combi boiler probs

[MidJeff]

hi can anyone help had a look at an excalibur 100 combi boiler, pressure gauge needle moves when you tap it' and also when they call for hot water all is ok but when they turn off hot water the central heating kicks in even tho they're not calling for it does anyone have any ideas on what the problem could be? something else there seems to be a link in between the flow and return on heating with 15mm ballafix valve turn off in the middle cheers

 

[newbie1]

quick guess but the valve might be a crude bypass
and as regards the problem with calling for heating when you turn hot water off thats a bit wierd

 

[Plouasne]

I would agree with you Newbie about a crude form of by-pass, could this be part of the problem; when boiler shuts down on finish of hot water demand, could the pump kick in to dissipate the residual heat in the boiler, so sending hot water around the heating system

 

[newbie1]

a photo would help with this one to see what they have done
when you say the boiler calls for heating is this a short burst or sustained call for heating ie boiler stays firing and rads get hot..what is time frame between shutting off hot water and how long will boiler then fire on heating mode as it doesnt make sense that boiler would call for heating for sustained amount of time