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.

 

[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.

 

[davesparks]

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 a 12kW water heater to fill the kitchen sink is also a little ridiculous when far lower powered instantaneous water heaters exist which will serve the same purpose.

You can now get a tap with a built in 3kW instantaneous heater to provide boiling water on tap, so why would you need a 12kW heater to get water at a around 60degrees?

 

[sean_ork]

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.

10l maximum ? then its 10? minutes wait till for more hot water - that's the reason folks want high current instantaneous heating

 

[Dave OCD]

10l maximum ? then its 10? minutes wait till for more hot water - that's the reason folks want high current instantaneous heating

Isn't 10 litres enough to wash your hands, have a shave or wash a few dishes then ?

 

[sean_ork]

You can now get a tap with a built in 3kW instantaneous heater to provide boiling water on tap, so why would you need a 12kW heater to get water at a around 60degrees?

What's the flow rate ?

How many litres does the average kitchen sink hold ?

 

[sean_ork]

Isn't 10 litres enough to wash your hands, have a shave or wash a few dishes then ?

Probably, but doing a few sinks worth of dishes could get tedious

 

[Dave OCD]

Probably, but doing a few sinks worth of dishes could get tedious

Well you shouldn't be lazy and let them build up like that.

 

[davesparks]

What's the flow rate ?

How many litres does the average kitchen sink hold ?

How on earth should I know? You'd need the flow rate at the point of connection to find out what it will be out of the tap!
From experience the boiling water is not noticeably slower than the regular hot from a tap.

Again how the hell should I know the average volume of a kitchen sink?

I'm only asking why such a large amount of power is necessary to achieve the same result as can be achieve with much less power?

 

[davesparks]

Probably, but doing a few sinks worth of dishes could get tedious

I thought the whole point of this was energy efficiency?
Using a few sinks worth of dishes to cook a meal is not very energy efficient when meals can be cooked with far fewer dishes!

 

[Deleted member 26818]

I prefer instantaneous heating over tanks.
RedRing do one that is suitable for 2/3 sinks, or one sink and shower, cost me £145 when I purchased it.

 

[Midwest]

Probably, but doing a few sinks worth of dishes could get tedious

Get a dishwasher :smiley2: