Q about Fitting 3KW Heater to a 15A radial on Wylex CU

[jonathanheard]

Hi Folks,
I've recently installed a 3KW Air Curtain type heater for a friend at their new shop (they had no heating at all and were freezing!).. I am not a qualified Spark however I believe I am competent to be safe. Please do not flame me or this thread about certifications, I am aware that certificates may be required (are these different from the certs for domestic installations??)

What I am asking for in this post is for really two things:
a) Have I contravened any wiring regs and if so have can I bring my work into compliance?
and
b) Options to avoid overloading the circuit - perhaps it's fine but I don't think 15A is enough for 3Kw Appliance + 2x 13A Sockets.

The shop has an old Wylex Consumer Unit with two separate banks of unlabelled fuses (8 each side I think). Unsurprisingly there is no RCD (I'm going to try and suggest that my friend buys some RCD sockets to replace the existing ones).
When establishing which fuse runs the Double 13A Sockets nearest the New Heater, I went straight for the two 30Amp fuses in the box but discovered that the two sockets were actually on a 15Amp fuse. So far as I could see/test, they were not part of a ring and were a radial circuit from the the CU.

At present the circuit is as follows:
15A Fuse in CU --> 2.5mm Grey PVC Black/Red LN+E Cable [approx 3 metres] --> Double 13A Socket --> 2.5mm White PVC Black/Red LN+E Cable [approx 4 metres in PVC Trunking] --> 13AMP Fused Double-Pole Switch with Neon --> 13A Mains Flex --> 2.5mm Choc Block above ceiling --> Heater's Flex.
N.B The bare earths have all been fitted with Green/Yellow sleeving.

There was no simple option to add a dedicated spur from the CU as it appears to be fully populated (although I did not have good access to it and could not remove the cover to see if any of the fuses were unused). Personsolly, I think both of this friend's shops need new CUs, but that's a job to save in case I get myself qualified.

At present the only other load on the circuit is a display case with 4x low wattage halogen display lamps (no more than 200W max load, but they're probably 25W or less each) - These get back to the double-socket via a 4-way extension lead. I have down-graded the fuse in this extension to 5A for the moment.
I have instructed the staff that high current items such as hoovers, kettles or other heaters are not to be connected to the sockets on this circuit and have labelled them accordingly. This is obviously not satisfactory long-term.

So *if* I am correct and the 15A Fuse in question feeds *only* those sockets and the heater then I should be able to up-rate the fuse to at least 20 Amps (poss. 25A ?)

I would like to hear people's opinions about this and what options would be best:

OPTION: I could totally remove the double socket, thus dedicating the 15A line to the Heater (leaving the 13A fused switch inline)
Question: Can anyone think of any reasons this would not be safe or any caveats?

OPTION: I could increase the Fuse Rating....
Question: Given that the wire is 2.5mm all through, what's the maximum safe Fuse rating? (MCB Rating?)
Question: Can I replace a single Wylex fuse with one of their MCBs or must the whole board be done?
Question: Regardless of the cable thickness, what minimum Fuse rating would officially be required to support a 3KW Heater plus two 13A sockets on one spur? (I've seen mention of calculations based on 30% of load above 10A for things like domestic Ovens/Cookers, but I think this heater draws a far more consistent current - Can anyone tell me the formula)
-- Sub-Option: I could also replace the double socket with a single if it would help.

OPTION: I could replace the Double Socket with 5A Round-Pin sockets, perhaps??
Question: Wild idea which would avoid anything but lights being connected - any comments?

Thanks in advance to anyone who replies.

Regards
Jonathan

 

[Spark123]

Please call in a competent electrician.
Yes, they are different from domestic installation certs, it isn't a domestic installation
Ideally any fixed appliance over 2kw should be on its own circuit. A fuse should never be replaced with a fuse with a greater size unless it is determined that the circuit is up to it, a full EIC is required, iirc a 20A rewirable and 2.5 doesn't mix either.
An electrician will be insured and trained to deal with this type of installation, they may choose to remove the socket or determine another way of complying with the regs.
If anything should go wrong your best friend will become your worst enemy!

 

[EdwardCurrent]

Hello Johnathan,

The first thing I would do is return to the shop and pull that fuse.
Then you can work out what to do next.

Ed

 

[jonathanheard]

Thanks for the replies - I appreciate the thoughts and I understand the deal with the Certs.

Based on your advice so far:
The shop owner has another friend who is a qualified electrician. This person was unable to spare any time to install the heater, but I will try and get him to come in *ASAP* to do the EIC and assess any necessary changes.

So why did I do this?
Right now my friend's business is struggling (like most) and they did not have the funds to pay for a qualified Spark (other than the friend that didn't have time). More importantly, they were losing what little business they had because customer's wouldn't stay in the shop long and the staff were miserable.
I know - Excuses, excuses.....And a lawsuit would be a significantly greater cost than even the priciest electrician - But let's not have that conversation

Regardless of what I'm about to say below - You can rest assured that I will get my installation certified by a qualified electrician (or removed) ASAP - Even if my friend has to pay one for the time to asses it......

We can all get too bound up in rules and regs sometimes though

While the fuse remains at the original 15A I envisage the worst-case scenario to be a blown fuse if someone ignores the clearly labelled socket and plugs a hoover in while the heater's running flat out.

I want to learn (and I am about to attend a college open day to determine the best way to get qualified), so:
Again, taking aside the regulations and looking just at the physics; If my envisaged worst-case is wrong I will gladly listen and learn from any explanation of why I'm wrong..

Some of my thoughts on Certs and Regulations:

But first a question - Is part P applicable in any way to business premises. My lay understanding is that part P Building Regs are only relevent to domestic premises - Is this bit true?
And another question...Had I fitted a UK Mains plug to said heater and plugged it into an existing socket, would a certificate be required in that scenario?

I see so very many homes and businesses which have electrical installations which certainly would fail even my limited knowledge of the current wiring regulations, and I see regular dangerous practice: Plugs wired the wrong way round, 240v Ceiling Lights running via 13 Amp Mains Plugs, damaged insluation etc, etc.
My point is this: If an electrical inspector visited all the shops in my local precinct and assessed their compliance with current building and wiring regulations (even much earlier editions), I am 100% certain that not a single building would pass without at least some minor failures; possibly with the exception of a newly-built big-name store.
In my housing estate, I suspect only the social housing would stand any chance of passing. While my house was professionally re-wired before I bought it, I'm already out of step because not all circuits are on the RCD - So against current regs it is not legal.

Both the shops I've worked in and many other places I have seen, have no RCDs of any kind, no covers on the fuses in the fuse box, multiway adaptors hanging off of multiways hanging off of multiways. This is certainly not unique to friend's shops in any way.

Likewise, another friend asked me for help with a new ceiling light because after he fitted it the fuse was blowing (He'd wired live, via the switch, directly to neutral!) I sorted it out, but the metal patress for the metal light switch was unearthed! - His landlord claimed to have a valid inspection certificate for the premises.

So I understand the need for regulations and the whole reason I am posting on here (albeit retrospectively) is to make sure that the final result on this heater is a compliant installation; Although when you're working on a system that is years behind the current regs, it is difficult to worry about the latest regs without wanting to strip the whole lot out and start from scratch.

If I make it to becoming a qualified Spark on day, I never want to become a fly-by-night bodger.. But neither do I want to turn into a rule-book citing jobs-worth.

 

[333rocky333]

While the fuse remains at the original 15A I envisage the worst-case scenario to be a blown fuse if someone ignores the clearly labelled socket and plugs a hoover in while the heater's running flat out.

The trouble with these boards is although the carriage is marked 15 amp, the actual wire fitted in it, is not always 15 amp rated, and sometimes replaced with something totally inadequate.

Did you check what was fitted.

 

[jonathanheard]

The trouble with these boards is although the carriage is marked 15 amp, the actual wire fitted in it, is not always 15 amp rated, and sometimes replaced with something totally inadequate.

Good point! It didn't occur to me to check that, except I probably had little chance of accurately telling... I suppose to be sure I could just replace whatever's in the cartridge with a new piece of 15A to be sure.

To be honest, if a qualified guy tests the cable and thinks that up-rating the fuse is okay then I will be insistent on using a plug in MCB...

Any ideas what the deal would be with Certs had I just stuck a plug on the heater??

[/quote]

 

[rebuke]

You are correct that Part P only applies to dwellings, not to commercial premises.

BS7671 (the wiring regulations) is not law, so you do not legally have to follow it. The electricty at work regulations however are, and in a practical sense you'd have to have a very good reason to do work that's against BS7671 to still comply with the EAWR.

If you'd just stuck a plug on the heater, it's a little ambiguous - individual appliances don't need to have EICs (obviously), they should probably be PAT tested, but that's a different matter, however, because it's a permanent installation, it could be arguable that it shouldn't have a plug on it at all - I'm not sure of exactly what the regs say about this, without a copy in front of me to refer to...

In response to your comments about other domestic premises and shops - just because someone else has dodgy electrical set ups, does not act as justification for you having/creating a dodgy set up. You could hardly try and tell a judge "Oh but there's all these other people stealing things" if you were caught shoplifting.

You mention that it's difficult to worry about the latest regs without wanting to strip the whole lot out etc - in some cases unfortunately that is what is required to make new work compliant. Often you can just add to the existing set up in a compliant way, but sometimes it does need a huge amount of work done to bring it up to spec to be able to add something - it's no justification to do something non compliant just because of this...

 

[jonathanheard]

Hi Rebuke - Thanks for giving a really helpful and balanced reply.

I totally agree with your analogy about shoplifting - I was trying to avoid sounding like that I guess I failed

Interesting to hear your views about the plug approach - I'll see if I can check if the regs say anything specific about this.

But of course, although what I've done is certainly a permanent installation in all respects, the two big differences being that the 13A fuse is inside an SFCU not a plug and of couse wiring into the back of the double socket means there's two sockets left unoccupied instead of one. There's no reason why the container for the 13A fuse should make any difference, but I guess the second is significant.... But downgrading it to a single socket would make it comparible again (But *still* needing an EIC!)

Of couse, my 'what if' analogy is a litte daft because if there were a socket near the heater we might have just added a plug. I did contemplate simply extending the flex and adding a plug, but decided that was a bodge.
Besides the cable I used is proper PVC insulated 2.5mm whereas the only reel of flex I have is Rubber insulated and I didn't want to mess with 3Kw through that - It should be fine, but I have more faith in plastic).

Actually, this might make a very interesting point. Can an EIC be completed where cable with old colours has been used?

The cable in question was bought a few months before the colours changed, so I'm certain its physical characteristics are up to spec, but the conductors are red/black not blue/brown.....
But then we're dealing with the same Euro-Morons who have switched black for blue as neutral and royally shafted all logic by making th Blue-Phase use a black wire. I witnessed the result of someone getting that wrong on a new dish-washer (Not me! I don't mess with TP) - I just helped the repair guy source a local replacement for a fried 240v Contactor - He summised that its coil ened up between two phases and burned.

My fiancee made a valid point when I was discussing this - There's a chance the floor staff may have connected a couple of electric heaters to each of the sockets - more than one portable 2kw heater on that same circuit would almost certainly have popped the fuse.

All this chat is really by the by - I have emailed my friend to ask her for her electrician friend's number. I've also explained to her that we will need to pay someone else to inspect and certify the installation if he can't do it..
I'll post the final outcome when it happens, but I'm still interested in people experiences or other opinions about all this. It all part of the learning process!

Thanks
Jonathan

 

[Spark123]

You are correct that Part P only applies to dwellings, not to commercial premises.

Part P does apply to a commercial premises if it shares a common supply with a domestic dwelling.

 

[rebuke]

Part P does apply to a commercial premises if it shares a common supply with a domestic dwelling.

Ah good point, I'd forgotten that...

 

[flameport]

At present the circuit is as follows:
15A Fuse in CU --> 2.5mm Grey PVC Black/Red LN+E Cable [approx 3 metres] --> Double 13A Socket --> 2.5mm White PVC Black/Red LN+E Cable [approx 4 metres in PVC Trunking] --> 13AMP Fused Double-Pole Switch with Neon --> 13A Mains Flex --> 2.5mm Choc Block above ceiling --> Heater's Flex.

That is an untidy mess, but not necessarily dangerous, other than the choc block - why is it there, and is this fixed to anything or contained in any kind of enclosure? There is no such thing as a 2.5mm choc block either.

As for the rest of the questions - while asking questions is a useful way to improve understanding, from the type and number of questions you are asking, you clearly are way out of your depth and should not be working on electrical installations.

As for your friend using cost as an excuse - this is never acceptable. Besides, fitting a single heater is usually a straighforward job - did the friend even get a quote from an electrician?

 

[ban-all-sheds]

Besides the cable I used is proper PVC insulated 2.5mm whereas the only reel of flex I have is Rubber insulated and I didn't want to mess with 3Kw through that - It should be fine, but I have more faith in plastic).

Rubber is better in many ways - it has better mechanical strength, better resistance to many chemicals, better UV resistance and can tolerate higher temperatures....

Actually, this might make a very interesting point. Can an EIC be completed where cable with old colours has been used?

Ignoring the fact that an EIC probably now can't be completed at all, old colours are not, technically, a bar as it can be documented as a departure.

But then we're dealing with the same Euro-Morons who have switched black for blue as neutral and royally shafted all logic by making th Blue-Phase use a black wire.

That's not how it happened at all - there were very sound reasons for making the change (remind me again how long ago we changed flex colours), and it wasn't only the UK that had to change to get to a harmonised scheme. And the process was not decided by morons.

I witnessed the result of someone getting that wrong on a new dish-washer (Not me! I don't mess with TP) - I just helped the repair guy source a local replacement for a fried 240v Contactor - He summised that its coil ened up between two phases and burned.

No - what you witnessed was the result of someone incompetent making conceptually the same mistake that ignorant DIYers make when they assume that all blacks at a light are neutrals.

My fiancee made a valid point when I was discussing this - There's a chance the floor staff may have connected a couple of electric heaters to each of the sockets - more than one portable 2kw heater on that same circuit would almost certainly have popped the fuse.

A 15A BS3036 will pass 27A indefinitely, and could take an hour to blow at 30A..

 

[jonathanheard]

That is an untidy mess, but not necessarily dangerous, other than the choc block - why is it there, and is this fixed to anything or contained in any kind of enclosure? There is no such thing as a 2.5mm choc block either.

Flameport - I think you're being a bit unfair, I was only describing the components on the wire. The first half of it up to the Double Socket is the original installation which is all behind a wood-clad wall. The work I did comes very neatly through the wall and is fully enclosed in trunking up to the SFCU. At no point is the 2.5mm cable visible outside the trunking.

The reason the Choc Block (16AMP rated, by the way) is involved is to extend the very short flex on the heater - I didn't have an enclosure spare but the block is securely screwed to the wall and the cable is fully supported by regular clips from start to finish.
The block is above the suspended ceiling, so completely out of reach.

If the use of terminal blocks in this way is generally not acceptable it can easily be enclosed or replaced with as junction box.

Hey, ban-all-sheds (what have you got against sheds anyway?)
Sorry about the 'Euro-Moron' comments. I do understand the reason they changed it. The repair guy who came out to the aforementioned dishwasher told me he had seen several qualified electricians get the blue/black change wrong. I guess all we need to do now is rename the Blue Phase to Black and then we're sorted
My 'Euro-Moron' comment was inspired by the folks that thought it would be clever to made all fire-extinguishers red, regardless of their contents. Yeah, it's standard now across Europe but our system was miles better. Ho hum.

mistake that ignorant DIYers make when they assume that all blacks at a light are neutrals.

Funny that - It's exactly what my friend with the light problems had done. I never quite understand why so many people are simply amazed to find more than two (or even four) wires in a ceiling rose. Oh, and obviously the red sleeve placed on the live return from the switch is just to look pretty

A 15A BS3036 will pass 27A indefinitely, and could take an hour to blow at 30A..

Which explains why stepping up to a 20A fuse is not likely to mix safely with 2.5mm then.

Anyway - to bed with me, I've got to get up for work in <6 hours

 

[Spark123]

[If the use of terminal blocks in this way is generally not acceptable it can easily be enclosed or replaced with as junction box.

It is a fundamental principle that you should not be able to come into direct contact with a live conductor, if you look in the regs it comes under basic protection, one method of basic protection is to use enclosures.
It isn't what you know which will bite you, it is what you don't know
Please stop and call a qualified electrician in.

 

[ban-all-sheds]

Hey, ban-all-sheds (what have you got against sheds anyway?)

I mean this:

not this:

Which explains why stepping up to a 20A fuse is not likely to mix safely with 2.5mm then.

It's just about OK for Installation Method 20 - see para 3 page 6.