Pros and cons of a W-plan system?

[Roger Mills]

That is a valid concern, and one which I had overlooked when I suggested that different flow temperatures for HW and CH may be easier to achieve with a W-Plan system.

[Mathew Newton]

I think I may have solved it by utilising the changeover function in the HW timer rather than the cylinder stat:

if there is a demand for CH yet no timer demand for HW (and cylinder stat not satisfied) then the valve will be energised and CH will function as desired.

Would you agree? Or have a broken something else?!

Mathew

[ARWadsworth]

That might be the W plans only plus. You can have a quick bath and the water will then be hot enough for some one else to have a bath 15 minutes after you.

If no-one has a bath after you then you are wasting energy.

[ARWadsworth]

:-)

[Mathew Newton]

Dammit... Think I've worked out the gotcha. In my revised configuration if the HW timer is calling then even if the cylinder stat is satisfied there can be no CH demand... Now *thats* what I call HW priority... It might still fit my needs though as we can continue running the HW for an hour or whatever first thing in the morning and if we need to hit the temporary boost button later in the day we'll just have to do without CH for the duration regardless of whether the cylinder is upto temp.

Mathew

[Roger Mills]

The arrangement as shown will only run the CH when the HW is off at the programmer. If they're both on, you won't get any CH even when the HW is satisfied. You need an extra connection from 2 on the cylstat to OFF in the controller. That way, the input to the CH timer switch will be powered both when HW is switched off *and* when it's switched on and satisfied.

[Andrew Gabriel]

Well, I installed something like that - a system condensing boiler that just does the heating, and a separate multipoint water heater which just does the hot water. The reason was that the multipoint water heater was relatively new when I put the central heating in (having had to be replaced in an emergency a year beforehand*), and I couldn't see much point in removing it and it works very well, and it's very much simpler than a combi boiler.

The boiler is normally set to 45C, as the heating operates at 45/35 for high boiler efficiency.

I do have a mid position valve, but that just selects upstairs heating, downstairs heating, or both, in a 2-zone system.

[John Rumm]

With a well insulated cylinder it will keep...

[John Rumm]

ISTM that 2 is only ever connected to the HW demand to the boiler or nothing?

[ARWadsworth]

Not unless the cylinder is as well insulated as harry's house.

[John Rumm]

No chance, there would be no room for the cylinder ;-)