Hot Spring Heater Tripping GFCI

[Isaac-1]

I recently replaced the "No-Fault" 1.5/6KW heater in my '98 Jetsetter J tub due to a leak that had developed on the U bend end of the old one (about a month ago).    Then last week we had a major thunderstorm with multiple nearby lighting strikes, which resulted in the loss of multiple appliances (microwave oven, computer monitor, etc.), at the same time the hot tub started tripping its GFCI  (Connected in 120V mode), a bit of diagnoses through disconnecting and reconnecting accessories lead me to the heater as the cause of the GFCI trip (confirmed by reconnecting and disconnecting it twice).   I reinstalled the functioning, but dripping heater and it heats and does not trip the GFCI.      I also compared the Ohm readings for the old leaking heater and the new/GFCI tripping heater using a Fluke 117 multimeter and get nearly dentical readings line to neutral (9.8 vs 9.9 Ohm), and fairly similar readings line or neutral to ground (about 6-M-Ohm on the one that is tripping GFCI and 3M-Ohm on the one that is dripping ,but not tripping GFCI )

Does anyone have a guess why this is happening?

[Tman122]

I recently replaced the "No-Fault" 1.5/6KW heater in my '98 Jetsetter J tub due to a leak that had developed on the U bend end of the old one (about a month ago).    Then last week we had a major thunderstorm with multiple nearby lighting strikes, which resulted in the loss of multiple appliances (microwave oven, computer monitor, etc.), at the same time the hot tub started tripping its GFCI  (Connected in 120V mode), a bit of diagnoses through disconnecting and reconnecting accessories lead me to the heater as the cause of the GFCI trip (confirmed by reconnecting and disconnecting it twice).   I reinstalled the functioning, but dripping heater and it heats and does not trip the GFCI.      I also compared the Ohm readings for the old leaking heater and the new/GFCI tripping heater using a Fluke 117 multimeter and get nearly dentical readings line to neutral (9.8 vs 9.9 Ohm), and fairly similar readings line or neutral to ground (about 6-M-Ohm on the one that is tripping GFCI and 3M-Ohm on the one that is dripping ,but not tripping GFCI )

Does anyone have a guess why this is happening?

It's possible your GFCI may be malfunctioning.

[bud16415]

If the old heater works and doesn’t trip the GFCI and the new one does and they both have the same reading. I would say your new heater has a slight leakage of current to ground. Take it back and get a different one.

[Isaac-1]

Unfortunately I bought it from an ebay seller that lists lots of these out of Houston TX, but  now will not reply to messages

[BoxieBoy]

The only reliable way to test a component for a ground earth fault is to carryout a 250V/500Vdc insulation test. A low voltage resistance tester will not always detect a partial short to earth, you need to "pressurise the system using voltage just like a plumber pressurises pipes to see if they leak.  You do however need a special insulation tester, that most none electricians do not have. So ask around for a loan;)   To do the test, power the system down and isolate! Do not remove the heater unit, its best when it is filled with water. Disconnect the heater wires from the PCB board, (vital to protect the electronics). Connect a shorting link across the heater terminals. Then connect one test lead to any heater terminal, the other to the earth stud. Set your insulation test meter to >200Meg Ohm  and test voltage to 250Vdc for 120Vac equipment or 500Vdc for 230Vac equipment. Operate the tester, any reading less than 1Meg Ohm is a bad heating element and need to be replaced.
If you need to find the correct resistance of a good element, use this formula: Resistance =Voltage² /Element Power rating
Hope this helps
Regards

[bud16415]

As BoxieBoy mentioned there are ways to test for current leakage under full power. It is a bit complicated and I think you have already concluded that part “A” works but leaks and switching it to part “B” the new part causes a GFCI fault. I haven’t had one at the heater but internet information says the common place is where the heater element enters the water path. They will start weeping there and some moisture finds the electrical connector and causes a slight path to ground.

You have to understand how a GFCI works to totally grasp just how slight a short to ground has to be to trigger a GFCI. They are there for your safety and if you came in contact with a live wire it would detect the path to ground thru your body and trip before you would be shocked.

The ebay problem is a good reason to trust your source of parts quite well before sending them your money.

I’m fairly sure you got a dud heater and the fact the company won’t reply makes me even more sure it is bad. To be certain follow the test above. Or find a reputable source and get another heater and try it. As far as I know there is no way to repair the one you have.

[Isaac-1]

I just wanted to follow up with the post mortem results on the ground faulting 1 month old heater, after disassembly I found the orange silicone rubber ring that was the closest to the green ground wire stud partly melted and the heating element at the U bend next to this point slightly bulged.  Therefore I am back to suspecting nearby lightning strike causing the heating element to arc to ground at this point releasing enough energy to melt the orange silicone ring.    Given that even cheap silicone rubber is good to over 400 degrees F, and it was submersed in water it must have got very hot, very fast before the GFCI could trip.

Alternatively since this was an ebay deal, it may have been previously installed and connected without water in the heater tube, which I would be more inclined to believe from a one off ebay sale, not a dealer that lists dozens of heaters at a time, still you never know when some service tech might have done an oopsy and returned a damaged heater to stock vs getting in trouble to a newbie mistake.

p.s. I have swapped the newish orange rings over to the old leaking heater in hopes it will stop the leak, will know soon, I ran out of time to work on the tub, but will be refilling it later this weekend.

[bud16415]

Knowing what the problem is, is 90% of the battle.