Blocked heat exchanger - remove boiler to clean?

[C.J]

I bought a used valiant eco tec 415 (paid £120 for a supposedly 6 month old one that had come from a demolition job) to replace an ancient inefficient conventional heat only boiler and had it fitted, my gas fitter didn't think it necessary to flush the system prior to fitting the boiler as all my radiators were getting hot and when drained down the water ran reasonably clear, he instead opted to fit a magnetic filter on the boiler return.
The replacement boiler has been noisy from the start kettling and pipes banging so first I changed the pump as I had a spare, this made no difference, then I added some fernox F2 boiler silencer which has reduced the pipe noise to just ticking but the boiler is still kettling quite badly, now as this is a heat only boiler it's my understanding that as it is just circulating the same water through it and not heating fresh water it can't become scaled so it must be blocked with sludge - probably from it's prior use, so I need to flush it through, my thoughts are rather than dismantling it to remove the heat exchanger that it would be quite easy to remove the whole boiler and take it outside and run a pressure washer through the water inlet and outlet pipes, but first I would like some professional opinions

 

[Agile]

Sounds like you were "had".

Removed because it was scaled up or partly blocked.

Those heat exchangers have three ( ? ) loops which are in parallel so its impossible to do much to force cleaning liquids throu=gh the blocked loop.

We do not give DIY gas advice here so taking it off the wall would be a definite no-no.

But you could connect flexible hoses to the boiler and force chemicals through it and see what effect, if any, that had. Or just close all the rads and add chemicals during cylinder heating.

When a boiler costs £750 new it sounds too much of a bargain at £120 to be believed!

So if there was a gas fitter then what did he say about the noise?

Can you edit your profile to say where you are located?

Tony

 

[mogget]

Four loops I think.

OP, your boiler should have been fitted with compression fittings on the flow and return. So if you want to reverse flush with hoses, you could use 2x compression elbows 22mm, reduce to 15mm and attach the hoses with jubilee clips. A pressure washer will be no good as you'll need plenty of flow.

As Tony says though, you'll be lucky to get the muck out, I suspect.

 

[bernardgreen]

Removed because it was scaled up or partly blocked.

Probably previously installed by a cowboy in a system that wasn't flushed out and thus had to be replaced when it clogged up. Hence the low price.

 

[simond]

OP hasn't said how long 415 has been fitted in his house, bearing in mind no system preparation was taken.

 

[Dan Robinson]

Or quite possibly system design

 

[C.J]

Thanks for the input guys, I think the next thing for me to do is add some chemicals to try and dissolve the sludge, can I ask for recommendations on which might work best without a power flushing machine
Cheers

 

[C.J]

From looking on google I think Fernox F3 is the one I'll try unless anyone has a better idea or maybe Sentinel X800?

 

[mogget]

You could give it a go, but I think it's unlikely you'll get the dirt out if it's one loop that's blocked. It will effectively be baked in.

 

[Agile]

I would add "most" unlikely to that.

Although for an experienced engineer, who does not choose chemicals from Google, the success rate could be quite a lot higher.

Tony

 

[C.J]

Well for a tenner it's got to be worth a go, if all else fails I guess it's a new heat exchanger, still a lot less than a new boiler would have cost

 

[Agile]

When you see the cost of a new HE you may try to find an engineer to attempt to clean it for you.

Tony

 

[C.J]

I ran the boiler for about a week with sentinel X800 in and then thoroughly flushed with clean water it has made a massive difference, must be 80% less noisy, so now I'm thinking I need to add more X800 and reverse the flow through the boiler, can I just turn the pump around and run as normal, I realise my trv's will need to be either left open or closed as they are directional but can anyone (tony?) advise. Thanks

 

[mogget]

You can run it round backwards COLD, but don't let any gas into the boiler.

If it was banging really badly before, the oval tubes of the heat exchanger may be distorted which could lead to ongoing hot spots even if perfectly clean.

Which is louder now, the kettling or the fan/flame? My ultracom 15hxi has 'sung' slightly even at new on a spotlessly clean system, when running at a high flow temperature. (for other forum members, yes the pump is sufficient, dT 17deg)

If you don't need the full 15kw you could turn the max output down to say 12kw.

Might be worth another lot of x800, but I will reiterate that I am not an rgi, just a diyer who owns the cut down glow worm version of your boiler.

 

[matz]

its beyond my comprehension why any boiler manufacturer would produce a heat exchanger that not only blocks relatively easily if the boiler goes onto an existing system but that it cant be flushed out easily either ie separate loops......

edit to say, I presume its because the manufacturers are ever striving to produce the ultimate efficient boiler whereas in reality the average customer would happily pay slightly extra running costs per year to have something more forgiving