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#168081 08/26/07 08:56 PM
Joined: Jul 2007
Posts: 9
AWL Offline OP
New Member
I hooked up a moved hot tub that a friend of mine had given to him. I hooked it all up and left. He got it filled and turned on the circuit for the heaters and it immediately tripped. I returned and swapped the gfi breaker out for a regular breaker and it held so now Im lost is it the gfi bad or something else?

Joined: Jan 2005
Posts: 5,316
Cat Servant
I suggest you start looking for the place where curerent is leaking.

Joined: Jul 2007
Posts: 9
AWL Offline OP
New Member
I just looked at it quick and assumed that it was a bad breaker the breaker was a used(like the tub) 30 amp dp gfi. It has to be something internal on the tub its only when then heaters are turned on with the gfi breaker in. and no i didnt keep it hooked up with that breaker in there

Joined: Jan 2006
Posts: 558
Only trips when there is a call for heat? COULD be the control circuit for the heaters but I doubt that, I am gonna call it being the heating element itself


Joined: Aug 2007
Posts: 61
I did somewhat of the same job for a friend and the GFI was tripping as well. Turned out the heater element had burned through the box it was in and had rusted the control circuit box. Ended up buying a new spa pack. Then found out a pump had seized. Friend decided to can the whole project. Just glad I didnt pay for the wire! Also - The spa I worked on had some sort of ionizer that was hooked to a relay that let the smoke out when I turned the breaker on. Never put money into a free spa off craigslist!


I would rather beg for forgiveness then beg for permission.
Joined: May 2007
Posts: 169
I'm no expert on spas but it seems if you disconnected the heater terminals, power off of course and measured with a good ohm meter (not somthing like a Fluke T6 that only goes up to 1K) you should see a very high resistance between each leg and ground. My guess on the math, please correct me if I'm wrong, would 120/.005=24K ohms to trip a 5 miliamp GFI.
I recently read here that the GFI breakers have a higher tolerance, around 30 miliamps so that would be 120/.03= 4K ohms.
I guess that would assume a single point of leakage right in the middle of the element though.
With leakage right at one end of the element it would be 240/.005=48K for the 5 mili and 240/.03=8k for the 30 mili.

Would it be true that with a 30 miliamp GFI it should be possible to tolerate down to as low as 4K between a hot leg and ground before she blows?

Joined: Jul 2004
Posts: 9,696
Likes: 11
Actually if you had a dead short to ground right in the electrical center of the element it would not show a ground fault unless there was unbalanced current from other equipment on the circuit.
The volts to ground is highest right where the connection to the element is and that is 120v nominal.

Think about a multiwire circuit.

Greg Fretwell
Joined: May 2007
Posts: 169
My question was structured around trying to test the element by means of unpowered, open circuit resistance measuring to determine if it were the cause of a GFI trip. That lead me to wondering just how much leakage would be possible without tripping the GFI. Again, I am no expert.
However voltage wise I would have to agree with what your saying. Assuming good bonding you wouldn't even feel it, if the element remained stable in that "center tapped" state of failure. Kirchoff and the superposition theorem both say that there would be no leakage under that condition.
I overlooked that in my original question, even though I used dead center as my first example. Oops.
I guess at that point you would need the manufacturers specs on resistance between L1 and L2 and if you measure 1/2 of that between either lead and ground then that must be the case.
Scary. But how probable? The center of the element would have the lowest tension to ground if I'm thinking straight.
It seems more likely to fail where the tension was higher, more toward one of the ends.
But it wouldn't trip at the center without 120V loads to imbalance it so it's probably not AWL's problem and he could still have an off center fault that could explain the tripping. Of course a non-tripping spa could have an imbalanced failure as above being balanced by 120V loads so all appears good!
I'm never getting in one of those things again!!!
Probably best to just get the specs and test properly.
Thanks for the insight.

Joined: Mar 2004
Posts: 785
Why don't you just unhook the heater leads then see if the breaker holds?

Joined: May 2007
Posts: 169
No, that would be too easy:)
That should let you know if an element replacement is necessary but I always get nervous swapping expensive and difficult to access parts without knowing for sure that I need to.

But I'm still wondering how much leakage the average GFI breaker you would find protecting a spa would let through before tripping.

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