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electrifier
electrifier, Master Electrician
Category: Electrical
Satisfied Customers: 1633
Experience:  Electrical contractor and electrical inspector for over 24 years with phone and networking expertise
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I have a hot tub that trips the GFCI immediately when reset.

Resolved Question:

I have a hot tub that trips the GFCI immediately when reset. I disconnected all the pumps & it still trips. When the low voltage transformer plug is disconnected the GFCI stays on. The circuit board with all the relays is still connected to the line coming in. I ordered & replaced the circuit board. It trips the GFCI. I checked out the tranformer. It is not shorted to ground. How do I test the GFCI?
Submitted: 8 years ago.
Category: Electrical
Expert:  electrifier replied 8 years ago.
GFCI troubleshooting is extremely precise. What you do physically I have to understand exactly so I can determine the correction for your tub.

You say when everything is connected and only the low voltage transformer plug is disconnected the GFCI stay on. The key words here are "everything" and "only". Is this true?
Customer: replied 8 years ago.
There is a small 5 wire connector to the transformer. when that plug is removed the GFCI does not trip., however, there is no activity in the tub.
Expert:  electrifier replied 8 years ago.
When that is plugged in it trips the GFCI with no other changes, correct?
Customer: replied 8 years ago.
Correct.
Expert:  electrifier replied 8 years ago.
Is only the transformer connected to this plug?
Customer: replied 8 years ago.
Yes, it 's labeled 240v Ct. the 2 center wires are connected together on the primary and there are 3 wires on the secondary. I should have told you earlier that a car hit a pole somewhere near us & we lost power momentarily. When power came back on the lights were very dim. I didn't check the hot tub till about 1 week later. That's when I found the GFCI tripping.
Expert:  electrifier replied 8 years ago.
Do you have a meter available for checking resistance?
Customer: replied 8 years ago.
Yes, But the weather is not good outside right now. I have experience with both electrical & electronics.
Expert:  electrifier replied 8 years ago.
I'm glad to hear of your experience and some understanding of all this. You understand then my statement earlier about the precision of testing of a GFCI problem. The GFCI trips because there is a short circuit someplace. The GFCI measures the current in the 2 hot wires from the breaker as well as the white neutral wire. There must be a balance between these 3 wires, there can be NO current returning on the grounding conductor or thru the earth. It is sensitive to .005 ampere so it doesn't take much. If neutral and ground touch anyplace after the GFCI breaker it will trip. If .005 ampere passes back other than the 3 conductors it trips. If the transformer is somehow shorted at all it will trip the GFCI. I need you to unplug the transformer and check resistance between each wire on the transformer and ground. The 2 most important would be the 240 volt leads to the transformer. The secondary side could be grounded by design. Reply back here when you have the resistance reading for me. We will get to the bottom of this.
Customer: replied 8 years ago.
The primary side measures 74 ohms, the secondary is a short. There is no resisitance between any leg & the frame with the ohm meter on it's hightest setting. I don't have a megometer.
Expert:  electrifier replied 8 years ago.
Do you have access to a known good transformer to comapare to? It doesn't sound good to me. 74 ohms sounds low and the secondary sounds bad as well. The voltage deal the other week could have shorted the transformer. We could be looking at overcurrent instead of GFCI problems.
Customer: replied 8 years ago.

NO. That's the only xfmr I have.

 

Expert:  electrifier replied 8 years ago.
Do you have a source for a new transformer available locally? If you do check resistance values with them. The secondary should show some resistance, not a dead short.
Customer: replied 8 years ago.
OK, I'll do that. Thanks for your help. Should I try putting a load on the GFCI to test it?
Expert:  electrifier replied 8 years ago.
You can do that to check it. As long as the load is between the 3 wires from the breaker it should not trip. If neutral and ground touch on the load it will trip the GFCI.
Be sure and come back here and let me know if this was the problem or if it still is there. You can return to this question with more even after you accept it.
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