On Wed, 5 Nov 2003 15:08:50 -0000, "David Hearn"
wrote:


"Christian McArdle" wrote in message
et...
Ahh, as I'd like to keep my existing pump etc (its working, why replace
it,
and its easy enough to replace myself if necessary) am I therefore
restricting myself to not having a system boiler? Are there any
modulating
non-system boilers out there?

Yes. The Ideal Icos might be ideal for you (excuse the pun). It is
available
without pump and will run on a feed/expansion tank. (I wouldn't recommend
doing so, though, as sealed pressurised operation is better).

Some system boilers with integral pump have the pump under control of
the electronics as well. Either it is three steps like an external
pump or continuously over a range.

This is beneficial because the flow can be adjusted automatically as
the heat load varies - e.g. as the TRVs operate and provides improved
control and quieter operation.


Hmm, what sort of work is needed to convert from feed/expansion to sealed
pressurised? What sort of benefits can be gained? And why isn't it
recommended?

There are a lot of benefits such as

- easier cleaning
- limited water escape if there's a leak.
- no opportunity for air to enter to corrode the system
- easier to eliminate air for bleeding.

Some boilers will work unpressurised but increasingly pressurised
operation is mandated. Most boilers for sealed operation include
the expansion vessel and controls either inside or as a kit.
Ed's FAQ has more details......







Thanks

D


..andy

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