Adequate HW flow for shower?

[Rustychain]

Hi

I'm just deciding between two combi biolers and wanted some advice on HW flow. The lower power one can do 12.7 l/min and the higher power one can do 15.2 l/min.

I appreciate they can only acheive these rates if I've got enough mains flow (so I'll measure that tonight). On the basis that the mains can deliver adequate flow, would 12.7 give a reasonable shower (it would pass through a thermostatic mixer)?

Thanks

 

[ChrisR]

"Can do" is with a particular temperature rise. Check them.
the boilers will be flow-restricted to make sure you get water hot enough for a bath in winter.
28kW upwards is usually thought of as fine, though 24's are OK.
Electric showers are only 10kW or so, after all.

 

[bengasman]

Size of gaspipe is also a point. If your existing would be fine for the smaller one, but the larger model will need upgrade, your bit of extra water will come at a high price. If pipe makes no difference, go for the bigger one

 

[Rustychain]

For the figures I've quoted, the spec sheet for the boilers say - "triangle" T (which I assumes means change in temp) = 35 K rise.

The flow rate at the factory set temperature rise ("traingle" T = 42 K) for the lower power boiler drops down to 10.6 L per minute. I guess this is the realistic figure once it's installed?

As for mains water flow, I got 17+ L/min at the boiler position (in the garage). The plumber is putting in a new gas pipe from the meter, so I anticipate that means there will be enough gas flow for the higher rated boiler.