Shower

floorboard222

If a shower is on full power for more than 15 minutes, can it cause a 32 amp fuse to blow?

meercat

floorboard222 wrote: »

If a shower is on full power for more than 15 minutes, can it cause a 32 amp fuse to blow?

Depending on the loading then possibly yes. Your shower should have an mcb tripswitch with rcd protection (rcbo combined unit)however

Sleeper12

floorboard222 wrote:

If a shower is on full power for more than 15 minutes, can it cause a 32 amp fuse to blow?

The KW of the shower makes a huge difference. I'm guessing that you need a 40amp rcbo rather than a 32amp trip switch

2011

As already stated to a large extent this depends on the size of the load.

I've seen 9.5 kW instantaneous showers showers on 32A B type MCB's running for years without tripping. That is of course over the rating of the MCB but it can take MCB's a long time to trip on an overload of this magnitude.

A fuse can be a different matter and the OP appears to be talking about a fuse. These can fatigue over time so yes they can blow instantly even when below the rated current. Just like bulbs, they can last 40 years or sometimes 2 seconds.

2011

As can be seen in the fusing characteristic curve below a 32A B type MCB will not operate when there is 40A flowing through it continuously:

Risteard81

2011 wrote: »

As already stated to a large extent this depends on the size of the load.

I've seen 9.5 kW instantaneous showers showers on 32A B type MCB's running for years without tripping. That is of course over the rating of the MCB but it can take MCB's a long time to trip on an overload of this magnitude.

A fuse can be a different matter and the OP appears to be talking about a fuse. These can fatigue over time so yes they can blow instantly even when below the rated current. Just like bulbs, they can last 40 years or sometimes 2 seconds.

An MCB must not operate below 1.13 In (rated current), and must operate within the conventional time (1 hour) at 1.45 In. So there are no guarantees with a 41A load on a 32A MCB.

That said, the fact that an MCB doesn't trip does not make it acceptable to use one rated less than the load it is expected to be carrying.

Risteard81

2011 wrote: »

As can be seen in the fusing characteristic curve below a 32A B type MCB will not operate when there is 40A flowing through it continuously:

Not quite true. Like I mentioned it must not operate with 1.13 In but must operate within 1 hour at 1.45 In. So with 40A flowing through it then it may or may not operate, and may take a substantial period of time to operate if it does.

2011

Risteard81 wrote: »

That said, the fact that an MCB doesn't trip does not make it acceptable to use one rated less than the load it is expected to be carrying.

A bit off topic, but agreed.

Risteard81 wrote: »

Not quite true.

I am just describing what is depicted.
Are you disagreeing with my interpretation of a the trend shown?

Like I mentioned it must not operate with 1.13 In but must operate within 1 hour at 1.45 In.

I didn't disagree with this.

So with 40A flowing through it then it may or may not operate, and may take a substantial period of time to operate if it does.

Yes, that I what I said and what the fusing characteristic curve illustrates.

So I'm confused, what is the bit we are supposed to disagree on ???

Risteard81

2011 wrote: »

So I confused, what is the bit we are supposed to disagree on ???

Apologies. I thought you were suggesting that it would definitely not operate as opposed to the characteristics being unknown and differing between devices at this current. I don't think we do disagree but have just misunderstood what each other was suggesting.

2011

Risteard81 wrote: »

Apologies. I thought you were suggesting that it would definitely not operate as opposed to the characteristics being unknown and differing between devices at this current. I don't think we do disagree but have just misunderstood what each other was suggesting.

Grand so

Maewyn Succat

floorboard222 wrote: »

If a shower is on full power for more than 15 minutes, can it cause a 32 amp fuse to blow?

Can you clarify if the shower is actually on a 32 amp fuse(highly unusual and not recommended) or if it's on a 32amp mcb or a 32amp rcbo(preferred but 40 would be better depending on size of shower).

floorboard222

The shower is 8.5kW. The shower's trip switch is 32 amps.

The 35 amp fuse that blew is a white cylinder fuse on the input to the trip switch panel. I'm curious as to why the 35 amp fuse blew before the 32 amp trip switch tripped.

Could it be explained by the fact that the shower had been powered on for 10 to 15 minutes?

Maewyn Succat

floorboard222 wrote: »

The shower is 8.5kW. The shower's trip switch is 32 amps.

The 35 amp fuse that blew is a white cylinder fuse on the input to the trip switch panel. I'm curious as to why the 35 amp fuse blew before the 32 amp trip switch tripped.

Could it be explained by the fact that the shower had been powered on for 10 to 15 minutes?

Is the 32 amp trip switch an rcd or an mcb? I'm guessing it's an rcd and that's why it didn't trip. There would be no good reason to put a 35 amp fuse and a 32 amp mcb on the same circuit.

listermint

floorboard222 wrote: »

The shower is 8.5kW. The shower's trip switch is 32 amps.

The 35 amp fuse that blew is a white cylinder fuse on the input to the trip switch panel. I'm curious as to why the 35 amp fuse blew before the 32 amp trip switch tripped.

Could it be explained by the fact that the shower had been powered on for 10 to 15 minutes?

Cylinder fuse on input to panel ?

Any photos

meercat

floorboard222 wrote: »

The shower is 8.5kW. The shower's trip switch is 32 amps.

The 35 amp fuse that blew is a white cylinder fuse on the input to the trip switch panel. I'm curious as to why the 35 amp fuse blew before the 32 amp trip switch tripped.

Could it be explained by the fact that the shower had been powered on for 10 to 15 minutes?

Is the fuse that’s blowing,the main fuse (knocking of all the power in the house)
If so then it should be rated higher (63amp)
Perhaps it would be prudent to have a rec check the installation

floorboard222

meercat wrote: »

Is the fuse that’s blowing,the main fuse (knocking of all the power in the house)
If so then it should be rated higher (63amp)
Perhaps it would be prudent to have a rec check the installation

Yes, the fuse that’s blowing is the main fuse (knocking off all the power in the house).

The house has 17 rooms, an emersion, and a shower.

floorboard222

meercat wrote: »

Is the fuse that’s blowing,the main fuse (knocking of all the power in the house)
If so then it should be rated higher (63amp)
Perhaps it would be prudent to have a rec check the installation

Before the electricity meter, there is a black box with 60/80A written on it. Would that be the house fuse you mentioned?

Deagol

Not an electrician so don't take much notice of me but!

I've seen on panels ELCB(?) with a small 32A round fuse as part of the same 'block', is this perhaps what the OP is talking about? From memory I think mine only knocks off sockets not lighting circuits if it trips.

I'm not at home so can't take a photo of what I'm talking about to hopefully someone else understands me!

floorboard222

Deagol wrote: »

I've seen on panels ELCB(?) with a small 32A round fuse as part of the same 'block',

Yes, the 35 amp fuse is on the panel. To access it you pull down a hinged plastic cover and screw open a plastic cap containing the fuse.

Deagol

Like this? Says it's the main switch but I think that is only for one part of the board?

floorboard222

Deagol wrote: »

Like this? Says it's the main switch but I think that is only for one part of the board?

Yes, the image looks similar.

63 A is written on the plastic cover. 63 A seems to be written on the one in the image.

Should the 35 amp fuse be replaced with a 63 amp fuse?

meercat

floorboard222 wrote: »

Yes, the 35 amp fuse is on the panel. To access it you pull down a hinged plastic cover and screw open a plastic cap containing the fuse.

What you have is a main neon switch fuse
Most domestic installations are protected by a 63amp fuse so I would say you should install a 63amp fuse instead of 35amp

Maewyn Succat

floorboard222 wrote: »

Yes, the image looks similar.

63 A is written on the plastic cover. 63 A seems to be written on the one in the image.

Should the 35 amp fuse be replaced with a 63 amp fuse?

Yes definitely. How long has the 35 amp fuse been there?

This would be why the 32 amp trip switch didn't operate. It wasn't the shower on it's own that blew the 35 amp fuse...it was the shower plus anything else that was using electricity in the house while the shower was on.

floorboard222

Maewyn Succat wrote: »

Yes definitely. How long has the 35 amp fuse been there?

It has been there for several years. Would it be a safety hazard?

Maewyn Succat

floorboard222 wrote: »

It has been there for several years. Would it be a safety hazard?

Did all of the power in your house go out when this fuse blew including lights and sockets?

2011

floorboard222 wrote: »

Should the 35 amp fuse be replaced with a 63 amp fuse?

DO NOT DO ThIS!!!

Normally the main fuse is 63A but it is impossible to assess the situation properly over the internet. A larger 63A fuse will permit larger currents to flow. Your board may not be able to safely handle these larger currents. The smaller fuse size may have been installed for safety reasons. Only a REC (Registered Electrical Contractor) should make this call following a proper assessment.

My advice is:

1) Replace the fuse with a 35A fuse if you know how to safely do this.
2) Call a REC.
3) Don’t use the shower in the meantime.

The 63A fuse will most likely be ok but you simply can’t take that chance.

As your home has 17 rooms if done properly I would expect much of the wiring and board to be “beefed up” as it would be for a commercial installation. As you seem to have the opposite (35A fuse) it raises questions about the standard of wiring in place.

Maewyn Succat

2011 wrote: »

DO NOT DO ThIS!!!

Normally the main fuse is 63A but it is impossible to assess the situation properly over the internet. A larger 63A fuse will permit larger currents to flow. Your board may not be able to safely handle these larger currents. The smaller fuse size may have been installed for safety reasons. Only a REC (Registered Electrical Contractor) should make this call following a proper assessment.

My advice is:

1) Replace the fuse with a 35A fuse if you know how to safely do this.
2) Call a REC.
3) Don’t use the shower in the meantime.

The 63A fuse will most likely be ok but you simply can’t take that chance.

As your home has 17 rooms if done properly I would expect much of the wiring and board to be “beefed up” as it would be for a commercial installation. As you seem to have the opposite (35A fuse) it raises questions about the standard of wiring in place.

This is the best advice and the reason why I asked above if all of the power went out with the 35 amp fuse. If it didn't then you should definitely get your board checked by a REC.
Has there been additional wiring done? I'm assuming it an older house.

floorboard222

Maewyn Succat wrote: »

Has there been additional wiring done? I'm assuming it an older house.

It's a 200-year-old house that was completely rewired in 1988. The shower was added in 2009.

2011

floorboard222 wrote: »

It's a 200-year-old house that was completely rewired in 1988. The shower was added in 2009.

Enough said.
Even more reason to get it looked at by a professional.

Best of luck.

Risteard81

meercat wrote: »

What you have is a main neon switch fuse

Neozed ;-)

meercat

Risteard81 wrote: »

Neozed ;-)

Cheers (autocorrect)