Self Build Advice Please - consumer units, sockets & switches...

[janner43]

Hi all,

We are doing a self build 2 bed bungalow in Devon which is going to be very highly insulated with u-values of..
Floor 0.15
Walls 0.14
Ceiling 0.11

With an air tightness factor of 0.8
MVHR with 89% efficiency

* Our other design spec includes no central heating system (not required with the previous specs), we'll just add a panel heater to act as a top up for the stored heat within the home when required. The MVHR should do the rest.

* An "experiment" with no central hot water - just local instantaneous water heaters (3 @ 12kw) where required. Half the plumbing, no dead leg of water, no waste hot water stored. We are not having a bath, so an instantaneous electric shower (9.5kw)

* We are having a 3.7kw solar array. The whole concept is based on the PassivHaus model with a couple of tweaks.

I don't really want to debate the design concepts - feel free to comment if you like, though .
The whole idea has been predicated on thinking differently about the designs when it comes to the heating and water heating together with an avoidance of the connection costs, plumbing, boiler purchase, boiler servicing costs associated with a gas connection (which is available).

We have a great, fully qualified sparky on the project who grew up with our son & is a good guy. I know he'll give us good advice, but I would appreciate several points of view on this please. He is kindly not supplying materials & is letting me source those to save some money. He is also arranging for a pal with the MCS ticket to commission the solar array at mates rates.

That's the background, now to the questions...

1) Consumer Unit...
I wondered if it would be a good idea to have two consumer units...
One for the heavy items - three 12kw water heaters and one 9.5kw shower
One for everything else

Or just get one large unit?

Would there be an issue with the solar array connectivity if we had two consumer units?

I like the idea of splitting as many of the circuits as possible, so what sort of config would you design if this was your build?

2) What brands are the best value for money - I'm familiar (Dad was an electrician for decades, started his trade in the 1950s) with MK, Wylex - but are they as good now as they were or are other names just as good?

3) Any recommendation on which make of sockets & switches to get?

4) Any recommendations as to the cheapest place to buy the gear from please? I already have a Trade Account at Travis Perkins (and Trade Point - don't laugh, it might be handy... )

I hope I have given you enough information & thanks in advance for taking the time to read this and for any answers / opinions / recommends you might be willing to give.

Cheers all.

 

[jackhammerJIM]

We have a great, fully qualified sparky on the project who grew up with our son & is a good guy. I know he'll give us good advice, but I would appreciate several points of view on this please. He is kindly not supplying materials & is letting me source those to save some money.


I like the idea of splitting as many of the circuits as possible, so what sort of config would you design if this was your build?

This does not make sense to me . Get him to design the circuits and mains layout . Get him to supply the materials as he will get them cheaper than you will .

 

[janner43]

He will design the circuits. But as I said, I'm interested in viewpoints from other experienced electricians.

He'll buy materials if I ask him too - but he doesn't have the time to search out bargain deals & wholesalers aren't always the best at deals... Not supplying materials was his suggestion, not mine.

 

[Andy78]

For decent quality materials a wholesaler will always have the best deals for account holding electricians.
The public will always be able to get get the same shopping list cheaper, but its going to be the poor quality junk that makes up a large portion of the market.

The electrician running the job will be able to debate circuit design, circuit division, and distribution board arrangements with you, and will be best placed to having first hand experience of the project.

 

[andyb]

I don't really want to debate the design concepts.

Not sure about 3 x 12Kw water heaters and a 9.5Kw instantaneous shower.
Talk to your electrician.

 

[Jimbosmith]

First off im not qualified yet so wait for someone with more experience than me. But il give it a shot

3x 12kw heaters and the shower is a hell of a load before you even get into the rest of the circuits for the house.

I would personally go down the route of a Contactum Metal clad with RCBO for the lighting, sockets and the rest of the stuff.

For the Heaters i wouldnt even know where to start, comes to like 52A per heater and as to my knowledge you cant diversify the load. I just hope they dont all get turned on at once.

Your sparks should just design everything and then give you a list of things to order.

 

[jackhammerJIM]

He will design the circuits. But as I said, I'm interested in viewpoints from other experienced electricians.

he doesn't have the time to search out bargain deals & wholesalers aren't always the best at deals...

If he is as good as you say he is then he already knows the best products at best prices and where to get them .

 

[janner43]

Not sure about 3 x 12Kw water heaters and a 9.5Kw instantaneous shower.
Talk to your electrician.

I did wonder myself & checked with him before we bought them, but he felt that diversity meant it would be OK. There are only two of us living there & at worst we'd only have 2 running at the same time.

 

[andyb]

I did wonder myself & checked with him before we bought them, but he felt that diversity meant it would be OK. There are only two of us living there & at worst we'd only have 2 running at the same time.

That's fine then.

 

[davesparks]

You want value for money in your consumer unit I personally would go for a Schneider DB fitted with rcbos as I think that would be the best quality option at what are pretty reasonable prices these days.
But of course if what you actually want is the cheapest option then go and get something off the shelf in screwfix.

As far as splitting loads across 2x CUs I would split the loads equally across the two boards, so that you don't put heavy load on one and light load on the other. That way the 'value for money' components in the CUs will be less likely to fail too soon.

 

[Electric Magic]

2) What brands are the best value for money - I'm familiar (Dad was an electrician for decades, started his trade in the 1950s) with MK, Wylex - but are they as good now as they were or are other names just as good?

3) Any recommendation on which make of sockets & switches to get?

Regarding question 2, I've found the quality of terminal screws on the earth and neutral bars in more recent Wylex boards to be poor (though I haven't fitted one of the new metal ones). Crabtree Starbreaker are made by the same company as Wylex but are much better quality and the MCBs and RCBOs plug in (quicker installation and arguably a safer product) though they cost a bit more. The MK boards are pretty cheap but a reasonable quality and better in my view than other similarly priced boards I've seen from BG and others. I've only seen plastic Schneider boards and not the new metal ones but as a respected forum member like Davesparks rates them I'll probably give one a go myself at some point.

Regarding question 3, if you are going for standard white pvc fittings, my personal favourite is the Hager Sollysta range. Like Stella Artois it is reassuringly expensive (but not that expensive, a bit of shopping around on the internet - don't just use Google people pay to get to the top of that use other engines too - and you can find double sockets for £2.32 and single switches for £0.56). The terminals use good screws and are arranged sensibly for installation and testing; they look good; and the light switches have a neutral terminal for those wanting to wire from the switch (which means even though the switch might cost a few pence more you'll save a bit on not using a connector of some kind). I also use Click Mode stuff, which is a bit cheaper than Hager (and a little lower quality but still pretty good), because it can be used alongside Click Minigrid stuff (a modular system that is pretty flexible).

 

[janner43]

My sparks agrees with you & Dave - he likes Schneider & Hager. So have decided on Schneider CU and Hager Sollysta plugs, switches etc.

 

[joehat]

I did wonder myself & checked with him before we bought them, but he felt that diversity meant it would be OK. There are only two of us living there & at worst we'd only have 2 running at the same time.

Maybe for you but maybe not so good with guests of future owner!!

 

[joehat]

I would go for an electric combi boiler, long run its overall better.
Think about replacement of water heaters Ect, it will mount up, that was you could also have better pressure of water.

 

[Midwest]

Op, please excuse me, but I have suspicious nature. I'm just wondering if your electrician really exist? If you have a 'fully qualified sparky' on the project, then most of the questions you're asking, could easily be answered by him. Some of the ways you have replied, are like the royal 'We'. I'm aware of self build projects, where the owners take on most if not all of the different trades. There are self build forums dedicated for that purpose. I question the viability of having 3 x 12kw instantaneous water heaters and a 9.5kw shower, albeit there's only two of you, it may overload your supply. If are considering some of ths work yourself, it may be you should consider asking joining the DIY part of this forum, where you questions will still receive a good response.

 

[davesparks]

Regarding question 2, I've found the quality of terminal screws on the earth and neutral bars in more recent Wylex boards to be poor (though I haven't fitted one of the new metal ones). Crabtree Starbreaker are made by the same company as Wylex but are much better quality and the MCBs and RCBOs plug in (quicker installation and arguably a safer product) though they cost a bit more. The MK boards are pretty cheap but a reasonable quality and better in my view than other similarly priced boards I've seen from BG and others. I've only seen plastic Schneider boards and not the new metal ones but as a respected forum member like Davesparks rates them I'll probably give one a go myself at some point.

I don't fit Wylex, Crabtree or any other electrium stuff since they recalled mcbs when they started catching fire a few years ago

Note I said DB rather than CU, the Schneider CUs aren't particularly great but their DBs (acti 9/Merlin Gerin) are the dogs dangles

 

[janner43]

Op, please excuse me, but I have suspicious nature. I'm just wondering if your electrician really exist? If you have a 'fully qualified sparky' on the project, then most of the questions you're asking, could easily be answered by him. Some of the ways you have replied, are like the royal 'We'. I'm aware of self build projects, where the owners take on most if not all of the different trades. There are self build forums dedicated for that purpose. I question the viability of having 3 x 12kw instantaneous water heaters and a 9.5kw shower, albeit there's only two of you, it may overload your supply. If are considering some of ths work yourself, it may be you should consider asking joining the DIY part of this forum, where you questions will still receive a good response.

I don't mind the question at all. I can understand why you are asking it, too. But your suspicions are unfounded. I like to be informed and to glean wisdom from a number of sources. As far as doing some work myself, then yes, I'll be installing the kitchen, laying the oak floor throughout and doing all the decorating. I'll also be doing all the garden greenscaping and planting.

The electrics, plumbing and plastering are all subbed out. If the thread is in the wrong section, my apologies and perhaps if a mod agrees with that, then they would be so kind as to move it.

I can also understand you questioning the viability of the water heaters. I could have specced lower kW models, but given the water heating is something of an experiment, that's what we are going with. If they prove too large, I'll swap one or two out. Could have specced all sorts of things - ground source heat pumps, air source heat pumps, solar water heating - mains gas is also available.

I could have looked at other solutions too - such as an electric boiler, but that would miss out on the avoidance of long pipe runs etc. It would also miss the point of a serious thought process of how much hot water anyone actually uses from a tap these days. With a dishwasher and a washing machine, and no bath the amount of water to be run at any one time is no more than a couple of litres at worst - and then only occasionally.

As far as any future owners are concerned, I'll leave them to worry about how they heat water. We are building a home for us for the rest of our lives, not some type of investment vehicle.

I know some of the design is a little left field for the UK, but it isn't an unusual way of doing things everywhere in the world.

 

[joehat]

BANG!! , Main Fuse!!

Over and out!!

 

[Octopus]

There's nothing worse than a "self build" project manager buying kit off the internet. I charge my hourly rate for ALL issues and time spent wasted or on resolutions I have to do.......or even wait for parts to arrive!

Just saying

 

[janner43]

BANG!! , Main Fuse!!

Over and out!!

For Normal domestic 100Amp Fuses to BS 1361, these are the graph given figures of TIME V. CURRENT, to Rupture the fuse:-
0.1 second @ 1800Amps
1 second @ 950Amps
5 seconds @ 630Amps
3 MINUTES @ 360Amps
10 MINUTES @ 250Amps - (Fuse does get Hot)
1 HOUR @ 170Amps

 

[davesparks]

For Normal domestic 100Amp Fuses to BS 1361, these are the graph given figures of TIME V. CURRENT, to Rupture the fuse:-
0.1 second @ 1800Amps
1 second @ 950Amps
5 seconds @ 630Amps
3 MINUTES @ 360Amps
10 MINUTES @ 250Amps - (Fuse does get Hot)
1 HOUR @ 170Amps

You should not plan an installation which relies on this though, the fuse will weaken with time as it is subjected to such overloads and the terminals etc of the cutout won't necessarily be rated for the duty.

 

[hasel5]

Use the gas supply simples

 

[janner43]

Use the gas supply simples

Sigh...


Urban.co.uk News and Views Blog | Flame goes out for gas in the UK


The UN's Paris climate deal 'signals end to gas cookers' say experts | Daily Mail Online


Huge change facing property world as gas looks set to be phased out - Property Industry Eye


and this from 2014...
Forget your gas cooker ? we?re headed for 'zero carbon? Britain - Telegraph

 

[7029 dave]

On your opening post, you say the Electrician will be advising you, does that mean he is not working on the installation.?

 

[janner43]

You should not plan an installation which relies on this though, the fuse will weaken with time as it is subjected to such overloads and the terminals etc of the cutout won't necessarily be rated for the duty.

I agree.

I cannot see anything more than 26kw (113amp) ever being used at once - and then only on rare occasions and only for 90 seconds maximum. But I must admit that I would have been happier if the water heaters were on the smaller side, but have decided to go with these (already bought)

 

[janner43]

On your opening post, you say the Electrician will be advising you, does that mean he is not working on the installation.?

He is doing all the electrical work. Perhaps I should have been more semantically correct and said "I know he will give us good advice and perform an excellent & professional service for us"

Good grief, I am beginning to wish I hadn't asked!!

 

[davesparks]

Sigh...


Urban.co.uk News and Views Blog | Flame goes out for gas in the UK


The UN's Paris climate deal 'signals end to gas cookers' say experts | Daily Mail Online


Huge change facing property world as gas looks set to be phased out - Property Industry Eye


and this from 2014...
Forget your gas cooker ? we?re headed for 'zero carbon? Britain - Telegraph

Yeah right, our electricity networks are a patchwork of ancient cables and distribution waiting to fall apart. A mass move to electric heating and cooking will result in one heck of a lot of power cuts!

 

[jackhammerJIM]

Good grief, I am beginning to wish I hadn't asked!!

Your on here for advice which is being given . It is just advice "do whatever you want to "

 

[janner43]

You should not plan an installation which relies on this though, the fuse will weaken with time as it is subjected to such overloads and the terminals etc of the cutout won't necessarily be rated for the duty.

I agree.

I cannot see anything more than 26kw (113amp) ever being used at once - and then only on rare occasions and only for 90 seconds maximum. But I must admit that I would have been happier if the water heaters were on the smaller side, but have decided to go with these (already bought)

You have made me think though Dave. I will give some consideration to a 3kw 5litre hot water solution for the kitchen. It is the kitchen tap which will be used most and possibly at the same time as the shower (9.5kw) or a bathroom tap (12kw).

 

[janner43]

Yeah right, our electricity networks are a patchwork of ancient cables and distribution waiting to fall apart. A mass move to electric heating and cooking will result in one heck of a lot of power cuts!

It isn't what we think about it that matters though Dave, is it. Apparently that is a serious proposal that is being considered - I know it seems hard to believe, but I only know what I have read...

 

[7029 dave]

IMO these questions should be discussed with your Electrician on site, are you doubting his integrity, If I were him would not be best pleased in the slightest, sorry but if you are going to have an hissy fit over some Q's then IMO there is no other spark is there.!! It's an selfie.

 

[davesparks]

It isn't what we think about it that matters though Dave, is it. Apparently that is a serious proposal that is being considered - I know it seems hard to believe, but I only know what I have read...

And I know what I've read, in one of the DNO's technical papers detailing how chunks of the distribution system are still working on DC distribution from around 100 years ago.

 

[jackhammerJIM]

It isn't what we think about it that matters though Dave, is it. Apparently that is a serious proposal that is being considered - I know it seems hard to believe, but I only know what I have read...

The muppets that run this country are not going to scrap gas . For one the energy companies themselves would not allow this as a loss of revenue (they are powerful) .

We are on the limit for power as is . Not enough power stations and fear of brown outs in the near future if they don't get arses in gear !

They look like genuine articles but this is the first i have heard of the idea . Not going to happen , If gas is available you would be foolish not to utilise it .

 

[Octopus]

the property should be built with gas, electricity and a wood burner - then you've got the bases covered!

 

[Lagentium]

I'd go ground source heat pump and forget those instant water heaters rated at 12kw, they are a daft option IMHO, but that is just my opinion.

 

[janner43]

OK, thanks to everyone for your advice.

The thread can be closed now as far as I'm concerned.

 

[gaz101]

No diversity allowed on water heaters
what's the cost of a 50kva+ supply?

 

[Midwest]

The muppets that run this country are not going to scrap gas . For one the energy companies themselves would not allow this as a loss of revenue (they are powerful) .

We are on the limit for power as is . Not enough power stations and fear of brown outs in the near future if they don't get arses in gear !

They look like genuine articles but this is the first i have heard of the idea . Not going to happen , If gas is available you would be foolish not to utilise it .

There was a debate here, on this issue a short while ago. Can't be bothered to locate it, but suffice to say the UN Climate Change Conference 2015, agreed on a reduction of 2' of global warming, and less reliance on fossil fuels, by 2030. Whether it will happen or not, as the agreement doesn't appear to be biding. In the UK, apart from fuel for vehicles, a lot of our carbon emissions come from, gas heating and gas cooking. Whilst some effort is being made on carbon emissions from vehicles, little is being done with our gas consumption. Hence the headlines about the demise of domestic gas boilers and hobs.

 

[joehat]

You should not plan an installation which relies on this though, the fuse will weaken with time as it is subjected to such overloads and the terminals etc of the cutout won't necessarily be rated for the duty.

Agree, gonna have a look in abit as I'm nosy ,but do you remember where you found this info Reg Ect.

 

[joehat]

You should not plan an installation which relies on this though, the fuse will weaken with time as it is subjected to such overloads and the terminals etc of the cutout won't necessarily be rated for the duty.

Specially with the cheap and cheerful options.

 

[Leesparkykent]

Agree, gonna have a look in abit as I'm nosy ,but do you remember where you found this info Reg Ect.

Its common sense really but 433 covers protection against overload current. 433.1, 433.1.1 and so on.

 

[davesparks]

Agree, gonna have a look in abit as I'm nosy ,but do you remember where you found this info Reg Ect.

Common sense and experience is where I got it from.
Common sense: don't design an installation which relies on a fuse running at more than it's rated current.
Experience: fuses which run at their rating/just over there rating get weak and blow for no apparent reasons.
Also from experience a 100A cutout being regularly loaded to 120A will get very very hot and smell rather nasty (overload revealed from a load study carried out after the cutout was replaced)

 

[plugsandsparks]

100A fuse ? I would get that in writing before making such a design assumption. 63A more likely me thinks

 

[sean_ork]

OK, thanks to everyone for your advice.

The thread can be closed now as far as I'm concerned.

Don't be disheartened, many trades in this Country don't like change, most builders still think block/brick build is the only way - ask them about air tightness testing and you'll get the same belligerent responses as you've seen here.

We've done very similar to what you are aiming at, but before PH became trendy - luckily we have an almost endless supply of energy blowing past so our energy source was easy to pick. Your calcs probably show you won't need any significant energy input for space heating, as did ours - but we specified all flooring to be highly insulated 8'' conc with both electric loose laid heating, and wet UFH - and a fairly large TS - with plenty of coils, stat probes and three immersions - lots of thermal mass.

Your instantaneous heater proposal is sound - heat at the point of use, and only heat what you need is a concept clearly lost so far in this thread.

But do ensure you pander to those who might live in the house after you by ensuring gas is at least piped to the likely areas of use, you don't need to have a supply, just a feed from your utility box.

We spent time in Norway and Sweden before signing off, they know how to build properly over there - hopefully trades in this Country might catch them up eventually.

You'll likely be aware already, the Green Building Forum will be much more receptive of your "wild" ideas - also talk to Viking House, they have some innovative MHVR solutions - also their general building and detailing drawings are a goldmine of ideas.

Good luck.

 

[joehat]

Its common sense really but 433 covers protection against overload current. 433.1, 433.1.1 and so on.

I would have looked in that section yes but would never design above 100a do didn't know it has that in the regs book as its not ours to touch,, soso!!

 

[Lagentium]

I don't think this thread is all it appears to be to be honest!!! Why start a thread then say it can be locked? Once you've started the ball rolling it will roll and roll!

 

[Dave OCD]

I know the OP has lost interest in this thread now but using 12kW water heaters to provide hot water to a kitchen sink and shower room wash basin respectively seems insane to me, a couple of small unvented water heaters which hold a small amount of water with thermostatic control and consuming under 3kW each such as the Ariston type would surely be far more sensible ?

 

[Midwest]

Don't be disheartened, many trades in this Country don't like change, most builders still think block/brick build is the only way - ask them about air tightness testing and you'll get the same belligerent responses as you've seen here.


Your instantaneous heater proposal is sound - heat at the point of use, and only heat what you need is a concept clearly lost so far in this thread.

But do ensure you pander to those who might live in the house after you by ensuring gas is at least piped to the likely areas of use, you don't need to have a supply, just a feed from your utility box.

I could not agree more on a soundly built house full of insulation, and save on my bills, don't care what it's made of, straw & mud wouldn't bother me. Not sure whay the OP wants a 12kw water to wash up the dishes for? The Redring one I looked at by the way, said unsuitable for kitchen sinks? Good advice re the gas supply though, future proofing. Although, if you believe the headlines, no use after 2030!

 

[sean_ork]

a couple of small unvented water heaters which hold a small amount of water with thermostatic control and consuming under 3kW each such as the Ariston type would surely be far more sensible ?

Do you keep a kettle of boiling water ready at all times for those few times during the day when you want a brew ?

 

[Dave OCD]

Do you keep a kettle of boiling water ready at all times for those few times during the day when you want a brew ?

No but I don't start up a small nuclear reactor to boil a couple of pints of water either.
And unlike a kettle the type of heater I described is very well insulated so once the thermostat temp is reached the water will stay hot for a long time without further current being drawn.