home built rcd test isolator

[riverstyx]

I was looking at the likes of the seaward ntb-1 portable rcd isolator (for testing plug-in RCDs without risk of tripping an upstream RCD in the CU) but it seems pretty expensive for the amount of use I'm likely to make of it.

I am now considering constructing something similar using a standard 13A socket outlet and the isolating transformer from an old shaver socket - with one end of the secondary winding connected to the line terminal of the socket, and the other end of the winding commoned to both the neutral and earth terminals.

Does anyone have any thoughts on this or envisage any issues with this approach?

 

[Evans Electric]

Do you mean the primary earth term ?

In which case it will trip the upstream device . Methinks .

Someone with a brain will be on shortly no doubt , at the moment you only have me.

 

[riverstyx]

Nope, I mean something like this:-

L in ---- P | S ----- L out

N in ---- P | S ----- N & E out

'in' being the supply, and 'out' being the 13A socket to which the plug in RCD under test will be connected

Apologies for the crude transformer drawing ; -)

 

[steptoe]

whats the point?

surely the design is wrong if NO discrimination has been provided?

 

[riverstyx]

whats the point?surely the design is wrong if NO discrimination has been provided?

I'd agree if we were talking about fixed RCD sockets or RCDs in sub DBs where there is another RCD upstream, but I'm talking about plug in RCDs that I encounter on the rare occasions I let someone drag me in to doing some PAT testing where the supply I'm using to test them may not be the supply they will ultimately be used on.

 

[steptoe]

so then you test them at source,

remember, if you are testing an RCD then you test it at source, if you simply test it at a random point then you are also testing the cabling to that point as well,

does that come under your PATing?

couldnt you test them on your extension lead setting?

 

[SPECIAL LOCATION]

Why are you bothering with an isolating transformer?

Do you plan on PAT testing in the bathroom???

Just make a very short extn lead:-

Live @ plug -> Live @ socket

Neutral @ plug -> Neutral @ socket

Earth @ plug NOT connected

Earth @ socket strapped to Neutral @ socket.

Bang a nice big label on the plug and socket making it clear that it is for test purposes only....

Job Done!!!!!

Guinness

 

[steptoe]

^ jobs a good'un

 

[SPECIAL LOCATION]

so then you test them at source,remember, if you are testing an RCD then you test it at source, if you simply test it at a random point then you are also testing the cabling to that point as well,

does that come under your PATing?

couldnt you test them on your extension lead setting?

I think he's on about testing one of these sort of plug in adaptor thingies..

Masterplug RCD Adaptor | Screwfix.com

when you are not 100% that the power source you are connected to hasn't already got a 30ma RCD on it...

AND

you don't want to accidentally trip the main RCD @ the CU!

GuinnessGuinness

 

[ProDave]

IF I am reading it correct, then he's inserting the transformer so that when the RCD under test trips it DOES NOT also trip any other RCD that may be feeding the socket he has plugged the tester into.

When PAT testing, and testing a plug in RCD he would be very unpopular is his test setup tripped out a whole room of PC's in an office when he pushed the button to test the plug in RCD.

Hence the isolating transformer to ensure the RCD fault current through the RCD under test does not cause an imbalance to the supply source and trip another RCD as well.

Personally I would use a larger isolating transformer than one from an old shaver socket, but I guess that should work.

 

[NozSpark]

Why are you bothering with an isolating transformer?Do you plan on PAT testing in the bathroom???

Just make a very short extn lead:-

Live @ plug -> Live @ socket

Neutral @ plug -> Neutral @ socket

Earth @ plug NOT connected

Earth @ socket strapped to Neutral @ socket.

Bang a nice big label on the plug and socket making it clear that it is for test purposes only....

Job Done!!!!!

Guinness

I've got one of those somewhere for testing extension leads for portable hot tubs.