ECN Forum Forums Code Related Discussion NEC & other Code issues Do I need a starter?

Reno, Of course the NEC required overload protection



Overload protection will seldom (ever?) be provided by the same device that gives you over current protection since that must be able to sustain starting current. Typically in an inverse time breaker that will still be 250% of FLA and if you have an instantaneous trip device, it reaches scary numbers. Thermal and overload protection is commonly the same device. Maybe that is what you were thinking.

Reno:

Greg is correct - the term is "overload" when we are talking about motor protection. The term is "branch circuit, short circuit and ground fault protection" when we are talking about the circuit protection. I would also draw your attention to 430.55 ('08 NEC) where we are permitted to use a single device to serve both needs. The caveat being we must protect the motor from overload based on 430.32 in the process. The reality of it is this only works on smaller motors.

I know others out here have had to replace a complete overload relay assembly and it's heater element because the co-ordination was not proper in the circuit and something had to give and it was the heater element melting and destroying the overload assembly.

Just a side note since Greg mentioned disconnect, we would need a disconnect within sight of the motor and the controller if it were a non-combination type starter.

Greg, you are correct, and I thank you for the clarification.

However, there are plenty of situations where even motors are not required to have any manner of 'overload' protection - whether internally, or as part of a separate starter. That these are invariably either small motors, or part of a specific appliance really isn't the point.

Rather, the question was whether 'starters' were required. There is no such requirement. While it's been a while, I recall seeing motors controlled by a collection of separatly enclosed widgets - one for the disco, one for the fuses, one for the contactor - and it being anyone's guess where the 'heaters' might be located.

After all, we've all seen motors that 'let the smoke out.' and I think this manner of 'enforcement' beats any codebook for effectiveness.

We can't, as Bill Engvalls observed, fix 'stupid.'

It's not all doom and gloom, though. I've been quite impressed by the newer 'electronic overloads' some starters have. These gizmos protect the motor from a number of things in addition to a basic overload. With all this focus on 'code,' sometimes we overlook the effect the free market can have.

Another detail ....

Remember that another component of a 'starter' is the contactor. I can think of no code requirement for there to be any manner of contactor; the use of full-power rated switches and plugs is allowed.

If you had 'heaters' but no contactor, you would not have a 'starter.'

Lest some newcomer try to read something into my comments that I'm not saying, I'll be the first to extoll the advantages of using a contactor; that's another discussion.

I suspect that even the small motors that have no obvious O/L protection will still have a thermal fuse in them if they want the U/L seal of approval.
There are still a lot of hand held tools that will go until they burn up.

I'm not sure that all motor starters necessarily contain overload protection.
I know that Hubbell/Bryant makes 30A 3-pole manual motor starters with no overload protection. I've installed them on 5HP 208V 3-phase disposals in commercial kitchens before. The disposals had their own built in thermal protector.

The only heaters I'm familiar with use bimetallic physics to break the hold circuit for the contactor coil.

I'm trying to imagine any other layout...

How would a heater operate without a contactor?

Again, it comes down to vocabulary - and out maddening exceptions to our rules!

A 'starter,' by definition, has an overload protective element in it .... except for the 'drum switch,' which is considered a reversing motor starter, though there is no overload protection in it.

As for the term 'heater,' that seems to be trade slang for 'overload protection element.' I suppose that's because it takes heat to make most of them trip. While there are some that use a bimetallic element, most seem to use some manner of ratching mechanism, springs, and solder. When the solder melts, the 'gear' is rotated by the spring and the connection opens. Once the solder cools, your reset button re-loads tension on the spring as it closes the contacts.

"Heater" contacts are fairly small, so they are not capable of handling very much current. They only need to open the control circuit. The solder, by contrast, is directly heated by the full load current. Open the control circuit, and the contactor opens - interrupting the current flow through the solder.