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UL safety for circuit on 240V

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carmusic

New Member
I am designing a small prototype of electronic board, it wil be powered by split-phase 240V (america) with no neutral. Do i need to put 2 fuse on main of transformer or only one is ok? Transformer will be grounded. No parts are acessible for touching. This board will control heaters on 240V that are not fuse (protected by distribution breaker of house)
 

Sceadwian

Banned
I'd fuse both sides in case there's a short to some external ground (like a person) Make damn sure you have everything isolated and keep in mind unless you're an electrician the installation is illegal. You can make it legal by having an electrician come in afterward and sign off on it in some cases but I'm not sure if that applies to something like what you're making. If there is damage injury or death that can be traced back to a device you hand made you can be held criminally liable, worse case scenario think manslaughter charges.... So please make sure you run this by a qualified electrician.
 
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tcmtech

Banned
Most Helpful Member
Standard American NEC code states all line sources must have properly sized fuse or circuit breaker disconnects.

For personal use in your home there are giant grey areas though relating to custom control devices.
Inspection is not needed if you meet the proper safety requirements relating to amp capacity, voltage, grounding and physical shielding.

Personally I recommend that everyone that does any home wiring or custom modifications of home appliances or electrical systems or just has an electrician over in general get the most current NEC code book.
They get printed every three years and cost around $40 on line if you know where to shop. ;)
Its money well spent and if you do need work done by an electrician it will save you far more than $40 the first time you can call BS on some thing they say you need done that is not required by the code book! That happens a lot! :eek:
I have personally found far too many professional electricians that do not even own a current issue code book let alone know how to properly look up and use information from one!:eek: Rather scary when I learned that! :mad:
 

carmusic

New Member
it is not for a personnal modification but for a new model of water heater, i will go through UL inspection but i must make sure before i go there that my prototype is ok for UL to start production
 

Sceadwian

Banned
I don't know the specs but since it's not isolated I'd say you should fuse both sides, I would at least.
 
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