Roger Mills wrote:

In an earlier contribution to this discussion,
Dave wrote:


It looks like my set-up is an S plan with a valve missing from the hot
water tank heating. All mine consists of is a valve that is controlled
by the room stat that open/closes the pumped supply to the central
heating. (Both hot water and rads are pumped with the same pump)
There are two separate circuits that are fed by one pipe from the
pump, then split for hot water and CH, with a valve in-between the
rads and the boiler and on their return to the boiler. Is this an S
type?

What you have described doesn't equate to *any* of the standard plans! It
sounds as if you have a system which, while being fully pumped, suffers from
many of the disavantages of a gravity HW and pumped CH system - in that
there is apparently no control of the HW temperature, and no boiler
interlock to turn the boiler off when HW and CH demands are both satisfied.

I use the boiler stat to control the heat of the water, so that if the
power shower handle points vertically, you get water coming out that is
neither too hot, or too cold. The seams to work OK

You would need another valve and a tank stat, and some adjustments to the
wiring to convert it to a pukka S-Plan system.

I did have a tank stat on the old system, so I'll dig it out and wire it in.

I have a slightly different question to ask.
When the new boiler was installed, the plumber didn't wire it up as it
should have been and the pump runs all the time that the boiler is
powered up (not just when it is fired up). It it better to leave it
like that, or should I find the pump terminal, on the boiler, that
shuts down 15 minutes after the boiler ceases firing each time/cycle?



The pump needs to run whenever there is a heat demand on the boiler -
including times when the boiler's internal thermostat has turned the burner
off. The pump shouldn't run when there's no demand on the boiler. If it
does, it's wired wrongly. If the boiler has dedicated pump connection
terminals to enable it to control the pump, that's where it should be
connected.

That is what I thought.

Many thanks for your info. I'll get round to correcting all this when
the weather warms up a bit and we can live on one tank of hot water for
a while.

Regards

Dave