Vaillant ecoTEC 824e hot water going cold....

[oriontc]

Hi all, ill try to make it as short and straight to the point.

normal central heating works fine.

when I use the hot water from the bathroom sink tap the boiler fires up on a full flame then stops, then starts again after a few seconds back on full flame. so its very on and off, it doesnt lower the flame etc, just on full or off. but the water stays hot....

if i turn the bath tap on which is a stronger flow, the boiler goes on a full flame, then instead of turning off like the previous tap does it will go to a low flame... but too low to keep the water hot... the water then goes very luke warm/cold...

to test this we turned the bath tap down to about 50% power, it did the exact same thing as the bathroom sink tap...

a plumber replaced a heat sensor in the boiler thinking it could be that and its still the same problem. we are both a bit stuck now

the flow from the bath tap is about 9 litres per minute on full power.

thanks in advance.

 

[wull67]

Press the I button when the boiler goes to low flame, this will tell you what status the boiler is at, ie s53 is a code that would suggest poor circulation.
S codes will be in your manufacturers instructions

 

[oriontc]

will there always be an S code displayed? ill give it a go though when im at home.

 

[wull67]

Yes when you press the I the display will show you the status (s code) the boiler is at, what it's doing

 

[oriontc]

excellent, ill try that cheers

 

[jeff the gasman]

excellent, ill try that cheers

Sounds like the plate heat exchanger is blocked.
Jeff

 

[oriontc]

ok i made 2 youtube videos to give you an idea of the sound etc and what it's doing.

the code both times was S.14

Boiler when bath tap running
http://www.youtube.com/watch?v=ETa8UJZ4njE
you can hear the hissing, and the water is luke warm.

Boiler with bathroom sink tap running
http://www.youtube.com/watch?v=4VFKFRwJKhg
no hissing and the water stays hot. less flow than the bath tap

it seemed to behave differently to yesterday, i didnt notice the boiler kicking in on high flame then low flame etc. i took the videos for better real world evaluation hopefully it helps

cheers

 

[wull67]

Reduce the flow on the bath to 30percent and your temp will increase, how long have you had the boiler?

Your boiler is the 824 which heats up water by 35° at 9.4 litres a minute, to measure this, get the flow rate to 9ish litres a min, check the temp of the cold water at the tap + 35°, this should be close to the temp on the boiler.

At this time of year your cold water temp will be below 10°+35° will give you a temp of 45° at 9 litres a min, no very hot.

 

[oriontc]

Correct if I turn the bath tap down it stays hot. The flow from the bath tap is around 9-10 litres a min on full flow.

The boiler is in the loft which prob doesn't help with the heat.

So is the hissing sound normal? Is it just a case of the water is too cold to warm up quick enough for the flow?

I moved into the house last year so not sure about the previous issued with boiler, pressure drops on occasion. Its at least a few years old

 

[wull67]

Your boiler is working normally, as it's only a 24kw boiler and the water coming into it is cooler in the winter you'll need to reduce the flow from the hot tap to achieve a good bathing temp.

 

[oriontc]

thought id reply and tell you all I had it power flushed and now it works perfectly. water is nice and hot. i did also fit a flow reducer to the shower which must help a little. but the flush did it the world of good. flame stays on high now.

cheers all!