Replace Combi With Viessman System Boiler?

macman

Thanks, yes the cylinder would be internal, but against an external wall.
11.2 is the rated flow, I've never actually measured it to check!

Canucklehead

Hi

Being pedantic here.

Are you reading the data correctly?

The usual output figures are based on a 35 degree temperature rise.
Some quote l/m output at 30 degrees rise so the comparison is skewed.


GSR

macman

Well spotted. SIME quote both: 11.2l/min at 30 degree rise, and 9.6l/min at 35 degree rise.
So even the lowest rated Viessmann combi (25kW) gives me an improvement on that of 10.7l/min. I'd probably go for the 30kW giving 12.3l/min.

macman

Canucklehead wrote: »

Hi,

I would go with 180 litres. I got the impression the cylinder location was internal, but as it's not then that seems be a good place to fit it.

I thought a higher output combi would suit your needs as the most economical method of getting heat and hot water.

Do you get 11.2 from your 24kw combi? 9.8l/m is the best you'll get from most.


GSR

I decided to check the actual flow this mornng and (measured from the bathroom hot tap) I am getting about 7.5l/min against the rated 9.6l/min. Not brilliant.
But does any combi achieve it's rated flow under real conditions, or is it just a theoretical figure?

Canucklehead

Hi,


That's actual flow.


GSR.