Multiple FCUs

[JohnW2]

I refer the honourable gentlemen to my previous response: I avoid using double sockets on an unfused spur.....
That is what I do: I don't put double sockets on unfused spurs.

Ah, you must have confused me a bit. When you wrote:

I design and install to BS 7671: Amd 1. That allows me to install double sockets on an unfused spur. However, I prefer to wire accessories on the ring. That still doesn't stop clients overloading a double socket. But I always tell clients that double sockets are still 13A rated and should not be overloaded and will put that in writing so that we both have a copy.

... I took that to mean that you do install double sockets on unfused spurs (as do most electricians, as far as I can make out), although you prefer not to use spurs at all (which I'm sure goes for most of us - but convenience/expeditiousness sometimes prevails!). Apologies for the misunderstanding.

Kind Regards, John.

 

[securespark]

I would not think, for example, that your RF circuit has three accessories spurred off each other, but they are only running low-current appliances so not a danger.

Just out of interest -

If you came across the above, three FCUs side by side, how would you 'think' they were wired?
Having discovered that they are all 3A fuses, would you think that each subsequent FCU was wired from the load side of the previous FCU?

So that the second was protected by two fuses and the third by three?
Would you think the only logical way would actually be as is proposed?
Would you not have to check before any alterations?

1. I would like to think they had been wired in accordance with 7671, but would check.

2. No, I wouldn't think, I would check.

What's your point?

 

[JohnW2]

spark";p="2120004"]When I assess an installation for safety, I would not think, for example, that your RF circuit has three accessories spurred off each other, but they are only running low-current appliances so not a danger. I would record it as a potential at risk situation.

I can't quite see why I'm getting a bit of a grilling about documenting a potentially at risk situation.

You're not The discussion has moved on a fair way from there.

If you're being 'grilled' about anything (at least, by me) it's that you appeared to be suggesting that you would not document an unfused spur serving a double socket as a 'potentially at risk situation' if the spur was 2.5mm² and not all 'clipped direct', even though you knew that (despite your verbal and written instructions) either the present householder or a subsequent occupant could possibly plug 26A's worth of load into that double socket... but is seems that there may have been some confusions/ misunderstandings.

So, the question remains as to whether, if you came across it (rather than installed it) would you document the aforementioned double socket spur as being a 'potentially at risk situation'? (... and, if not, why not?)

Kind Regards, John.

 

[securespark]

Ah, you must have confused me a bit.

Now, hang on! Getting confused around here is my job. Hands off!

One of my pet hates is laziness in electrical design & installation. I hate it with a passion.

Why put a double socket where it's clearly intended to run two heavy-duty white goods machines? Why not run singles for each or switched spurs?

And doubles on spurs! Don't be lazy: there's always a better way. Either a triple or a double connected on the ring, rather than via an unfused spur.

I've just been to a job today: client complaining fuse is tripping and one side of double socket is not working.

Circuit is 2,5 radial fed from 15A 3036 to a double socket for a washer and a drier, then the radial continues to a second double.

One of the washer/drier sockets was burnt-out and the 15A fuse was popping with both machines on.... and a "qualified spark" had installed this knowing what the intended loads were. LAZY ****!!

 

[JohnW2]

1. I would like to think they had been wired in accordance with 7671, but would check. 2. No, I wouldn't think, I would check. What's your point?

I think EFLI has managed to make his point, by eliciting your answer (2) from you.

In other words, on finding three 3A FCUs sitting side-by-side, you would not assume that they had all been wired such that you could happily change the three fuses to 13A and then wire 3kW loads into each of them. Instead, you would (as I hope any of us would) check what was going on before you undertook any such potentially dangerous changes 'blind'. Or, put another way, you would not behave like the infamous Mr A.N.Other.

[in passing, I wonder what you mean by your answer (1) - i.e. what would you like to think was the manner in which these three 3A FCUs had been wired? All protected by an upstream 13A FCU, somehow separately wired from the ring final circuit, or what?]

Kind Regards, John.

 

[westie101]

Circuit is 2,5 radial fed from 15A 3036 to a double socket for a washer and a drier, then the radial continues to a second double.

One of the washer/drier sockets was burnt-out and the 15A fuse was popping with both machines on.... and a "qualified spark" had installed this knowing what the intended loads were. LAZY ****!!

Slightly off topic
But that pleases me that in a recent project for a washer, dryer & 2.5 kW water heater I installed 3 x 16A spurs.

 

[securespark]

Sorry, I missed that.

Yes, I would! It may be compliant but if there is a potential danger then I would feel I had to mention it.

Part of the problem comes because double sockets are not fused to 13A like triples are, therefore they are subject to abuse. A bit of common sense is needed. For example, a double socket in a lounge behind a TV is unlikely to be overloaded.

But abuse of an installation all goes back to design: if an electrician asks relevant questions when planning an installation, that can be minimised.

APOLOGIES: OMITTED WORDS ADDED.

 

[securespark]

Circuit is 2,5 radial fed from 15A 3036 to a double socket for a washer and a drier, then the radial continues to a second double.

One of the washer/drier sockets was burnt-out and the 15A fuse was popping with both machines on.... and a "qualified spark" had installed this knowing what the intended loads were. LAZY ****!!

Slightly off topic
But that pleases me that in a recent project for a washer, dryer & 2.5 kW water heater I installed 3 x 16A spurs.

The regs do recommend fitting dedicated circuits now for any appliance >2kW.

 

[JohnW2]

Now, hang on! Getting confused around here is my job. Hands off!

I'm afraid that the forum rules clearly state that no one member is allowed a monopoly on getting confused, or on confusing others

NowOne of my pet hates is laziness in electrical design & installation. I hate it with a passion. Why put a double socket where it's clearly intended to run two heavy-duty white goods machines? Why not run singles for each or switched spurs? And doubles on spurs! Don't be lazy: there's always a better way. Either a triple or a double connected on the ring, rather than via an unfused spur.

I totally agree with all that, and hope that many/most people do think in that way about new installations. The problem is that electrical installations evolve, and it's then when 'laziness' often rears it's head a bit more - usually in the guise of convenience, practicality and expeditiousness/ economy.

I'm obviously at least as guilty as anyone, as witness this thread. Whether or not I include the fourth FCU is really neither here nor their in terms of time/effort/cost - but it's been very interesting to see the spectrum of views about it. However, I obviously could wire all three FCUs into the ring but, given that a spur is already there (and particularly given the loads I'm designing for), I am being 'lazy' is sticking with the spur (and, yes, with the 4th one, to keep everyone happy )

Kind Regards, John.

 

[securespark]

[in passing, I wonder what you mean by your answer (1) - i.e. what would you like to think was the manner in which these three 3A FCUs had been wired? All protected by an upstream 13A FCU, somehow separately wired from the ring final circuit, or what?]

Kind Regards, John.

I was just saying I would hope that they were compliant: either on the ring or protected by a 13A FCU prior if they were spurred off each other.

 

[JohnW2]

Sorry, I missed that. Yes, I would! It may be compliant but if there is a potential danger then I would feel I had to mention it.

Dare I mention 'confused' again? I thought the above meant that you would document a 2.5mm² unfused double socket spur as a 'potential danger' if any of the cable was not 'clipped direct' (on the basis that someone may unwittingly load it up to 26A), but then you go on to say ...

A bit of common sense is needed. For example, a double socket is unlikely to be overloaded.

...so I'm now not so sure what you meant!

Kind Regards, John.

 

[westie101]

Threads like this are certainly thought provoking!

As an example of it going horribly wrong. We design our LV system based on various ADMD figures, these usually work until other factors intervene.

Over Christmas 2009 the gas board had a major issue in the patch and gave out lots of electric heaters to their customers! Of course they took no account of our system which was quickly overloaded. The final upshot being the failure of about £10,000 worth of transformer.

 

[JohnW2]

I was just saying I would hope that they were compliant: either on the ring or protected by a 13A FCU prior if they were spurred off each other.

Fair enough - but you'd still obviously have to investigate which of those situations was the case since, even though compliant, the former of those possibilities would not allow you to wire in 3 x 3kW loads.

... all of which underlines the fact that you wouldn't "do a Mr A.N.Other" and rush straigh in to wiring those high loads without prior investigation of the circuit.

Kind Regards, John.

 

[JohnW2]

We design our LV system based on various ADMD figures, these usually work until other factors intervene.
Over Christmas 2009 the gas board had a major issue in the patch and gave out lots of electric heaters to their customers! Of course they took no account of our system which was quickly overloaded. The final upshot being the failure of about £10,000 worth of transformer.

There surely must be a design fault there - there surely should be some protection in place to prevent an excessive demand killing one of your transformers?

Kind Regards, John

 

[securespark]

Sorry, I missed that. Yes, I would! It may be compliant but if there is a potential danger then I would feel I had to mention it.

Dare I mention 'confused' again? I thought the above meant that you would document a 2.5mm² unfused double socket spur as a 'potential danger' if any of the cable was not 'clipped direct' (on the basis that someone may unwittingly load it up to 26A), but then you go on to say ...

A bit of common sense is needed. For example, a double socket is unlikely to be overloaded.

...so I'm now not so sure what you meant!

Kind Regards, John.

John, I am so sorry! It's late and I really should be giving it Z's at the moment and it shows!

The comment you quoted above should have read:

A bit of common sense is needed. For example, a double socket in a lounge behind a TV is unlikely to be overloaded.

My brain wanted to write this down, but my fingers obviously did not...


I'm off to bed. Sweet dreams!