potterton netaheat, hot water probs

[colclare]

Can anyone shed some light on a problem i have.
I currently have a potterton netaheat(not sure what model, around 1986 ish) when i call for just hot water i get heat through some of my upstairs rads.
Straight away i thought it may be a problem with the zone valve, but then after having a look realised this system does not use one, it has a secondary pump on top of the boiler.
Can any shed some light on this for me.

 

[kevplumb]

it has a secondary pump on top of the boiler.

where is the primary pump then

 

[colclare]

in the airing cupboard

 

[kevplumb]

do yer wanna hoy some info ower aboot the system

now in english (not geordie)

can you give us a bit more detail IE pumps pipes valves etc

 

[colclare]

Ok, I have a pump in the airing cupboard, which is just off to the right hand side of the cylinder and there is another pump located above the boiler which seems to run into the flow.
When i fire up just hot water some of the rads upstairs get hot.
4 pipes run off the top of boiler
Hope this helps