Three phase question

[sajeel]

Hi
Just did a three phase consumer unit, tested insulation and continuity before commission tested three phase in correct order. When I switched on it sparked and took out l1 and l2 fuse, incomer has two faulty lock screws at top apart from that any other ideas ?

 

[Sintra]

Thanks to all who responded productively, the supply is 3 phase 420v fused by two 100a and one 60a this is fed Into ryefield board 5 way which is feeding shop and 2 flats by of 5 60a fuses. See pictures attached. This is then fed using armoured cable to db. Have done continuity tests live phases to earth and neutral no fault found. Insulation resistance is 675m ohm and passes fine. When I fit l1 fuse in ryefield db works fine, however if I fit l2 fuse and test it blows fuse l1 and l2 but the flats are unaffected as they are fed direct off supply. Any productive help will be appreciated. By the way phases are correct and even if they would not that should not blow fuse on ryefield.

What about an IR and continuity test between phases. What way is the SWA glanded into the bottom of the ryefield.

 

[Darkwood]

Yes as Sintra points out you say you have Insulation tested to earth but because its taking out 2-phasesthe fault is clearly ph-ph have you insulation tested between phases????

You state all outgoing loads are off line so the fault has to either be the cable, the main switch or issue with the busbars in the board... when you do your ph-ph testing i assume the dist' board main switch is in the on position with supply de-energised upstream.

This is basic testing and theory and thus im not surprised some choose to ridicule you.. your playing with electrics yet you come across as lacking competence with regards to the nature of this thread.

Your either not supplying the vital info we need here or your slightly fabricating the truth a little about the testing or the loads connected when energised otherwise you would be aware of where the problem lies.

 

[Engineer54]

Apart from what has been stated above, you still haven't explained what's been ''rattling'' you certainly haven't shown us any isolator switches or the like, in the photos you posted!! So we're not getting a clear picture of this supply distribution system at all....

 

[sajeel]

What about an IR and continuity test between phases. What way is the SWA glanded into the bottom of the ryefield.

I will perform some more tests, performed ir live phases to neutral will do between live phases. Did perform continuity test between phases.
Will post back with readings.

 

[trev]

I will perform some more tests, performed ir live phases to neutral will do between live phases. Did perform continuity test between phases.
Will post back with readings.

Any reason why you didn't perform the full spread of test while you were there? The problem could probably have been bottomed out by now.

 

[Sintra]

IR tests on TP&N should always be a 10 point test. Still interested to know how that SWA has been made off.

 

[sajeel]

IR tests on TP&N should always be a 10 point test. Still interested to know how that SWA has been made off.

The swa cable is 5 core fed directly into ryefield board, and i have terminated after meter into cu with a 25mm gland, i only used armour so i would not need to fit trunking as space was limited and thats why i used 5 core so i would have a good earth, not use armour as main earth.
The run is very short around 2-3M, before the shop was fed off henley blocks and the supply was shared from one meter.

 

[Knobhead]

So in 2 days you haven’t done any real testing and you’re still floundering about. Did everything work before you started?

You must have some very tolerant customers, I’d be jumping up and down screaming at you.

I hope you aren’t charging for this extra time.

 

[trev]

So in 2 days you haven’t done any real testing and you’re still floundering about. Did everything work before you started?

You must have some very tolerant customers, I’d be jumping up and down screaming at you.

I hope you aren’t charging for this extra time.

Careful Tony. He did say he only wanted positive things said, must be a sensitive little soul

 

[Knobhead]

I didn't swear or use words like incompetent.

I was being nice (for me).

 

[sajeel]

So in 2 days you haven’t done any real testing and you’re still floundering about. Did everything work before you started?

You must have some very tolerant customers, I’d be jumping up and down screaming at you.

I hope you aren’t charging for this extra time.

Hmm as always jumping the gun before knowing the facts, the install was single phase before re wire so there was no issues. Even now the db works in single phase mode. The supply was shared by way of henly blocks, I fitted 5 way ryefield board to split 2 flats and 3 phase for shop.

Just for your information the shop is empty, and i have been doing other works there not sleeping for 2 days.

Making remarks is easy giving useful advice is harder !

 

[GLENNSPARK]

Hmm as always jumping the gun before knowing the facts, the install was single phase before re wire so there was no issues. Even now the db works in single phase mode. The supply was shared by way of henly blocks, I fitted 5 way ryefield board to split 2 flats and 3 phase for shop.

Just for your information the shop is empty, and i have been doing other works there not sleeping for 2 days.

Making remarks is easy giving useful advice is harder !

just do as you`v been told and get it tested properly....
if the fault is there....you will/should find it...
i dont hold my breath after reading this mind you but....

 

[Sintra]

When you say it works in single phase did you link out the incomer?

 

[Flanders]

Just Had a look at the picture. You say you have made of the SWA one end but how have you made off the swa in the Ryefilld unit . The armering could easily cut into the cable with that bend on it and short two phases together . As most have pointed out doing the ir test between phase is what you should of done in the first place a continuity test will not find the fault unless its a deed shor

 

[Gazthesparky]

Thanks to all who responded productively, the supply is 3 phase 420v fused by two 100a and one 60a this is fed Into ryefield board 5 way which is feeding shop and 2 flats by of 5 60a fuses. See pictures attached. This is then fed using armoured cable to db. Have done continuity tests live phases to earth and neutral no fault found. Insulation resistance is 675m ohm and passes fine. When I fit l1 fuse in ryefield db works fine, however if I fit l2 fuse and test it blows fuse l1 and l2 but the flats are unaffected as they are fed direct off supply. Any productive help will be appreciated. By the way phases are correct and even if they would not that should not blow fuse on ryefield.

Am I missing something here you need to test this properly as has been said insulation testing a TPN supply is a 10 point test

You obviously have a problem between l1 and l2 if you put power onto l1 and test l2 do you get a voltage

The fact that the fuses blow when l1and l2 are energised suggests that you are shorting 2 phased together

I would look at that poor termination of the armour it should be glanded properly even though your not relying on the armour.

Have you nicked the insulation of the cores as you have cut and terminated the armour