Ed Sirett wrote in message
news
On Mon, 15 Nov 2004 16:40:21 +0000, John Aston wrote:

The drawing HD01 at http://tinyurl.com/3zv2g shows the proposed
hydraulic
design for a large domestic heating system.
snip

This is similar to a system I installed a couple of years ago. with a 170L
HWC and a Keston C40 (that's about 37kW output but runs at about 35kW due
to service main inadequacy). It works fine. Except I used a 5-way S-plan
and no UFH.


Ed, how do you rate the C40? I'm intending to buy this boiler and Keston's
Spa 300L cylinder.

Since this is a sealed primary what does the 'top up' unit mean?


I was going to use it to add inhibitor to the heating system.

snip

Design:

The mains cold water supply is treated by a water softener (bottom
left).
The softened water is fed to a 250L cylinder under pressure from an
accumulator which keeps the cold water at about 2.5 bar and provides a
high
flow rate to all taps.

I take it that you have an inadequate water main?

It's borderline. Gemonix sell a 300 litre expansion vessel part ZI-318300
for £266.64+VAT.
http://www.geminox-uk.com/expansion_vessels.html
I hope that that will be OK for my application.


The water in the cylinder is heated indirectly by the primary of a 38kW
fully-modulating condensing boiler in the room below the cylinder. Hot
water
is circulated to the taps by means of a secondary pump. Because the
system
is unvented, the hot water is also at a pressure of about 2.5 bar.

Bronze pump needed will (cost will equal total of all the other pumps).
8-(


Thanks, Ed. Maybe I'll lay the pipe for the secondary loop and only add the pump later if the dead legs are a big problem.