Burnham ES2 ES23
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.
Key figures
- Max input
- 70 MBH
- Max CSA output
- —
- AFUE
- 85 %
- Min input
- —
Input is gas energy consumed; output is heat delivered. Never size from input alone.
Burnham ES2 ES23 in practice
The ES23 is the smallest ES2 ('Efficiency Series 2') boiler from U.S. Boiler Company: a fixed 70 MBH input (no modulation) for 59 MBH DOE heating capacity and a 51 MBH net AHRI water rating at 85% AFUE, per the ES2 ratings table (Doc 103780-11, 4/25). The heat exchanger is cast iron and the design is deliberately NON-condensing: a natural-draft boiler with a 4" draft hood, vented as Category I into an existing lined chimney — U.S. Boiler positions the ES2 as a replacement boiler for homes with existing chimneys.
The ES23 ships at 254 lb (180 lb empty) with 1-1/4" NPT supply/return and 1/2" NPT gas connections, runs on natural or LP gas with the IQ Boiler Control System (outdoor-reset and LWCO option cards available), and is rated 50 psi MAWP, shipped with a 30 psi relief valve. Boiler water temperatures run 130–220°F supply with a 110°F minimum return. Family dimensions across the 2–9-section build are 33–35" deep, 12-3/4"–30-3/4" wide and 41" high; the ES23 is the smallest-width member (12-3/4") of the family. A licensed contractor performs installation, gas and venting work.
Best suited to
- Smaller homes whose chimney-vented load fits a fixed 70 MBH input
- Boiler replacements that must reuse an existing lined chimney (Category I, draft hood)
- Owners who want cast-iron longevity with a simple non-modulating control platform
Applicability and support
- Model number
- ES23
- 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.
Specifications
Published specifications
Values as published by Burnham. Units are shown with every value; notes flag conflicting sources or missing figures.
| Specification | Value | Note |
|---|---|---|
| Input | ||
| Input | 70 MBH | Fixed input (no modulation) per the ES2 ratings table (Doc 103780-11); ratings apply to elevations up to 2,000 ft. |
| Output | ||
| DOE heating capacity | 59 MBH | Per the ES2 ratings table. |
| Net AHRI water rating | 51 MBH | Net AHRI water rating based on a piping and pickup allowance of 1.15, per the ES2 ratings table. |
| Efficiency | ||
| Efficiency (AFUE) | 85 % | 85% AFUE — a NON-condensing rating; the ES2 is a natural-draft cast-iron boiler, not a condensing design. |
| Domestic hot water | ||
| Domestic hot water | Heating-only boiler — domestic hot water comes from a separate indirect tank or water heater | |
| Venting and air | ||
| Venting | Category I natural draft — draft hood into an existing lined chimney (Type B/L gas vent); 4" draft hood | Non-condensing, natural-draft design: NOT a direct-vent or condensing boiler. Draft hood sizes per the ES2 I&O manual specifications. |
| Physical and connections | ||
| Shipping weight | 254 lb | Shipping weight 254 lb; empty (uncrated) boiler weight 180 lb, per the ES2 I&O manual weights and volume table. |
| Supply/return connections | 1-1/4" NPT | Supply and return both 1-1/4" NPT; relief valve 3/4" and drain 3/4" per the ES2 I&O manual. |
| Gas connection | 1/2" NPT | 1/2" NPT gas connection (ES23–ES26); ES27–ES29 use 3/4" NPT. |
| Electrical | ||
| Electrical | 120 VAC, 60 Hz, 1-phase, 15 A | Per the ES2 I&O manual specifications. |
| Operating limits and other | ||
| Maximum allowable working pressure (MAWP) | 50 psi | 50 psi MAWP; the boiler ships from the factory with a 30 psi safety relief valve. |
| Control | IQ Boiler Control System | IQ control with optional outdoor-reset and LWCO IQ option cards; the control flashes 'Err' + number for faults. |
Frequently asked questions
Is the ES23 a condensing boiler?
No. The ES2 is a non-condensing cast-iron boiler at 85% AFUE with a natural-draft draft hood and Category I venting into an existing chimney.
What are the ES23's ratings?
70 MBH fixed input, 59 MBH DOE heating capacity, a 51 MBH net AHRI water rating and 85% AFUE per the ES2 ratings table.
Does the ES23 modulate?
No — input is fixed. The ES2 line uses the IQ Boiler Control System but fires at a single rate.
Questions about the Burnham ES2 ES23?
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
- U.S. Boiler Company — ES2 High Efficiency Gas-Fired Water Boiler product page · accessed September 8, 2026
- U.S. Boiler Company — Technical Literature (Alpine/ES2 I&O manual listings) · accessed September 8, 2026
- ES2 Gas Boiler — Installation, Operating & Service Instructions, Doc 103780-11 (PDF) · 103780-11 · accessed September 8, 2026
Facts checked September 8, 2026. Last updated September 8, 2026. Technical reviewer: not yet assigned.