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De Dietrich · GT Series

De Dietrich GT 339A

The De Dietrich GT 339A is a 9-section eutectic cast-iron 3-pass commercial boiler rated 1442 MBH gas input / 1229 MBH output (10 GPH on oil) at a printed 85.2% gas efficiency (oil +3 points), with 2-1/2" welded pipe with distributor tube supply and return.

CurrentSold in Canada
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Key figures

Max input
1,442 MBH
Max CSA output
1,229 MBH
AFUE
—
Min input
—
Natural gasPropaneDHW: unknowncommercial

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

De Dietrich GT 339A in practice

The GT 339A is the 9-section size of the GT 330A series, the mid-size commercial line of De Dietrich's eutectic cast-iron family. The GT 330A brochure prints 1442 MBH CSA gas input, 1229 MBH CSA output, a 10 GPH No. 2 oil input and a dry weight of 2712 lb, with a 8" vent connection and ASME IV Class 30 rating at 90 psi water.

Supply and return are 2-1/2" welded pipe with distributor tube and the operating range is 86–185 °F with a 248 °F maximum water temperature. The brochure's efficiency note states '85.2% efficiency is the published efficiency (oil is +3%)'. Submittals for every size from GT-334A to GT-339A are published on DDR Americas letterhead from Cambridge, Ontario.

Best suited to

  • Commercial plants whose calculated load fits 1229 MBH output
  • Low-temperature hydronic systems that use the eutectic iron's thermal-shock resistance
  • Buildings replacing a large sectional cast-iron boiler on a like-for-like footprint

Applicability and support

Model number
GT 339A
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.

See all service areas

Specifications

Published specifications

Values as published by De Dietrich. Units are shown with every value; notes flag conflicting sources or missing figures.

De Dietrich GT 339A specifications
SpecificationValueNote
Input
CSA gas input1,442 MBHPrinted in the GT 330A brochure technical specifications.
CSA No. 2 fuel oil input10 GPHPrinted in the GT 330A brochure technical specifications.
Output
CSA output (gas-oil)1,229 MBHPrinted in the GT 330A brochure; outputs are rounded in the source.
Efficiency
Published efficiency (as printed)85.2% gas (oil +3 points)Brochure note: '85.2% efficiency is the published efficiency (oil is +3%)'. No per-model AFUE column is printed for this line.
Venting and air
Boiler vent connection8 inPrinted in the GT 330A brochure; gas-vent categories I, II, III or IV.
Physical and connections
Cast-iron sections9Printed in the GT 330A brochure dimensions table.
Heating supply / return2-1/2" welded pipe with distributor tube supply and returnPrinted in the GT 330A brochure dimensions notes (items 2 and 3).
Weight (dry)2,712 lbPrinted in the GT 330A brochure.
MAWP (water)ASME IV Rating Class 30 (90 psi)Printed in the GT 330A brochure.
Operating limits and other
Operating temperature range86–185 °FPrinted in the GT 330A brochure; max water temp 248 °F.
FuelNatural gas or propane; No. 2 oil firing documentedThe GT 330A brochure describes 'propane firing'; No. 2 oil input is printed per model, and the GT-series pages list gas/oil/dual-fuel options.

Manuals

Alerts documented for this model

None documented yet.

Services

Related parts & service

Frequently asked questions

What is the output of the GT 339A?

The GT 330A brochure prints 1442 MBH CSA gas input and 1229 MBH CSA output for this size, with a 10 GPH No. 2 oil input.

What efficiency does the GT 339A have?

The brochure prints 85.2% published efficiency on gas with oil +3 points. No per-model AFUE column is printed for the GT 330A line.

What water connections does the GT 339A use?

This size uses 2-1/2" welded pipe with distributor tube supply and return connections per the GT 330A brochure dimensions notes.

Questions about the De Dietrich GT 339A?

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

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Sources and verification

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

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