"Ed Sirett" wrote in message
news
On Wed, 28 Sep 2005 13:43:02 +0100, Mr Fizzion wrote:

Can you have such a thing or is this one of Doctor Evil's fantasies?

If you can...how would you do it?


For me this is just plain nonsense.

On what does he base this wild claim on....we shall see....

1) I doubt very much whether any manufacture would permit the boiler to be
used in this way.

The boiler is not being monkied about with.

2) The boiler is not designed to take luke warm let alone hot water as
it's input.

Some are and most are really. See makers. Many accept very hot water from
solar preheated water. Eco-Hometec for e.g. The cold inlet to most combi's
is just a pipe to a plate heat exchanger and a flow switch. Nothing there
to say 40C water will screw the system up.

3) All the while the 2ndry pump is going the boiler is in DHW mode. When
does the house get heated?

You really can't figure this out can you. A highly insulated loop from the
outlet to the inlet with pipe stat set to 40C means that the loop will be
warm within a minute or so and then be switched off, amd stay off for a long
time. There are keep warm boilers around. The same thing but extended to
outside the boiler casing.

4) The whole system would rely on the boiler shutting down because the
primary is at or over its maximum temperature for DHW mode.

What are you on about?

This will only
happen when the DHW temperature is very hot. Ergo the heat losses on the
2ndry loop will be huge.

Again. What are you on about?

5) Whilst the burner is shutdown the fan will still be going so that the
primary will be losing heat at a rate comparable with the burner rating
i.e. tens of kW. This is going straight out the flue!

More confusion.

6) The water bylaws
forbid the permanent connection of the mains to a closed circuit.

Not so. Thermal store are done this way. Here are The DPS Heat bank makers
giving advice on uk.d-i-y on how to connect up a heat bank using "exactly"
this method.
http://tinyurl.com/cfet8

If a house needs a secondary loop it also needs a grown up heating system
that will include a stored HW of some type (vented, unvented or thermal
store).

What tripe. The basin and washroom may be way off from the combi, so
looping the DHW makes sense. In fact a secondary circulation loop saves a
hell of a lot of water and gives instant DHW at the taps, which is a great
convenience.

Have a look at the one box AVC Heatmaster for a system in your view is not
grown up.

...and you are a professional? Struth.