Calling all Electricians: Residential DB Design and Wiring - Please Help

[DuncanCT]

So hoping anyone can help. Found some useful threads on some house stuff here.

I'm busy finishing up renovations and would like to make sure the DB is done right (I'm a little OCD about the things I do. This will probably be over done but it's what makes me happy). I've done a mock up of the DB so far see attached. I know mostly 20A MCBs are spec'ed for plugs but if everything is geared to spec'ing for wire protection but them the plug point itself is left unprotected so whats the point?

One of my big problems would be include RCDs but not sure how to do it. On googling images:'17th edition db distribution board' it looks like the RCDs are grouped to sets of MCB. What would be the right way of doing it. Also have seen discussions of whether to use RCD for things like geysers as they can result in nuisance tripping. Also do RCD negate the use of earth leakage protection?

Also lighting to be controlled by relays triggered from a Siemens Logo. (See here: http://mybroadband.co.za/vb/showthread.php/656947-Home-Automation-Siemens-Logo) No MCB added for the lighting as not sure of the loads yet. Should all be LED so don't think it'll be to heavy.

Any info would be greatly appreciated. Thanks!

Disclaimer: I know enough about electricity to be a danger! :wtf:

 

[Mars]

Are you wiring this yourself? You do realise that if you do wire it yourself and you have a house fire your insurance wont pay out? Even if you did a perfect job and the wiring wasn't the cause?

 

[Gnome]

So hoping anyone can help. Found some useful threads on some house stuff here.

I'm busy finishing up renovations and would like to make sure the DB is done right (I'm a little OCD about the things I do. This will probably be over done but it's what makes me happy). I've done a mock up of the DB so far see attached. I know mostly 20A MCBs are spec'ed for plugs but if everything is geared to spec'ing for wire protection but them the plug point itself is left unprotected so whats the point?

SANS requires that no device may be sold that consumes more than 16 amps on a plug socket.

To push more than 16 amps through a single plug, you really need to be trying very hard and be very stupid. Like wire a permanent install device (eg. stove, geyser, air conditioner) through a plug when the manual tells you explicitly that it is not legal to do so.

The 20 amp breaker is because multiple sockets are on a single cable run.

One of my big problems would be include RCDs but not sure how to do it. On googling images:'17th edition db distribution board' it looks like the RCDs are grouped to sets of MCB. What would be the right way of doing it. Also have seen discussions of whether to use RCD for things like geysers as they can result in nuisance tripping.

Nuisance tripping is a nice term for bad quality installation.
Things that generally cause "nuisance tripping":
- High copper losses (eg. wiring heating up), which means the wiring isn't adequate to begin with.
- Faulty elements and/or faulty equipment (eg. shunting current to ground)
- Unsafe wiring. (neutral/earth fault, high resistance live/earth fault)

There is really no reason an entire house shouldn't be on an RCD and most homes today are sold with everything on the RCD for safety.

In the UK generally newer homes have two or more RCDs. So it is a good idea to put your stove, geyser and lights on one RCD and plugs on another (example).

Or if you are using 3 phase, simply get a 3 phase RCD and split everything across the 3 phases with each phase having a 30mA limit means you have the equivalent of 3xRCDs.

Also do RCD negate the use of earth leakage protection?

Earth leakage and RCD are for all intents and purposes the same thing in South Africa.

An earth leakge refers to a different mechanism but SA stuck to the name Earth Leakage whereas the other countries use the name RCD to avoid confusion.

Also lighting to be controlled by relays triggered from a Siemens Logo. (See here: http://mybroadband.co.za/vb/showthread.php/656947-Home-Automation-Siemens-Logo) No MCB added for the lighting as not sure of the loads yet. Should all be LED so don't think it'll be to heavy.

What are you saying? All circuits from your board need to be on an RCD and and MCB. Things like relays can have additional requirements.

Are you wiring this yourself? You do realise that if you do wire it yourself and you have a house fire your insurance wont pay out? Even if you did a perfect job and the wiring wasn't the cause?

If I understood him correctly, he just wants to make sure it was done correctly? (Hope so for his part)

 

[Mortymoose]

You need to have a wireman's license before you start wiring up buildings boet!

 

[DuncanCT]

Again please excuse my ignorance, these questions might be stupid.

SANS requires that no device may be sold that consumes more than 16 amps on a plug socket.

To push more than 16 amps through a single plug, you really need to be trying very hard and be very stupid. Like wire a permanent install device (eg. stove, geyser, air conditioner) through a plug when the manual tells you explicitly that it is not legal to do so.

The 20 amp breaker is because multiple sockets are on a single cable run.

I understand that it would be hard to draw more than 16 amps from one socket under normal use but this scenario might be highly unlikely but if there is a fault and an appliance draws less than 20 amps but more than 16 amps not sure if your plug point could melt/burn?

There is really no reason an entire house shouldn't be on an RCD and most homes today are sold with everything on the RCD for safety.

Just to check you're say that an entire house SHOULD be on a RCD. Again i'm not claiming to know anything but conflicting views on what appliance should be on RCD here... http://forums.whirlpool.net.au/archive/1949785. Just looking for the science of why or why not. Also what do SANS regs say about RCDs?

Or if you are using 3 phase, simply get a 3 phase RCD and split everything across the 3 phases with each phase having a 30mA limit means you have the equivalent of 3xRCDs.

Ok so this bring up something else that I haven't mentioned in the first my first post. We do have a 3 phase supply but I'm unsure if I need to use all three? Prior to the renovations we only had a single phase supply. Have done a little bit of research into a solar system and a 3 phase inveter would be more expensive. Keeping in simple and going single phase seems easier.

What are you saying? All circuits from your board need to be on an RCD and and MCB. Things like relays can have additional requirements.

We're in Claremont.

So from MY understanding the relays would be just the same concept at the switch on the wall only now controlled by the Logo, all other elements of the circuit to conform with the above MCB/RCD. Looking to do a 24v Logo module to all the switching points so they can be wired with SELV.

If I understood him correctly, he just wants to make sure it was done correctly? (Hope so for his part)

Yes, that's correct.

Thanks for the responses.

 

[Gnome]

I understand that it would be hard to draw more than 16 amps from one socket under normal use but this scenario might be highly unlikely but if there is a fault and an appliance draws less than 20 amps but more than 16 amps not sure if your plug point could melt/burn?

SA plugs are rated to 16 amps yes but the actual plug can handle more than that. Again, the sale of such things are incredible highly regulated. You simply couldn't sell something like that easily. And buying products that require more than 16 amps and installing them on a plug would mean you would need to ignore multiple warnings. Such products are sold with massive warnings pasted over the wiring terminals that explicitly say that wiring it to a plug is strictly prohibited.

Factories in SA have tried selling non SANS approved things before and it isn't a mistake they'll likely make again. The one instance resulted in all stock being seized, a fine imposed and the factory had to stop operations for 6 months while it was reviewed.

Believe me you don't simply sell such products without consequence.

Just to check you're say that an entire house SHOULD be on a RCD. Again i'm not claiming to know anything but conflicting views on what appliance should be on RCD here... http://forums.whirlpool.net.au/archive/1949785. Just looking for the science of why or why not. Also what do SANS regs say about RCDs?

I'm not really into reading opinions on whirlpool because there is a lot of misinformation there. So I didn't even read it.

SANS has different regulations depending on the situation. RCD is always recommended or in 95% of the cases required unless some very specific requirements are met.

Ok so this bring up something else that I haven't mentioned in the first my first post. We do have a 3 phase supply but I'm unsure if I need to use all three? Prior to the renovations we only had a single phase supply. Have done a little bit of research into a solar system and a 3 phase inveter would be more expensive. Keeping in simple and going single phase seems easier.

Most houses have single phase. Some houses were built with 3 phase. You should use all 3 phases, but that doesn't mean you need a 3 phase solar system.

Again, you sound like you are considering doing this yourself. I would advice strongly you re-consider. 3 phase installations are a bit more complicated.

In a 3 phase install to a domestic residence everything can still be single phase. The load is just distributed across 3 phases. This reduces current.

So from MY understanding the relays would be just the same concept at the switch on the wall only now controlled by the Logo, all other elements of the circuit to conform with the above MCB/RCD. Looking to do a 24v Logo module to all the switching points so they can be wired with SELV.

Shock hazards get lower with lower voltages. But fire hazards get higher with lower voltages.

It is therefore highly regulated. Again I advice you to not consider doing this DIY. Off the shelf products that are SANS approved should always be used in a manner that is SANS approved with a CoC. The fire risk is very real.

Low voltage installations are prone to fire. Do not underestimate it. You will most certainly not get a claim approved for a low voltage installation that did not follow SANS regulations.

 

[itareanlnotani]

Are you wiring this yourself? You do realise that if you do wire it yourself and you have a house fire your insurance wont pay out? Even if you did a perfect job and the wiring wasn't the cause?

Not true. Doing the work yourself, and having a licenced person sign off on it is perfectly fine.

You can do the wiring yourself, then have a CoC (Certificate of Completion) performed by a registered electrician or wireman.
They'll test the wiring and check it complies, and issue a certificate, or advise of changes to be made in order to comply.

As long as you have the CoC issued, and keep a copy on file, you're fine.