Vaillant TurboMax hot water problems

[kirkle]

I have a TurboMax VUW282E which has given many years of good service, however over the past week it has developed a problem with the DHW supply.

When drawing hot water the boiler starts as normal but then after about 15-20 seconds shuts down and then after about 7 seconds starts up again. This happens even when there is full demand for hot water. The water is reaching temperature but then of course, when the boiler shuts off, the temperature slowly drops until the boiler reignites. Which means you get a supply of hot water fluctuating from a good supply of hot water to just warm and back up to normal again.

I have ruled out problems with gas supply, burner, DHW microswitch and the diverter valve. The boiler is running perfectly for the CH reaching temperature, modulating etc.

Setting the hot water temperature control high or low makes no difference. The flow from the hot water taps is fine we have no thermostatic showers or anything like that.

I have concluded that it must be a problem with the DHW heat exchanger, the overheat thermostat or the water section diaphragm. The boiler is not making any funny noises so I don't think the water on eitherr side of the DHW heat exchanger is getting too hot and boiling.

I have read many threads where it has become and expensive trial and error replacement of components to eventually cure the problem and I want to avoid this scenario if possible. As the boiler is now over 12 years old I suspect that many engineers may not be familiar with this model.

Does anyone have any idea of how I can work out which component may be at fault or give enough information to a plumber so the fault can be quickly discovered and rectified?

Many thanks

 

[johnnojob]

so this is an older boiler and as per the rules of owning an gas appliance you have had it serviced to the makers instructions.
just pull out the previous paperwork and ask a previous service agent to come around and fix it.
say it has not been serviced for 4 years,then you have a spare £400 in your pocket to spend on it.
good boilers last longer with expert attention.

 

[kirkle]

The boiler has been serviced in the last year. I just wanted to try understand what might be going. Just the same with the car, washing machine etc. Not trying to do an expert out of work.

 

[Agile]

I have ruled out problems with gas supply, burner, DHW microswitch and the diverter valve. The boiler is running perfectly for the CH reaching temperature, modulating etc.

Does anyone have any idea of how I can work out which component may be at fault or give enough information to a plumber so the fault can be quickly discovered and rectified?

Many thanks

How did you manage to rule anything in or out?

Why are you calling a plumber instead of a boiler engineer?

Surely if you called anyone who was competent to repair your boiler then he would have the necessary skills to quickly diagnose and repair the boiler without you having to ask questions on a forum to engineers who have not visited or tested the boiler.

All the indications are that it's YOU who want to fix it yourself and you dont want us to tell your ( incompetent ) plumber but you want us to tell YOU.

Whats his name?

Tony

 

[joe-90]

Scrap! Scrap!

 

[kirkle]

Apologies I seem to have caused a problem.

My use of word plumber was general. Should I be looking for a boiler engineer? Can a plumber be a boiler engineer or visa versa?

As to ruling anything in or out I have used the fault finding section in the installation and service manual. This I described in my first post.

I haven't contacted the guys I use to service the boiler yet as I would like to try to understand what may be going on myself. Just the same when something goes wrong with the washing machine, car etc.

I don't expect anyone to tell me exactly what is wrong on the basis of a posting on this forum. I am just trying to be a bit more informed before I get someone in to advise on what they feel the best course of action is. I have found in the past, to my cost, that not all so called experts are what they proclaim to be.

 

[mickyg]

plate heat exchanger blocked/scaled.

 

[Morris40]

DHW heat exchanger sludged up, could be

 

[kirkle]

Thanks for the advice. Gives me a better idea of what to expect when engineer has a look.

 

[garyatkinson]

Kirkle thank you for posting- you brave person you- really pleased it wasn't me!!

Similar problem to you but unlike EVERY OTHER Gas Boiler owner (it seems to be suggested) I haven't had a regular annual service.

My problem with fluctuating water temperature was down to a gunked HW heat exchanger.

Thanks to all the helpful posts.

 

[kirkle]

Brave I was not. I failed to read the diyNOT forum title properly and posted without anticipating such extreme responses.

It was the DHW heat exchanger full of gunk and I was told it will need replacing soon. Looking at what was required to do take the exchanger out, which didn't involve tampering with the gas supply in any way, it is not complicated. With the right tools and a bit of mechanical experience it would not be impossible to DIY it!

Thanks for everyones advice.