Load capacity of parallel concuctor circuit

This is not legal (paralleling 14ga conductors) but if we suspend the law for a minute and answer a theoretical question ;

That is somewhere between #10 and #8 ... say 35a?

You might even push the envelop and say each 14ga is worth 15a but you get into derating because you have more than 3 current carrying conductors. Then we have to know what the type of conductor it is.

Bear in mind, after all of this it is still against code to parallel

Only conductors of 1/0 and larger can be paralled with the further requirements of same length, same conductor material, same size in circular mil area, same insulation, and terminated in the same manner.

NEC 310-4

Bill Kaszeta Photovoltaic Resources Int'l Tempe Arizona USA snipped-for-privacy@pvri-removethis.biz

Thanks for the response to my questions. Okay, it's not legal. It's there. Is there anything essentially unsafe about it so that I might want to change it?

Other than it is wrong and potentially dangerous.

The NEC rules are not arbitrary there is sound electrical principals behind the decisions. The NEC is considered the minimum safety requirement. If you have a fire and something burns down. If the investigator was to find non compliant wiring, the insurance claim might be voided. Heck they might even try to prosecute you.

The really sad part is there are folks that will ignore them and "do it their way". The biggest reason I know of that the book is getting bigger not smaller.

It is discouraged by the code simply because you have an extra level of complexity and more places for it to fail. If this is wire in pipe you should pull it out and replace it with the proper conductors. OTOH it is also illegal to run multiple circuits to a building so you are already going to burn in NEC hell. ;-)

Things that spring to mind...

A poor connection at the end of one conductor could lead to different path resistances and unbalanced current, causing the others to overheat. In the degenerate case, a complete failure of one connection will result in the other two taking all the load.

The circuit protection is going to be inappropriately too high in the case of a conductor shorting. The impedance of the thin conductor could limit the current such that the protective device takes too long to break the circuit and a fire is started. In some cases of a cable break and short, the short circuit current could be flowing to the far end through two of the conductors, and then back to the breakage through a single conductor, resulting in an excessively long path all through conductors which are significantly thinner than the circuit protection is designed for.

Parallel conductors are allowed in the UK, but the circuit protection is required to ensure each operates safely, which in this case would probably require a 6-pole ganged breaker. It is most unlikely this would ever be the cheapest way to achieve the aim of providing a specified power over the required distance.