Re: Isolation Transformer

Posted by John T on July 07, 2016 at 07:53:31 from (216.249.81.101):

In Reply to: Isolation Transformer posted by Moonlite37 on July 07, 2016 at 06:03:23:

Moonlite, with all due respect to electrician you spoke to, its my professional electrical engineers opinion what he said "isn't necessarily always exactly true" (it depends on how you wire and use it, see below).

Heres the real deal: If its a true ISOLATION Transformer NOT an autotransformer, it has no wired physical connection between the Input and Output, the Primary over to Secondary energy transfer takes place by electromagnetic induction.

THEREFORE if you're using it and come in contact with one of its outputs while your bare feet or other hand or whatever is on wet ground or a grounded metal work bench etc YOU "more then likely" DONT GET ANY BAD SHOCK (notwithstanding capacitive or inductive low energy transfer). The isolation x formers voltage is ONLY with respect to the other transformer terminal NOT earth ground or grounded metal objects (unless its bonded to the other isolation transformer terminal which usually its not). HOWEVER if you were using the utility (NON Isolated source) its Neutral is tied to mother earth and the equipment grounding conductor (third green safety ground wire) so touching one of those wires while barefotted on wet ground or touching a grounded metal work bench can give a bad shock.

TO MY OLD TIRED ENGINEERS BRAIN, THAT DOES AFFORD SOME DEGREE OF PROTECTION when used properly. That's one reason for SAFETY (among others) they design make and use isolation transformers in certain situations.

HOWEVER there is a degree of truth to what the electrician said. If using the utility, the grounding electrode conductor is wired to the outer metallic conductive case/frame/shell of a tool or appliance and can have contact with a metal work bench etc. THEREFORE if there's a hot to case short, the grounding conductor carries fault current back to the panel so the breaker trips. With a 2 terminal isolation transformer there's normally no equipment grounding conductor arrangement.

THIS IS THE SAME THEORY I TRIED TO EXPLAIN LAST WEEK (but unfortunately most non electricians failed to understand OSHA and the NEC rules) WHY OSHA AND THE NEC don't earth ground portable generators on job sites (the OSHA article says it can create an electrocution hazard) that serve plug and cord connected tools via onboard receptacles. If you did earth ground the generator and on wet ground you ACCIDENTALLY COME IN CONTACT WITH A HOT WIRE YOU GET SHOCKED, buttttttttt if there was no reference to mother earth (by having NO earth ground rod) if you touch a hot wire you most LIKELY DO NOT. That's why instructions that come with generators etc say ground per the NEC because the NEC and OSHA cover all the different situations when you earth ground and when you do not. ALSO lay gents do not understand the difference between Neutral BONDING and Neutral GROUNDING and EARTH GROUNDING and what's a GROUNDING ELECTRODE. Hey that's NOT a bad thing about non sparkies, it can take years of training and experience to get it and some never do lol

NO WARRANTY no way I can cover all the bases and every conceivable situation nor explain in a paragraph what takes whole books so this is ONLY a short approximated abbreviated NOT 100% PERFECT ALL CORRECT answer, I just do the best I can in a short time to help and try to save a life, SO THERE TAKE OR LEAVE IT or do what Billy Bob and his brother in law Bubba tell you, its your life. Other electricians or non electicians may have different opinions, to each their own, this is mine FWIW which is nothing, same as what was paid for lol

John T

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