50A supply

Effects · 01-05-2014 8:44am #1

Taking a look at a job installing a shower at the moment. Fuse board looks old enough. Probably about 20-25 years old. The main fuse is a 50A and taking a look at the meter cabinet it looks like the cable from the meter is only a 10sq. Were many houses done like this in the past and is it capable of taking a T90 shower?

01-05-2014 9:09am

Effects wrote: »

Taking a look at a job installing a shower at the moment. Fuse board looks old enough. Probably about 20-25 years old. The main fuse is a 50A and taking a look at the meter cabinet it looks like the cable from the meter is only a 10sq. Were many houses done like this in the past and is it capable of taking a T90 shower?

I have seen houses with 4 sq. tails :eek:

In short, the answer is no.
The tails should be at least 16 sq. and by the sound of it the board needs replacing. There is a reasonable chance that the installation will need to be rewired. It would be best to get a registered electrical contractor to carry out a survey.

tp25 · 01-05-2014 9:10am

I think it is a fire hazard.

rewire

tomdempsey200 · 01-05-2014 9:26am

10sq tails and 50amp fuse was standard on domestic installations before the 16/63

not generally suitable for addition of an instant shower

tomdempsey200 · 01-05-2014 9:27am

tp25 wrote: »

I think it is a fire hazard.

rewire

speculation

you don't know that

homes all over the country are 10sq/50amp with no fires resulting

Effects · 01-05-2014 9:27am

So is it a case that it will probably trip out a lot?

tomdempsey200 · 01-05-2014 9:30am

Effects wrote: »

So is it a case that it will probably trip out a lot?

maybe excessive voltage drop

possible problems with main fuse

and any other unknown issues

if the meter was adjacent to board the tails would be rated for 63amp but best get a REC

Effects · 01-05-2014 9:37am

The main breaker is 63A but I think the old neozed fuse was only 50A.

tomdempsey200 wrote: »

if the meter was adjacent to board the tails would be rated for 63amp but best get a REC

About 4 metres from board to meter.

tomdempsey200 · 01-05-2014 9:47am

Effects wrote: »

The main breaker is 63A but I think the old neozed fuse was only 50A.

About 4 metres from board to meter.

a piece of 10sq clipped to a wall is rated for 63 amps

but then you've other considerations like the board and earthrod and bonding which may be related to size of main ocpd(fuse)

as well as esbn equipment which may or may not be relevant

Effects · 01-05-2014 9:52am

There's no earth to the hotpress so I was going to run a new one up and can't seem to find an earthrod but think it was sunk below the meter box as I can see a cable through the bottom of the box and it runs to the fuseboard. Can't do harm to put a new one in. As regards smoke detectors, there's none at the moment so is it something they have to have done if I'm carrying out the other work or can I just recommend it?

tomdempsey200 · 01-05-2014 9:58am

Effects wrote: »

There's no earth to the hotpress so I was going to run a new one up and can't seem to find an earthrod but think it was sunk below the meter box as I can see a cable through the bottom of the box and it runs to the fuseboard. Can't do harm to put a new one in. As regards smoke detectors, there's none at the moment so is it something they have to have done if I'm carrying out the other work or can I just recommend it?

get a REC and let them upgrade

Sir Arthur Daley · 01-05-2014 8:03pm

Effects wrote: »

There's no earth to the hotpress so I was going to run a new one up

Why do you feel it necessary to do this?

Effects · 02-05-2014 8:41am

Sir Arthur Daley wrote: »

Why do you feel it necessary to do this?

In the past I've always had to bring a 10sq to the hotpress and cross bond everything to that.

Sir Arthur Daley · 02-05-2014 9:33am

Effects wrote: »

In the past I've always had to bring a 10sq to the hotpress and cross bond everything to that.

I havent bonded a hotpress in nearly 15 years, whats the point?

tomdempsey200 · 02-05-2014 9:44am

Sir Arthur Daley wrote: »

I havent bonded a hotpress in nearly 15 years, whats the point?

you you mean when wiring a shower or what?

Sir Arthur Daley · 02-05-2014 9:46am

tomdempsey200 wrote: »

you you mean when wiring a shower or what?

Just a hotpress in general, what bonding would a shower need?

tomdempsey200 · 02-05-2014 9:55am

Sir Arthur Daley wrote: »

Just a hotpress in general, what bonding would a shower need?

none usually

Effects · 02-05-2014 5:14pm

So was I always instructed incorrectly in the past when told to bring a 10 sq to the hotpress?

tomdempsey200 · 02-05-2014 5:29pm

Effects wrote: »

So was I always instructed incorrectly in the past when told to bring a 10 sq to the hotpress?

there's usually some bonding in place

unless the installation needs upgrading

Bruthal · 02-05-2014 7:05pm

Sir Arthur Daley wrote: »

I havent bonded a hotpress in nearly 15 years, whats the point?

The main point of it is to reduce or eliminate the chance of potential differences in different metal parts in an installation.

In neutralized installations this is important for keeping everything at equal potential in the event of neutral failure upstream of the installation neutralizing point.

Sir Arthur Daley · 13-05-2014 9:18pm

Bruthal wrote: »

The main point of it is to reduce or eliminate the chance of potential differences in different metal parts in an installation.

In neutralized installations this is important for keeping everything at equal potential in the event of neutral failure upstream of the installation neutralizing point.

Hot-presses now and with a long time only use short bits of copper, the rest of a plumbing installation would be plastic pipe e.g qualplex or acorn. If you bond these bits of copper you are introducing a path by which an electrical charge could become present on metal, which, in the absence of the earth conductor, would have no possible means of generating or becoming charged with voltage.
If an electric immersion heater is fitted to the cylinder it must of course be earthed, as is the case with every electrical appliance, but the earth in the circuit supplying the immersion heater complies with ETCI Wiring Rules.

Bruthal · 13-05-2014 9:31pm

Well you can avoid hot press bonding if you like, thats up to you.

If the cylinder is indeed isolated from all else, that won't be easily proven.

But besides that, a bonded cylinder will pose little risk, as the events leading to the bonding rising above 0v, such as a failed neutral pre neutraslizing point, will have all properly earthed metal in the house at equal potential. And that's what is preferable, not different metals at different potentials.

Still though, with all the qualpex now, its not quite as it used to be.

tomdempsey200 · 13-05-2014 9:41pm

Sir Arthur Daley wrote: »

Hot-presses now and with a long time only use short bits of copper, the rest of a plumbing installation would be plastic pipe e.g qualplex or acorn. If you bond these bits of copper you are introducing a path by which an electrical charge could become present on metal, which, in the absence of the earth conductor, would have no possible means of generating or becoming charged with voltage.
If an electric immersion heater is fitted to the cylinder it must of course be earthed, as is the case with every electrical appliance, but the earth in the circuit supplying the immersion heater complies with ETCI Wiring Rules.

yes there is no need to bond a copper cylinder in isolation

but not all houses are plumbed in plastic by a long shot

tomdempsey200 · 13-05-2014 9:43pm

Bruthal wrote: »

Well you can avoid hot press bonding if you like, thats up to you.

If the cylinder is indeed isolated from all else, that won't be easily proven.

shouldnt be hard to prove

Sir Arthur Daley · 13-05-2014 9:47pm

Bruthal wrote: »

Well you can avoid hot press bonding if you like, thats up to you.

Its not my personal choice, bonding a hotpress with visible stubs of copper joined to plastic pipes which go throughout the installation is the wrong thing to do. Its the same as treating it as a radiator or bath that is plumbed with plastic pipe.

Bruthal · 13-05-2014 9:55pm

Sir Arthur Daley wrote: »

Its not my personal choice, bonding a hotpress with visible stubs of copper joined to plastic pipes which go throughout the installation is the wrong thing to do. Its the same as treating it as a radiator or bath that is plumbed with plastic pipe.

Radiators are unlikely to ever have immersion heater fitted to them, or motorised valves, shower pumps etc.

If its wrong to bond it, fair enough. I'm wrong then, nothing unusual about that. Its not a contest here. If it was, you're the winner:)

Sir Arthur Daley · 13-05-2014 10:03pm

Bruthal wrote: »

Radiators are unlikely to ever have immersion heater fitted to them, or motorised valves, shower pumps etc.

The earth in the circuit supplying what you have mentioned above is sufficient to earth that device.

If its wrong to bond it, fair enough.

Would you bond a hotpress with visible stubs of copper joined to plastic pipes, immersion fitted also?

Bruthal · 13-05-2014 10:05pm

tomdempsey200 wrote: »

shouldnt be hard to prove

How would you prove it? You're in a house, cylinder is tight in a hot press, maybe hidden pipes at the back? Not as easy in reality as hypothetically.

I have not seen many where you have copper cylinder, and all other pipes leaving it are easily visible, and qualpex.

Bruthal · 13-05-2014 10:16pm

Sir Arthur Daley wrote: »

The earth in the circuit supplying what you have mentioned above is sufficient to earth that device.

I think you miss the point of bonding, judging by that.

Now you have the earthed device, it is possible for potential difference to exist between it and the nearby metal of cylinder, should the device earth potential rise. I guess you will say that's not possible.

Would you bond a hotpress with visible stubs of copper joined to plastic pipes, immersion fitted also?

In my opinion such a cylinder should be bonded. You have said the immersion earth is enough. I have not yet seen a cylinder where every pipe leaving the hot press is qualpex.

tomdempsey200 · 13-05-2014 10:17pm

hotpress bonding is just a convenient location for main bonding of metallic service pipes

if they're there they get a bond

a cylinder with bits of copper doesn't need a bond

the main metallic service pipes may need main bonding somewhere else if only ground floor rads are plumbed in copper

Bruthal · 13-05-2014 10:34pm

tomdempsey200 wrote: »

hotpress bonding is just a convenient location for main bonding of metallic service pipes

Its a good location for potential difference to occur between bonded and unbonded pipes. If you can bond them all somewhere else then no need to do them there, but its hard to do them somewhere else and show they are properly bonded in the location they are easiest to touch,,,, the hot press.

The whole idea of bonding is to lock all metal to the same potential.

If the cylinder us totally isolated with no copper leaving the hot press, no bonding needed there, so arthur is right about that.

Sir Arthur Daley · 13-05-2014 10:35pm

Bruthal wrote: »

I think you miss the point of bonding, judging by that.

Do you feel that a hotpress needs to be bonded if an electrical component gets added to it? Just for clarity the house is plumbed in plastic pipe, 100% visible.

Bruthal · 13-05-2014 10:40pm

Sir Arthur Daley wrote: »

Do you feel that a hotpress needs to be bonded if an electrical component gets added to it? Just for clarity the house is plumbed in plastic pipe, 100% visible.

If the cylinder is connected to nothing only qualpex, no bonding is needed. Don't think I seen one yet that was exclusively qualpex.

Sir Arthur Daley · 13-05-2014 10:43pm

Bruthal wrote: »

If the cylinder is connected to nothing only qualpex, no bonding is needed.

Not alone is it not needed it should not be introduced, by doing so you are introducing a path by which an electrical charge could become present on metal, which, in the absence of the earth conductor, would have no possible means of generating or becoming charged with voltage.

Bruthal · 13-05-2014 10:48pm

Sir Arthur Daley wrote: »

Not alone is it not needed it should not be introduced, by doing so you are introducing a path by which an electrical charge could become present on metal, which, in the absence of the earth conductor, would have no possible means of generating or becoming charged with voltage.

In what circumstances would it become "charged" with voltage?

Sir Arthur Daley · 13-05-2014 10:49pm

Bruthal wrote: »

In what circumstances would it become "charged" with voltage?

Bad use of wording, presence of voltage.

Bruthal · 13-05-2014 10:51pm

Sir Arthur Daley wrote: »

Bad use of wording, presence of voltage.

Well I knew what you meant, but what circumstances will lead to that?

Sir Arthur Daley · 13-05-2014 10:53pm

Bruthal wrote: »

Well I knew what you meant, but what circumstances will lead to that?

If you had it bonded, like you said earlier if the earth potential rises.

Bruthal · 13-05-2014 10:55pm

Sir Arthur Daley wrote: »

If you had it bonded, like you said earlier if the earth potential rises.

And where is this voltage going to be perceived, what points of contact? Just curious now. Consider that every bonded item in the house is now at equal voltage.

Sir Arthur Daley · 13-05-2014 11:06pm

Bruthal wrote: »

And where is this voltage going to be perceived, what points of contact? Just curious now. Consider that every bonded item in the house is now at equal voltage.

Bonded items should not have a presence of voltage if the installation is 100% correct.

Bruthal · 13-05-2014 11:08pm

Sir Arthur Daley wrote: »

Bonded items should not have a presence of voltage if the installation is 100% correct.

A failed neutral at a mini pillar would disagree with you there.

Sir Arthur Daley · 13-05-2014 11:11pm

Bruthal wrote: »

A failed neutral at a mini pillar would disagree with you there.

The incoming neutral failing you mean?

Bruthal · 13-05-2014 11:23pm

Sir Arthur Daley wrote: »

The incoming neutral failing you mean?

Main neutral to mini pillar bar fails, we now have several houses with 3 phases but no neutral, like an imbalanced load.

Or, neural to one house fails before neutralising point.

So now we have voltage on bonded items in a perfectly wired installation.

Sir Arthur Daley · 14-05-2014 12:27am

Bruthal wrote: »

So now we have voltage on bonded items in a perfectly wired installation.

If nothing was on in the house we dont.

Bruthal · 14-05-2014 5:42am

An unrealistic scenario. And with the neutral failure to several houses, nothing on in a house won't mean 0v on it's neutral/earth.

14-05-2014 7:51pm

Sir Arthur Daley wrote: »

Not alone is it not needed it should not be introduced, by doing so you are introducing a path by which an electrical charge could become present on metal, which, in the absence of the earth conductor, would have no possible means of generating or becoming charged with voltage.

I know that you are referring to a small domestic installation and you are stating what the regulations are.

However this is not something that those of us that work in large electrical installations would normally see. When it comes to industrial installations standard procedure is to bond anything that is metal. This even applies to large conductive parts that are bolted together such as structural steel, ductwork, pipework, metal stairs, reenforced steel bars etc..

tomdempsey200 · 14-05-2014 7:57pm

I saw over on the UK forums that the structural steel can be used as a main bonding conductor

after it has been bonded itself

not sure if it's allowed here

Sir Arthur Daley · 14-05-2014 10:44pm

2011 wrote: »

When it comes to industrial installations standard procedure is to bond anything that is metal. This even applies to large conductive parts that are bolted together such as structural steel, ductwork, pipework, metal stairs, reenforced steel bars etc..

Lets take a metal stairs in an industrial unit, in you opinion is it better or worse being bonded, im not knocking the procedure or practice just curious of your opinion.

14-05-2014 10:57pm

Sir Arthur Daley wrote: »

Lets take a metal stairs in an industrial unit, in you opinion is it better or worse being bonded, im not knocking the procedure or practice just curious of your opinion.

Better for a number of reasons. This would include reducing the likelihood of "flashover" should there be a lightning strike. Better is not just my opinion, it is the opinion of a team of engineers that issued drawings and a detailed scope of work documentation specifically on the earthing and bonding of a large project that I was involved with.

Sir Arthur Daley · 14-05-2014 11:00pm

2011 wrote: »

Better for a number of reasons. This would include reducing the likelihood of "flashover" should there be a lightning strike.

You would be referring to an external stairs here though?

15-05-2014 5:46am

Sir Arthur Daley wrote: »

You would be referring to an external stairs here though?

Internal and external.
I will try to get you some photos.

50A supply

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