Vaillant Turbomax Plus 824E Hot Water Problem

Foundation · 18 Jan 2010

Hi, I need some advice; I have been looking though the posts over the past few days and can’t seem to find the answer to my problem;

I have the above boiler which is around 7 years old, was serviced about 18 - 24 months ago and had lots of parts changed due to hot water problems, only had hot water every now and then and had to reset bolier.

It has been fine until the past couple of weeks, CH is great, but the hot water will only heat up to around 58 degrees and not matter what I set the temp to will not get any higher.

Can someone tell me if this is the diverter valve issue that seems to happen a lot or the heat exchanger?

I have not turned off the system to see if the rads get hot as the wife won’t let me!

Sorry if I am asking an obvious question.

Appreciate any help or advice?

Thanks.

Agile · 18 Jan 2010

The simple answer is that I dont know because you will not do the simple test which would indicate a failed diverter valve. If its never been changed then it probably is sticking or about to do so.

However, your description might indicate a different fault.

Most people have their boilers serviced every 12 months as the manufacturers recommend.

Tony

Foundation · 18 Jan 2010

Thanks for the quick reply, I will do the test first thing in the morning before the heating comes on and let you know.

Will I need to check all of the rads or just the ones nearest to the bolier?

Thanks.

Foundation · 18 Jan 2010

Hi Agile, I decided not to wait, I turned off the heating and left it for an hour, I checked all of the rads and they were cold, tunred on the hot water and let it run for 10 minutes, temp went up slightly to 60 degrees but all of the rads are still cold also checked the pipes going in and out of them all.

Any ideas?

Thanks,

Agile · 19 Jan 2010

That would suggest the diverter valve is still OK.

Can you measure the boiler flow and return temperatures in d40 and d41 using the diagnostic features?

The can you measure the DHW flow rate in li/min?

Can you measure the water temperature using a thermometer?

Look at FAQ and do a gas rate on the boiler while its giving DHW.

Tony

Foundation · 19 Jan 2010

Hi, OK I ran the following tests;

D36 - (All I got was a "-")
D40 - (I got 58 )
D41 - (All I got was a "-")

I think I have read the gas flow as per instructions and it takes 12 seconds when DHW is running for the fastest moving dial to do one rev.

I will have to go out and try and get a thermometer.

Any other ideas?

Thanks.

Agile · 19 Jan 2010

You need to measure flow rate with a bucket and second hand in litres per minute.

Gas rate is wrong for an imperial meter. Look at FAQ and do it again with no other gas appliances on.

Tony

Foundation · 19 Jan 2010

Hi, ok water flow rate is 1 litres in 6.2 seconds and gas rate is 0.072 = 23.11kw?

Agile · 19 Jan 2010

Thats 10 litres per minute which is more than your boiler can heat at this time of year.

Reduce that to about 8 and see how happy you are with that.

I have not checked the calc of the power input but its about 20% low but would need a gas engineer to check and set correctly.

So your flow rate is too high and the boiler set anout 20% low !

Tony

Foundation · 19 Jan 2010

Thanks for you help Tony, so I just reduce the main stop cock until the water temp rises?

As for the gas, is this something for a corgi plumber or British Gas to look at?

Cheers,

Alan.

Agile · 20 Jan 2010

You can reduce the water flow bu not opening the tap so much ! Or under the boiler on th cold water inlet. But that could be opened later in the year when the water comes in warmer.

The gas settings need a competent gas registered engineer.

Tony

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Vaillant Turbomax Plus 824E Hot Water Problem

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