On Wed, 7 Jan 2004 00:17:15 +0000 (UTC), wrote:

In article ,
Andy Hall wrote:

reverse circulation
------+-------------+---------- CH flow (off)- || --+
RAD RAD |
reverse^circulation V |
| | Pump |
+---A-------------B------------------Boiler --X----MV
| |
CYL |
| |
+----------------------------------O---HW flow ----+


It is better to connect to a common point, as you say. You can get
around the problem with appropriately placed zone valves and that may
be a more practical solution if the CH return pipe is not easily
accessible.

What about just installing one-way valves on both the cylinder return and
new CH return just before the two returns join? That will prevent the HW
return from supplying hot water into the new rads, won't it? Actually the
one-way valve on the cylinder side would not be necessary as it wouldn't
matter if hot water returning from the radiators made its way into the
cylinder coil, would it?

Zane.

It may work.

You don't want water flowing through the cylinder coil either when not
wanted, because it may transfer heat out of the cylinder.

There are three basic kinds of non return valve, as far as I am aware.

- The first is typically used in a mains water supply to prevent back
flow of water and is normally based on a spring loaded plunger.
I am not sure that you can get these suitable for the low pressures in
a heating circuit.

- The second type is intended for vertical mounting with an upward
water flow and has a small weight or flap inside. These are typically
used in the pumped heating part of a system when a back boiler is in
use with gravity hot water.

- The third type is based on a metal disc which swings. These can be
mounted horizontally or again vertically on an upward flow.

Look at www.bes.ltd.uk part 7463 and 7464




..andy

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