45 Amp MCB 'Buzzing'

[nottsnutts]

Evening all, I wonder if you can help.
I have an old Wylex type fuse box in my house with re-wireable cartridge fuses in it, the main box has 4 Cartridge Fuses and then I have a seperate box with a 45Amp cartridge in it that runs my shower.

Today I exchanged the 45Amp re-wireable cartridge fuse for a '45Amp minitrip MCB Type B' that I bought from Wickes (I know that this can be deemed reportable). When I did it I turned the main supply back on and then flipped the MCB to ON and then turned the shower on and came back to the box and the MCB was 'Buzzing'??

The Shower is 8.5Kw the circuit runs from directly beneath the meter into the seperate fuse board (containing the one MCB I fitted) to a pull cord switch and then into the Shower. It runs on 10mm Cable.

My question is what is the Buzzing?? is their a problem that has been there a while but that did not show up previously due to it being a re-wireable fuse?? also after searching I believe that maybe a 8.5Kw shower should be on a 40Amp MCB?? is this true and would this cause the buzzing??

I have turned the shower off at the fuse and the MCB untill I get a little help

 

[Spark123]

45A rewirable? A cartridge fuse isn't a rewirable!
Are all the connections tight?
My first thoughts are if it wasn't broken then why fix it?

 

[nottsnutts]

Apologies Spark I meant the old type Re-Wireable (two prongs and the wire is fed through the inside)
All I have done is pulled the old fuse out and replaced it with a new MCB so I'm unsure if the connections are tight. I understand what you are saying about why fix it but I believed a new MCB would be better than the old type fuse where wire is needed etc.

Is the 45amp overated or not and would this cause a buzzing? Also as I only have rewireable fuses on the other board I am unsure if the buzzing is normal or indicative of a problem that I wouldn't have found had I not changed the fuse?

Thanks for your response

 

[Spark123]

It's just I have not yet come across a 45A rewirable in a fuse board, they have always for some reason been cartridge fuses. The biggest I see is 30A . What make and colour fuse holder?
As long as the old one wasn't abused then there is little to go wrong with a fuselink. An MCB is a mechanical device - I haven't heard them buzzing loudly before. It could possibly be a faulty MCB, or could be a quiet sound being amplified by something?
Your shower will take 35A ish at full load, as long as the wiring etc is rated at 45A then this shouldn't pose a problem. It would have of course been beneficial to have tested the circuit to ensure that the loop impedance is low enough to trip the MCB if the shower went faulty.
You could try sticking the fuse back in and see if that cures it, I'd be tempted to check everything it tight too first but be careful of the meter tails as these will still be live with the main switch off.
If it is safety you are after then you may be better getting a spark in to replace the CU with one incoporating an RCD, assuming you haven't already got any RCD protection of course.

 

[kevindgas]

post some pictures of the original fuse and the replacement plus the board it is fitted to then i'm sure one of us can advise you properly

kev

 

[nottsnutts]

Hello all!
Since reading Spark123 post earlier about everything being tight I took the MCB out and had a good look at it and placed it back in and turned the Shower on and it was still buzzing a little so I 'wiggled' it a bit and the buzzing stopped- I get the impression it was just not a 'tight' fit originally as all seems well now.

Sorry if I wasted time but I was alittle bit worried and thought it best to ask. Thanks a lot guys, and Spark I do intend to have my CU replaced as soon as poss its on my iminent list

Once again Thank You both much apreciated.