On my fully pumped (not gravity HW) indirect (coil in the water tank) primatic (header tanks in the loft) system (phew!) hot water comes up from the boiler and meets the pump. From here it splits in two. One goes to a zone valve and then the hot water coil; the other goes to a zone valve and then to the rads.
My timer (which I just upgraded to digital) allows me to open or close either zone valve (although this is overidden by the cylinder stat and room stat). Hope that helps.
My timer (which I just upgraded to digital) allows me to open or close either zone valve (although this is overidden by the cylinder stat and room stat). Hope that helps.