P I R 300ma

[rob196]

I have just done a PIR on a TT system on a house and it has a 300ma as its main switch, all reading are very good ( low ze, zs's, ect ) 300ma reading is 31.4 ms

this was the slowest reading........do i need to make any reference to there not being a 30ma rcd for additional protection? 415.1.1 and there is no discrimination of the circuits? any thoughts will be much appreciated....

 

[spinlondon]

Seems odd that it's 300mA, and not 100mA.

You shold code the lack of 30mA RCD, on sockets, cables concealed in walls less than 50mm and circuits in special locations.

Yes the installation should be divided, allthough with the 300mA RCD they probablly don't suffer nuisance trips very often, if ever.

I'd use a code 4 for each.

 

[PBC_1966]

Seems odd that it's 300mA, and not 100mA.

300mA was pretty common before 100mA became the norm.

Agree on code 4.

 

[binky]

Lack of 30ma for lighting code 4, but would suggest code 2 for 300mA main incomer because that doesn't even comply with 16th edition. Not clear from your post, but if no 30mA for sockets likely to supply portable equipment outdoors, then would code 2 that aswell.

 

[spinlondon]

Although, the ESC consider lack of 30mA RCD protection for socket-outlets for equipment used outdoors, I don't think the difference between 300 and 30mA is that dangerous to warrent a code 2.

The likelyhood, is that a fault causing an RCD to operate, is going to be a lot more than 300mA, so either should work in the same time.

 

[rob196]

Although, the ESC consider lack of 30mA RCD protection for socket-outlets for equipment used outdoors, I don't think the difference between 300 and 30mA is that dangerous to warrent a code 2.The likelyhood, is that a fault causing an RCD to operate, is going to be a lot more than 300mA, so either should work in the same time.

Yes was thinking the same thing as the reading for the 300ma rcd was operating at 31.4ms when tested......

 

[binky]

Although, the ESC consider lack of 30mA RCD protection for socket-outlets for equipment used outdoors, I don't think the difference between 300 and 30mA is that dangerous to warrent a code 2.The likelyhood, is that a fault causing an RCD to operate, is going to be a lot more than 300mA, so either should work in the same time.

The whole point of 30mA is that is lower than the 50mA it takes to kill people, ergo 300mA is not giving sufficient protection, but obviously better than none, hance code 2. As for RCD operation given that earth leakge from appliances operates them quite happily the fault current needed to cause them to trip isn't going to be massive like a fuse for example, and although the RCD is tripping quickly when tested indicating good condition, you could still get fingers in places they don't belong, receiving a belt of 200mA cos your'e wearing rubber soled shoes providing partial insulation, and RCD will allow you to fry - gently

 

[seajayess]

Although, the ESC consider lack of 30mA RCD protection for socket-outlets for equipment used outdoors, I don't think the difference between 300 and 30mA is that dangerous to warrent a code 2.The likelyhood, is that a fault causing an RCD to operate, is going to be a lot more than 300mA, so either should work in the same time.

Unless you happen to ground the fault and then you may have wished it was 30mA CJS

 

[spinlondon]

Unless you happen to ground the fault and then you may have wished it was 30mA CJS

Why would that be then?

 

[PBC_1966]

would suggest code 2 for 300mA main incomer because that doesn't even comply with 16th edition.

Why not, subject to loop impedance being low enough to meet disconnection times?

The only specific RCD requirement was for sockets likely to be used for equipment outdoors.

The whole point of 30mA is that is lower than the 50mA it takes to kill people

A prolonged shock at <30mA through certain parts of the body can prove lethal.

 

[spinlondon]

In some circumstances, 15mA can be leathal.

Didn't notice that bit about the 300mA not being allowed by the 16th.

My understanding was that up to 500mA was allowed

 

[PBC_1966]

Precisely. I really don't like the way that 30mA RCD's have been portrayed as some sort of ultimate protection against electrocution, since currents well below 30mA can prove fatal in some circumstances. And that's not to mention the fact that if you get yourself across L & N, without there being sufficient current to earth as well, the RCD isn't going to do a thing to help you.

 

[spinlondon]

I suppose it's expected that the AC will throw you away.

Although, I believe that the frequency can play a part in that, and I seem to recall that between 50 to 60Hz was considered to be the most dangerous frequency range.

 

[rob196]

In some circumstances, 15mA can be leathal.Didn't notice that bit about the 300mA not being allowed by the 16th.

My understanding was that up to 500mA was allowed

Thought the max for a 30ma is 300ms?.......which is the same for a 300ma.....

 

[batty]

Thought the max for a 30ma is 300ms?.......which is the same for a 300ma.....

Depends what standard they were manufactured to.

 

[binky]

The only specific RCD requirement was for sockets likely to be used for equipment outdoors.

.

And 100mA Type S for main incomer on TT systems to meet higher disconnection times due to rod impedance