Vaillant EcoMAX Pro 28E 6 months old suddenly banging..

Bit of urgent advice from anyone who knows the Vaillant 28E please?
Boiler fitted new 6 months ago, after our 18 rad system was *fully* pressure washed and descaled etc. The 'new' system was then topped up with a 4Ltr dose of Fernox MB1 inhibitor. The system has been working fine all winter at a working temp of 65 degrees until recently when there's been a slight build up of sizzling (kettling?) noise from the boiler. Now, very suddenly, the boiler's started thumping and banging with all the symptoms of local boiling - even when set down to 45 degrees. The pump seems fine, and is set to full flow rate to ensure enough pressure. With all rads and indirect hot water turned on to 'dump' the heat, and even with the boiler turned down to 50 degrees (at which there seems no problem tracking) the violent thumping begins after less than a minute's running. Input and output temps seem quite sensible on the diagnostic section of the display.
We're in a slightly hard water area so the initial fill of the system won't have been that perfect, however I would have thought the Fernox would have reduced/prevented any scaling up.
As we're now without heating, any ideas before I just do what I would have thought was a premature descale and probably replace the pump just to be *very* sure about the flow?
Thanks for any help (Ed, if you're watching, what are your thoughts and experiences of the Eco Pro 28E? - and TIA) now about to go out shopping :-((
--
Bob bobATthecopseDOTnet

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I don't suppose someone has turned all the rad valves off or trvs closed due to mild weather?
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In a message posted Sat, 31 Mar 2007 05:18:43, you wrote...

Thanks for the thought, oh how I wish it were that simple!
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Bob bob~AT+thecopse~DOT+net

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On Sat, 31 Mar 2007 11:10:24 +0100, bob wrote:
---8<---
You don't mention whether you've checked the system pressure ....?
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Hi John, thanks for the thoughts,
In a message posted Sat, 31 Mar 2007 14:55:09, you wrote...

Open system, two storey house, H/E tank in roof, and... .. correct water level, ball valve not jammed and no blockages in the feed pipe, confirmed by the self top-up after the pump was exchanged today.
Beats me, except as I replied to Ed, an unbelievable amount (for me) of scale and gunge partially blocking the rotor on what is now the 'old' pump. Would have thought the Fernox tipped in when the boiler was fitted would have largely prevented it. I jumped for joy when I saw this, thinking that it would be an end to the problem.. Sadly not :-((
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Bob bob~AT+thecopse~DOT+net

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On Sat, 31 Mar 2007 11:10:24 +0100, bob wrote:

Just eliminate a few simple things: 1) System pressure reasonable? (it should not operate if it's too low but even so) 2) Pump working OK?
Has the internal bypass valve been adjusted? Is an external bypass needed?
This is the season for all TRV closed and boilers over-heating.
The boiler is still under guarantee so get Vaillant out. 0870 6060 777
... The Ecotec "Pro" series are identical to the "Plus" series except that they are reduced in price, have no internal filing loop, only a 12 month guarantee, and lack the preformed pipework requiring the installer to roll his own. They are then sold at about 100-150 cheaper.
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Ed Sirett - Property maintainer and registered gas fitter.
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In a message posted Sat, 31 Mar 2007 19:21:59, you wrote...

Thanks for the reply, Ed, much appreciated!
1) Open (vented) system... 2) Have just split the pump to find the rotor badly clogged with scale and debris, which was a slight surprise considering the thorough power-wash given to the system using the old boiler, DS40 and flusher inserted in place of the pump. All this immediately prior to installation of new boiler.
However, I have just fitted a brand new (Grundfos) 6m head pump set to Max, and the banging is still there even at the minimum 38 degree output setting with full flow (set!) through all rads :-(

No internal bypass on this model that I can see, and..

Yes, and it's fitted correctly beyond the minimum loop distance from the boiler. It's also set to its lowest setting just in case of the usual TRV problems.

Indeed, and that was the first item to be eliminated from the list!

Very tempting - at this point I wish it weren't a DIY installation, (but I hope you couldn't tell :-) )
Despite the new pump in circuit, I cannot *guarantee* an adequate flow rate through the boiler because I have no idea whether the boiler itself now has some debris lodged in the heat-exchanger.
This is where I bow to your knowledge of the dimensions of the pipe section in the coiled heat exchanger. Is it likely or even possible that this could suddenly become blocked with a typical piece of radiator scale or am I being overly pessimistic? Furthermore, if it is partially blocked, am I likely to be able clear it with a week of Fernox DS40?
For the last few weeks the boiler has been 'hunting' noticeably to find the correct heat input, almost to the point of instability when given the 'step function' of say, the hot water circuit cutting in. This has given me the suspicion of reducing flow rate despite the old pump having been set to max (out of desperation). Clearly all the TRV's are shutting down, but I've been aware of the hot water heating being similarly affected. Having now dismantled pump and found (to my horror) the debris clogging the rotor I guess the boiler has indeed been starved of sufficient flow rate, hence the occasional instability. The new pump should have fixed this at least...
But very suddenly, this morning came the violent thumping, and thus my current suspicion of scaled and partially blocked heat exchanger despite its youth!
I should also have said that the input/output temperatures seem OK using the service-mode on the panel. In other words, a typical case now (when set to 38C demand) is output varying gently between 37C to 40C, while the input might be a steady 26C. Normal, except that after a minute, we now get sizzle, bang, bang, bang, and a probable 3 min shutdown :-((

Thanks for that; when inspecting mine prior to fitting, besides finding the inlet bent about 10 deg from vertical, I also found the flow (outlet) over-temp thermistor cockled over at an angle, half clipped onto the pipe and hardly touching it. Good start!
Ed?
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Bob bobATthecopseDOTnet

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On Sat, 31 Mar 2007 23:09:03 +0100, bob wrote:

Looks like this boiler might have been dropped in transit. However I doubt that is the cause of your problems.
In general I've never had a Vaillant with any obvious transit damage or any problem that stopped it working out of the box. [Unlike the Alpha which I fitted last week (customer's choice of boiler) which had loose water connections the DHW side inside the boiler.]
For what ever reason the initial clean out has not been good enough. Without having been on site I can't really say just how bad things were before the new boiler was fitted and whether or not power flushing was adequate or not. If there has been so much debris that the pump got filled with crap then it's a fair bet to say the heat exchanger will also be suffering. Just possibly one of those "magnaclean" gadgets may have helped but frankly getting the system reasonable clean before you start is the game.
If the debris is mostly scale I'd reckon it coming from the area around the feed pipe. it might even be that the MB-1 is loosening very old crud that was fairly secure when you power flushed the old system.
I'm not sure what to advise at this point. Certainly a lot of work is now required to clean out the heat exchanger and possibly the right chemical to break down the scale.
I take it that the pipework layout was corrected from the layout which caused so much crap in the old system?
--
Ed Sirett - Property maintainer and registered gas fitter.
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In a message posted Sun, 1 Apr 2007 21:23:58, you wrote...

Thanks again for the reply, Ed, so far the DS40 is working and we *seem* to have a happy ending.

Agreed. The inner front sealing panel was slightly distorted, but having assumed reasonable robustness and shock resistance of the heat exchanger, there seemed no reason to reject it.

Good to know, thanks.

Duh!
The power flushing appeared adequate at the time, plenty of black gunge running through to clear on each rad, though with hindsight, a week's descaling in advance might have loosened stuff we're now seeing. Funnily enough I had thought about a Magnaclean filter when I installed the boiler but had observed that the typical red powdery suspension in earlier F/E tank washings didn't seem to be attracted to the magnet I dropped in the bucket and anyway, it was going to be difficult to fit here because of adjacent pipes. Having now tested the scale from the pump with a magnet I'm sure it would have saved me :-(

The story so far, and sorry for the essay... Conventional Y plan, feed and return system, pump located horizontally about 1 foot to the side of the boiler outlet feed and hence there's a rather cramped collection of fittings to cater for the 22mm expansion and 15mm feed (in that order from the boiler) down from the roof space. It's in a 15 year old two storey house, but we're pretty sure that the previous occupants cared as little for the heating system as they did for the rest of the (desecrated) place. The original boiler was a Myson Economist which was unloved because even at the lowest temp setting it had a tendency to boil up occasionally and pop the overtemp trip as the TRVs closed even with towel rails and a small rad wastefully wide open for it. And yes, pump overrun was wired and working correctly :-) Just watching it pour kWs of heat into the open sky was the last straw.
When we bought the place 4 years ago we flushed and (DS40) cleaned the system, fitted a new pump and gave it a good dose of inhibitor. Scaling around the feed pipe was so bad at that time that when draining down, water would only gurgle slowly from the F/E tank through a pinhole in the crud. Took a hell of a blast with 6bar of compressed air to (dramatically..) clear that. Since then we'd had no reason to suspect problems - no air build up in the rads, bottom of the F/E tank now pretty clean and clean water when rads have been removed for painting.
So last Summer, after much lurking here in uk.d-i-y I chose the Vaillant unit, then hired the Kamco kit, spent a happy 20 hour day with SWMBO (less happy) chemically washing the system using the old Myson for heat then sluicing out all the sooty black water to fresh clean. I then left clean water parked in all the rads whilst fitting the new 28E boiler and a new bypass valve. To my eternal regret I refitted the 'old' pump again, seeing as it was a mere 3.5 years old by then and pumping well. The system was then fully drained, reflushed with clean water and finally given a big dose of MB1.
So, 6 months later I have to agree entirely with your analysis, whilst plenty of fine sludge was cleared at the time, there must have been well secured scale that wasn't shifted in that power wash. Perhaps the grand kids have recently been better at thumping radiators than I was. The washings presently coming from the system are crystal clear with just very occasional tea leaf/finger nail sized flakes of black scale. It seems that the pump and boiler have probably been the only constrictions to filter these flakes.

In parallel with your kind authoring of this, I managed to coax the entire dissolved contents of the DS40 tub into the boiler and hot water circuit with almost none left in the F/E tank. Having found and set the continuous pump option for the boiler we noticed a much more encouraging gurgling water flow noise after just a few minutes even before firing the boiler. I set the boiler output to a 5kW limit and let it run with just the hot water load for a while until braving a higher output. After a good few hours running with the full concentrate in the hot water loop we've opened the system up to one big radiator in the lounge (SWMBO was shivering..) and the boiler has since been run up to almost full output at 75 degrees without even a sizzle. This is how it's remained with the pump at 24/7 until this morning when later on I shall gradually add more of the rads back into play and leave the DS40 for the rest of the week.

Well, it appeared correct to me; simply that the previous occupants had probably let it run 'spongy' for years with air in the rads allowing constant pumping over. It had all seemed fairly clean after our initial purge and subsequent attention to bleeding rads. My big mistake was not to fit another new pump along with the boiler and to assume without splitting and examining it, that it was probably quite clean at 3.5 yrs. The warning signs of slight vibration were probably there on reflection :-(
So thanks again for your thoughts and suggestions, I *seem* to be headed for happy ending, unless you now point out to me where the pipework layout is wrong and I've missed it...

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Bob bob~AT+thecopse~DOT+net

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On Mon, 02 Apr 2007 10:02:46 +0100, bob wrote:

I have seen this type of debris once before on the aftermath of a previously very badly abused system. The flaky scaly bits seem to make a bee line to the the plate heat exchanger in a combi). Eventually I think you'll win.
The only thing I would have done differently is to use a sealed system boiler and scrap the header tank and the suspect pipework near the boiler.
One of the passive descalers ( I think these are essentially washing soda/Calgon/phosphate based) might be useful to help soften and break up any remaining leaves.
I think DS40 is not meant to be left for any length of time, IIRC.
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Ed Sirett - Property maintainer and registered gas fitter.
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In a message posted Mon, 2 Apr 2007 21:48:17, Ed Sirett wrote...

Thanks again for taking the trouble to follow up, Ed. Latest update is that about 5 or 6 of the rads are now in circuit and the boiler's been purring away all the way up to a full 30kW output without a murmur, so I think I may have got away lightly...
From the Fernox site:- "During system de-scaling DS-40 should be circulated for about 7 days under normal operating conditions (maximum of 4 hours is aluminium components are fitted). When separately de-scaling boilers, DS-40 should be circulated hot (restricted circuit see "Preparing the system") for 24 hours."
It was the contrast between the 7 days and 4 hours dependent on Al parts which amused me ;-)
So having given the boiler a super concentrated initial purge, I'll probably open up the rest of the rads by the end of tomorrow and risk it until the weekend. The pump will remain on 24/7 'til we drain it down. Then we'll see what floats out amongst the iron sulphamate and apple juice!
Thanks for the tip about the alkaline stuff, I'll bear it in mind if the tea leaves continue to pour out.
As a final thought, (and pushing my luck with the time you've devoted to this already), ever since installation with the standard horizontal flue kit (#303 933 - IIRC) the flue begins to howl/moan banshee style as the airflow picks up with output from 25 - 30kW. It develops one distinct pitch rather like a breathy pan-pipe quite noticeable 15-20 yards away. Is this typical or am I just plain unlucky? Now I promise I'll leave you alone! Thanks again to those who've contributed and followed the thread.
--
Bob bob~AT+thecopse~DOT+net

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replying to bob, nearlydeafmike wrote: We have had the same high air flow howl/moan from our EcoMax Pro 28E for 10 years now, but we're almost used to it now! That makes it possible our boilers were made about the same time, whatever that might imply. The point of this post is to ask if you ever got rid on this intrusive noise. I thought it might be down to flue length so I extended it by 3 metres for a short test. The noise stayed the same. In addition the boiler's started to make a clunking noise when the modulation gets to about half full flame. Then it stops when the modulation reduces. It sounds like it's from the combustion chamber and the only way I have nearly stopped this is to drop the outlet to 60C from 75C (when the clunking was nearly continuous). This is a problem that concerns me like your boiler's banging did you but there's no powerwash inheritance and the primary water's very clear.
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On 07/02/2017 12:44, nearlydeafmike wrote:

Are you also nearly blind ???..
You are replying to a post made *10* years ago..
Please stop using that silly website and install a proper newgroup reader.
Failing that, just read the bloody date !!.
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On 07/02/2017 13:15, Andrew wrote:

Interesting that we moved to this new build house about ten years ago and also had a similar issue with our new Vaillant boiler. Of course only being a few months old at the time we got the installer out who fixed it (not sure what he did). The faulty part was sent back to the boiler manufacturer at their request so perhaps they had a faulty build at around that time?
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