garden shed Ze

[£££sjim]

I have a question.How do I get the Ze for my shed ? do I get it at the intake to the small consumer unit inside my shed then do the usuall Zs= Ze + (R1+R2)The source of supply is from a socket in the garden that is direct from the house CU RCD protected. or would I have to use the Ze from the house intake position. My shed is stand alone with a light circuit 6amp mcb and two radial circuits 20amp mcb all protected by RCD. another problem I have is if the shed CU trips the house Cu trips too. both protected by 30ma RCDs the garden sockets are 32amp mcb.

 

[Pete999]

Yes it should and I deliberately miss-spelled it just as the op did!

And yes - you ARE being picky and I don't suppose that's going to change any time soon!

Well hush my mouth, and you are correct I wont change

 

[Geordie Spark]

Well hush my mouth, and you are correct I wont change

Good lad,

Billy Joel - Just The Way You Are - YouTube

 

[nickblake]

All you need to do is as you have said measure your r1r2 then Ze at the board of the main house then Zs at the shed board can be done by calculation r1r2 + ze = Zs as its taken from a circuit at the house db it will be Zs not Ze . and the RCD's are not in series they will be in parallel

 

[trev]

Gary moore - over the hills and far away - YouTube
Led Zeppelin - Over The Hills And Far Away (HQ) - YouTube
There ye gan Fatha. 2 o them.

 

[nickblake]

Gary moore - over the hills and far away - YouTube
Led Zeppelin - Over The Hills And Far Away (HQ) - YouTube
There ye gan Fatha. 2 o them.

you missed one where are the tele tubbies

 

[trev]

you missed one where are the tele tubbies

Cba mate, sorry if my omission of your favourites offended you in any way

 

[£££sjim]

All you need to do is as you have said measure your r1r2 then Ze at the board of the main house then Zs at the shed board can be done by calculation r1r2 + ze = Zs as its taken from a circuit at the house db it will be Zs not Ze . and the RCD's are not in series they will be in parallel

Thanks for the sensible reply. That's what i thought but thought maybe just maybe!

 

[PEG]

well, i've got 2 RCDs in series on one of my jobs. it's a stables layout and i'd hate to see a horse die if 1 RCD failed to trip. so there.!

...If you really care,they would both have to be 10 Ma,as they seem to knack if you walk briskly across a nylon carpet,and pat the boogers...:stooge_curly:

 

[davesparks]

well, i've got 2 RCDs in series on one of my jobs. it's a stables layout and i'd hate to see a horse die if 1 RCD failed to trip. so there.!

What trip current are those RCDs?

 

[Pete999]

Thanks for the sensible reply. That's what i thought but thought maybe just maybe!

r1r2 on a radial shouldn't that be R1+R2+ZE= ZS at the shed DB

 

[Octopus]

All you need to do is as you have said measure your r1r2 then Ze at the board of the main house then Zs at the shed board can be done by calculation r1r2 + ze = Zs as its taken from a circuit at the house db it will be Zs not Ze . and the RCD's are not in series they will be in parallel[/QUOTE]

I have to disagree with you:

"The source of supply is from a socket in the garden that is direct from the house CU RCD protected. or would I have to use the Ze from the house intake position. My shed is stand alone with a light circuit 6amp mcb and two radial circuits 20amp mcb all protected by RCD. another problem I have is if the shed CU trips the house Cu trips too. both protected by 30ma RCDs the garden sockets are 32amp mcb"

????

 

[telectrix]

What trip current are those RCDs?

they are both 30mA. the situation arose when the stables sub-main was installed with a 30mA RCD and no RCD protection at the supply end of the SWA. the main board was upgraded to RCD protected when some sockets were added to it. as there have not been any tripping issues for 3 years, i decided to leave well alone.

 

[brucelee]

Better to have to possibly reset 2 RCDs rather than try reset the Horse once fried lol is that your thinking mate

 

[brucelee]

To the Op your Ze at your shed is the Zs of your sub circuit some call it Zdb the only place you find Ze is the(Origin)
so Ze + ( R1+R2 Sub Main) this is your( Ze,Zdb, Zs) for the sub board then if you want the whole Zs then add (R1+R2 Final circuit)

Hows that clear as mud lol

 

[nickblake]

They are still in parallel L and N are the same where ever it comes from even if the supply is fed off the sockets its still Live and neutral , if it was in series then the live would enter the first rcd come out of the neutral of that RCD as a live to the live of the next RCD and the neutral would be connected to the last RCD,

 

[Pete999]

They are still in parallel L and N are the same where ever it comes from even if the supply is fed off the sockets its still Live and neutral , if it was in series then the live would enter the first rcd come out of the neutral of that RCD as a live to the live of the next RCD and the neutral would be connected to the last RCD,

View attachment 25957

Nick I think you may have misunderstood the point, 2 RCDs on the same leg of a circuit is not recommended unless some form of discrimination has been applied, perhaps with using a time delay RCD or 2 of differing mA ratings.
I get the impression you are trying to make a point about the difference between Series and Parallel, most of us know the difference.

 

[Octopus]

They are still in parallel L and N are the same where ever it comes from even if the supply is fed off the sockets its still Live and neutral , if it was in series then the live would enter the first rcd come out of the neutral of that RCD as a live to the live of the next RCD and the neutral would be connected to the last RCD,

View attachment 25957

So its Ok to have 2 RCD's in series then? I'm obviously missing your point.

The socket circuit supplying the shed is protected by a 30mA, then the shed has a 30mA RCD in it??

Thats how I read the OP

 

[nickblake]

Nick I think you may have misunderstood the point, 2 RCDs on the same leg of a circuit is not recommended unless some form of discrimination has been applied, perhaps with using a time delay RCD or 2 of differing mA ratings.
I get the impression you are trying to make a point about the difference between Series and Parallel, most of us know the difference.

Yes Pete i fully understand this and im not misunderstanding the point but when it is referred to as series it is incorrect ,they are in parallel simple as , and im not having a jab at any one, its just something that keeps cropping up and just wanted to point it out , any way every one nit pic's my posts so its my turn Lol

 

[Silly Sausage]

I disagree, RCDs aren't a load, they are devices connected in series, as in one is downstream from the upstream one!

 

[Pete999]

Yes Pete i fully understand this and im not misunderstanding the point but when it is referred to as series it is incorrect ,they are in parallel simple as , and im not having a jab at any one, its just something that keeps cropping up and just wanted to point it out , any way every one nit pic's my posts so its my turn Lol

I wasn't nitpicking mate just trying to clarify

 

[nickblake]

I know mate didnt think for a moment you where , archi they are still in parallel regardless of if they are a load or not lives are connected to lives neutrals to neutrals that is parallel

 

[Octopus]

I know mate didnt think for a moment you where , archi they are still in parallel regardless of if they are a load or not lives are connected to lives neutrals to neutrals that is parallel

ha ha, I see your point!

I still say having 2 x 30mA RCD's on the same circuit is bad practice - whether they be parallel or series!!

 

[Silly Sausage]

I know mate didnt think for a moment you where , archi they are still in parallel regardless of if they are a load or not lives are connected to lives neutrals to neutrals that is parallel

OK, they're not electrically in series, L & N are effectively electrically separate, but you could argue they are magnetically in parallel!

Me and everyone else will keep refering to them as being in series.

 

[Barry White]

Agree they are in series remove or trip the first and the second is dead in parallel it would still be energised. Either one or both may trip in fault conditions therefore no discrimination is the point that being made.
If the feeds were in parallel only the the one with a fault would trip

 

[davesparks]

Yes Pete i fully understand this and im not misunderstanding the point but when it is referred to as series it is incorrect ,they are in parallel simple as , and im not having a jab at any one, its just something that keeps cropping up and just wanted to point it out , any way every one nit pic's my posts so its my turn Lol

The coils of the RCD are in series rather than parallel, the current passes through the first live coil, then the second, then the second neutral coil then the first