Max PFC

[danzor]

anyone know where I can find a guideline to PFC.

I get the reading when I test Ze, but like most people I don't actually know if the reading is to high/low. Or if there's any tables to follow. ta

 

[SPECIAL LOCATION]

anyone know where I can find a guideline to PFC.I get the reading when I test Ze, but like most people I don't actually know if the reading is to high/low. Or if there's any tables to follow. ta

Hello Danzor,

Welcome

With the PFC, we are looking at the Maximum fault current that will flow in the event of a short circuit fault on the installtion...

The maximum current that flows must be less than the Maximum braking capacity of the overload protection switch gear, so that it can disconnect the supply without the circuit breaker or main switch exploding.

Table 7.4, Page 57 of the On Site guide give typical max breaking capacities for various protective devices.

e.g. your normal Type B MCB is 6KA (6000a)

typically this is indicated on the front of the MCB as a little number [6] or [6000] in a box .

the main house fuse e.g. 80A BS88 is a 16.5KA.

 

[kme]

The reading is the reading.

It relates solely to the loop to the supply transformer (p-e or p-n). Almost always P-N. It is simply the current that could flow at that point in the event of a dead short (i.e. of negligable resistance) occuring. Basic ohms law (I=v/r) means that, for whatever U/Uo is, divided by the resistance of the loop, equals the current in amps, or KA.

i.e. if P-N is 240V, and 0.1 ohm, I=240/0.1 = 2400A, or 2.4KA

HTH

KME

SL - I`ve changed my mind - start typing slowly again!

 

[sparky999]

The reading is the reading. Basic ohms law (I=v/r) means that, for whatever U/Uo is, divided by the resistance of the loop,

When u say this does this mean the ZE or is it summit else?

 

[DonkeyDong]

hi there,

As you are measuring the pefc at the origin (normally), then the resistance is in fact ze.

When you are measuring psfc at the origin (normally), then the resistance is the value between phase and neutral (at the incomer/tails)

D.

 

[kme]

When u say this does this mean the ZE or is it summit else?

As DD`s post after yours clarifies (I hope)

The loop will be Ze if you`re testing the Earth Fault Loop. Which should be the same as the Prospective Short Circuit current on a TN-C-S.

For a TN-S, it is possible to get a higher fault current ( lower resistance) on the phase earth path.

And, on a TT the Phase-Neutral should, under normal circumstances, be the PFC.

Basically, measure both at the incomer. The highest current reading goes into the PSC box.

 

[Mike P]

As I understand the PFC noted in the report is whichever the highest PSC or PFC.

 

[kme]

As I understand the PFC noted in the report is whichever the highest PSC or PFC.

Basically, measure both at the incomer. The highest current reading goes into the PSC box.

Fink that wot I saidBlushing? :|

 

[heathelect]

Hello Danzor,Welcome

With the PFC, we are looking at the Maximum fault current that will flow in the event of a short circuit fault on the installtion...

The maximum current that flows must be less than the Maximum braking capacity of the overload protection switch gear, so that it can disconnect the supply without the circuit breaker or main switch exploding.

Table 7.4, Page 57 of the On Site guide give typical max breaking capacities for various protective devices.

e.g. your normal Type B MCB is 6KA (6000a)

typically this is indicated on the front of the MCB as a little number [6] or [6000] in a box .

the main house fuse e.g. 80A BS88 is a 16.5KA.

Main house fuses are often bs 1361 type 2b, 100a,as well. dave

 

[no1electrician]

three phase psc .phase to phase short circuit is higher ,so the value you get when you measure phase to earth has to be doubled .

 

[SLIPSHOD & SLAPDASH]

You will find that most house main fuses for the past 30 years have been BS1361 pt2 which have a 33KA rating

 

[SPECIAL LOCATION]

Main house fuses are often bs 1361 type 2b, 100a,as well. dave

Indeed, Dave...

I was just quoting an example out of the book, as a point of reference where you can veriy if your pfc is too high for your ciruit breakers etc.. as per danzors opening point!

 

[Nicky Tesla]

Does anyone know the max ratings for bs3036 rewireable fuses

 

[kme]

Depends on the rating, but, as a rule on domestic sizes, they`re 1 or 1.5KA AFAIK

KME

 

[danzor]

thanks for the help Pray

 

[kme]

Anytime

 

[SPECIAL LOCATION]

Does anyone know the max ratings for bs3036 rewireable fuses

On Site Guide Pg 57 give the following.. BS 3036:-

designation,

S1A...1kA,

S2A...2kA,

S4A...4kA.

You are going to have to get your wallet out Nicky, buy that OSG m8! ; \

 

[Nicky Tesla]

On Site Guide Pg 57 give the following.. BS 3036:-designation,

S1A...1kA,

S2A...2kA,

S4A...4kA.

You are going to have to get your wallet out Nicky, buy that OSG m8! ; \

wots S1A, S2A and S4A in relation to 5, 15, 20, 30 and 45amp?

Ive been to waterstones bookshop this week but they'd sold out of the OSG

 

[kme]

wots S1A, S2A and S4A in relation to 5, 15, 20, 30 and 45amp?Ive been to waterstones bookshop this week but they'd sold out of the OSG

NICEIC have it in stock, as do TLC

 

[Apache]

NICEIC have it in stock, as do TLC

Amazon have them in stock @