megger readings

[var]

I was sent to trouble shoot a gfi brkr tripping on a hot tub, they had already called the spa guy and he said it was electrical and he had checked and everything is ok with the tub.

It is a 50 amp circuit with #6 thwn approx. 100 ft from panel to hot tub.
I (after removing the conductors from the hot tub board) megged the conductors from egc to all others, grounded conductor to all others and so forth, at 250 volts my reading was approx. 245 mega ohms, and at 500 volts it was approx. 550 mega ohms.

The megger charged to the selected voltage and held it just fine with all the readings (I usually notice the voltage not getting up to the selected voltage when there is a problem with the conductors).
With those readings I think the conductors are fine and the breaker holds ok when the conductors are unhooked from the hot tub.

I also tried a different gfi breaker and it tripped, actually looked like a short when it tripped because the lights in the house dimmed when tripping.
This tub operates fine on a regular breaker but when hooked to gfi it trips.

Home owner was kinda mad that I wouldnt leave the regular 50 amp in and left it unhooked till we can figure this out.

question 1) Do you think that those are sufficient readings with the megger to call the conductors ok?

Question 2) Has anyone ever had this sort of problem and if so what did ya find.

Thanks in advance for any info or thoughts on this.:smile:

 

[Cow]

I think you're doing fine Var, you've tested the wires(they test ok), you've even swapped the breaker and yet it still trips. It's the hot tub. Tell the homeowner to get the spa guy back out there, and you'll show up too if he'd like, and one way or another you guys will get it figured out.

I've only had one or two "hot tub tripped GFI's" service calls, it seems like burned out heater elements are most often the culprit. If you do go back out there, I'd megger the hot tub myself. I'd check everything to ground but not between each other, you don't want to fry a board.

 

[mcclary's electrical]

Standard meg for 600 volt cable is 1000 volts. It's possible to not see the fault at 500v meg. Step your test up to 1000v

 

[Pierre C Belarge]

You have mentioned that the length of conductor from the GFCI breaker to the tub is approximately 100 feet.

The length of the conductors may be a contributing factor. Conductors have a small amount of leakage current along the length, as the length increases, the amount of leakage current increases, maybe enough to create the inconvienence of tripping the GFCI breaker.

If the equipment used to run fine, and is now tripping, it is possible there is some leakage current in the equipment and the conductor length adding together to create this situation.

Try using a standard breaker, and install the GFCI at the spa location...see if that does not stop the tripping.

 

[var]

Thank you for the replys,

I didnt test at 1000 volts because I thought with the wiring being rated at 600 volts I wouldnt want to exceed that.

And thats a good idea of trying the gfi breaker at the unit itself.
If the hot tub guy cant figure it out that gives me a copuple more things to try.

Again, Thanks to all who replied.:smile:

 

[brian john]

I was sent to trouble shoot a gfi brkr tripping on a hot tub, they had already called the spa guy and he said it was electrical and he had checked and everything is ok with the tub.

That seems more than logical, GFCI trips it is ALWAYS an electrical problem!

It is a 50 amp circuit with #6 thwn approx. 100 ft from panel to hot tub.
I (after removing the conductors from the hot tub board) megged the conductors from egc to all others, grounded conductor to all others and so forth, at 250 volts my reading was approx. 245 mega ohms, and at 500 volts it was approx. 550 mega ohms.

Why would you not switch to 1000 VDC for testing these conductors.



.

.

question 1) Do you think that those are sufficient readings with the megger to call the conductors ok?

I think you need to test at 1000 VDC

Question 2) Has anyone ever had this sort of problem and if so what did ya find.[/quote]

Where is the GFCI in the panel or at the tub?

If in the panel 100 feet away, relocate to the tub relocation.