Ze & Pfc (Pefc & Pscc)

[Joshhosk]

I hope someone can help me as im getting different answers off different people

3P & N Supply

Ze:
Disconnect main earth
Set tester to 2 lead high L+PE (is this correct?) test between L1 - E / L2 - E / L3 - E recording the highest reading Ze (reconnect main earth)

Pfc (Pefc)
Set tester to 2 lead high L+PE (is this correct?) test between L1 - E / L2 - E / L3 - E

Pfc (Pscc)
Set tester to 2 lead high L+L/L+N (is this correct?) test between L1 - N / L2 - N / L3 - N

taking the highest reading of pefc and pscc and X2 (normally is L+L)

In what circumstances do you use 2 lead low / 2 lead high / 3 lead low?

can someone please guide me on this

 

[JamesL2022]

That sounds like the correct procedure to me, it’s certainly how I recently done it on my AM2 and the assessor was happy with it. From what I know, a hi current test will trip a downstream rcd. I usually Stick to low current and do what the tester says making sure the leads I probe on with are the correct polarity.

 

[Risteard]

I hope someone can help me as im getting different answers off different people

3P & N Supply

Ze:
Disconnect main earth
Set tester to 2 lead high L+PE (is this correct?) test between L1 - E / L2 - E / L3 - E recording the highest reading Ze (reconnect main earth)

Pfc (Pefc)
Set tester to 2 lead high L+PE (is this correct?) test between L1 - E / L2 - E / L3 - E

Pfc (Pscc)
Set tester to 2 lead high L+L/L+N (is this correct?) test between L1 - N / L2 - N / L3 - N

taking the highest reading of pefc and pscc and X2 (normally is L+L)

In what circumstances do you use 2 lead low / 2 lead high / 3 lead low?

can someone please guide me on this

For a three phase installation you needn't bother measuring PEFC as PSCC will always be the greater value. Either measure directly between phases if your meter can, or take the highest phase to neutral value and double it.

In fact there is an argument for using the doubled value regardless of whether your equipment can measure between phases as a bolted fault between all three phases simultaneously will be nearer this value than the 1.732 (root 3) value.

 

[Joshhosk]

It is for my AM2 mate i'm pretty sure they want you to demonstrate that you are capable and have the knowledge to carry out both tests even though in most cases pscc would be the higher value. thanks for your comment

 

[HappyHippyDad]

@Joshhosk
With regards the 2 lead low, 2 lead high and 3 lead low, these are the functions on my megger for use with Ze or Zs.

Both the 'low' functions are for when you have an RCD that you do not want to trip. I.e it puts a 'low' enough current through the system so as not to trip the RCD. The 2 lead low test involves connecting the live and earth only and can still obtain a Ze without the need to connect to the neutral. This can be very handy for say a switch that doesn't have a neutral.

The 2 lead high test is for testing Ze or Zs when there is no RCD that will trip, therefore a higher current is used.

The 3 lead low test uses live, neutral and earth and a low current.

 

[Joshhosk]

@Joshhosk
With regards the 2 lead low, 2 lead high and 3 lead low, these are the functions on my megger for use with Ze or Zs.

Both the 'low' functions are for when you have an RCD that you do not want to trip. I.e it puts a 'low' enough current through the system so as not to trip the RCD. The 2 lead low test involves connecting the live and earth only and can still obtain a Ze without the need to connect to the neutral. This can be very handy for say a switch that doesn't have a neutral.

The 2 lead high test is for testing Ze or Zs when there is no RCD that will trip, therefore a higher current is used.

The 3 lead low test uses live, neutral and earth and a low current.

Thanks for your reply, that is very helpful to me. I have tried to figure this out for a while now as all videos are 2 lead high that i can find.

I have my am2 next week do you suggest me asking the examiner if the am2 test board i will be working has a rcd present on the supply board? at least this shows knowledge and can chose the test settings accordingly

 

[JamesL2022]

Thanks for your reply, that is very helpful to me. I have tried to figure this out for a while now as all videos are 2 lead high that i can find.

I have my am2 next week do you suggest me asking the examiner if the am2 test board i will be working has a rcd present on the supply board? at least this shows knowledge and can chose the test settings accordingly

On my AM2 last week, the examiner had a control panel on the wall, which contained rcd protection for each installation bay. They do try to give you as much help as they are allowed to, I found there wasn’t anything to trip you up as such and they will answer such questions as is there rcd protection on my board elsewhere.

The only time he over-rides it via his over-ride switch is for when you do the rcd test on the rcbo of your ring final circuit.

If you stick to low current and don’t mix up your probes you should be fine.

one piece of advice for the testing I would give you is make sure you know your way around a schedule of inspections, like the tick off sheets as you can gain a lot of time to spend on the actual testing by doing the paperwork quickly.

 

[Joshhosk]

On my AM2 last week, the examiner had a control panel on the wall, which contained rcd protection for each installation bay. They do try to give you as much help as they are allowed to, I found there wasn’t anything to trip you up as such and they will answer such questions as is there rcd protection on my board elsewhere.

The only time he over-rides it via his over-ride switch is for when you do the rcd test on the rcbo of your ring final circuit.

If you stick to low current and don’t mix up your probes you should be fine.

one piece of advice for the testing I would give you is make sure you know your way around a schedule of inspections, like the tick off sheets as you can gain a lot of time to spend on the actual testing by doing the paperwork quickly.

Thanks mate! was your board a 3p&N supply? in that case you used 3 lead low right? any other tips you might find useful for me would be appreciated. I'm just trying to be as prepared as possible!

 

[HappyHippyDad]

Thanks mate! was your board a 3p&N supply? in that case you used 3 lead low right? any other tips you might find useful for me would be appreciated. I'm just trying to be as prepared as possible!

One thing I would do is play with your megger (or whichever MFT you have) as much as possible so you understand all it's functions and become familiar with it. Have a practise at home as much as you can.

 

[JamesL2022]

Thanks mate! was your board a 3p&N supply? in that case you used 3 lead low right? any other tips you might find useful for me would be appreciated. I'm just trying to be as prepared as possible!

Yes mate, it’s a TP&N supply and board. Mine was a Schneider with the slider switches for each way if that makes sense, remember to turn these on as well as the circuit breakers depending on the way you want to test. I did a global insulation resistance test with everything on, I bypassed the dol starter, disconnected the light, carbon detector, rcbo, and left the heating spur off as you don’t test the load side of the heating system. Just remember to operate all your light switches so you test every piece of cable. I forgot to do that on my insulation resistance but he’d watched me do it for my R1+R2 so he let me off thankfully as you do find yourself clock watching and stressing more than you would at work. Where are you taking the test?

 

[Joshhosk]

Yes mate, it’s a TP&N supply and board. Mine was a Schneider with the slider switches for each way if that makes sense, remember to turn these on as well as the circuit breakers depending on the way you want to test. I did a global insulation resistance test with everything on, I bypassed the dol starter, disconnected the light, carbon detector, rcbo, and left the heating spur off as you don’t test the load side of the heating system. Just remember to operate all your light switches so you test every piece of cable. I forgot to do that on my insulation resistance but he’d watched me do it for my R1+R2 so he let me off thankfully as you do find yourself clock watching and stressing more than you would at work. Where are you taking the test?

This reply has helped me so much mate I really appreciate it! I’m doing mine at JTL Birmingham mate same Schneider board, yeah I’ll get him to switch switches on on continuity and IR. did you have to carry the neutral through switches for your 2 way and intermediate

 

[JamesL2022]

This reply has helped me so much mate I really appreciate it! I’m doing mine at JTL Birmingham mate same Schneider board, yeah I’ll get him to switch switches on on continuity and IR. did you have to carry the neutral through switches for your 2 way and intermediate

I’m glad I’m able to help. I think if you sort of expect what’s coming it helps with the nerves a bit. Yeah on the lighting you’ll take a twin and earth to the first switch, a 3 core to the intermediate, a three core to the last switch and another twin up to the light, wago the neutrals and earth using grey as neutral and black and brown as your strappers. The feed from db to first switch the brown goes in the common. It’s exactly like this picture mate. Just watch the spec. As they have 1mm twin and 1mm 3core out to pick from but the spec says use 1.5mm so check everything’s the same as on the spec drawing you get.

 

[Joshhosk]

I’m glad I’m able to help. I think if you sort of expect what’s coming it helps with the nerves a bit. Yeah on the lighting you’ll take a twin and earth to the first switch, a 3 core to the intermediate, a three core to the last switch and another twin up to the light, wago the neutrals and earth using grey as neutral and black and brown as your strappers. The feed from db to first switch the brown goes in the common. It’s exactly like this picture mate. Just watch the spec. As they have 1mm twin and 1mm 3core out to pick from but the spec says use 1.5mm so check everything’s the same as on the spec drawing you get.

View attachment 52882

Legend mate!! Yeah I’m little nervous but I think I’ve prepared enough to have a good crack at it. I’m just nervous about live testing. I am assuming the supply to the testing board will have a rcd so I’m going to ask him to ensure I select the right settings to avoid tripping the rcd (3 lead low) I have told we have to do pfc (pefc) + (pscc) and take the highest reading X2 but as it’s 3p&N the highest reading would normally be between L-L/L-N. I’m just trying to practise filling out test certificates as I would hate for that to be the reason I fail. Any other tips you can give would be appreciated a lot. Thanks for your help mate
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One thing I would do is play with your megger (or whichever MFT you have) as much as possible so you understand all it's functions and become familiar with it. Have a practise at home as much as you can.

I have a metrel Mft but I believe on the AM2 it’s a megger mft

 

[JAWS]

Josh have you had a look through this. This may be of some help if you havent already got it.

https://jeffway.co.uk/training/wp-content/uploads/2019/09/NET-AM2-Candidate-Checklist-WE.pdf

 

[Joshhosk]

Josh have you had a look through this. This may be of some help if you havent already got it.

https://jeffway.co.uk/training/wp-content/uploads/2019/09/NET-AM2-Candidate-Checklist-WE.pdf

I’ve had a read through thanks mate!