I've lost count of how many times I've come across this.
Supply to a garage:
When will people learn
Supply to a garage:
When will people learn
And again...
- Thread starter RF Lighting
- Start date
Sponsored Links
No overcurrent protection.
No it's just my DTs that make it look like it!
It was quite a neat installation, and has by the looks of it been installed by a professional, which makes it even worse to me that some one who ought to know better thinks an RCD provides overcurrent protection.
It was quite a neat installation, and has by the looks of it been installed by a professional, which makes it even worse to me that some one who ought to know better thinks an RCD provides overcurrent protection.
Sponsored Links
I'm really staggered by this.
This is a forum that from time to time screeches 'get a professional, get a professional - you don't know what you're doing', and yet, as a reasonably competent DIY'er even I could immediately spot what was wrong here.
If it was installed by a 'professional' I suppose it goes to show that you can't always rely on 'the trade' but more importantly, it goes to show that sometimes when people come here and ask for advice on how to do things, they may actually produce a result that is more professional than the 'professional'!
Is that enough 'professional's in one post? Christ I hope it really does only have one 'f'.
This is a forum that from time to time screeches 'get a professional, get a professional - you don't know what you're doing', and yet, as a reasonably competent DIY'er even I could immediately spot what was wrong here.
If it was installed by a 'professional' I suppose it goes to show that you can't always rely on 'the trade' but more importantly, it goes to show that sometimes when people come here and ask for advice on how to do things, they may actually produce a result that is more professional than the 'professional'!
Is that enough 'professional's in one post? Christ I hope it really does only have one 'f'.
- Joined
- 11 Jan 2004
- Messages
- 42,741
- Reaction score
- 2,634
- Country
It's very common for me too. I've seen it twice this month.
First, an RCD protected supply for two sockets in the porch. Bless him, he'd bothered to run a RFC for them on a 32A RCD, but no CPD.
Second, just like your pic, a garage supply ('cept mine was a Wylex RCD!). Again, no CPD.
What are these guys thinking?
Like yours, the one I saw was run in SWA, so it gives an air of knowledge to the install, but obviouslt there's a vital chunk missing!
First, an RCD protected supply for two sockets in the porch. Bless him, he'd bothered to run a RFC for them on a 32A RCD, but no CPD.
Second, just like your pic, a garage supply ('cept mine was a Wylex RCD!). Again, no CPD.
What are these guys thinking?
Like yours, the one I saw was run in SWA, so it gives an air of knowledge to the install, but obviouslt there's a vital chunk missing!
The Hager device in the picture with the SWA coming out of the bottom.
It is an RCD so it does not provide any overcurrent protection.
This should be a double pole RCBO at the appropriate current rating for the armoured cable.
When you buy an RCD it may say 30mA, 40amp on it. The 30mA is the earth leakage trip current, but the 40amp relates to the current that the contacts can handle without frying.
In the picture the current on the armoured cable is only limited by the DNO's service fuse (100amp or so). So a large fault on the SWA (eg a pitchfork through the cable) would cause all sorts of large frying, melting, etc.
It is an RCD so it does not provide any overcurrent protection.
This should be a double pole RCBO at the appropriate current rating for the armoured cable.
When you buy an RCD it may say 30mA, 40amp on it. The 30mA is the earth leakage trip current, but the 40amp relates to the current that the contacts can handle without frying.
In the picture the current on the armoured cable is only limited by the DNO's service fuse (100amp or so). So a large fault on the SWA (eg a pitchfork through the cable) would cause all sorts of large frying, melting, etc.
Yep, me to RF - Seen it too many times, and usually just like this!
Seen a few showers done like this too.
Me too, and there's usually another RCD in the outbuilding too
- Joined
- 27 Jan 2008
- Messages
- 23,669
- Reaction score
- 2,667
- Location
- Llanfair Caereinion, Nr Welshpool
- Country
I have many times picked up fellow tradesmen for selecting an RCD instead of a RCBO or an isolator instead of a MCB. The LoadMaster range of MCB/Isolators were a common error where up to 70A they were MCB's but the 100A which looked the same bar for the red plastic on the operating leaver was a isolator only.
Of course the orignal may have been a RCBO which has been changed later for a RCD.
Of course the orignal may have been a RCBO which has been changed later for a RCD.
Can someone point out the obvious please. Always like to learn
Lots of people have said 'overcurrent protection' but to make this clear in laymans...
It should have some means of protecting the circuit against overload and/or short circuit. In simple parlance, this is a 'fuse', but nowadays more likely a miniature circuit breaker (MCB). This will sense if too much current is drawn through the circuit, for example, by plugging in lots of heaters, which could potentially ecxeed the current carrying capacity of the wiring leading to a fire, maybe somewhere hidden like the loft. Or it may sense a sudden short circuit. Maybe if you hammered a nail through the wire.
In the picture the circuit is fitted with a Residual Current Device (RCD). I won't go into details (because I don't know them) but this senses a different set of faults common when one might be about to electrocute oneself and disconnects the power pretty much instantaneously.
So, a massive simplification... Your over current device (fuse,MCB) is designed to protect the circuit and by extension, your property, whereas the RCD is designed to protect YOU! Whilst a number of the fault conditions that may trigger the MCB might also trigger the RCD it is not designed to specifically do this, and therefore you can't rely on it.
While I appreciate this is not the way to do it - I do by the way assume that there is a MCB protected CU at the garage end - in broad terms the method used here is/was used for TT systems that failed to meet the disconection times. I.e. stick an RCD between Distrubutors fuse and the Consumer Unit.
So playing devils advocate if it was good enough for earlier regs why is not now?
So playing devils advocate if it was good enough for earlier regs why is not now?
Not uncommon to have SWA rises, and even PVC T&E rises to flats straight off the DNO isolator, dependent entirely on the main service fuse.
See this regularly. Perhaps regs have change subsequently.
View media item 42367
See this regularly. Perhaps regs have change subsequently.
View media item 42367
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
