intermittent pump / 3 port valve failure

[srixon]

Hi all,
New to this site but have a problem.....
I have a intermittent fault. I have a conventional Y plan system and not sure if the fault lies with either part (pump or valve). Is there any way to carry out a test to find out which part is faulty....? I am a qualified electrician so have knowledge of fault finding.

 

[namsag]

Our usual mind reader is of ill this week so could you give us a clue what the fault symptons are

 

[srixon]

Sorry mate,
hot water only...
when the stat calls for heat the boiler fires up but no heat is reaching the x2 expansion radiators so therefore no temp gain in the tank. after about 5 mins the boiler cuts out and has to be reset (presume because of overheat).

 

[spacethegas]

i'm not ill.

expansion radiators

but i didn't see that one coming.

 

[srixon]

Thats a gut at work called them.... lol
whenever the hot water comes on I have x2 radiators in the bathrooms which get hot.

 

[twgas]

the GUT at work has a strange turn of phrase - if the 2 rads usually come on with the hot water they are known as summer operation, or by-pass rads.

check you're getting output from roomstat (white wire on valve) if yes most likely sychron motor.

 

[srixon]

The gut (guy) at work is site foreman and basically a joe know it all....
Will try your advice tomorrow evening and keep you posted...
Cheers mate.

 

[namsag]

If i understand you right
On hot water demand you normally get the cylinder heated and 2 rads, at present none of them heat and the boiler cuts out on overheat after approx 5 minutes.

Sounds like your pump is not working check its getting 240v if it is then check to see if its actually spinning by removing centre screw