Vaillant combi - fan noisy

[olo]

Hi folks,

I have Ecotec Plus 837 combi boiler. Few days ago I noticed that when I open multiple taps, the boiler starts to make slight noise. Everything is quiet when CH is on or with just one tap open.

I removed the cover to localise the noise and I suspect it's coming from the fan. To me it sounds like it's out of balance, kind of like washing machine when not properly leveled. Not very loud though - just doesn't sound like normal operation.

I have entered diagnostic mode to display fan speed and indeed - noise starts when revs > 380 rpm. I have entered second diagnostic mode and offset maximum fan speed from factory -26 to -100 (lowest value). That improved it slightly, but not 100%.

Is this behaviour common or does boiler need attention ? Is there anything I can further do or check ?

hope someone can shed some light ...

[The Natural Philosopher]

run out bearings do get noisy at certain RPM..but will continue to work for years in that state,.

Do you really care?

When the cost of fan bearing replacement is likely to be quite significant..

[Andy Hall]

This sounds as though the fan bearings are going class F.

Mr Geoff (cetltd) will be pleased to help you with a replacement I am sure

[geoff]

In message , olo writes

You don't know what you are doing, live with it and stop fiddling with the boiler - or pay serious money for a new fan

[geoff]

He is turning business away ATM because he can't cope with the sudden surge

[Andy Hall]

You mean everybody is fiddling with their Ecotec Plus 837 boiler?

[Ed Sirett]

Firstly: unless you really know what the "offset fan speed from factory" is for and what it really does I suggest you put it back like you found it.

How old is the boiler? If it's under two years it'll be under warranty and Vaillant will fix it for free.

How bad is the noise at maximum speed? What is causing the noise? Is it combustion instability (mixture too weak)? Is it bad fan bearings, balance or knocking on something?

[olo]

thanks for all your comments - see answers inline

ok, will do, I was thinking it lowers maximum fan speed by X rpm (from range 0-99), am I wrong ?

it's 6 months old, I have registered it with Vaillant and received 2 year guarantee. I know it's covered, but it's just my curiosity, I quite enjoy learning new things. Also I wasn't sure whether this is indeed fault as boiler operates just fine.

not too bad, although I can hear it with cupboard's doors closed, no big deal, but annoying because it's a bl**dy new boiler and it should be pleasure to operate!

it bad fan bearings,

that's the thing, the more I listen to where it's coming from the more I am unsure =( it's not knocking, it's not constant, like something was unbalanced, it may be coming from heat exchanger ...

Is it likely that fan bearing would go bad after just 6 months ?

How can I check whether it's combustion instability ?

cheers

[geoff]

In message , olo writes

Do you understand the ramifications of altering the set fan speed ?

no - you don't

You are changing one of the parameters in a feedback mechanism

then learn to leave things alone

by letting the Vaillant fitter tell you

[Ed Sirett]

My GUESS and I stress GUESS is that this parameter limits the maximum fan speed. It mayhave improved matters by simply capping the RPM of the fan. In effect this turns your 37kW boiler into a lesser model. I GUESS that this might be useful in a work around situation to prevent an excessive gas rate interfering with other gas appliances.

They are probably rushed off their feet ATM but there again you've paid for the right for them to come and fix it.

They will be slightly audible at full power (DHW) but if the noise is new then it's a problem. I find they are more or less inaudible when doing CH except at CH startup.

Inhibitor? Even after you've added it you'll need to wait a month for it take effect.

Not IME but Vaillant can sell a defective fan just like anyone else.

The noise is very distinctive about 5-25Hz. It would be unusual, every one I've fitted (about 6 units) has been absolutely correct out of the box. It is cause by having too weak a mixture of gas, it usually shows itself at ignition time and last no more than 10 seconds. In fact the noise is quite similar to an out of balance washing machine hence my suggestion. If you had a very poor gas supply you might get it at full power.

[olo]

It's probably good guess. There is other parameter (informative only) which displays actual and target fan speed. When I run my boiler on full DHW (all taps open) I get maximum fan speed ~470 rpm (with offset value set to -100). When I change the offset value to factory default (-27) I get maximum speed ~535 rpm.

Never thought of this. I have restored the parameter back to -27 (factory default) so it's not limiting boiler's output

the noise is new, boiler was quiet at full power (DHW) during initial few months (summer & autumn). Noise started a week, or so ago, coincidentally to very cold temperatures recently. Is it possible that the increased demand for gas is dropping pressure in network ?

How do you mean - is it normal that inhibitor cause noises ? It was added in August.

no funny noises at ignition time, only at full power

would it help to diagnose this if I measure gas pressure at meter/ boiler ?

cheers Ed,

[Ed Sirett]

No! the inhibitor also inhibits kettling but the effect is not instant.

I think you would be better to wait for Vaillant, if they think it's the gas pressure then they'll certainly measure it.

However whoever installed it should have made sure that the gas supply was adequate. This is quite demanding for a 37kW appliance.

[olo]

sure, I'll call them in the new year, as I don't want them faffing with the boiler during xmas, also they should have more time then and able to take more time to diagnose the problem

I am well aware of that. Original gas pipe had to be replaced with

28mm one as it's almost 15m from meter to boiler, I also have gas hob and gas fire connected to it. However, I don't see any change in noise behaviour if I run my two other appliances on the top of boiler

When boiler was commisioned, pressure drop was within allowed range, but that was during summer and I'm thinking if higher demand for gas now could put big strain on the network ...

Anyway thanks to all for *useful* contributions,

cheers