Vaillant Combi boiler - how do I remove the heat exchanger?

[marchesini]

Hi all,

first post here and hopefully you'll be able to help. First of, I'm used to bits of DIY and reasonably competent at most things so I thought I'd try and fix this boiler problem myself rather than looking at another expensive repair bill. Please bear in mind that I don't know any of the correct terminology so bear with me.

We have a Vaillant Turbomax Plus 282 which was installed about 5 years ago. Had some problems with the old boiler so had this one installed but really had nothing but problems with it ever since. We didn't do it on the cheap - had a certified Corgi Engineer install it, had the Ferodox inhibitor in the system etc. In that time I've had one powerflush, 2 or 3 heat exchangers, and at least 5 call-outs - been grateful for the warranty.

However, almost without fail, every February, the hot water gets cooler and cooler until we have to call out Vaillant. Not really a problem as they have always sorted problems quickly but inconvenient nevertheless. As we kept having problems, I continued the warranty with their Gold Service package which includes a service and continues the manufacturers warranty. Unfortunately, I have since found out that my cover lapsed last year and so I'm no longer covered. I have taken another policy out with Homeserve but I have a 28 days before I can call them out for any repairs so for another 2.5 weeks, I'm on my own.

So last week, the water's not getting really hot anymore. The usual routine is that I shut off the boiler, release the pressure and then clean out the two filters on the hot and cold pipes. Sure enough, there are bits of metal in the hot pipe filter and small amounts in the cold. Clean them out and we have hot water again until today. So I go through the routine again but this time the water remains cool. Hmm.

I remember when one of the Vaillant engineers was here, he cleaned the heat exchanger as he said that they can often get blocked. I remember him washing it through in the sink which sorted the problem.

So I'm thinking, could I remove the heat exchanger and give it a clean in the hope it'll sort the hot water? I'm sorry to say, I can't even remember what it looks like so could anyone give me idiot proof instructions on how to do it? Be great if there were pictures as well!!

If I get this sorted, I'll be back for tips on how to prevent the problem.

Thanks for any advice

Best

Simon


ps. is the heat exchanger, the large sardine can looking thing about 6 inches long?

 

[Gasguru]

Turn off power and isolate the cold feed to the boiler, open all hot taps.

Drain primary side of boiler with the two drain-offs underneath.

Undo the lower left screwed fitting and remove the other 3 O ring clips.

Gently lever off the plate heat exchanger.

It's a slow job as the boiler doesn't drain down particulalry well. It's also worth unscrewing the motorhead from the diverter valve and using long nose pliers to set the diverter in mid position to help draining.

You will need a new 1/2 inch fibre washer, the O rings should be OK but worth getting a tub of silicon GREASE not sealant.

Clean the plate by back washing with the shower hose and a rubber hammer to loosen the flakes. Then use kettle descaler.

You need to sort out the corrosion problem, have you got a leak and are you constantly topping up the system?

Hard water has nothing to do with this problem. What are the filters, AFAIK the only filter on this boiler is the cold mains in the flow sensor brasswork..

 

[marchesini]

Turn off power and isolate the cold feed to the boiler, open all hot taps.

There are small screws underneath each of the pipes going to / from the boiler. I assume each of these, when turned, stop the flow. The large pipes are for the hot/cold water water and the smaller pipes for the heating. A further one marked gas, is also marked.

When you say 'isolate the cold feed', do you mean turn it off? Which one - the large pipes on the right going into the boiler?

What do you mean by 'open all hot taps'?. Physically open all of the taps inside the house? And leave them open?

I told you I needed idiot proof instructions - with pictures!!

Drain primary side of boiler with the two drain-offs underneath.

My boiler has drain off pipe to the back right of the boiler which releases the pressure as well. The pipe has been extended so that it flows to the outside of the garage. I simply turn a white knob and it releases the pressure and lets water out. Is this what you mean as there is only one of these knobs.

It's also worth unscrewing the motorhead from the diverter valve and using long nose pliers to set the diverter in mid position to help draining.

What is the motorhead - the red/burgundy coloured pump? Likewise, what is the diverter valve and where should I be looking to set this diverter valve?

You will need a new 1/2 inch fibre washer, the O rings should be OK but worth getting a tub of silicon GREASE not sealant.

Can I get these from any DIY store (Wickes / B&Q) or do I need to go to a specialist plumbing shop for these. Are they common parts?

You need to sort out the corrosion problem, have you got a leak and are you constantly topping up the system?

No leak as far as I am aware of. When you mean 'topping up' do you mean resetting the pressure? It should be at 1.5 bar and I occasionally need to build it back up - it can drop to below 1 sometimes but other times it can stay at 1.5 for months.

Hard water has nothing to do with this problem. What are the filters, AFAIK the only filter on this boiler is the cold mains in the flow sensor brasswork..

The filters are brass 'y' fittings that where fitted after we had the initial scale problems getting into the system on the advice of the Vaillant engineer. There is one on the hot water pipe out of the boiler an another on the cold water pipe. They have a 'cap' which unbolts and inside is a metal tube filter that collects the scale. This is what I was referring to when talking about filters - most of the time, there are metal flakes in the hot water filter.

Thanks for taking the time to answer and apologise for the 'newbie' nature of my response. Just want to ensure I'm doing it right and don't blow myself up or cause further damage.

Best

Simon

 

[Gasguru]

I think you could end up struggling to do this with your lack of the most basic understanding of a boiler and we could be here all day explaining.

Have you at least got the manual?

Removing the plate on these is actually one of the easiest repairs we encounter on boilers.

The 22mm pipes left and right have the drain-offs indicated. Turn the knurled part and hold a hose over them...they are pretty useless (Vaillant went downhill fast with this one). Use an allen (hex) key to isolate the cold feed into the boiler...arrow on the brass rectangular item. Open hot taps.

It is not normally necessary (or wise) to isolate the heating pipes provided there is a short rise of pipework up to the boiler ie you don't need to drain the whole heating system.

No more time off to an Ideal Sprint Rapide

 

[1FlameLift]

Hi
Thats a nice pic. I saw these Service cocks today and was thinking what a joke. Im a new Gas Engineer so im used to installing and servicing new boilers (A Rated), and im glad to say Vaillant have made draining down their boilers much easier.

 

[Agile]

I always isolate the boiler at the hex valves on that model as they dont leak.

Tony

 

[eddie_ed]

Turn off power and isolate the cold feed to the boiler, open all hot taps.

Drain primary side of boiler with the two drain-offs underneath.

Undo the lower left screwed fitting and remove the other 3 O ring clips.

Gently lever off the plate heat exchanger.

It's a slow job as the boiler doesn't drain down particulalry well. It's also worth unscrewing the motorhead from the diverter valve and using long nose pliers to set the diverter in mid position to help draining.

You will need a new 1/2 inch fibre washer, the O rings should be OK but worth getting a tub of silicon GREASE not sealant.

Clean the plate by back washing with the shower hose and a rubber hammer to loosen the flakes. Then use kettle descaler.

You need to sort out the corrosion problem, have you got a leak and are you constantly topping up the system?

Hard water has nothing to do with this problem. What are the filters, AFAIK the only filter on this boiler is the cold mains in the flow sensor brasswork..

I just want to say thank you for this post. It enabled me to remove and clean the heat exchanger on my vaillent which stopped the hot water hitting 85c and the boiler shutting down. It now runs at a steady 75c and no more hot/cool shower!

I ended up cleaning the exchanger with sulphuric acid (one shot drain cleaner) which was dangerous but highly effective.

 

[Roger928]

This was back in the day when you were actually helped with a gas boiler problem.
Today the jobsworths would deem it dangerous.

 

[Agile]

Also not very sensible because calcium sulphate is not soluble!

That's why you should use HCl instead if you must use a strong acid!

Tony

 

[eddie_ed]

Also not very sensible because calcium sulphate is not soluble!

That's why you should use HCl instead if you must use a strong acid!

Tony

Oh. Well it worked so that's good but should I be concerned?

 

[Agile]

It all depends on what the dirt was.

Usually its metal oxides on the primary side but sometimes it is lime compounds on the secondary side.

When cleaning them I always clean both sides!

Most metal sulphates are somewhat soluble. But none as soluble as chlorides!

Tony

 

[eddie_ed]

It all depends on what the dirt was.

Usually its metal oxides on the primary side but sometimes it is lime compounds on the secondary side.

When cleaning them I always clean both sides!

Most metal sulphates are somewhat soluble. But none as soluble as chlorides!

Tony

Ok, well the side for the hot water (please excuse my lack of knowledge of correct terminology!) seemed clear, the other side however had black deposits around the ends of the connectors and inside (as as I could see).

The acid did away with all the black, I also chucked some white vinegar through the hot water side afterwards in the hope of dealing with any limescale but I don't know how effective that would have been.

As it stands the system is working well so I'm happy with the result, how long it will last remains to be seen!

Thanks for your help.

 

[wannocks]

This was back in the day when you were actually helped with a gas boiler problem.
Today the jobsworths would deem it dangerous.

That's because on this boiler the job could be done without opening the combustion chamber

 

[Gasguru]

And bare in mind that everything on the Turbomax is obsolete technology save for the thermistors. Modern boilers are inherently far more dangerous by their design and also much more fragile to work on.

A simple seal that to an owner may seen of little importance could render the boiler lethal...combustion being very precise nowadays.

Having attended several boilers owned by posters on this forum you should trust me when I say how horrendous the state l've found some of them in from half ar5ed repairs. Unfortunately many on here don't know their limits and shouldn't be trusted to re-wire a plug let alone work on their boilers.

 

[Agile]

A customer's neighbour told us that BG always turned off her boiler saying it was dangerous and she waited for them to go an just turned it back on again!

Said she had done that for five years!