On Wed, 22 Sep 2004 13:09:32 +0100, "Set Square"
wrote:

In an earlier contribution to this discussion,
Andy Hall wrote:


it's suitable for a normal boiler as well, since if the bypass opens,
the flow increases anyway.


The thing that worries me about this discussion, though, is that if the
Alpha has reduced its power/speed/head because the flow has reduced, there
may not be enough head to open the by-pass.

True, or if the bypass opens before the alpha "effect" kicks in what
is the point of an alpha? Basically they both do similar things so
its debatable which you need.

There may not then be enough
flow through the boiler to remove the residual heat after it stops firing.
How do you ensure that this doesn't happen?

How does a bypass remove residual heat? For that the pump has to run
so you need pump overrun not bypass. However, you may need a bypass
and pump overrun to cover the situation of all rads with TRVs (which
you shouldn't have) and needing to get rid of some heat (to the pipe
work presumably).



--

Malcolm

Malcolm Reeves BSc CEng MIEE MIRSE, Full Circuit Ltd, Chippenham, UK
, or ).
Design Service for Analogue/Digital H/W & S/W Railway Signalling and Power
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