combi Boiler fan turns on after using colder water

[amin]

Hi,

I have a not so old valliant ecoTech831 combination boiler and every time i use cold water the boiler fan turns on for about 30 seconds. Is this normal?

Also when the heating is on and there is a demand for hot water the heating turns off which means if someone takes a long shower the radiators start to cool off, again is this normal?

 

[Agile]

You have a "dead leg" in your hot water pipework.

Not any problem but might be more expensive to cure. Lofts are a common place for the problem!

A combi boiler only provides hot water OR heating.

During a prolonged hot water demand it may be noticed that radiators will cool down. Thats normal!

Tony

 

[spacethegas]

wot corgi.

Untitled

• spacethegas
• 8 Oct 2008
• 1

this one

ah ah corgi gone now Agile.

 

[muggles]

You might find that a check valve on the cold supply to the boiler will cure it...

 

[Agile]

wot corgi.

Untitled

• spacethegas
• 8 Oct 2008
• 1

this one

ah ah corgi gone now Agile.

Yes, the CORGI has gone now!

From now on its ARGI !

Tony

 

[Deleted member 105431]

You might find that a check valve on the cold supply to the boiler will cure it...

a single check valve on the hot water outlet is preferable as it allows for expansion of the heated water in the plate h/exch back down the water main. Or remove the dead leg of pipework.

 

[amin]

thanks for all the advise, I'll have the dead leg checked out.

 

[gas4you]

Check the airing cupboard or where the HW cylinder used to be (if you had one), usually the most common place for a dead leg.

Apart from your problem, you do not want any water sitting in dead legs going 'stale' as this could present legionella riska.

 

[amin]

I used to have a hot water cylinder and now have taken out the old boiler and cylinder and converted to a combination boiler.

The cylinder used to be in the airing cuboard and there isn't any pipework there now. Anyhow, at the moment the combi boiler is supplying hotwater throughtout the house and only heating to the downstairs rads (this is intended). I have disconnected the upstairs rads.

Its only when I turn on any of the cold water taps and then turn is off, that is when the boilder fan kicks in and switchs off after 20 seconds.

The dead must be somewhere in the cold water pipes, how do you go about removing a dead leg?

 

[Deleted member 105431]

You might find that a check valve on the cold supply to the boiler will cure it...

a single check valve on the hot water outlet is preferable as it allows for expansion of the heated water in the plate h/exch back down the water main. Or remove the dead leg of pipework.