Hot Fuse

Johnnypanic

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Jul 28, 2001, 4:44:19 PM7/28/01

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Hi,

a 30amp fuse on my consumer unit has recently blow.

I`ve replaced the fuse but have noticed that it is quite hot to touch,
although still working. I assume this is not normal ?

BTW, the fuse is for an electric shower.

Any advice welcomed.

Thanks,

Johnnypanic

M Millar

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Jul 28, 2001, 6:13:56 PM7/28/01

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What wattage? I have a 40Amp breaker on mine, its a 8.5KW

Is the cable warm when the shower is running (Don't try and touch it while
in the shower! lol)

--
Regards

M Millar
ICQ: 59367262
"Johnnypanic" <johnh...@anythingirish.ie> wrote in message
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Ian Cooke

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Jul 29, 2001, 10:01:49 AM7/29/01

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To find the correct size fuse divide the wattage of your shower by 230, if
you find that the fuse you have now is to small, ask an electrician to check
that the installation complies to BS7671

Regards

Ian
M Millar <michael...@bigfoot.com> wrote in message
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Johnnypanic

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Jul 29, 2001, 4:10:07 PM7/29/01

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Ian Cooke <I...@ICooke.Freeserve.Co.Uk> wrote in message
news:9k14nj$1rc$1...@newsg1.svr.pol.co.uk...

> To find the correct size fuse divide the wattage of your shower by 230, if
> you find that the fuse you have now is to small, ask an electrician to
check
> that the installation complies to BS7671
>
> Regards
>
> Ian

Our house was only built 3 years ago and the showers were installed by the
electricians wiring the house at this time.
So it should be okay. (I hope!)

One thing I do find strange - I have another shower (exact same type) in our
ensuite. This also has a 30amp fuse, but is on the RCB protected circuits.
Is this significant ?

Thanks,

Johnnypanic

ch...@areti.co.uk

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Jul 30, 2001, 4:30:22 AM7/30/01

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Do you mean MCB (Miniature Circuit Breaker) or RCD (Residual Current
Dectector), they are two different beasts. I expect you mean MCB.
What is the current rating of the MCB protecting the shower in your
ensuite?

An 8.4kW shower will take about 36 amps at 230 volts so a 30 amp wired
fuse *will* get hot and, after several weeks or months will blow.

--
Chris Green (cgr...@x-1.net)

Johnnypanic

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Jul 30, 2001, 3:11:53 PM7/30/01

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> > Our house was only built 3 years ago and the showers were installed by
the
> > electricians wiring the house at this time.
> > So it should be okay. (I hope!)
> >
> > One thing I do find strange - I have another shower (exact same type) in
our
> > ensuite. This also has a 30amp fuse, but is on the RCB protected
circuits.
> > Is this significant ?
> >
> Do you mean MCB (Miniature Circuit Breaker) or RCD (Residual Current
> Dectector), they are two different beasts. I expect you mean MCB.
> What is the current rating of the MCB protecting the shower in your
> ensuite?
>
> An 8.4kW shower will take about 36 amps at 230 volts so a 30 amp wired
> fuse *will* get hot and, after several weeks or months will blow.
>
> --
> Chris Green (cgr...@x-1.net)

Sorry for the spelling mistake, I meant RCD.

Would it be sufficent enough to just replace both fuses (main bathroom &
ensuite) with 40amp fuses ?

Thanks,

Johnnypanic

Ian Cooke

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Jul 30, 2001, 3:59:49 PM7/30/01

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Johnny

As the house is only 3 years old I presume that the shower is protected by a
MCB if this is getting warm then there is either one of two things wrong

1) The showers current consumption exceeded the rated value of the MCB
or
2) There is heat conducted into and from a loose connection where the MCB is
affixed to the internal buss rail.

Check to see if the connections are tight, (isolate first of course :-) )

If is a semi enclosed rewireable fuse (BS3036) working at is rated current
then it will get warm after a period of time, I would suggest replacing with
a sufficiently rated MCB and for added protection a RCD as in your ensuite.

Johnnypanic <johnh...@anythingirish.ie> wrote in message

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ch...@areti.co.uk

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Jul 31, 2001, 4:38:10 AM7/31/01

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Only if the wiring is up to it, which I doubt. In general (there are
some exceptions relating to lengths of runs, type of enclosure, etc.)
if the shower is wired with 6mm^2 wire then it should be protected by
a 30 amp wired fuse or a 32 amp MCB. It needs to have 10mm^2 cross
section cable if you're going to change to a 45 amp MCB (for which I
*think* the equivalent wired fuse is 40 amp but I'm not sure about
that).

--
Chris Green (cgr...@x-1.net)

Dave

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Jul 31, 2001, 6:39:20 PM7/31/01

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Correct .. the fuse or breaker is there to protect the cable as well as the
appliance, just upping the size of the fuse because it is getting hot is a
no no, the information that is needed to make an assessment of your problem
is, what is the kiwi of the shower / s, what size cable feeds them, and what
is the rough length of run of the cable, if the installation has been
designed correctly the fact that the fuse is getting hot may indicate that
you have a loose connection, if you are unsure of any of the above I suggest
you get a electrician to take a look, better that than burning your house
down !

[DG]uk

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Dave

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Jul 31, 2001, 6:44:39 PM7/31/01

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Sorry
what is the KIWI of the shower / s, obviously should say kw (kilowatt) of
the shower /s
HA spell checkers you ether love um or you hate um.
[DG]uk

"Dave" <dave...@ntlworld.com> wrote in message
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Johnnypanic

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Aug 1, 2001, 6:41:00 PM8/1/01

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Dave <dave...@ntlworld.com> wrote in message
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> Correct .. the fuse or breaker is there to protect the cable as well as
the
> appliance, just upping the size of the fuse because it is getting hot is a
> no no, the information that is needed to make an assessment of your
problem
> is, what is the kiwi of the shower / s, what size cable feeds them, and
what
> is the rough length of run of the cable, if the installation has been
> designed correctly the fact that the fuse is getting hot may indicate that
> you have a loose connection, if you are unsure of any of the above I
suggest
> you get a electrician to take a look, better that than burning your house
> down !

Would the trip switch not activate?

BTW, the showers is 9.5KW.

I`ll check the connections in the attic at the weekend (or should I be
giving this a higher priority ?)

Thanks,

Johnnypanic

Kevin Spicer

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Aug 2, 2001, 7:19:46 AM8/2/01

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>
> Would the trip switch not activate?
>
> BTW, the showers is 9.5KW.
>
> I`ll check the connections in the attic at the weekend (or should I be
> giving this a higher priority ?)
>
> Thanks,
>
> Johnnypanic

9500W / 230V = 41A
Hardly suprising it blows a 30A fuse. Its probably only survived for so
long because cartridge fuses 'go' when the low melting point wire inside
them melts thus breaking the connection. Showers only tend to run for a few
minutes, not long enough for the fuse wire to melt through, but it will
weaken over time and eventually blow. Suggest
a) see if the cables get hot when the shower is running, if yes then your
shower is over rated for the cable - take baths!
b) call an electrician to properly check the rating of the cable & the
installation

If the installation can take the load of the shower, get the electrician to
upgrade the fuse.
If it can't, either get the installation upgraded to an appropriate cable
and fuse, or replace your shower with a lower rated one (30A fuse should
supply a 6.5Kw shower okay) - cheaper possibly but a 6.5Kw shower might not
be enough in winter.

Personally I would much rather have a circuit breaker (and RCD) on anything
electrical in the bathroom.