Range Powermax 155x buzzing noise - I know what it isn't!

[eagle2]

Hi all,
Can anyone offer a though as to what the buzzing noise in my Powermax 155x might be please?

Basically, if the boiler starts up from cold/warm (e.g. after being off overnight), then over the course of about 5 mins a loudish buzz develops that can be heard around the house. If the boiler kicks in from being recently on (i.e. is warmer to start with) then the buzz starts much quicker / almost instantly. Thermal expansion and two interfering parts I perhaps hear you cry! Well, that's what I thought, but I don't believe it so (at least not the prime cause). Here's why....

• Buzz sounds about 50Hz-100Hz ish to my untrained ear.
  
  With the front Lower and Upper covers removed it definitely sounds like it's coming from the top end somewhere. Fan area or behind that.

Now here's the killer info!...

• If the boiler has been on recently and is thus warm, the burner doesn't kick in instantly (as the store is warm of course). So if I start either the C/H or turn on H/W, then I hear those respective pumps running - near silently. It's not those.
  
  When the stat kicks in to trigger the burner to top up the heat, first of all the Fan starts up... still no buzz, so it's not seemingly that either. HOWEVER about 5s after the Fan has kicked in the Burner is triggered, and it is then when the noise INSTANTLY appears. No delay, not even a couple of seconds. Burner light ON = top end buzz. I can manually turn the system on / off by the switch and the buzz comes / goes in direct relation to the Burner activation / deactivation - irrespective of all other pumps / fans.

So, that's what I have discovered. The bit I'm stuck on is having read the manual and the circuit diagram, I'm not clear what control logic follows the Fan power up, and what components are commanded on by the Burner activation. Is there another fan somewhere? Is this something related to the ignitor / gas valve perhaps? Is it perhaps a buzzing relay?

Any thoughts please good and knowledgeable people?

Many thanks.


(Disclaimer for the nervous types out there.... I'm an aircraft engineer, so am more than comfortable tinkering and fixing equipments / components that have gone wrong. But I'm not a gas engineer and won't tinker with the gas side of the system if that's what we think it may be. I'm just not the type to fork out for service visit, without concluding I can't fix it first. So there )

 

[Agile]

Sounds like the gas valve buzzing!

That can be the valve itself or the PCB.

But we dont give DIY gas advice on this forum.

Please grease the screw studdings well on the Boeings!

Tony

 

[eagle2]

Hi Tony,

Thanks for the input.

I can understand not giving DIY gas advice - that's fair enough. (As mentioned I wouldn't tinker on that side of the system anyway, but I understand that others might try).

For my own curiosity if you please:

Are these typically a component that fail, or is it a little rarer to have these go?

A quick google suggests these would be about £100. Are these treated as 'serviceable' or will a technician just simply replace it and throw the old one? (i.e Am I looking at £100 in parts to start with before labour on top?)

Finally, when I've had probs with the 155x in the past I had a horrendous experience with a local engineer, and ended up calling Heateam - on the advice of this forum, who I didn't know about until I was pointed their way. HT did a great job and got to the bottom of the problem straight away... but it was about £280. So is this a component that you'd expect most gas technicians to be able to fit, or would you just bite the bullet and call Heateam?

Cheers.

 

[Terry7556]

the heatteam lads will have received the necessary training to fit and set the gas valve up correctly (with a differential pressure meter).
the independant guy may or may not be qualified to do the work

 

[Agile]

Few independents have the skill or knowledge to easily diagnose those kind of problems.


I am not going to tell you which component is failed because that needs testing on site and is against our rules here anyway.

Please keep the Pitot tubes covered when not in use! Dont want any bugs getting in when parked!

Tony

 

[eagle2]

Tony,

Ok that's fair enough. I'm sure you can understand that I'm just after as much confidence as I can reasonably get that this is something gas-related, rather than something I'd attempt myself. I'd be a bit miffed if I paid ~£280 for a visit and it turned out to be a relay or something that I could fix myself!

If I could rephrase the question; based upon the info I've given, a buzz which develops over time as the system warms up, but once warm, generally always seems to be there and is directly linked to the Burner going on / off, (and is not fan / pumps), is something that in your experience *could* likely be a gas valve issue requiring Heateam to look at it?

Sure, you can't be definitive without testing, and sure my info might be incomplete/incorrect (so I'd not send you the £280 bill - don't worry!! ), but so far the gas valve is the likely candidate?

(Pitot tubes full of all sorts are a problem I once worked on - You'd be surprised what gets in those small holes!)

Terence / Tony - Thanks guys. Point taken on HT vs. an Independent. I have used both previously, but I know a fair few Independents tend to open the airing cupboard door, see a Powermax and then think 'What's this then?'!

 

[skodaman007]

you can pin point the buzzing noise to the gas valve.

BUT
You need to establish that you can work on live boiler electrical parts,satisfy yourself you know where the moving parts are and know where the hot parts are.
if you cannot STOP now.

If this was my boiler i would take front & top off of boiler,turn boiler on,wait for buzzing noise,pull off the plastic plug that connects the wires to the gas valve,if buzzing stops immediately its the gas valve,do not attempt to fit the plastic plug but turn off the electric to the boiler and then reconnect plastic plug.reset lockout if necessary.

I know i will get told off by the experts but this is a diy forum and i am now off to Aruba for 3 weeks so www.aruba.com/weather.aspx

 

[Agile]

In my view it is unlikely to be the gas valve at fault!

If you have the skill to do this safely, then use an oscilloscope to view the ripple on the supply line on the PCB.

Tony

 

[eagle2]

BINGO!!! I know exactly what it is now. Gas Valve Solenoids.

Had the top cover off. A listening-stick on anything connected to the Gas Valve carries the buzzing noise. Hence the noise is being transmitted along the gas supply pipe and radiating throughout the house. Gentle pressure applied to the side of the Solenoid completely stops the disturbance. What's suprising is just how loud the buzz is around the entire house vs. how small and quiet it is at the device itself. I guess the problem takes a few mins to emerge as the Solenoids are initially cold with less clearance between the cores / laminations. Once warm it's a rattling good fit on an AC signal.

Annoyingly the problem could have been eliminated in the first place if these were DC Solenoids (or better quality AC ones), but that would have course required a small rectifier unit and a cost increase to the boiler. Far easier to stay AC and then pass the cost on to the consumer a few years down the line when the buzzing starts and new parts are required!

Question now is what to do as it is literally the light pressure of a screwdriver and a finger that gives silence and nothing more. If it was not a gas-side part, then I'd just change it myself, but now I'm looking at quite a fee for the valve plus labour.

I'm feeling a non-ferrous, non-flammable 'wedge' coming on - at least temporarily

Anyways, thanks for all the pointers so far. I'll weigh up the options slower time.

Skodaman - cheers for the practical approach. A good suggestion, although I didn't quite get as far as needing to disconnect the supply at the valve. You'd be out the blast-radius in Aruba anyway

 

[DP]

Tony do you have a scope you carry around when you go to repair boilers? What chance is there of an end user having this instrument on hand.

 

[eagle2]

DP - Not sure if I'm reading it right, but it sounds like you're having a minor pop at Tony for offering advice that's 'too technical'?? Sincere apologies if I've read that wrong, but with respect....

In Tony's defence some people do have access to such equipments and know how to use them. (and have some understanding of supply ripples, filters, EMC/EMI, etc - plus in this case how un-clean power may not help an AC solenoid). I'm one of them. I design, test and interrogate mechanical and electrical systems for a living... But not on domestic boilers and C/H systems - hence my posting here was in seeking the guidance as to where to go from my initial checks. In this case more candid and technical answers were a real help.

Thanks to you chaps on here, I saved myself a potentially large fee now as the buzz is fixed with not a penny spent.

As I say apologies if I took your comment the wrong way, but just how I read it

 

[Agile]

What have you done to cure the buzz? Can you post a photo?

A very few gas valves do use a DC solenoid but not many.

One design problem is that its essential that the gas valves turn off reliably!

DC solenoids have a tendency to permanently magnetise the armature and that can cause them to stick !

Also since our mains is AC, then its best used as AC without the expense of components to convert to DC.

Tony

 

[eagle2]

Actually all I did in the end was torque the single bolt between the solenoids down a bit harder. It was tight to start and having initially removed it I noted it's only an M4 thread, so couldn't go too much, but it went just enough to preload the assembly sufficiently to stop the buzz... for now anyway. At least now the house doesn't sound like a big ultrasonic cleaning bath, which it did before