headline capriz ~~~~ headache job

[Ted808]

Before I get shot down.... I never specified. I fitted boiler, did pf and added mag.
Old boiler not working at all so no testing. All OK so far. Until I open the hot tap, and get no hot water! !! Brand new boiler and no hot? Boiler runs, pipe under boiler gets red hot but nearest tap doesn't even get Luke warm! Then flame goes out. Obviously up to temp. Blocked p 2 p? But hot supply under boiler gets red hot. So I'm scratching my head.. Did it work b4¿ I've no idea cust dodging answer.
Just sometimes I get fed up. Like NOW! All hot taps - same results
So any advice from the panel please?

 

[stevetheplumber]

cold main back feeding some where? cut hot pipe below boiler run it into a bucket or hose see if it gets hot then

 

[Ted808]

That was my next plan. Cheers Steve

 

[GasmanxxxR1]

Had the same problem last year, turns out the shower was back filling the hot with cold, no hot water at the taps. Fitted NRVs under the bath and hey presto

 

[1Steven]

How did you get on?

 

[Paulplumb]

+1 for the check valves on a shower

 

[Ted808]

Not been back yet.... Tho took out a headline and had a play taking it apart... Found interesting bits to check.

 

[Ted808]

Post above i meant...... took out another HEATLINE and, took it to bits and found amazinly, lots of little pebbles, grit in the cold supply, more than half blocked! ....must've had work done on the mains.... AND the filter from the heat ex to the P-Pex full of black corn flakes- no wonder that boiler wasn't working.
Anyway, went back to my boiler - checked the hot outlets and one by one isolated them, there are several basin mixer taps - found the culprit back feeding the cold!!
A sensor tap. ie. tap when you wave your hands in front, it comes on. Who ever installled didn't install check valves! So that's that- had me scratching my head though.
Going back next week to fit check valves..woo - hooo result!