Appliance isolator switches

[JohnHarrison]

Multiple circuits, one per appliance, "in case" is bonkers.

What experience do you have of faults which make it seem like a good idea?

My experience of faults is irrelevant. Each appliance has an isolator and does not affect another if a fault. Sounds V good to me. Not expensive either for what it offers.

 

[ban-all-sheds]

My experience of faults is irrelevant.

Quite so, if your idea of design principles is that you base the design on imagination and fancies.

But if you believe that design should have some basis in reality, your experience, and that of a larger population, is far from irrelevant.

Each appliance has an isolator and does not affect another if a fault. Sounds V good to me. Not expensive either for what it offers.

Reputable makes of RCBOs come in at £20+. Then there's the need for a considerably bigger CU, more cables to be run, more testing to be done.

Gut feel is you'll be looking at getting on for an extra £100 per appliance.

And if you cannot show that your own, or general, experience is that appliance faults are so common that a dedicated circuit for each one is worthwhile then it offers you nothing.

But hey - it's your money and your wall space. If that's what you want, then go for it, but please don't try to insult our intelligence by claiming that it is anything other than a total indulgence on your part.

 

[JohnHarrison]

Quite so, if your idea of design principles is that you base the design on imagination and fancies.

All contributed were positive except you. You are some sort of know-it-all idiot, with little clue. Please go away.

 

[JohnW2]

Multiple circuits, one per appliance, "in case" is bonkers.

It's not "bonkers" - it's just a very risk-averse attitude, and there's nothing wrong with that.

Kind Regards, John

 

[ericmark]

Each appliance has an isolator

That is the point single pole with TT is not isolation it is only switching. So let us take a 12 way consumer unit filled with 30 mA RCBO's so in theroy 12 x 30 mA can flow without tripping, yes I know it will never reach that limit but it means 360 mA so to ensure the earth electrode never reaches 50 volt it must have an earth loop impedance of 139Ω. Not the 200Ω considered as the value which if exceeded is unstable. So in real terms we can expect up to 20 volts earth electrode to true earth.

This means the chances of neutral ~ earth faults tripping a RCD are quite high compared with a TN-C-S supply. I would have no hesitation with a TN supply all RCBO and only one single isolator is not a problem. With TT however there is a lot to be said for twin isolators. There is nothing to stop one configuring the board to have two isolators feeding the RCBO's but for extra cost I would say worth while having double pole switching RCBO's even if not double pole sensing for over current.

To me best isolator is a plug and socket. There is no way they can be still connected. There is no need for proving dead you know it is dead.

 

[EFLImpudence]

OP:

In view of the original title and question...

Appliance isolator switches

Do these have to be double pole? One idea is to run a large cable to a small sub CU in a kitchen cupboard and have an MCB for each appliance. This will not be DP of course.

...and your subsequent ideas,

what are you now trying to achieve?

 

[JohnW2]

So in real terms we can expect up to 20 volts earth electrode to true earth.

That can, in theory, also happen with TN-C-S. However, in either case I'm not sure that (within reason) the voltage between the installation's 'earth' (i.e. CPCs) and true earth is necessarily all that important, provided that everything is correctly bonded to the MET. The inside of the building can be an "equipotential zone" regardless of what that "equipotential" is relative to true earth.

Kind Regards, John

 

[ban-all-sheds]

It's not "bonkers" - it's just a very risk-averse attitude, and there's nothing wrong with that.

There comes a point where acting in a way driven by extreme risk aversion is bonkers.

 

[winston1]

Multiple circuits, one per appliance, "in case" is bonkers.

It's not "bonkers" - it's just a very risk-averse attitude, and there's nothing wrong with that.

Kind Regards, John

I wonder if he has thought of a separate RCBO for every light point. After all you don't want one blown bulb to take out all the lights on one floor!

 

[ban-all-sheds]

All contributed were positive except you.

Jolly lucky for you then that I'm here, isn't it.

You are some sort of know-it-all

Not all.

But a great deal - probably more than you.

idiot, with little clue.

There you provide more evidence of your hard-of-thinking irrationality.

Please go away.

No.

 

[JohnW2]

There comes a point where acting in a way driven by extreme risk aversion is bonkers.

If risk-aversion becomes as extreme and irrational as to be paranoia, then you would sometimes be right. However, there are a good few perfectly 'sane' people who are, 'rationally', very risk-averse.

Kind Regards, John

 

[ban-all-sheds]

If risk-aversion becomes as extreme and irrational as to be paranoia, then you would sometimes be right. However, there are a good few perfectly 'sane' people who are, 'rationally', very risk-averse.

I see no rationality involved in having one circuit per appliance in order to guard against a fault in one stopping others from working.

 

[JohnHarrison]

There comes a point where acting in a way driven by extreme risk aversion is bonkers.

If risk-aversion becomes as extreme and irrational as to be paranoia, then you would sometimes be right. However, there are a good few perfectly 'sane' people who are, 'rationally', very risk-averse.

Kind Regards, John

In my case:

1. The integrated appliances have full isolation.
2. Freezer contents are protected from faults of other appliances that trip.
3. Boiler is protected from faults of other appliances.
4. Easy to fault find.
5. One appliance does not affect another in a fault situation.
6. Faults are easy to isolate.
7. No ugly fused spur switches over worktops.
8. Isolators all in one place and labelled.
9. Only one ring need be installed as it will take only light loads.
10. Takes heavy appliances off the ring.

All positive and sensible.

Thanks and...............

 

[JohnHarrison]

OP:

In view of the original title and question...

Appliance isolator switches

Do these have to be double pole? One idea is to run a large cable to a small sub CU in a kitchen cupboard and have an MCB for each appliance. This will not be DP of course.

...and your subsequent ideas,

what are you now trying to achieve?

It has stayed that way. Just replace the mcb's with RCBO's single or DP. Divide & rule. Simplicity.

 

[JohnHarrison]

Each appliance has an isolator

I would have no hesitation with a TN supply all RCBO and only one single isolator is not a problem. With TT however there is a lot to be said for twin isolators. There is nothing to stop one configuring the board to have two isolators feeding the RCBO's but for extra cost I would say worth while having double pole switching RCBO's even if not double pole sensing for over current.

To me best isolator is a plug and socket. There is no way they can be still connected. There is no need for proving dead you know it is dead.

Thanks Eric. Yes, switching and isolation are not the same. A plug & socket is the best isolation, but when appliances are integrated the matter is different. A DP RCBO when off is full isolation and safe to work on the appliance in some way.

Thanks and.....