Galvanic Isolator

[Chewbacka]

4 hours ago, hider said:

I wonder why I bothered posting on here. I thought I may be able to help, seems that at every turn I am wrong. I know why my mate Sam bu**ered off now.

I never suggested that with their limited knowledge the OP made their own.

And to answer what current under fault conditions my cheapy alternative £4 GI would stand, at least 45 Amps. As to how long, well the mains would have tripped long before the diodes got even warm.

But just ignore me and I'll stop posting then you could all continue with the inane childish clown postings instead. How utterly boring.

Your £4 jobbie also ignores the failure mode where (just example) 13A flows continuously via the earth lead and the RCD fails to trip.  Rare but with a faulty RCD it could happen, In which case the diodes will be dissipating about 20W which will burn out diodes if they are not bonded to an adequate heat sink.  

So your low cost DIY job will work fine whilst there are no catastrophic electrical faults protecting the boat from galvanic corrosion, but in the event of a catastrophic failure of your electrical system you would end up burning out the diodes and potentially ending up with a live hull, which would be extremely risky to anyone getting on or off the boat etc.   It's a bit like seat belt wearing, been driving for 40 years and never had a crash that needed a seat belt, but I still use one.