Shed rcd

[pickles]

I have an rcd that protects all the circuits in my shed.

2 questions

I also have an rcd in the house protecting the power circuits, including the armoured cable to the shed. Do I actually need a seperate rcd in the shed. I want to keep it because it prevents the house going out if there is a fault

It is old, circa 1985/86 and is enclosed in a plastic waterproof box and cover. It works perfectly on the test button and worked about 5 years ago when I cut the lawnmower cable by accident. The wiring is in good order, terminals clean and corrosion free etc. Do these things ever wear out or go soft so that they don't trip fast enough. If they do is there any way I can test it

Thanks

 

[SwindonSpark]

Yes you can test it, assuming it is 30mA and providing supplementary protection for direct contact.

Using your RCD tester apply I(delta)n x 0.5 and it shouldn't trip. Then change the phase angle and repeat.

Then apply I(delta)n x 1 and it should trip within 200ms. Then change the phase angle and repeat.

Then apply I(delta)n x 5 and it should trip within 40ms. Then change the phase angle and repeat.

Lo and behold, you have tested your RCD in full!

 

[JohnD]

I think I can pick up a subtext here, about a Periodic Inspection Report by someone with the right training and equipment



But Pickles is doing the right householder thing by using the test button. Sometimes RCDs get sticky and don't trip, better to find that with the test button than with your skin. The buttons I believe give quite a heavy simulated fault.

 

[ban-all-sheds]

I want to keep it because it prevents the house going out if there is a fault

That not guaranteed.

That it happened the right way once is just luck.

Best bet is to keep the RCD in the shed, assuming it is OK - a proper test would be a good idea, given it's age, and move the supply cable to the non-RCD side of the house CU.

 

[pickles]

Using your RCD tester

How much do they cost to buy

 

[Adam_151]

Circa £250, personally I probably wouldn't bother with a stand alone RCD tester, I'd probably get an all in one such as the megger MFT1502 for about £600 (if you shop around... have a look on ebay)