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De Dietrich · Series
The De Dietrich GT Series is a flexible eutectic (graphite-flake) cast-iron sectional boiler line — non-condensing, in NA since 1997 and assembled/warehoused in Cambridge, Ontario — spanning the GT120A (94–166 MBH input) up to the GT 530A/AE Plus.
Series facts
The GT Series is De Dietrich's NA non-condensing line: 'flexible eutectic cast iron' sectional boilers introduced to the North American market in 1997 through distribution, with DDR Americas assembling and warehousing units in Cambridge, Ontario. The official pages print the GT120A with an input range of 94 to 166 MBH and the GT 530A/AE with an input range of 3,749 to 8,190 MBH, with GT 220A, 330A and 430A sizes between them.
The GT120A page describes a eutectic cast-iron 3-pass boiler with efficiency up to 88%, low-temperature operation down to 85°F return with indoor/outdoor reset, and 'Residential Gas or Oil' labelling; the GT530A/AE page describes a 4-pass boiler with efficiency up to 87.8%, low-temperature operation to 105°F and 'Commercial Gas/Oil/Dual fuel' labelling — De Dietrich's eutectic cast iron is said to be 30% more flexible than competitive cast iron, allowing safe low-temperature operation.
Because GT efficiency figures differ by page (88% on GT120A, 87.8% on GT530A/AE), the series hub leaves the structured efficiency field empty and prints each page's figure in the text. Public I&O, submittal and brochure PDFs exist per product page; the GT-120A set is linked from this hub.
Highlights
Models
One canonical page per model with input, output and efficiency kept separate.
De Dietrich
The De Dietrich GT 123A is a 3-section eutectic cast-iron 3-pass boiler rated 94 MBH gas input / 80 MBH output (0.65 GPH on oil) at a printed AFUE of 85.5% gas / 88% oil, with 1-1/4" supply and return connections.
De Dietrich
The De Dietrich GT 124A is a 4-section eutectic cast-iron 3-pass boiler rated 115 MBH gas input / 98 MBH output (0.8 GPH on oil) at a printed AFUE of 85.5% gas / 88% oil, with 1-1/4" supply and return connections.
De Dietrich
The De Dietrich GT 125A is a 5-section eutectic cast-iron 3-pass boiler rated 144 MBH gas input / 122 MBH output (1 GPH on oil) at a printed AFUE of 85.5% gas / 88% oil, with 1-1/4" supply and return connections.
De Dietrich
The De Dietrich GT 126A is a 6-section eutectic cast-iron 3-pass boiler rated 166 MBH gas input / 141 MBH output (1.15 GPH on oil) at a printed AFUE of 85.5% gas / 88% oil, with 1-1/4" supply and return connections.
De Dietrich
The De Dietrich GT 224A is a 4-section eutectic cast-iron 3-pass commercial boiler rated 173 MBH gas input / 147 MBH output (1.2 GPH on oil) at a printed 85.2% gas efficiency (oil +3 points), with R1 1/4 supply and return connections.
De Dietrich
The De Dietrich GT 225A is a 5-section eutectic cast-iron 3-pass commercial boiler rated 224 MBH gas input / 190 MBH output (1.55 GPH on oil) at a printed 85.2% gas efficiency (oil +3 points), with R1 1/4 supply and return connections.
De Dietrich
The De Dietrich GT 226A is a 6-section eutectic cast-iron 3-pass commercial boiler rated 274 MBH gas input / 233 MBH output (1.9 GPH on oil) at a printed 85.2% gas efficiency (oil +3 points), with R1 1/2 supply and return connections.
De Dietrich
The De Dietrich GT 227A is a 7-section eutectic cast-iron 3-pass commercial boiler rated 324 MBH gas input / 276 MBH output (2.25 GPH on oil) at a printed 85.2% gas efficiency (oil +3 points), with R1 1/2 supply and return connections.
De Dietrich
The De Dietrich GT 228A is a 8-section eutectic cast-iron 3-pass commercial boiler rated 361 MBH gas input / 307 MBH output (2.5 GPH on oil) at a printed 85.2% gas efficiency (oil +3 points), with R1 1/2 supply and return connections.
De Dietrich
The De Dietrich GT 334A is a 4-section eutectic cast-iron 3-pass commercial boiler rated 404 MBH gas input / 344 MBH output (2.8 GPH on oil) at a printed 85.2% gas efficiency (oil +3 points), with 2-1/2" threaded female supply and return.
De Dietrich
The De Dietrich GT 335A is a 5-section eutectic cast-iron 3-pass commercial boiler rated 598 MBH gas input / 510 MBH output (4.15 GPH on oil) at a printed 85.2% gas efficiency (oil +3 points), with 2-1/2" threaded female supply and return.
De Dietrich
The De Dietrich GT 336A is a 6-section eutectic cast-iron 3-pass commercial boiler rated 808 MBH gas input / 688 MBH output (5.6 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.
De Dietrich
The De Dietrich GT 337A is a 7-section eutectic cast-iron 3-pass commercial boiler rated 1024 MBH gas input / 872 MBH output (7.1 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.
De Dietrich
The De Dietrich GT 338A is a 8-section eutectic cast-iron 3-pass commercial boiler rated 1226 MBH gas input / 1044 MBH output (8.5 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.
De Dietrich
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.
| Specification | De Dietrich GT 123A | De Dietrich GT 124A | De Dietrich GT 125A | De Dietrich GT 126A | De Dietrich GT 224A | De Dietrich GT 225A | De Dietrich GT 226A | De Dietrich GT 227A | De Dietrich GT 228A | De Dietrich GT 334A | De Dietrich GT 335A | De Dietrich GT 336A | De Dietrich GT 337A | De Dietrich GT 338A | De Dietrich GT 339A |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| input-min | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| CSA gas input | 94 MBH | 115 MBH | 144 MBH | 166 MBH | 173 MBH | 224 MBH | 274 MBH | 324 MBH | 361 MBH | 404 MBH | 598 MBH | 808 MBH | 1,024 MBH | 1,226 MBH | 1,442 MBH |
| CSA output (gas-oil) | 80 MBH | 98 MBH | 122 MBH | 141 MBH | 147 MBH | 190 MBH | 233 MBH | 276 MBH | 307 MBH | 344 MBH | 510 MBH | 688 MBH | 872 MBH | 1,044 MBH | 1,229 MBH |
| AFUE (as printed) | Gas 85.5% / Oil 88% | Gas 85.5% / Oil 88% | Gas 85.5% / Oil 88% | Gas 85.5% / Oil 88% | — | — | — | — | — | — | — | — | — | — | — |
| turndown | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| vent-max-3 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| vent-max-2 | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Weight (dry) | 302 lb | 357 lb | 412 lb | 470 lb | 481 lb | 567 lb | 655 lb | 741 lb | 827 lb | 1,349 lb | 1,623 lb | 1,865 lb | 2,163 lb | 2,432 lb | 2,712 lb |
Read the full comparison: De Dietrich GT 123A vs GT 125A →
Read the full comparison: De Dietrich GT 124A vs GT 126A →
Read the full comparison: De Dietrich GT 224A vs GT 228A →
Read the full comparison: De Dietrich GT 226A vs GT 227A →
Error codes and alerts
No alerts documented for this series yet.
Manuals
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.
Services for De Dietrich boilers
No. The GT Series is a non-condensing eutectic cast-iron sectional line; De Dietrich's condensing NA line is the MCA Pro.
The GT120A prints an input range of 94 to 166 MBH and the GT 530A/AE prints 3,749 to 8,190 MBH, with GT 220A / 330A / 430A sizes between them on the NA site.
DDR Americas Inc. states it warehouses and assembles De Dietrich boilers at its Cambridge, Ontario facility to serve the USA and Canada markets.
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
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.