Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
The Royal CO-90 and CH-80 are size-equivalents at the bottom of the Royal range — the CO-90 fires 9-80 MBH and the CH-80 8-80 MBH, both at 74 MBH heating capacity and a 64 MBH net AHRI water rating — so the decision is whether the home wants the CO-90's built-in on-demand domestic hot water (90 MBH, 2.5 GPM) or keeps hot water on a separate tank with the heating-only CH-80.
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Dunkirk Royal CO-90 | Dunkirk Royal CH-80 |
|---|---|---|
| Central-heating input, minimum | 9 MBH | 8 MBH |
| Central-heating input, maximum | 80 MBH | 80 MBH |
| DHW input, minimum | 9 MBH | — |
| DHW input, maximum | 90 MBH | — |
| DHW flow rate at 70 °F rise | 2.5 gpm | — |
| AFUE | 95.2 % | 95.2 % |
| Heating capacity | 74 MBH | 74 MBH |
| Net AHRI water rating | 64 MBH | 64 MBH |
| Turndown | Up to 10:1 | Up to 10:1 |
| Dimensions (H x W x D) | 28.23" x 17.4" x 16.93" | 28.23" x 17.4" x 16.93" |
Both models are wall-hung residential Royals at 95.2% AFUE with up to 10:1 turndown in the shared 28.23 x 17.4 x 16.93 in cabinet. The brochure table prints CH input of 9-80 MBH on the CO-90 and 8-80 MBH on the CH-80, with identical heating capacity (74 MBH) and net AHRI water ratings (64 MBH) — the smallest of the 80,000-200,000 BTU/hr combi range and the 80,000-180,000 BTU/hr heating range.
The difference is domestic hot water. The CO-90's DHW side runs 9-90 MBH input at 2.5 GPM and a 70 °F rise and eliminates the separate water heater; the CH-80 produces no DHW, leaving hot water to a tank or water heater (Dunkirk pairs the heat-only models with its optional H2O indirect tanks).
The CO-90's 9 MBH minimum fire is 1 MBH above the CH-80's 8 MBH floor, so day-to-day condensing behaviour is effectively the same; the choice is about hot-water strategy, gas sizing (the combi's DHW draws need the gas line sized for 90 MBH) and what fails independently if one appliance needs service.
Dunkirk Boilers
The Royal CO-90 is Dunkirk's 90 MBH-class wall-hung residential combi: 9 to 80 MBH central-heating input with DHW input from 9 to 90 MBH (2.5 GPM at a 70 °F rise), 95.2% AFUE, 74 MBH heating capacity and up to 10:1 turndown.
Dunkirk Boilers
The Royal CH-80 is Dunkirk's 80 MBH-class wall-hung residential heating-only boiler: 8 to 80 MBH central-heating input at 95.2% AFUE with 74 MBH heating capacity, a 64 MBH net AHRI water rating and up to 10:1 turndown.
Effectively — the brochure table prints 74 MBH heating capacity and a 64 MBH net AHRI water rating for both, with CH input of 9-80 MBH (CO-90) and 8-80 MBH (CH-80).
On-demand domestic hot water: DHW input of 9-90 MBH at 2.5 GPM and a 70 °F rise, removing the separate water heater from the system.
When the household's hot-water pattern suits a tank or indirect water heater, when the gas line is sized for heating only, or when keeping heating and hot water on separate appliances is preferred.
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 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.