"Doctor Drivel" wrote in message
eenews.net...

"richman" wrote in message
oups.com...

We converted a five bed house in London for students and the plumber
put in a gas Vaillant turbomax plus 828 to serve a shower and a bath.
All the old pipe work from the old conventional system is still insitu
just blanked off. Frankly the combi is just poor; baths are just not
worth having and the shower flow is disturbed so much by washing
machines, dishwashers etc.I thought I could get away with it because we
all know students dont wash but this lot do....

I have read what you all say about combis but think that they are
useless for more than one old lady in a flat, I am afraid.

I'm afraid you and your "plumber", so not know much about combi's. :-)
High flow models are available; I doubt if he has seen one. This sounds a
typical cheapo landlords effort to me. Well firstly I would have properly
assessed the DHW demand. How many people are using this house? Why a
bath,
when students only need a shower? A bath takes space and somthing else to
maintain and keep clean.

There are high flowrate combi's around and I would have gone for one of
those. Also I would have arranged the pipework properly. This sounds
like
15mm cold water mains pipe snaking around the house and all appliances
teed
off this, of which the combi is one. The combi, ideally should have it
own
dedicated cold supply from the stop cock, with the cold supply to the
shower
taken off this combi supply just before the combi inlet. This way when a
toilet is flushed it doesn't affect the combi DHW.

We now want to put in a an en suite
shower room on the second floor,
exactly where the old airing cupboard/immersion
heater was. The boiler is on the ground floor
in the kitchen and the existing bathroom is on
first floor.

I want to put a megaflow or similar
unvented storage with an upgraded
new boiler.

The same applies to an unvented cylinder regarding the pipework. A 22mm
supply pipe back to the stop cock. Go for a low pressure heat bank rather
than an unvented cylinder. No explosions, and students can do silly
things
when drunk, like ****ing about with the cylinder controls.

The vaillant is nearly new and I wonder if some clever internal
rearrangement will turn it into a sealed system boiler or should I just
bite the bullet and buy a new proper one.

What do you reckon?

The Vaillant can be turned into a system boiler. That is easy as that is
what it is with a DHW section added.

CH demands? CH zoned? If not is it better to have separte timed zones? A
mains pressure system: combi, unvented, heat bank, is dependent on the
flow
and pressure of the mains

Start at the beginning. Give me your DHW demands: number of people in the
house, Number of showers, sinks, size of cold water mains, idea of
flowrate,
etc.



The Vaillant Turbomax 828 can deliver 11ltrs/min wth a temperature rise of
30C.
It'll run a shower easily, and a bath in less than 10minutes.

As others have stated, perhaps your pipework is not very good. Test it by
seeing what
the cold bath tap will deliver at full whack, or even the kitchen cold tap.
It should be
considerably more than 11litres/min to give you some margin. My cold water
taps
can deliver 19litres/min. Even so, a pressure equalisation valve will help
stop slugs
of cold water coming through a shower in a house wih so many people in it.

Andy.