Extra pump in C plan system

[TrickyDickie]

Hello
I am just adding a zone valve to my ancient gravity fed HW circuit and I was wondering why I shouldn't also add a pump in that circuit too to make sort of a pumped C plan circuit.
I could go the whole hog and convert to S plan but the two circuits currently exit the boiler on different sides so not easy from a pipework perspective. Is there a reason why I shouldn't add an extra pump on the HW circuit to achieve full 'S-plan' functionality? i.e. pumped HW and CH independent.

I assume if I do this then the zone valve on the HW should go after the pump rather than on the return side?

I can add a picture if the description above doesn't make any sense.

Thanks in advance
Richard

 

[Last Plumber]

Where in the pipe are you putting the valve?
If you put it in the wrong place it could be very dangerous!
If this is an open vented, gravity hot water, pumped heating system, it’s not as simple as installing valves and pumps.


Get a Heating Engineer in to look this over for you.

 

[Ric2013]

I think, from a safety perspective, we need to know where your open vent pipe and cold feed pipe are. Neither of these pipes can safely have valves installed on them.

 

[TrickyDickie]

Thanks Ric,
The fill is in the HW loop. Since this is a loop I don't think that putting a valve in one side will affect things (I know that the fill shouldn't be between any pump and valve that I install).
I haven't found a vent line, there is nothing over the header tank.

However, looking at the overall circuit I now realise that the pump is pumping into the boiler not out as I had assumed from initial inspection.
I'm confused now as I would have thought this would pressurise the whole of the HW loop and fill up the header tank?
I've obviously missed something here, any suggestions?

If it helps the house is 1960s build and I don't think it has been touched since then.

 

[ShaunCorbs]

One set of pipes 28mm also another set 22mm and maybe a 15mm one ?

 

[TrickyDickie]

This is what I think I have

 

[ShaunCorbs]

Yep you can't put a pump and zone valve on the cylinder side without major changes etc

 

[TrickyDickie]

ok, thanks. But nothing wrong with doing this though which was my original plan, i.e. two zones on CH side with auto bypass to keep flow and zone valve (no pump on HW side)?

 

[ShaunCorbs]

May I ask what your planing on doing and why ??

 

[TrickyDickie]

sure, there is an annex in the house which is currently on the same CH circuit. I would like to split it off to another zone and give it a separate thermostat.
While I was at it I was going to put the valve on the HW to make it a bit more efficient.

 

[ShaunCorbs]

Isn't there a citrol valve fitted on the return of the cylinder??

And then you could just zone the two heating circuits

 

[TrickyDickie]

nope, proper old school gravity feed. Always on if the heating is on.

 

[Last Plumber]

Where is the vent pipe?

 

[ShaunCorbs]

Where is the vent pipe?

Looks like combined

 

[Last Plumber]

Looks like combined

Never a fan !
Were you ?