Fuse blown - Switch did not trip

budgemook · 08-02-2012 12:22pm #1

Hey,

I have in my home what seems to be a pretty modern fuse board. There are a load of switches and one old style looking fuse.

The other day the fuse blew, the main switch didn't trip at all. Have no idea why, any ideas?

It happened again this morning. I'm going to have to find out what is causing the fuse to blow but for now I'm just wondering why the main switch didn't trip.

istabraq · 08-02-2012 1:06pm

Looks like you have a loose connection in your fuse board at the main fuse or isolating switch.the isolating switch will not trip as it is for isolation only.I would advise getting this checked fairly quickly because it is a fire hazard.

budgemook · 08-02-2012 1:25pm

Is the isolation switch the trip switch? As in the main switch?

istabraq · 08-02-2012 1:44pm

yeah its the main switch that looks like a trip switch.Check if the cover of the fuseboard is warm or if there is a smell from fuseboard

budgemook · 08-02-2012 3:02pm

istabraq wrote: »

yeah its the main switch that looks like a trip switch.Check if the cover of the fuseboard is warm or if there is a smell from fuseboard

Cheers, will do.

Bruthal · 08-02-2012 5:31pm

istabraq wrote: »

Looks like you have a loose connection in your fuse board at the main fuse or isolating switch.the isolating switch will not trip as it is for isolation only.I would advise getting this checked fairly quickly because it is a fire hazard.

Loose connections themselves dont usually blow fuses, although anything seems possible.

A loose fuse itself might contribute to it from severe overheating of the actual fuse.

The main switch is usually just an isolating switch alright, and wont trip.

How did you check the fuse was blown budgemook? There may be a loose connection and the fuse did not actually blow, but replacing it re-made the bad/loose connection for a while.

meercat · 08-02-2012 5:45pm

i wonder have you overloaded your fuseboard
what appliances(shower/immersion/cooker etc)were you using at the time

perhaps you replaced the fuse with a lower rating one
it should be 63amp if it is the main fuse
make sure you twist the fuse holder back in firmly

if you are unsure then its best to get an electrician to look at it

if you can post a pic of the fuse and board ,it may help

Solair · 08-02-2012 5:50pm

Most of those boards are set up like this:

Each final circuit (Feeding sockets/lights etc) has a circuit breaker (MCB) which trips if overloaded.

There's an RCD (which protects against electric shock) typically on older boards covering only the sockets, shower and a few other items.

The board itself is protected by a main fuse, which is the old-fashioned style bottle-shaped fuse in a screw in fuse-holder (Neozed / Diazed) and there's a main isolating switch which is just a heavy-duty switch. (Sometimes these are combined into a switch-fuse unit and sometimes it's an MCB instead of a fuse)

If, for whatever reason, you were running more appliances than the maximum rating of the board i.e. 63amps in most cases, then your main fuse might blow.

Nothing else would trip, as there might not be any fault.

You should call an electrician to get it checked over though, as there could be a more serious problem lurking like a lose connection causing a short circuit in the distribution board itself.

I would definitely get someone to look at it quite urgently though as it's not something that should blow under normal circumstances.

Bruthal · 08-02-2012 5:52pm

Good chance its simply an overloaded main fuse alright, many of them might of been 50 amp i think in them old style main ones. I forget now.

Solair · 08-02-2012 5:53pm

Did you, by any chance, have a lot of heating appliances on when it blew? (Heaters, water-heaters, electric showers, dishwashers, washing machines, dryers etc)

Or, have you added any major appliances, like electric showers to an older installation?

On a side note, 50A isn't THAT bad

My apartment in Spain, wired in the 1970s, had a single 16A RCBO for as the main fuse!!! The sockets and lights were on 6A and 16A MCBs. You could cut the power to the whole apartment if you tried washing clothes and boiling a kettle simultaneously!

1 bedroom apartment, with gas cooking and centrally provided hot-water and heating but, even so it was a VERY stingy electrical supply!

Bruthal · 08-02-2012 6:03pm

Solair wrote: »

On a side note, 50A isn't THAT bad My apartment in Spain, wired in the 1970s, had a single 16A RCBO for as the main fuse!!! The sockets and lights were on 6A and 16A MCBs. You could cut the power to the whole apartment if you tried washing clothes and boiling a kettle simultaneously!

1 bedroom apartment, with gas cooking and centrally provided hot-water and heating but, even so it was a VERY stingy electrical supply!

50A fuse will run for a fair while at 60 amps probably, but a shower on, and a couple of heaters or electric cooker rings, kettle etc would deteriorate it fairly quick id say.

budgemook · 08-02-2012 6:08pm

Thanks for all the replies

robbie7730 wrote: »

Loose connections themselves dont usually blow fuses, although anything seems possible.

A loose fuse itself might contribute to it from severe overheating of the actual fuse.

The main switch is usually just an isolating switch alright, and wont trip.

How did you check the fuse was blown budgemook? There may be a loose connection and the fuse did not actually blow, but replacing it re-made the bad/loose connection for a while.

The little thing in the back of the fuse popped out. I put tin foil in for a little while which made it work again until we got a new fuse.

meercat wrote: »

i wonder have you overloaded your fuseboard
what appliances(shower/immersion/cooker etc)were you using at the time

perhaps you replaced the fuse with a lower rating one
it should be 63amp if it is the main fuse
make sure you twist the fuse holder back in firmly

if you are unsure then its best to get an electrician to look at it

if you can post a pic of the fuse and board ,it may help

Yeah cooker, 2 blow heaters, shower, washing machine and some storage heaters were on. I understand that's too much, just surprised the trip switch didn't go. It was a 50 amp fuse in it so I replaced it with another 50 amp. I can post a photo later when I get home and I have notified the landlord who is going to get back to me shortly.

Solair wrote: »

Did you, by any chance, have a lot of heating appliances on when it blew? (Heaters, water-heaters, electric showers, dishwashers, washing machines, dryers etc)

Or, have you added any major appliances, like electric showers to an older installation?

On a side note, 50A isn't THAT bad My apartment in Spain, wired in the 1970s, had a single 16A RCBO for as the main fuse!!! The sockets and lights were on 6A and 16A MCBs. You could cut the power to the whole apartment if you tried washing clothes and boiling a kettle simultaneously!

1 bedroom apartment, with gas cooking and centrally provided hot-water and heating but, even so it was a VERY stingy electrical supply!

Lots of appliances

So it has 50 AMP. Would a 63AMP fuse even fit in?

EDIT - So what I gather from the above posts is my fuse, 50 amp, blew because I was running too many appliances and there was no other fault. Can I just fire in a 63 amp fuse or would the fuse board need replacing for that?

meercat · 08-02-2012 6:10pm

defo an overload so
try a 63amp replacement

you may want to get the timer for your storage heating contactor checked too

Bruthal · 08-02-2012 6:16pm

Yes in with the 63A. It will be the same size except for the contact cap at the end that goes in first, if its the old style one. That will be bigger, so hopefully there is a 63 amp guage ring at the back of the fuse holder.

budgemook · 08-02-2012 6:17pm

meercat wrote: »

defo an overload so
try a 63amp replacement

you may want to get the timer for your storage heating contactor checked too

Okay cool. 63 amp replacement will definitely fit? I'll go get one tomorrow.

Sorry, storage heaters weren't on, never turn those yokes on, it was the convection heaters built into the top of them. Rarely turn them on either but were on this occasion.

EDIT - Just saw second post. Thanks. Ah I'll just get one and if it fits it fits. No exactly a huge expense.

meercat · 08-02-2012 6:17pm

EDIT - So what I gather from the above posts is my fuse, 50 amp, blew because I was running too many appliances and there was no other fault. Can I just fire in a 63 amp fuse or would the fuse board need replacing for that?[/QUOTE]

in general,most fuseboards are designed to take a 63amp fuse

i would recommend an electrician to check the main cable size and your timer on the storage heating
he may check your loading with a clip on meter too

Bruthal · 08-02-2012 6:21pm

I wouldnt go using the shower or anything with much load on it, with tin foil in the fuse holder anyway. Wrapped around the old fuse is it?

budgemook · 08-02-2012 6:25pm

robbie7730 wrote: »

I wouldnt go using the shower or anything with much load on it, with tin foil in the fuse holder anyway. Wrapped around the old fuse is it?

It was until the fuse was replaced with another 50amp fuse. I know that's a dangerous thing to do.

meercat · 08-02-2012 6:27pm

robbie7730 wrote: »

I wouldnt go using the shower or anything with much load on it, with tin foil in the fuse holder anyway. Wrapped around the old fuse is it?

sorry robbie
just read back the last post
i agree with you

tin foil is a dangerous solution
replace with a fuse immediately budgemook

Solair · 08-02-2012 6:56pm

You can't just replace the 50A fuse with a 63A fuse without ensuring that the incoming cables and the installation can cope with that load!

A 50A fuse was installed because the electrician who designed your system back in the day knew the maximum load the wires were able to cope with. If you just put in a higher rated fuse, the cables are no longer protected and could just catch fire.

You should call an electrician and get it sorted out properly.

08-02-2012 9:20pm

robbie7730 wrote: »

A loose fuse itself might contribute to it from severe overheating of the actual fuse.

...which can sometimes cause the fuse wire to melt.

The main switch is usually just an isolating switch alright, and wont trip.

Exactly

meercat wrote: »

perhaps you replaced the fuse with a lower rating one

Why? What will this achieve?
The fuse is there to protect the cable. If the fuse has been correctly selected for the cable size replacing it with a smaller fuse is pointless.
There is nothing to suggest that the cable is under sized for the existing fuse size.

budgemook wrote: »

The little thing in the back of the fuse popped out. I put tin foil in for a little while which made it work again until we got a new fuse.

A great way to start a fire!

Solair wrote: »

You can't just replace the 50A fuse with a 63A fuse without ensuring that the incoming cables and the installation can cope with that load!

Exactly.

Get an electrician to check that the mains cable is no smaller than 16 sq.
If it is smaller than 16 sq. don't use a 63A fuse!

Changing fuse sizes up without knowing the cable size can be very dangerous. It can result in the cable melting before the fuse operates.

Bruthal · 08-02-2012 11:20pm

2011 wrote: »

...which can sometimes cause the fuse wire to melt.

Well i thought thats what i was saying. Perhaps not:)

2011 wrote: »

meercat wrote: »

perhaps you replaced the fuse with a lower rating one

Why? What will this achieve?
The fuse is there to protect the cable. If the fuse has been correctly selected for the cable size replacing it with a smaller fuse is pointless.
There is nothing to suggest that the cable is under sized for the existing fuse size.

I think your reading a post wrong again, i think meercat was suggesting the OP may have replaced the blown fuse with a smaller one, by mistake, not an unheard of cause for replaced main fuses to blow shortly after being replaced.

budgemook · 09-02-2012 12:05am

Solair wrote: »

You can't just replace the 50A fuse with a 63A fuse without ensuring that the incoming cables and the installation can cope with that load!

A 50A fuse was installed because the electrician who designed your system back in the day knew the maximum load the wires were able to cope with. If you just put in a higher rated fuse, the cables are no longer protected and could just catch fire.

You should call an electrician and get it sorted out properly.

Okay. Pretty clear fuse blew because a load of stuff was on. Replaced it with a 50amp fuse and won't be getting a 63amp fuse at all.

I knew I'd get a bit of stick for the tin foil but while the tin foil was on all that was left on in the house was the fridge and a light or two. I've done that loads of times and have loads of mates who have done the same for a quick fix (< 24 hours) and have never heard of a problem.

Thanks for the help everyone. I've notified landlord about what happened but I'd say it's just because of all the appliances being on at the same time. I was trying to understand why the trip just didn't go and to be honest, I still don't understand why but how and ever...

09-02-2012 12:30am

robbie7730 wrote: »

Well i thought thats what i was saying. Perhaps not:)

Yes, I was just "expanding" on your point.

I think your reading a post wrong again, i think meercat was suggesting the OP may have replaced the blown fuse with a smaller one, by mistake, not an unheard of cause for replaced main fuses to blow shortly after being replaced.

Yes, your right, my bad.
Pesky small scene on the iPhone!

Bruthal · 09-02-2012 12:33am

2011 wrote: »

Yes, your right, my bad.
Pesky small scene on the iPhone!

We will have a spec savers add for you soon, and i will be in the same que. Worse im getting myself with reading posts properly.

JOHNPT · 09-02-2012 12:51am

I think the 63amp fuse is slightly bigger than the 50amp fuse so it probably wont fit in the fuseboard if their is a gauge ring.

Fuse blown - Switch did not trip

Comments