Gravity fed, pumped CH - Potterton CH prob

[nysk2008]

Evening all,

I've got this problem I just cant get my head aroubd this.

Been at a customers today and carried out a powerflush, I powerflushed properly not one of these half hour jobs. Ive refilled and now 3 of the upstairs rads are not working.

I noticed that one of the downstairs rads was not hung straight and was cause air to get stuck so I have turned off and not included it in the circuit, I also noticed that the 3 port is on its last legs. Every rad warmed up lovely apart from these 3 (which customer tells me have caused probs before). Customers says they have come on randomly in the past sometimes when the hot water is on, so god knows - any suggesttions? Ive tried turning all rads off apart fro the problem ones and still nothing.

Cheers

 

[jtsplumbing]

Look for a non-return valve on pipe work, they may have had problems with rads heating up when on for hot water !

 

[tackleberry]

whats going to the rads 15mm or microbore??

 

[nysk2008]

its running 22mm main runs and 15mm tails to rads

 

[tackleberry]

right souds like mega air lock to me here is what i would try shut of all the good rads( both sides) switch of boiler so no power to three port valve,stick hose on outside tap and on to system drain off and blow cold main bk up through rads till it comes out feed and expansion tank.this will clear any air pockets.also it sounds like the return tee from hot water is not first tee on return pipe so when the hot water is heating up its bk ciculating throw these three rads.

 

[nysk2008]

thanks Tackleberry, appreciate your advice but now for the update. After blasting cold mains up the system the problem rads have been working lovely, until today. It would seem that the system is sucking in air somewhere and affecting the same rads. does anyone have anymore suggestions? cheers

 

[Mbear]

What head of pump do u have? 15/50 15/60 etc

And how high up are these last 3 rads from the pump

 

[nysk2008]

Hi MBear, i'll be totally honest im not sure sure on the head of pump but I can say the last rads are around 300mm below the pump level.