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Posted by on May 25, 2012 in Maintenance, Marine Electronics, Powerboating, Safety and Seamanship, Sailing, US | 1 comment

Electrical Terminal Stud Count: Four and No More

It's a bad idea to stack too many terminals on one stud. It concentrates heat, which can lead to melting. And fire.

Question: I recently had a survey done on my older boat to satisfy my insurance company’s requirements. One of the items on the survey sounds wrong to me. The photo below from my boat shows several studs where wires are terminated. The surveyor says that this set-up violates ABYC Standard E-11 recommendations and should be repaired immediately. Everything electrical on my boat works just fine; why is this a problem, or is my surveyor just making this up?

To prevent heat build-up, ABYC electrical standards limit the number of terminals attached to a stud to four.

To prevent heat build-up, ABYC electrical standards limit the number of terminals attached to a stud to four. Clearly, these studs are overloaded.

Answer: Your surveyor is not making this one up. The ABYC in its E-11 electrical standard does limit the number of terminals that can be attached to one stud at four. There are several good reasons for this requirement.

Wires and terminals are engineered to carry a specified amount of amperage without overheating and causing problems associated with excess heat like melting of components and, in the worse case, fires. When you have studs such as you show here, with many more wires and terminals stacked up, you create a focal point for excess heat build-up. Again, the ABYC recommends a maximum of four terminals on any one stud. There could in fact be more than four wires connected, as each terminal could have several small-gauge wires inserted into it.

Your surveyor’s recommendation here is a good one, and this wiring should get sorted out. I should also add that some of the crimps in the photo you supplied look a bit suspicious as well. They should all be subjected to a pull test to make sure they are not going to fall off.

- Ed Sherman

1 Comment

  1. I agree with your comment on the ABYC rules on terminal count. But a far bigger problem appears to be that the upper terminal is all ground wires — and the lower terminal is all HOT! That’s a short (and spark show) waiting to happen.