewed, so canadianStatus stays 'unknown'; commercial gas, combustion and venting work belongs with a licensed contractor against the model's own SVF boiler manual.

Best suited to

  • 850-MBH-class commercial heating loads
  • Plants comparing vertical fire-tube footprints in the SVF range
  • Buildings planning cascade or hybrid boiler systems with the Unity control

Applicability and support

Model number
SVF 850
Canadian availability
unknown
Production status
current
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.

See all service areas

Specifications

Published specifications

Values as published by Weil-McLain. Units are shown with every value; notes flag conflicting sources or missing figures.

Weil-McLain SVF 850 specifications
SpecificationValueNote
Input
Maximum input850 MBHMaximum input per the Technical Specs table on the official SVF product page.
Output
Gross output829 MBHGross output per the Technical Specs table on the official product page.
Net AHRI rating721 MBHNet AHRI rating per the Technical Specs table on the official product page.
Efficiency
Thermal efficiency97.5 %Thermal efficiency per the Technical Specs table; the SVF is certified ENERGY STAR and heat-pump ready per the product pages.
Domestic hot water
Domestic hot waterHeating-only commercial boiler — domestic hot water comes from a separate indirect tank or water heater
Venting and air
Air intake / exhaust vent diameter6"Vent diameter per the Technical Specs table; Category II/IV venting per the product pages, with a 3-in-1 vent adapter supplied.
Physical and connections
Maximum working pressure160 psiMaximum working pressure per the Technical Specs table.
Supply / return water connections2-1/2" NPTSupply/return water connection size per the Technical Specs table.
Gas connection size1-1/4" NPTGas connection size per the Technical Specs table.
Length x width x height42.2" x 24.9" x 49.8"Dimensions per the Technical Specs table.
Approximate shipping weight675 lbApproximate shipping weight per the Technical Specs table; integrated roller casters and a shipping ramp are standard.
Operating limits and other
Turn-down ratio12:1Turn-down ratio per the Technical Specs table.
ControlUnity 2.0 color touchscreen Nuro controlsPer the product pages: enhanced diagnostics, troubleshooting and remote monitoring; Modbus supplement published.
FuelNatural gasThe SVF product pages list gas only.

Manuals

Alerts documented for this model

None documented yet.

Services

Related parts & service

Frequently asked questions

What are the SVF 850's ratings?

850 MBH maximum input, 829 MBH gross output, a 721 MBH net AHRI rating and 97.5% thermal efficiency per the official Technical Specs table.

What vent size does the SVF 850 use?

The Technical Specs table prints a 6" air intake / exhaust vent diameter; the SVF line uses Category II/IV venting with a supplied 3-in-1 vent adapter.

What control does the SVF 850 use?

The Unity 2.0 color touchscreen Nuro control with enhanced diagnostics, troubleshooting and remote monitoring, per the official product pages.

Questions about the Weil-McLain SVF 850?

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.

Call 778-909-5731Request service

Compare and explore

Sources and verification

Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.

CallEmailEstimate