Roger Mills wrote:

I would, however, query the comment which goes with C-Plan about being
completely obsolete and unsuitable for either new systems or refurbishments.
I agree about new systems, but there are still a lot of gravity HW systems
out there which would benefit from being converted to C-Plan - which
requires very little plumbing and delivers considerable efficiency
improvements relative to the status quo. The only downside compared with a
fully pumped system is that when just HW is being heated, the boiler is on
for longer than it otherwise would be - albeit cycling on its stat rather
than firing continuously.

Does anyone have any evidence that this does not meet Part-L, and would thus
presumably be illegal as an upgrade from a 'conventional' gravity HW/pumped
CH system?

I found a website which stated this:

"Recent changes to the Building Regulations have made semi-gravity
non-compliant, so fully pumped is the only layout currently suitable for
new installations. The Building Regulations now control boiler
replacements too, and effectively require conversion of semi-gravity
systems to fully-pumped whenever a boiler is replaced."

Clearly, the author of the above doesn't cite his sources and I have to
say I didn't check them either. If you think the above statement is
********, then please let me know.


I'm still not sure about the way in which Y-Plan's mid-position valve is
depicted. As everyone knows, it has two microswitches and other components
in addition to the motor. I still tend to the view that we should either
show *all* internal connections (as for other types of valve) or *none* (as
per Honeywell's original Y-Plan diagram).

Ok, I thought about this. I am of the opinion that showing the full
internals of the mid-position valve would not be useful to the vast
majority of people and indeed, I couldn't draw it in the space available
at any reasonable scale. Also, I do not have such a valve to hand to
reverse-engineer the wiring details for. However, it is clear from
Honeywell documentation previously cited that the white and grey wires
assert the valve and the orange wire is a switched output - which is
what I have indicated on the schematic. I am inclined to leave it as it
is and I don't see a downside in doing so - it is after all standard
practice over a wide range of electrical/electronic industries to show a
simplified form of internal operation of a device.