The easy answer is something like the Baxi system boiler, this contains
pump, air vent, safety valve, expansion vessel, and of course the boiler.
just add two zone or one three port valve to connect to your system, and
remove the existing cold feed and vent. IMHO a Megaflow is better than a
thermal store not least because of the large volume of water to treat with
inhibitor in a thermal store, also thermal store are less efficient due to
there higher operating temp.

--
Muddy Paws
(remove muddy paws to reply)
"Ian Tracey" wrote in message
...
hi all,

been trawling through the search engines for two days and decided I
know less about the options I have than when I started.

The Problem:
I currently have an open vented heated system, that is under speced
from the boiler point of view and I am trying to suss out what is the
best road map to change the system to what I want without ripping it
all out in one go as I can not afford it.

Main issues to be sorted a
When the heating system runs the overflow overflows constantly
Hot water is at too low pressure
I would like to add a radiator in the loft at some point as it is a
walk in room

Solutions ?

I am thinking that using a thermal store will give me the mains
pressure hot water I want while still using the open vented system
Installing an airseperator from what I read on the net should stop the
overflow issue, but not found one that I can buy
convert the system at a later date to either a closed system or buy a
boiler that is already a closed system to get the hot water in the
loft. Can you get such boilers that are not combi boilers or do I
need to install the parts. If that's the case, do I need to put the
expansion vessel near the boiler and hence in the kitchen..

How would others tackle the problem ? useful urls for suppliers like
the air vent would be welcome, the ones I have found seem to be
targeted at just removing the air

many thanks and cheers

ian

ian tracey