19.1ka psc reading on a 2 bed small house!

[ch1cki]

Any ideas??

 

[ch1cki]

change it from TNCS to TT to bring it down?

 

[IQ Electrical]

Place a large screwdriver across line/neutral and use a thermometer to measure it's temperature?

Posting under the influence of alcohol, just blow into the mouthpiece please sir....

 

[johnboy6083]

change it from TNCS to TT to bring it down?

as IQ has already mentioned, that may well bring your PFC down, but will not affect PSCC which, as IQ said will be very close to your PEFC figure.

theres no way i would remove a PME to install a TT.
you have 2 options in my opinion.

1) ensure your main head is man enough to cope, ie it has a sufficient breaking capacity.
2) between your meter and your CU, install a switchfuse with a bs-88 fuse in it.

 

[IQ Electrical]

as IQ has already mentioned, that may well bring your PFC down, but will not affect PSCC which, as IQ said will be very close to your PEFC figure.

theres no way i would remove a PME to install a TT.
you have 2 options in my opinion.

1) ensure your main head is man enough to cope, ie it has a sufficient breaking capacity.
2) between your meter and your CU, install a switchfuse with a bs-88 fuse in it.

Option 2 is good but it MUST be a BS88-3 (formerly BS1361) to comply with the conditional rating in BS 60439-3.

 

[pushrod]

Option 2 is good but it MUST be a BS88-3 (formerly BS1361) to comply with the conditional rating in BS 60439-3.

I know the short circuit capacity of BS 1361 type l and type ll fuses are 16.5kA and 33kA respectively, but i was taught that a type ll (33kA) if coupled with protective devices inside an enclosure to BS EN 60439-3 (or BS 5486-13) were only suitable for fault currents up to 16kA. As per the OSG (P56). Here we are supposedly dealing with a fault current of 19kA+

It is the risk of exploding mcbs we are worried about isn't it? I would have guessed the route to take would be to improve/uprate the enclosure around the CU.

 

[johnboy6083]

It's the risk of the fault arcing over the protective device, and the device not being able to interrupt the fault current.

 

[pushrod]

It's the risk of the fault arcing over the protective device, and the device not being able to interrupt the fault current.

I appreciate that what you have said can happen, but in such a case if that was all that could happen, it would just be left to the main cut-out to interrupt the fault current.

I thought if the let through energy (I²*t) exceeds the manufacturer's specification then they make no guarantee about the integrity of the frame of the PD (ie it may come apart) - and that this is one of the aspects of enclosures to BS EN 60439-3, to offer increased protection for eg mcbs with just a 6kA short circuit capacity. But, as mentioned previously, this protection is only suitable for fault currents up to 16kA.
.

 

[IQ Electrical]

The testing for the conditional rating of UK Annex ZA is concerned with destruction of the downstream protective devices and continuity of the fault loop by way of 'arcing through'.

The test involves covering the consumer unit in clean, dry cheesecloth to assess any thermal damage etc.

Excellent night time reading, if anyone would like a copy.....

 

[Guest 004]

^ give that one a miss me thinks

 

[ch1cki]

My friends next door neighbour who has a degree in electrical engineering, and teaches at my local college said that by introducing an earth electrode to the property which in turn use to be TNCS you would be introducing parallel paths to the system or some bull**** like that (I got a bit lost with it) which in theory should half your PSCC, because it would be pretty much split in 2. He said that if i was TNS if would be a different matter (still lost) We went back to the property, put the rod in out of curiosity, changed it from PME, did a PSCC test and BANG it pretty much halved it. I didn't really follow anything he was saying but it pretty much sounded like that, he knows what he's talking about.

 

[Guest 004]

ok so you did not follow what he was saying, but have come on here blazing...............jeezz

 

[IQ Electrical]

It sounds to me like he was talking from his Arsenal, I'll ask for the last time in this thread, how does the addition or not of a rod affect the measured PSSC?

This is a measured value between line and neutral conductors!!!!!!!!!!!!!

Please beg/buy/steal a copy of Guidance Note 3 and all will become clear....

 

[Guest 004]

It sounds to me like he was talking from his Arsenal, I'll ask for the last time in this thread, how does the addition or not of a rod affect the measured PSSC?

This is a measured value between line and neutral conductors!!!!!!!!!!!!!

Please beg/buy/steal a copy of Guidance Note 3 and all will become clear....

we were both out, but alas have came back in again,

fecking kronenberg.............

 

[IQ Electrical]

we were both out, but alas have came back in again,

fecking kronenberg.............

I can't leave posts like that, some use these threads as 2391-10 revision etc. so it's important to explode the myths!

When the TWO tests to establish PFC are understood, the earth rod suggestion looks quite silly and that's the case whether you have the degree or not!

 

[Guest 004]

ok Ben got it??