Canada-wide gas boiler information · On-site service in Greater Vancouver, BC
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Comparison
Verdict in brief
Viessmann Vitocrossal 300 CA3B 4.0 and Viessmann Vitocrossal 300 CA3B 5.0 are two condensing boilers from the Viessmann Vitocrossal 300 (CA3B) line. The Viessmann Vitocrossal 300 CA3B 4.0 is documented at 400–4,000 MBH input and 96.1% thermal efficiency, while the Viessmann Vitocrossal 300 CA3B 5.0 is documented at 300–5,000 MBH input and 96.1% thermal efficiency. Viessmann Vitocrossal 300 CA3B 5.0 lists 1,000 MBH more input than Viessmann Vitocrossal 300 CA3B 4.0 (5,000 MBH against 4,000 MBH). Both list the same published thermal efficiency of 96.1%. Viessmann Vitocrossal 300 CA3B 5.0 lists 1,455 lb more shipping weight than Viessmann Vitocrossal 300 CA3B 4.0 (6,261 lb against 4,806 lb).
Published manufacturer figures. Input and output are kept separate; blanks mean the manufacturer did not publish that value.
| Specification | Viessmann Vitocrossal 300 CA3B 4.0 | Viessmann Vitocrossal 300 CA3B 5.0 |
|---|---|---|
| Minimum input (natural gas) | 400 MBH | 300 MBH |
| Maximum input (natural gas) | 4,000 MBH | 5,000 MBH |
| Thermal efficiency | 96.1 % | 96.1 % |
| Weight, single fuel | 4,806 lb | 6,261 lb |
| Maximum operating pressure | 160 psig | 160 psig |
Published ratings: the Viessmann Vitocrossal 300 CA3B 4.0 is rated 400–4,000 MBH input and 96.1% thermal efficiency; the Viessmann Vitocrossal 300 CA3B 5.0 is rated 300–5,000 MBH input and 96.1% thermal efficiency. Viessmann Vitocrossal 300 CA3B 5.0 lists 1,000 MBH more input than Viessmann Vitocrossal 300 CA3B 4.0 (5,000 MBH against 4,000 MBH). Both list the same published thermal efficiency of 96.1%.
Viessmann Vitocrossal 300 CA3B 5.0 lists 1,455 lb more shipping weight than Viessmann Vitocrossal 300 CA3B 4.0 (6,261 lb against 4,806 lb).
Both records print the same thermal efficiency (96.1%) and maximum operating pressure (160 psig), per the cited sources.
Viessmann
The Vitocrossal 300 CA3B 4.0 is the 4000 MBH size of the CA3B range: 400,000 to 4,000,000 BTU (117 to 1172 kW) of natural-gas input at 96.1% thermal efficiency, rated for 160 psi, weighing 4806 lb (2180 kg).
Viessmann
The Vitocrossal 300 CA3B 5.0 is the 5000 MBH size of the CA3B range: 300,000 to 5,000,000 BTU (88 to 1465 kW) of natural-gas input at 96.1% thermal efficiency, rated for 160 psi, in a 6261 lb (2840 kg) unit.
The Viessmann Vitocrossal 300 CA3B 5.0 lists 5,000 MBH, against 4,000 MBH on the Viessmann Vitocrossal 300 CA3B 4.0, per the cited documentation.
Both list the same thermal efficiency of 96.1%.
It ships at 6,261 lb against 4,806 lb for the Viessmann Vitocrossal 300 CA3B 4.0, per the cited sources.
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.