Ferroli Optimax 38HE Fault - Thumping Noise

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I wonder if anyone has come across the following fault in a Ferroli Optimax 38HE combi?

In central heating mode, some 30 seconds after the boiler first starts up, a motor/actuator can be heard to operate for just one second and then, 2 seconds after the motor stops there is often a loud thump/thud/bang. The boiler is in the loft, so the noise transmits as a thump. Inside the loft, the noise is more like the sort of noise you might hear if unburnt gas suddenly catches light - I'm not at all saying that's what the problem is (I really doubt it) but it's a good description of how the noise sounds close up and how different it sounds stood next to the boiler as opposed to on the floor below it.

In DHW mode, a similar thing sometimes occurs but timings are different: a motor/actuator starts only 5 secs after the hot tap is opened and runs for just one second; then, a second or so after it stops running, the thump - if it's going to happen - can be heard.

A few days after this started, the diverting valve stuck in CH mode. A plumber came out and did some investigation but did not remove the diverting valve. He drained some water off and diagnosed a faulty diverting valve. He was going to order a new one, but later I discovered the hot water was back online, so the diverting valve was now working, as was central heating. Nevertheless, the thumping noise is still sometimes occurring.

I don't know if the sticking diverting valve has anything to do with the noise or if it was a coincidence. If it is connected, then the continuation of the noise makes me think the valve may well stick again anytime at all.

Even though the boiler is 2.5 years old, I don't have a great deal of faith in it and am debating replacing it with a Vailant. I don't want to throw good money after bad e.g. paying for a new valve plus fitting only to find another snag etc. On the other hand, if I can identify this noise then I'll be in a better position to make an informed decision.

(Naturally, I've been wondering if that motor/actuator, which runs for a second, is the diverter valve's motor, in which case I'd be a liitle surprised that, in CH mode, a full 30 seconds passes before it operates, and I'd also be a little surpised that the diverter valve motor still runs even if the valve is already in the correct position - although if there is no position feedback, the boiler does not know where the valve is at any time and has to assume it's in the wrong position. If any of this is right, I wonder if the thump is a sticking valve suddenly freeing? However, I have noticed that the noise will occur in CH mode even if no hot tap was opened since the central heating last ran, in which case, unless the diverter valve always parks up in some neutral position, the valve should not have moved since last use?)

I'd really be grateful if anyone can shed light on what this thumping noise is.

Martin
 
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UPDATE TO POSTING

In my initial posting I said that, when stood next to the boiler, the thud/thump/bang sounded like unburnt gas suddenly catching light. Well, that must be what it is, because standing outside a few yards away from the vent, the noise is definitely an explosion - similar to a vehicle back-firing.

So that clears up any conjecture about the diverter valve suddenly releasing. Clearly, the sticking diverter valve problem was a separate fault (or at least an indirect fault).

Definitely time to replace this Ferroli pile of junk with something more reliable. And, having looked through the Which? site and had a taste of Vailant's consumer support, my focus is shifted towards a WB Greenstar 28CDi. I shall speak to Worcester Bosch consumer support with a few questions and hopefully I will come away with a warmer feeling than I had when speaking to Vailant.
 
Please tell me more; I'd very much welcome the benefit of your experience.

In what ways are Vailant boilers generally better than WB's?


Martin
 
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Sincere thanks. I know the Worcester Bosch Greenstar new CDi compact range possibly has not been around long enough to judge it fully, but do you feel this range also lags behind Vailant when it comes to reliability and build quality?

Martin
 
I'll wade in here and point out that Vaillant use a stainless steel heat exchanger and Worcester use Aluminium. Maybe it's just me but I don't trust ally heat exchangers.

I am not a pro, just an experienced DIYer.
 
I've fitted quite a few compacts. They look nice in the cupboard.

They are a pain to install and if they go wrong, they will be a pain to fix, which means bigger bills for you once it's out of warranty.

I'm not dead set against Worcester, i just think there are better options for the money.
 
I'll wade in here and point out that Vaillant use a stainless steel heat exchanger and Worcester use Aluminium. Maybe it's just me but I don't trust ally heat exchangers.

I am not a pro, just an experienced DIYer.

Having tig welded both aluminium and stainless steel and so got a real feel for the much greater thermal conductivity of aluminium over stainless, I can understand why they would want to use an aluminium heat exchanger. However, whether an aluminium heat exchanger gives any measurable improvement in efficiency would be another questiion. But I understand your hesitations. I wonder how long these aluminium exchangers have been in use - long enough to have a feel for long-term reliability? Is Worcester the first manufacturer to use aluminium heat exchangers? I know it's not quite the same, but aluminium cylinder heads are now taken for granted and provided corrosion inhibitors are used are problem free.

But it's another piece of the jigsaw for which I'm very grateful.


Martin
 
I think the reservations I have with ally heat exchangers are less to do with the water side of the system, than of corrosive combustion products coming into contact with the ally in the combustion chamber. Good point you raise about cylinder heads.

But I'm not allowed to go in there, so some input from experienced RGI's on the forum would be helpful.

My friend's Greenstar needed a new main heat exchanger after about 6 years. But WB have a good reputation. Certainly there are far worse boilers out there.
 
I've fitted quite a few compacts. They look nice in the cupboard.

They are a pain to install and if they go wrong, they will be a pain to fix, which means bigger bills for you once it's out of warranty.

I'm not dead set against Worcester, i just think there are better options for the money.

Fortunately, the boiler is in a well-lit, boarded-out loft with unlimited, unhindered access. So a compact would be pointless and an unnecessary maintenance handicap.


I get Which? magazine and I try to be somewhat circumspect over their recommendations (from experience). I also head for the customer reviews and the one-star reviews rather than the glowing 5-star ones. Having said all that, Worcester comes out top in brand reliability with Vailant so close behind as not to make any difference. And from my phone calls to both Vaillant and Worcester (and my use of their web sites), I can endorse the earlier comments about Worcester's better customer support.

But as to "I'm not dead set against Worcester, i just think there are better options for the money." which brands do you have in mind?

Martin
 
Vaillant and Intergas. I also fit slot of Glow worms.

It's amazing that Worcester seem to win Which almost ever year isn't it. Wow they really must be good. I wonder what the criterion for winning is ?

Do they have to pay large sums to have theyre products tested ? Quite a lot of kudos to winning that award. Not that engineers pay any attention, and rather go on they're experience of installing and repairing them.
 
Vaillant and Intergas. I also fit slot of Glow worms.

It's amazing that Worcester seem to win Which almost ever year isn't it. Wow they really must be good. I wonder what the criterion for winning is ?

Do they have to pay large sums to have theyre products tested ? Quite a lot of kudos to winning that award. Not that engineers pay any attention, and rather go on they're experience of installing and repairing them.

I don't think so; I think you can be totally assured of the impartiality of Which? They don't accept any advertisements at all - hence the relatively high cost of each mag when averaged out over the year. And I believe they go out and buy all the items under test rather than accept 'samples' from manufacturers. But it's one thing to do mainly technical testing and another to have real-life inputs from consumers and maintainers; and to Which's credit, their web site has the facility for customers' reviews of each product, and there are plenty of occasions where consumers have been scathing that they were swayed into buying a product that was a Which Best Buy. Hence, I use Which as just one piece in the jigsaw and then I like to hear the views of real people, which is why I'm so grateful for the advice I've had in this topic. So you're dead right to be sceptical but I think you can be sure they are impartial but you've got to keep an open mind and question things like: the weightings Which gives to various features that make up their scores as well as a host of other factors, otherwise you can drop a major clanger if you blindly chase the test scores. It's a bit like hearing that inflation has fallen to 2% and thinking which planet are these statisticians buying their groceries on?

Martin
 
really ? and at one point "Which" no1 boiler was a Ferolli if you want to know a proper opinion of boilers ask a breakdown engineer not an installer and definately not Which
 

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