1361 fuse

[Rob_the_rich]

So,asking a simple question on here was obviously a big mistake :facepalm:

why do you say that, I think you have been given good advice, amongst other things.

 

[jimmybobbob]

The good advice I take...its the other things  :slap

 

[steptoe]

The good advice I take...its the other things  :slap

like you cannot use an RCD to allow for a bad Zs on a TN system?

 

[jimmybobbob]

Where does 411.4.4 and 531.3.1 come in?

 

[steptoe]

what do they say?

do they relate to TT systems, or TN,  ?

 

[jimmybobbob]

TT

 

[steptoe]

TT

what do they say?

and, as they relate to TT why would you be using those for a TN system?

 

[jimmybobbob]

Hmmmm

 

[jimmybobbob]

So what does this conflicting regards actually mean?

 

[jimmybobbob]

Reg*

 

[steptoe]

I dont know,

I havent read it,

thats why I asked you

 

[jimmybobbob]

May take a long time to write it up tbh

 

[Rob_the_rich]

Where does 411.4.4 and 531.3.1 come in?

I will have a go.

531.3.1 is relevant to only part of a TN system, ie to a certain piece of equipment. it is not relevant to the origin of the installation (531.4.1 refers to the "origin" in TT systems)

You have fitted a TD 100mA rcd just downstream of the meter. This does not provide shock protection, overload protection nor fault protection between L and N. It only gives some protection against fire. 411.4.4 says if an RCD is used in a TN system an ocpd is also required. The DNO's ocpd can't be used to "protect" your cable if over 3metres. You will have to fit your own.

 

[steptoe]

I will have a go.

531.3.1 is relevant to only part of a TN system, ie to a certain piece of equipment. it is not relevant to the origin of the installation (531.4.1 refers to the "origin" in TT systems)

You have fitted a TD 100mA rcd just downstream of the meter. This does not provide shock protection, overload protection nor fault protection between L and N. It only gives some protection against fire. 411.4.4 says if an RCD is used in a TN system an ocpd is also required. The DNO's ocpd can't be used to "protect" your cable if over 3metres. You will have to fit your own.

thanks @Rob_the_rich

thats sort of what I was thinking,

but had no idea of the reg, and really had better stuff to be doing than going to the van for my book.

 

[Rob_the_rich]

I found a post on the iet forum about Ze readings and the DNO

EDFs maximum figure for 100A supplies with a BS161 fuse is 0.38 ohms.

For 80A 0.52Ohms
For 60A 0.73 Ohms
For 45A 1 Ohms
For 30A 1.92 Ohms
For 20A 2.93 Ohms
For15A 5.22 Ohms
For 5A 17.1 Ohms.         

 

so your 0.54 reading for 80A does seem ok.

 

[steptoe]

You mean on the internet for your photo of the front page :slap ......

I have a green one,

:red card

 

[Rob_the_rich]

I have a green one,

:red card

Sounds painful, you should get someone to inspect that fpr you.

If you have two 80A fuses in series, as in this case, and the consumer's one blows, the DNO's one would surely be damaged to the point of nearly breaking. Does anyone contact the DNO to suggest replacement?