In an earlier contribution to this discussion,
dbroms wrote:


Hi guys

many thanks for the replies. I am still trying to fully understand
what system i have at the moment. I think i have pumped central
heating and gravity hot water.
After the pump the pipe splits into two, one goes to the coil inside
my storage tank and the other (25mm) i assume goes to my radiators.

If this is *after* the pump, it means that the water going to the HW coil
has been through the pump - same as the CH water. If this is the case, your
system is fully pumped - and *not* gravity hot water.

I dont seem to have a stat on the tank, the only thing i can find is
on the coil outlet from the tank i have what looks like a trv valve
with a thermocouple wire from it which goes to an aluminium block
strapped to the tank.

That sounds like a device which shuts off the (pumped) flow to the heating
coil when the HW is up to temperature - to avoid over-heating the HW when
the CH is on.

I have been reading on here and people seem to convert to a C plan
arrangement.

C-Plan is only applicable to a gravity HW system, and that doesn't seem to
be what you've got!

Why cant i just fit a 3 way valve after the pump?

No reason at all. [Unless you take up my earlier idea of going for an S-Plan
system by putting a 2-port valve in each branch, instead]

I am sorry for what might seem basic questions but this gets more and
more confusing the more i read.

OK, just to be *sure* what you've got: Are there ever any circumstances when
the boiler fires but the pump doesn't run? Can you get at the wiring to see
how the boiler and pump are wired? If so, are they connected together so as
always to work in unison?

The answers to those questions should confirm - or otherwise - that you have
a fully pumped system.
--
Cheers,
Set Square
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