hi, looking for a bit of advice. Had a complete new system put in. Worcester greenstar with unvented cylinder. Been in use for 6 months over the winter. Never been short of DHW while the CH has been on morning/day/night. Have noticed that with the CH now hardly on that there is very little DHW. Long story short is, when I press to boost DHW it doesn't fire up the boiler. Fitter left all the programmer bumf and I'm satisfied the wiring is in place. I do suspect that the plumbing might be wrong tho. As it is right now the coil connector with the zone valve actuator on it is connected to the CH flow on the boiler. Am I right in thinking it should be connected to the return on the boiler. Can anyone advise on the water flow through the cylinder in terms of CH. does the water go through the cylinder coil before the zone valve actuator or is the ZVA on the outward flow from the cylinder? Big thanks to anyone who A. Understands my ramblings and B. Posts a reply.