Radiators only luke warm potterton suprima

[macca86]

hello,i have an s plan system with a potterton suprima boiler,the radiators only seem to get luke warm i dont no why.The zone valve body and motor have just been changed for the heating side,the pumps is brand new, but still no improvement?the boiler also seems to keep shutting off and wont run constant as if it thinks its got to heat when it cant have!
Any help would be greatly appreciated thanks.Also it has already had a new p.c.b some time ago.
John

 

[bengasman]

do the flow and return pipe get hot?

 

[seco services]

whats the condition of the system water like ? maybe sludged up

 

[macca86]

flow and return get hot yes,the system water isnt to bad its dirty but its not sludgy/also sometimes once a week or so it will work fine and be red hot,ive noticed as well just as the rads start to heat when the normal fault occurs the boiler shuts off thinking it has reached temp

 

[bengasman]

try turning all the rads off when system is cold.
make sure the hot water is off, and start the heating, if the flow and return get hot, your bypass is not working properly

 

[macca86]

the clock will not allow me to have heating only/i can have hot water and heating or hot water only, could this have anything to do with the p.c.b shutting down the boiler before it has got to temperature?
thanks for the help greatly appreciated

 

[bengasman]

if the resistance through the rads is high, the water can go simply through the cylinder and the boiler will reach desired temperature.
there is often a manual valve that regulates the flow through the cylinder. you can try shutting that for the test but you have to make sure the boiler still gets flow otherwise it can overheat.
if you are not sure you can do this safely, get an RGI to look at it.
if the system is not dirty, you need to clean it anyway regardless of whether you think it causes the problem.

 

[macca86]

hi i am corgi registered passed my ACS 3 weeks ago,so im newly qualified just trying to find my feet really, struggling a bit with faults as ive just been thrown into it a bit,what do u mean a manual valve for the cylinder?it seems as tho just when the rads start to get warm the boiler shuts its self off, cant get my head round it. tried the pump on all speeds,no difference, the thing as well that is confusing me is why every now and again its gets red hot!!

 

[seco services]

what do u mean a manual valve for the cylinder?

i take it you've done plumbing before your acs ?

 

[bengasman]

it seems as tho just when the rads start to get warm the boiler shuts its self off, cant get my head round it. tried the pump on all speeds,no difference, the thing as well that is confusing me is why every now and again its gets red hot!!

could be that when the cylinder is satisfied, the valve shuts

 

[macca86]

yeh ive done plumbing, then a 3 year gas apprenticeship but nothing really prepares you for going out alone with the repairs.would you suggest faulty cylinder stat then would that not affect the hot water also though? it used to be on a british gas contract and for some reason they have wired the clock so u cant have hot water and heating on seperately.apparantly its illegal they told the customer. i fought the whole point of an s plan was to have seperate heat and water,any ideas on this,any clues on the cause of the luke warm rads, ? really appreciate all your help,going back on thursday so need to get it fixed. lol

 

[seco services]

yeh ive done plumbing, then a 3 year gas apprenticeship but nothing really prepares you for going out alone with the repairs.

no but you should know the basics, like the gate vale on the cylinder return.

would you suggest faulty cylinder stat then would that not affect the hot water also though?

no nothing wrong with the hw. you can check the temp of the hw against the cyl stat.

it used to be on a british gas contract and for some reason they have wired the clock so u cant have hot water and heating on seperately.apparantly its illegal they told the customer.

wire it so it can. or as said see what happens to heating when hw satisfied.

 

[bengasman]

if it was intended not to have either one on alone, you would not need two valves.
load of cobblers that story, questions is: did customer understand it correctly or was the previous plumber talking brown smelly stuff?

 

[macca86]

well they used to use it as intended heating when wanted and water when wanted until a few years ago a bg engineer changed it.so u both seem to think its a system fault then? rather than a boiler fault ill try everything youve both sugested when i go back see if i can get it going,cant understand tho why the bg engineer changed the clock.