Noisy system (can't see the specific problem in the FAQ)

[geoffa]

As part of our house renovation last winter, the builder's plumber fitted a Viessman conventional boiler with an Ariston unvented cylinder. Next to the cylinder there is a motorised valve with three pipes attached which I think sets the combination of HW/CH, and on a separate pipe there is another motorised valve which only has two pipes so presumably on/off.

All was fine in the spring when we had HW and CH on at the same times, just some background noise of water going through pipes - however now when the HW only is on there is (some of the time) a rising and falling sound a bit like a jet engine revving up and down while taxiing (it's not actually that loud, just enough to be really irritating). When we turn on the heating this noise stops immediately and vice versa.

We've got the builder coming back in a week or so to look at it - I can gurantee 100% that he will say that it's normal noise - but it's much louder than anything in previous houses we've lived in.

Can anyone suggest any diagnosis I can do before he arrives which will give us a clue as to what the problem is? The whole system including piping is totally new.

Any help very much appreciated.

Geoff

 

[Llan1observer]

the valve with three pipes is your 3 port valve and does what you say, the other is there as a safety device for the unvented cylinder.

you first need to find where the noise is loudest. eg around the boiler or cylinder.

 

[Razor900]

Does the system have a bypass fitted after the pump and before the valve?

 

[jameshere]

" the builder's plumber " !, oh dear, oh dear, let's hope not.

Let's hope that was, the builders fully trained and qualified and registered heating engineer, who was also fully trained on that particular boiler, and who doesn't own a ten gallon hat, spurs, or a pair of six shooters.

What I would do is, contact the boiler maker, and find a qualified engineer in your area who has been trained by the manufacturer on their boilers, and get him to check out the system.

http://www.viessmann.co.uk/find_an_installer.php

If the builder is found to be at fault, present him with the bill for rectification when he arrives, he'll like that !.

Seriously, if his installer knew what he was doing, why did he leave the system with a fault in the first place, you are obviously, ( and probably rightly ), already suspicious of him, and perhaps an annoying noise was the least of his possible errors.

If nothing else, ask the manufacturer if those noises ARE normal, guess what their answer will be.

 

[DP]

Geoffa, you do not need a Viessman trained engineer as (most likely) fault is not within the boiler.

What you do need is a person who is qualified to fit unvented cylinder with in depth knowledge of system controls.

From your post it sounds as if one of the valves is not opening but boiler is getting a signal to fire and run. It seems a little stupid to fit a three port valve as well as a two port. I would have fitted two two ports and a bypass valve (unless the makers indicate otherwise)

I wonder is the redundant three port outlet could be plumbed to bypass valve.

 

[geoffa]

Thank you all for very swift suggestions, but apologies, I've misled you.

(Further info is that the cylinder is "solar-ready" in case the economics made it worth it at some stage. I know that before installation they took advice about connection to boiler only not solar, and at this stage can only assume they followed it!)

The system is actually controlled by two 2-way valves. So answer to Razor900 is that above the pump the pipe splits into two 22mm pipes - one goes to a two way valve (A) and then the water cylinder just below the centre; the other immediately splits - one 22mm goes into the other 2-way valve (B), then vertically down through the floor; the other is 15mm through a red gate valve (permanently open) which then joins a 22mm into the bottom of the cylinder (with valve by the tank), in the other direction again down under the floor.

It is when valve B moves (presumably to CH?) that the weird noise stops immediately. The only time I have seen valve A move is when the cylinder stat says the water is hot enough.

Like DP I (absolutely no expert) suspect that the problem isn't actually with the boiler (there was an immediate problem after installation for which the Viessman specialist came out and changed the whole control board(?) - but didn't examine the whole system as far as I know) - and anyway it is fine when HW and CH both on as they were in the winter.

I certainly need to take advice, but any further advice or suspicions would be most helpful in the meantime.

Thanks again and rgds

Geoff

 

[DP]

When you ask for HW on the programmer, does the valve open? Does the boiler fire right away or some 15 seconds later?

 

[geoffa]

Hi, I thought I'd replied to this earlier but it's not appearing, so I'm trying again.

The valve (A in previous posting) starts to move immediately (not sure if it's opening or closing but the manual valve moves from slightly slack to totally slack). The pump starts, and the boiler fires, ~11 secs afterwards.

thanks again,

Geoff

 

[gas4you]

which then joins a 22mm into the bottom of the cylinder (with valve by the tank)

Are you by any chance saying that this is another gate valve? If so open this further.

If it is, it could be being used as a balancing valve and has been shut too far.

 

[Agile]

We have to make some interpretations of the descriptions given by the OPs.

In this case I am pretty sure that what he is describing is the boiler varying its power output as that is pretty much the same kind of system as in an R-R RB211 jet engine anyway.

That guess can be confirmed by listening outside by the flue as it will be loudest just there.

Also I would guess that the early fault was the F4 fault and the grey ignition unit was changed for a black one. Sometimes the Viessmann service agents change the PCB as well but my local says they rarely fail and 98% of the time its only the ignition unit.

Back to the current problem! If I have guessed correctly then I expect its a temperature time control constant which is conflicting with cylinder flow.

One suspicious aspect is this 15mm red wheel gate valve which is fully open! I would guess this is a manual bypass! If the OP will close it and then open it just one and a half turns and see what effect this has on the situation it may help us to understand whats going on.

Knowing the size of the property and the boiler model would also help as its quite likely its oversized and not set to the actual power required.

Tony

 

[geoffa]

Folks I really appreciate the thought you are giving this. Unfortunately I am now working away from home for the rest of this week but will post additional info early on Saturday.

Rgds and thanks again

Geoff

 

[geoffa]

Some further info in response to questions/suggestions:
- the boiler is a Viessman Vitodens 100 and the fault was indeed an F4 fault (suspect someone here knows what they’re talking about…)
- the control panel is I think the bit which flaps down at the bottom front inside the outer casing? - if so it is dark grey (?black) and the smaller panel which clips on the front with the display and temp control is white
- it is installed in a 3 bedroom 2 (was 3 till last winter) recept house with 8 rads and 3 heated towel rails
- although I described the noise as like a jet engine, it is actually somewhere in the water circuit, not gas - perhaps more like a whine which sometimes varies in pitch as when taxiing. It vaies in annoyingness from very down to not audible at all
- the noise seems to be independent of the noise of water going through the pump etc – there is no equivalent noise from outside the flue
- the noise seems to be most noticeable after 45/60 minutes of operation.

I have done all tests with HW only, as turning on CH as well the noise immediately stops (though the pump is still audible). The pump (and the other noise if valve set to HW only) continue for a number of minutes after the HW demand stops, and they both eventually stop together. During this period, manually turning the valve to inc CH eliminates the noise immediately, and turning it back it again restarts the noise even though the boiler is off.

I tried turning the red gate valve off then half on - closing the valve made no noticeable difference, but opening a bit after few minutes there was an audible rush of water and the pipe through the valve got very hot.

Thanks again and rgds

Geoff

 

[Agile]

I tried turning the red gate valve off then half on - closing the valve made no noticeable difference, but opening a bit after few minutes there was an audible rush of water and the pipe through the valve got very hot.

Thanks again and rgds

Geoff

Yes but was moving this valve making any difference to this whine?

Tony

 

[geoffa]

Thanks again Tony, apols not clear.

Yes when it is making the whine, closing the red valve fully stops the whine and all that is left is the faint pump/water noise. Opening the valve after 15secs or so, the whine returns after a short delay

Geoff

 

[geoffa]

Unfortunately I've tried again after a few minutes and this time it didn't make very much difference at all - in fact opening the valve again it went quieter almost immediately before going back to the annoying level.

So answer seems to be sometimes it eliminates or reduces the whine, but it is defnitely making a difference of some sort.

Geoff