"Andy Hall" wrote in message
...
On Wed, 10 Mar 2004 00:52:28 +0000 (UTC), "Michael Chare"
wrote:

"Andy Hall" wrote in message
.. .

non system vs system
===================

whether or not the boiler has the pump and possibly controls and
expansion vessel inside the case.

From what I have seen some boiler manufacturers just use the word
'system' to
denote boilers which would be better described as 'sealed system'.

Michael Chare


Teminology is used loosely, which is what makes it confusing.

You really have to look past the names given and see what is actually
inside,

There are system boilers which will only run on open vented circuits
(not so many now) and some that will run on both as well as sealed
only.

Unfortunately, "system" seems to be used to describe anything which
contains more than a heat exchanger, gas valve, safety device and
thermostat (i.e. more than the bare minimum)

Terminology has now settled. A system boiler has a pump and pressure vessel
inside, so is only used for a sealed system - some may have a built-in
pressure loop, others do not. You just connect it up and still have to
install 3-way or 2-way zone valves. A "heating" boiler has no pump or
pressure vessel and can be open vented or sealed. You have to install all
the relevant pumps and kit yourself externally.

The terms heat bank and thermal store are still mixed up too:

- A heat bank uses a pump and a plate heat exchanger for the DHW take off.
- A thermal store has in integral immersed coil.