In an earlier contribution to this discussion,
Mark Trueman wrote:


Is there a reason why the vent has to connect at the same level as the
entry to the cylinder?

I'm not absolutely sure. The default with gravity systems seems to be to
connect the vent pipe to the highest point - but I'm not sure whether it's
de rigeur. Others may care to comment.

On my fully pumped Y-Plan system, it certainly *isn't* connected at the
highest point - both the vent and F&E pipes are connected into the flow pipe
under the airing cupboard floor, just before the pump. But the requirements
for gravity systems may be different.

Not sure about the overheat cutout stat. I was under the impression
that 99% of the old gravity heating boilers did have this (its an old
baxi bermuda 401 back boiler)

If it's similar to 2 Baxi Bermudas which I have owned in the past, it
*won't* have one. The Bermuda has a large heat exchanger - which holds a lot
of water - and can take care of being able to operate with virtually no flow
without any danger of the residual heat causing the water to overheat.

It seems that C-plan conversions are your niche Set Square. Looking
through previous posts on the subject, your name pops up more than
most.

I have certainly suggested them several times since converting a gravity
system to C-Plan is often the simplest way of providing a boiler interlock
where there wasn't one before. I have a very good understanding of how they
work - but have never been in a position where I have needed to implement
one myself.
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Cheers,
Set Square
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