Why does AFDD protection need to be per circuit?

[spud1]

Hi again!

Why does AFDD protection where provided need to be installed per circuit instead one AFDD covering several circuits, like for example RCDs in domestic split load CUs?

Is there a technical reason or is it another manufacturers money making myth!?

Thanks.

 

[Jon Bateson]

Hager released a memo on their required test currents. Need testing at 200 or 250 mA for 5x I think from memory

 

[telectrix]

Hager released a memo on their required test currents. Need testing at 200 or 250 mA for 5x I think from memory

that would mean all of us having to replace our MFTs with ones that do 200-250mA instead of 150mA.

 

[Jon Bateson]

that would mean all of us having to replace our MFTs with ones that do 200-250mA instead of 150mA.

Use the VAR setting. Sad but true

 

[telectrix]

Use the VAR setting. Sad but true

VAR? what's that?

 

[Jon Bateson]

VAR? what's that?

It’s the variable setting on your MFT to allow you to select desired trip test current.

 

[telectrix]

ain't got that. it's x1 or x5. that's it. so 30mA or 150mA. no way to achieve 200 or 250mA.

 

[Jon Bateson]

ain't got that. it's x1 or x5. that's it. so 30mA or 150mA. no way to achieve 200 or 250mA.

Don’t use Hager then

 

[Intoelectrics]

Hager released a memo on their required test currents. Need testing at 200 or 250 mA for 5x I think from memory

Then its no longer 5 x but 7 or 8 x for a 30mA

 

[Jon Bateson]

Then its no longer 5 x but 7 or 8 x for a 30mA

Yep that’s right. Only Hager have taken this approach I think
[automerge]1569937656[/automerge]
It’s permissible to use 300 mA test at 1x and record this result. Under 40ms is acceptable. This equates to a 5x test if you can’t test at 250mA