Isolation transformer in place of a GFCI

On 2018/03/11 7:41 PM, snipped-for-privacy@gmail.com wr ote:

s above his swimming pool. There is one 15 amp circuit for both the lighting and the pump motor circuit. Thi s circuit is not protected by a GFCI outlet. The light s however are high enough so that no one can ever reac h up and grab them while in the pool. We have had disc ussions about installing a GFCI on the pool circuit bu t as of the end of last Summer's swimming season it ha d not been done. One day last Summer I observed his ki ds in the pool shooting water blaster pistols in the a ir. Alarmed I quickly killed power to the lights. Natu rally my concern was that someone in the pool shooting water up at the lights could be electrocuted. This br ought about an interesting hypothetical discussion. Wh at if the pool lighting circuit were connected through an isolation transformer. In theory then you should b e able to grab each side of the secondary without bein g shocked right? I can't see how the motor could fail and become a shock hazard so I was more concerned abou t the lights.

If you grabbed each side of the secon dary you would receive a

100/115/120/220/240VAC shoc k (depending on where you live on Earth). If somehow one side of the secondary connected to earth ground t hen you would back to the same risk of electrical sh ock. Your decision to run GFCI is correct IMHO.

ool circuit for him before the start of swimming seaso n which will be coming up in a couple of months.. Than ks, Lenny

Best decision.

John :-#)#

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I would prefer "either" rather than "each". Certainly not "both"! We have road signs saying "Use both lanes" which appear to encourage straddling. Presumably the public are supposed not to understand "either"...

Mike.

An isolation transformer does not guard against electrocution if one insert s one's self into the circuit. All it does is isolate the primary from the secondary such that for that circuit, the secondary side is isolated from g round. A GFCI device is the _only_ valid choice in this situation.

Peter Wieck Melrose Park, PA

rts one's self into the circuit. All it does is isolate the primary from th e secondary such that for that circuit, the secondary side is isolated from ground. A GFCI device is the _only_ valid choice in this situation.

Disagree. A much better choice is to remove the lighting and replace with a low voltage string, or a solar/battery powered string, or eliminate it all together.

By low voltage, I don't mean a modern string of LED lights. I mean a transf ormer isolated 12v system. The transformer should still be on a GFCI circui t.

120V above the pool area is just foolish and dangerous.

The pool pump motor may not like being on a GFCI. Often, inductive motor lo ads will trip them under a heavy load such as startup or near stall. In tha t case, the GFCI will work better back at the load center (circuit breaker panel) where the inductance of the wiring does not compound the problem. I just dealt with this last summer on a boat lift circuit.

Terry

a low voltage string, or a solar/battery powered string, or eliminate it a ll together.

sformer isolated 12v system. The transformer should still be on a GFCI circ uit.

loads will trip them under a heavy load such as startup or near stall. In t hat case, the GFCI will work better back at the load center (circuit breake r panel) where the inductance of the wiring does not compound the problem. I just dealt with this last summer on a boat lift circuit.

Of course. But if 120 VAC must be used, a GFCI devices is the only valid ch oice.

We feed our hot-tubs from a 50A GFCI safety switch in a dry location away f rom the hot-tub, but not near the main panel. It is easily reached from the outside as well.

installing a GFCI on the pool circuit but as of the end of last Summer's swimming season it had not been done. One day last Summer I observed his kids in the pool shooting water blaster pistols in the air. Alarmed I quickly killed power to the lights. Naturally my concern was that someone in the pool shooting water up at the lights could be electrocuted. This brought about an interesting hypothetical discussion. What if the pool lighting circuit were connected through an isolation transformer. In theory then you should be able to grab each side of the secondary without being shocked right? I can't see how the motor could fail and become a shock hazard so I was more concerned about the lights.

An isolation transformer would be safe up to a point. If there is a breakdown in the insulation anywhere in the circuit, one side of the circuit becomes grounded by accident and no one notices it. Then if someone gets on the other side of the line, he is shocked or worse. That is one reason most circuits are grounded.

Further to this, one can purchase GFCI plugs that replace the original power cord plug and provide the same safety aspects as a GFCI outlet or circuit breaker. The advantage is you can add that to the power cord quickly...

Do get one that is not counterfeit - Amazon/eBay are not reliable sources as the dealers there are completely unregulated and will sell you fakes as easily as real items. Go to a bricks and mortar shop if you want proper electrical safety.

John :-#)#

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There is one 15 amp circuit for both the lighting and the pump motor circui t. This circuit is not protected by a GFCI outlet. The lights however are h igh enough so that no one can ever reach up and grab them while in the pool . We have had discussions about installing a GFCI on the pool circuit but a s of the end of last Summer's swimming season it had not been done. One day last Summer I observed his kids in the pool shooting water blaster pistols in the air. Alarmed I quickly killed power to the lights. Naturally my con cern was that someone in the pool shooting water up at the lights could be electrocuted. This brought about an interesting hypothetical discussion. Wh at if the pool lighting circuit were connected through an isolation transfo rmer. In theory then you should be able to grab each side of the secondary without being shocked right? I can't see how the motor could fail and becom e a shock hazard so I was more concerned about the lights.

re the start of swimming season which will be coming up in a couple of mont hs. Thanks, Lenny

The only sensible option is to remove them and fit LV lights if wished. But to explore the hypothetical - or in your case real situation:

1. I am far from the only person to have been shocked by touching one termi nal of an iso transformer. They aren't always set up to isolate, and there is interwinding capacitance too. And of course there are faulty transformer s.
2. In an ideal world, an iso protects against contact with one terminal. It offers no protection whatever against contact with 2.
3. 120v lights can fall into the water
4. RCDs/GFCIs & isos interact to some extent in that if you put the RCD bef ore the iso, the output is NOT RCD protected at all. If used together the R Cd must go after the iso.
5. Rain-like water drops don't conduct electricity downward. You can stand under HV lines in the rain, the gaps between drops keep you safe. But this does NOT occur if you fire a water pistol up at it.
6. Remove the lights now. People in bodies of water are extremely vulnerabl e to shock.

NT

ing of lights above his swimming pool. There is one 15 amp circuit for both the lighting and the pump motor circuit. This circuit is not protected by a GFCI outle t. The lights however are high enough so that no one c an ever reach up and grab them while in the pool. We h ave had discussions about installing a GFCI on the poo l circuit but as of the end of last Summer's swimming season it had not been done. One day last Summer I obs erved his kids in the pool shooting water blaster pist ols in the air. Alarmed I quickly killed power to the lights. Naturally my concern was that someone in the p ool shooting water up at the lights could be electrocu ted. This brought about an interesting hypothetical di scussion. What if the pool lighting circuit were conne cted through an isolation transformer. In theory then you should be able to grab each side of the secondary without being shocked right? I can't see how the motor could fail and become a shock hazard so I was more co ncerned about the lights.

ng to install a GFCI on his pool circuit for him befor e the start of swimming season which will be coming up in a couple of months. Thanks, Lenny

sensible option is to remove them and fit LV lights if wished. But to explore the hypothetical - or in your case real situation:

on to have been shocked by touching one terminal of an iso transformer. They aren't always set up to isolate , and there is interwinding capacitance too. And of co urse there are faulty transformers.

world, an iso protects against contact with one termin al. It offers no protection whatever against contact w ith 2.

RCDs/GFCIs & isos interact to some extent in that if you put the RCD before the iso, the output is NOT RCD protected at all. If used together the RCd must go aft er the iso.

electricity downward. You can stand under HV lines in the rain, the gaps between drops keep you safe. But th is does NOT occur if you fire a water pistol up at it.

r are extremely vulnerable to shock.

Yeah, mains voltages around pools are waiting for the above average idiot that no one can protect.

Depends on isolation transformer type too. Some ground secondaries for noise.

Greg

I can't see how the motor could fail and become a shock hazard so

be sure the motor frame and all metal pipes are well grounded.

m

On Sunday, March 11, 2018 at 10:41:15 PM UTC-4, snipped-for-privacy@gmail.com wrot e:

There is one 15 amp circuit for both the lighting and the pump motor circui t. This circuit is not protected by a GFCI outlet. The lights however are h igh enough so that no one can ever reach up and grab them while in the pool . We have had discussions about installing a GFCI on the pool circuit but a s of the end of last Summer's swimming season it had not been done. One day last Summer I observed his kids in the pool shooting water blaster pistols in the air. Alarmed I quickly killed power to the lights. Naturally my con cern was that someone in the pool shooting water up at the lights could be electrocuted. This brought about an interesting hypothetical discussion. Wh at if the pool lighting circuit were connected through an isolation transfo rmer. In theory then you should be able to grab each side of the secondary without being shocked right? I can't see how the motor could fail and becom e a shock hazard so I was more concerned about the lights.

re the start of swimming season which will be coming up in a couple of mont hs. Thanks, Lenny

I've heard about how the inductive spark at the run start switch on some o f these motors can cause GFCI's to randomly trip out and sometimes they are even destroyed by this. And I know also that with this guy if it starts to become a constant problem the GFCI will simply be replaced with a standard duplex receptacle. So I have to ask if on the off hand chance the motor wi ring shorts to ground, and if the motor frame is properly grounded in theor y there would be no chance that anyone in the pool would be affected by thi s....right? Lenny

to ask if on the off hand chance the motor wiring shorts to ground, and if the motor frame is properly grounded in theory there would be no chance that anyone in the pool would be affected by this....right? Lenny

The words Theory and Proper are correct, but sometimes the proper becomes undone and the theory goes out the window.

You're already screwed. You looked at it. Anything that happens now is your fault.

The only recourse you have now is to fix it correctly. And that means no stupid shit with an isolation transformer or any other "white trash" repair ideas you come up with.

Fix it properly, make sure EVERYTHING is bonded to grond properly and install a GFCI.

The alternative is to do nothing then make explanations after somebody's kid gets killed.

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You got that right. People think we have some eye power like Superman or something.

Actually an isolation transformer would work, but there is nothing to indicate an insidious fault. All it takes is enough static electricity like during a thunderstorm striking nearby or something and it no longer isolates.

So it would be wise to use a GFCI, and then of course you don't need the isolation transformer.

Circuit breakers and GFCI outlets are designed to minimize the possibility of a no trip failure mode. No such thing in an isolation transformer. It could make it worse actually.

I would still recommend a low voltage alternative for the lighting. And a GFCI because when you are all wet you can get a shock from 12 volts. Probably not lethal directly, but could prevent you from getting your head out of the water or something.

GFCIs are far from failsafe. Well worth having but not entirely reliable by any means, and not failsafe.

NT

Yup. At work we say, "you touch it, you own it."

by any means, and not failsafe.

Nothing is fail-safe other than a low-voltage, battery-operated system. Any thing that includes a primary source whether isolated or not, whether on a GFCI device, or not - there could be a way for primary power to migrate to the secondary side and/or jump the GFCI device. One may reduce the odds of failure via redundancy, or by other means. Or, one may take ordinary common

-sense precautions in the full understanding that nothing is perfect.

Kinda-sorta like spending one's life living under a rock, or taking the ord inary risks of daily life and enjoy what life one is allotted under such te rrible threats.

Peter Wieck Melrose Park, PA

e by any means, and not failsafe.

nything that includes a primary source whether isolated or not, whether on a GFCI device, or not - there could be a way for primary power to migrate t o the secondary side and/or jump the GFCI device. One may reduce the odds o f failure via redundancy, or by other means. Or, one may take ordinary comm on-sense precautions in the full understanding that nothing is perfect.

rdinary risks of daily life and enjoy what life one is allotted under such terrible threats.

That doesn't really tell us anything does it. Let me put it another way: RC D failures are no rarity. They're nowhere near failsafe. And of course they don't act on all shock/electrocution scenarios anyway.

NT