Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The ES23 and ES24 are the two smallest ES2 boilers — non-condensing cast iron at 85% AFUE with fixed inputs, 1-1/4" NPT water connections and 1/2" NPT gas. The ES24 fires 105 MBH against the ES23's 70 MBH, printing 89 MBH DOE capacity (59 on the ES23) and a 77 MBH net AHRI rating (51), with the draft hood growing from 4" to 5" and shipping weight from 254 to 304 lb.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Burnham ES2 ES23 | Burnham ES2 ES24 |
|---|---|---|
| Input | 70 MBH | 105 MBH |
| DOE heating capacity | 59 MBH | 89 MBH |
| Net AHRI water rating | 51 MBH | 77 MBH |
| Efficiency (AFUE) | 85 % | 85 % |
| Venting | Category I natural draft — draft hood into an existing lined chimney (Type B/L gas vent); 4" draft hood | Category I natural draft — draft hood into an existing lined chimney (Type B/L gas vent); 5" draft hood |
| Shipping weight | 254 lb | 304 lb |
| Gas connection | 1/2" NPT | 1/2" NPT |
| Supply/return connections | 1-1/4" NPT | 1-1/4" NPT |
| Maximum allowable working pressure (MAWP) | 50 psi | 50 psi |
| Electrical | 120 VAC, 60 Hz, 1-phase, 15 A | 120 VAC, 60 Hz, 1-phase, 15 A |
Both ES2 sizes are fixed-input (non-modulating) cast-iron boilers at 85% AFUE, vented as Category I natural draft through a draft hood into an existing lined chimney — the chimney-replacement design U.S. Boiler markets the ES2 as.
The ES24 adds 35 MBH of fixed input (105 vs 70 MBH), taking DOE heating capacity from 59 to 89 MBH and the net AHRI water rating from 51 to 77 MBH; its 5" draft hood replaces the ES23's 4".
Connections and controls are shared — 1-1/4" NPT supply/return, 1/2" NPT gas, IQ control, 50 psi MAWP with a 30 psi shipped relief — and weight grows from 254 to 304 lb shipping (180 to 231 lb empty). Neither size makes domestic hot water.
Burnham
The Burnham ES2 ES23 is the entry size of the ES2 cast-iron line: a fixed 70 MBH input for 59 MBH DOE heating capacity and a 51 MBH net AHRI rating at 85% AFUE — a non-condensing, Category I draft-hood boiler designed to replace a boiler in an existing chimney.
Burnham
The Burnham ES2 ES24 steps the cast-iron ES2 line to a fixed 105 MBH input: 89 MBH DOE heating capacity and a 77 MBH net AHRI rating at 85% AFUE, with a 5" draft hood for Category I chimney venting.
No — both are non-condensing cast-iron boilers at 85% AFUE with Category I draft-hood venting into an existing chimney.
The ES24 fires 105 MBH fixed input against the ES23's 70 MBH, for 89 vs 59 MBH DOE heating capacity and 77 vs 51 MBH net AHRI water rating.
Yes — 1-1/4" NPT supply/return, 1/2" NPT gas, and a 30 psi relief valve on the 50 psi MAWP boiler; only the draft hood (4" vs 5") and weight differ physically.
A consultation includes a heat-loss review so the size is right the first time.
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 8, 2026. Last updated September 8, 2026. Technical reviewer: not yet assigned.