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mhar

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Holiday let sleeping 8+. Gas ch (combi) and cooking. 2 x Wylex rewireable cu's, pme (6mm earthing conductor!), no rcd protection. 16mm dno supply, prob 100A dno fuse, no rating on meter but likely to be 80A
1 x cu for normal (lights, rfc's) etc. 2nd cu 60A rating with 3 x 45A fuses feeding 3 x 9kW showers.
Was called in for simple switch replacement today and discovered above without looking too hard!
It is entirely feasible that holidaymakers return home from beach, kettle on, clothes in wash machine and all go for showers at the same time.
I am going to inform customer by letter of my findings and it would be nice to offer a solution. As I see it the possibilities are :-
1) Plumbing solution. Pretty new Greenstar combi so no stored water so not realistic
2) Supply upgrade. Overhead supply now undergrounded, told that rising feed unlikely to have the additional capacity required (even though don't want to increase demand, just want to comply with 7671) so likely to be very expensive
3) Reduce demand with something like Garo 3 way non-priority shower unit (from Meteor) but not really at all satisfactory.
4) Post problem on forum and pick peoples brains.
An additional problem is that it has been this way for 10+ years without the dno fuse popping or the house catching fire so may be difficult to convince the customer of the need for any work.
Another thought I have had is to replace the shower cu with an 80A mcb supplying 3 x 32A mcb's for the showers as a way of limiting the load. So 16mm from Henleys into 100A main switch, N out to dp rcd, L out to 80A mcb supply, 80A L load to dp rcd in, assuming I can get supply upgraded to 25mm (or if dno don't care using existing which is buried for 3m in render). Far from ideal but a crude way of limiting demand by use of an mcb.
Another variation of this (and to my mind better) is to have one cu for the whole house, one shower off a 32A mcb with another 32A mcb supplying a 2 way shower priority switch, such as the Garo 2 way. I have then limited my short shower demand to around 70A leaving 30A for the rest of the house.
Comments / advice / solutions welcome please. In true op stylee I am shortly going out overnight so will not be able to respond until the morning
 
Hmm, have a good think about it.
Start with diversity.
6mm earth conductor - you've checked the potential fault current and done the adaibatic equation to confirm it is too small?
Boiler - what has that got to do with the electrician?
How many baths, and why would you want stored water when the place may be empty for the coldest months of the year?
Supply upgrade - why? The fuse has never blown.
Think about diversity.
Reduce demand? Why? It has run for years with no problem, so why does it need changing?
If it does, why not put one of the showers onto the combi boiler?
Why would it catch fire?
Arent the final circuits rated correctly for the fuses?
And finally, think about diversity.

If you are worried about safety, push for RCD protection on all circuits. But, is there really a need? The property is clearly maintained, and the Duty Holder must know of the safety implications. A single upfront RCD would make the property far safer, albeit not fully complying with the second part of 314.1 (i), but I would be happy with that, as it affords a better safety margin than relying on a fuse for fault and overload protection.
Have another think about diversity, and cancel your idea of a larger supply feed.
 
4) Post problem on forum and pick peoples brains.
An additional problem is that it has been this way for 10+ years without the dno fuse popping or the house catching fire so may be difficult to convince the customer of the need for any work.


How can the fact it's been working O.K for 10 years, be a problem?
 
"Was called in for simple switch replacement today"

Well, then replace switch, submit invoice and walk away...... There are millions of installations that don't meet the latest regs in the UK and you CAN'T make people spend money to upgrade!
 
1) Plumbing solution. Pretty new Greenstar combi so no stored water so not realistic

What do you mean ....... what's not "realistic" about a Worcester Greenstar??

If this job was mine I would be using it as a very "realistic" alternative to the three electric showers you mention at point 1.

Just make sure it's about 42kW and it will save all the farting about with electric showers, isolators, rcbos' Rcds and all the rest of the crap involved with them.

And why the hell would you want "stored hot water" when you have a combi??? .. that's the whole point of them!

Bear in mind if you do go down the 40kW combi road it could need a 28mm gas supply pipe depending on the distance the boiler is from the meter. (same as cable sizing ) ;)
 
Last edited by a moderator:
Thanks for the replies, not what I was expecting though!
I would not be happy seeing two showers through a 60A consumer unit, let alone 3 and the fact that there has not been a problem so far is no guarantee that there will not be a problem in the future.
Applying diversity just for the showers as per the osg = 90A through a 60A rated cu. Applying diversity specific to this situation comes out about the same.
Whilst the earthing conductor size may be ok when applying adiabatic, it doesn't comply with WPD requirements for providing a pme supply.
 
Holiday let sleeping 8+. Gas ch (combi) and cooking. 2 x Wylex rewireable cu's, pme (6mm earthing conductor!), no rcd protection. 16mm dno supply, prob 100A dno fuse, no rating on meter but likely to be 80A
1 x cu for normal (lights, rfc's) etc. 2nd cu 60A rating with 3 x 45A fuses feeding 3 x 9kW showers.
Was called in for simple switch replacement today and discovered above without looking too hard!
It is entirely feasible that holidaymakers return home from beach, kettle on, clothes in wash machine and all go for showers at the same time.
I am going to inform customer by letter of my findings and it would be nice to offer a solution. As I see it the possibilities are :-
1) Plumbing solution. Pretty new Greenstar combi so no stored water so not realistic
2) Supply upgrade. Overhead supply now undergrounded, told that rising feed unlikely to have the additional capacity required (even though don't want to increase demand, just want to comply with 7671) so likely to be very expensive
3) Reduce demand with something like Garo 3 way non-priority shower unit (from Meteor) but not really at all satisfactory.
4) Post problem on forum and pick peoples brains.
An additional problem is that it has been this way for 10+ years without the dno fuse popping or the house catching fire so may be difficult to convince the customer of the need for any work.
Another thought I have had is to replace the shower cu with an 80A mcb supplying 3 x 32A mcb's for the showers as a way of limiting the load. So 16mm from Henleys into 100A main switch, N out to dp rcd, L out to 80A mcb supply, 80A L load to dp rcd in, assuming I can get supply upgraded to 25mm (or if dno don't care using existing which is buried for 3m in render). Far from ideal but a crude way of limiting demand by use of an mcb.
Another variation of this (and to my mind better) is to have one cu for the whole house, one shower off a 32A mcb with another 32A mcb supplying a 2 way shower priority switch, such as the Garo 2 way. I have then limited my short shower demand to around 70A leaving 30A for the rest of the house.
Comments / advice / solutions welcome please. In true op stylee I am shortly going out overnight so will not be able to respond until the morning
I think Carpet world are looking for sales people, If I was interviewing you for any job after that post you would get it, congratulations.
 
Thanks for the replies, not what I was expecting though!
I would not be happy seeing two showers through a 60A consumer unit, let alone 3 and the fact that there has not been a problem so far is no guarantee that there will not be a problem in the future.
Applying diversity just for the showers as per the osg = 90A through a 60A rated cu. Applying diversity specific to this situation comes out about the same.
Whilst the earthing conductor size may be ok when applying adiabatic, it doesn't comply with WPD requirements for providing a pme supply.
Why whats the worse that can happen?
 
Ok. Am getting the message! Just seems wrong to me to exceed the rating of anything. The rating is the manufacturers statement of the load the unit is designed for. However if experienced members do not see this as an issue it is something I will take on board although it is something I will avoid as an installation practice
 
Holiday let sleeping 8+. Gas ch (combi) and cooking. 2 x Wylex rewireable cu's, pme (6mm earthing conductor!), no rcd protection. 16mm dno supply, prob 100A dno fuse, no rating on meter but likely to be 80A
1 x cu for normal (lights, rfc's) etc. 2nd cu 60A rating with 3 x 45A fuses feeding 3 x 9kW showers.
Was called in for simple switch replacement today and discovered above without looking too hard!
It is entirely feasible that holidaymakers return home from beach, kettle on, clothes in wash machine and all go for showers at the same time.
I am going to inform customer by letter of my findings and it would be nice to offer a solution. As I see it the possibilities are :-
1) Plumbing solution. Pretty new Greenstar combi so no stored water so not realistic
2) Supply upgrade. Overhead supply now undergrounded, told that rising feed unlikely to have the additional capacity required (even though don't want to increase demand, just want to comply with 7671) so likely to be very expensive
3) Reduce demand with something like Garo 3 way non-priority shower unit (from Meteor) but not really at all satisfactory.
4) Post problem on forum and pick peoples brains.
An additional problem is that it has been this way for 10+ years without the dno fuse popping or the house catching fire so may be difficult to convince the customer of the need for any work.
Another thought I have had is to replace the shower cu with an 80A mcb supplying 3 x 32A mcb's for the showers as a way of limiting the load. So 16mm from Henleys into 100A main switch, N out to dp rcd, L out to 80A mcb supply, 80A L load to dp rcd in, assuming I can get supply upgraded to 25mm (or if dno don't care using existing which is buried for 3m in render). Far from ideal but a crude way of limiting demand by use of an mcb.
Another variation of this (and to my mind better) is to have one cu for the whole house, one shower off a 32A mcb with another 32A mcb supplying a 2 way shower priority switch, such as the Garo 2 way. I have then limited my short shower demand to around 70A leaving 30A for the rest of the house.
Comments / advice / solutions welcome please. In true op stylee I am shortly going out overnight so will not be able to respond until the morning

So how much did you charge for all your investigations considering it was only a switch to change?
 
I would see the 60A main switch of the shower CU as a non-compliance, as it is not possible to operate more than one of the three showers without overloading the switch. This is not sufficiently accounted for by diversity and it is reasonable to think that although it has survived so far, it is routinely overloaded.
 
He was there to change a light switch, not do an EICR. There’s nothing to put a code on because the paperwork doesn’t exist.

Yes the situation isn’t ideal, but he’s overstepped the mark.
 
I suppose there is the "Comments on existing installation" box to note it down on. Not entirely sure how it was all noticed on the change of a switch though - I certainly wouldn't be calculating the likely load of showers to replace a broken light switch!
 
I wouldn't even get a pen or certificate out of the van for a light switch change personally, it is a very small insignificant job and not a snoopers paradise.
 
If he changed a switch he'd have visited the board. 3x 45A way in a 60A CU would catch my eye if I happened to be standing next to it. It doesn't take any calculation to realise that 45A fuseways in a domestic situation are often showers and therefore fully or nearly fully loaded, and that you can't run two at once off 60A. Evident on inspection, I would say. But I agree with Tony that it's something you mention or make a brief note of, not part of the job to investigate, unless there's real danger. I went to install an FCU and ended up shutting down a school. I spotted something I didn't like, and the more I looked the more I didn't like it!
 
No, there is a 100 or at least 80 amp DNO fuse, the issue is the fact the distribution board with the 3 45 amp fuses is a 60 amp board, there is no 60 amp fuse, just a 60 amp rated DB, assuming the lighting circuit was off the second distribution board there was no real need to snoop about, that said it is almost impossible to not notice a flaw, however writing a report out and posting it on line quite comical.
 

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