Unvented versus 440 Worcester Bosch Combi

[manx12]

The client would like to get better hot water distribution…
He is having a large extension done to the house, an extra 4 rads on the original 8 rad circuits. And a second bathroom (shower running off the boiler)
He has a new 37cdi Worcester bosch combi .. already installed.. but as usual when he is using the shower in the bathroom and the washing machine is on the flow rate and the hot water is reduced quite dramatically.

Options1:
Use the existing 37cdi and convert it to a system boiler which is then used to heat an unvented cylinder (megaflow or range?)

Options2:
Or possibly go to the 440 Worcester bosch combi which has a better flow rate
than the 37cdi and in the Worcester Bosch brochure it is designed to work with 2 bathrooms.

Has anyone installed the 440? Are they reliable?

Or are there any other options?
Also he will be replacing the incoming lead mains which will increase the follow rates..

 

[fuzzy]

i would choose the unvented for sure, pipe it up in 22mm and you get a super flow rate with little change when a number of outlets are opened, i always think combis are limeted

 

[justlead1]

Hi. I would agree. Codes of practice required system design to deliver 4 gallon per min to both hot and cold to a domestic bath. (but that seams to have got lost in the post over the years) Based on the max out put of combi boilers and the head loss due to friction there performance leaves much to be desired. Why not feed the kitchen sink via the combi and the heat exchange coil in the unvented cylinder via the heating circuit of the combi motorised valves and thermostats will be required to control the zones but it may be an option? Good Luck

 

[CharterGAS]

Forget Worcester they are crap

go for the Viessmann vitodens 333