Over Load

Status
Not open for further replies.
timm333 said:
Is it Ok to use over load relay on a feeder which is not motor?
Click to expand...

Use for what? An Over Load Relay senses current and changes the state of a control contact used in a contactor coil circuit. If what you want to do with is involves changing the state of a control circuit contact, then yes. But an OL relay does not qualify as an OCPD if that's what you mean.
 
And the possibilities to use this are limitless. If you wish to just have an output turn on when a specific current level is reached, you are better off using a current sensing relay that has adjustment on the setpoint. The motor overload will have current/time curve that must be met before it trips, many need manual resetting also. Just some bits of information to consider for your application.
 
I would bet the OP has an existing motor-starter with overload unit and is asking about using it to switch other types of loads.
 
iwire said:
I would bet the OP has an existing motor-starter with overload unit and is asking about using it to switch other types of loads.
Click to expand...
The overload relay can be removed/bypassed if there is any concerns in that kind of application. Not too often is there anything to be concerned about other then if the load will be more then the trip setting. Many solid state overloads you have the range of the contactor rating to deal with. Many bimetal overloads, especially on small frame sizes, you may be able to get more out of the contactor then some of the overloads that work with it. Of course melting alloy thermal units need changed to get the setpoint desired, but is cheaper to remove or bypass then to purchase new elements.
 
iwire said:
I would bet the OP has an existing motor-starter with overload unit and is asking about using it to switch other types of loads.
Click to expand...

Generally this comes up when the starter is a listed combination starter. The CB is a mag-only. Personal Opinion: 240.9 prohibits using for other than motor loads.

If it is a TM CB, jump the overloads and have at it.

ice
 
My question was that although it is unnecessary to use over-load on non-motor loads, still can someone use (if he wants due to some reason) it on non-motor feeders (like transformer, welder, lightning panel) even if changing the state of a control contact is not required, or does NEC imply that over load can only be used on motor feeders?
 
timm333 said:
It looks that I got the answer (240.9)
Click to expand...
If you have a combination starter with magnetic trip only circuit breaker that was the situation where that applied. Not all combination starters will have a magnetic trip only breaker, some may have a inverse time breaker, some may have fuses, and some are just a non fused disconnect.
 
kwired said:
.... Not all combination starters will have a magnetic trip only breaker ... and some are just a non fused disconnect.
Click to expand...

Hummm ... didn't know that. I don't think I have ever seen a combination starter that did not have OCP ahead of the contactor - fuses, TM, mag-only.

Code issues aside, that does not sound like good design. What is the short circuit protection?

ice
 
iceworm said:
Hummm ... didn't know that. I don't think I have ever seen a combination starter that did not have OCP ahead of the contactor - fuses, TM, mag-only.

Code issues aside, that does not sound like good design. What is the short circuit protection?

ice
Click to expand...

david luchini said:
The short circuit protection is the branch circuit breaker supplying the circuit.
Click to expand...
May not be something convenient for most applications you run into, but they are out there. If you already have branch circuit protection, why do you need such protection a second time?
 
kwired said:
May not be something convenient for most applications you run into, but they are out there. If you already have branch circuit protection, why do you need such protection a second time?
Click to expand...
Actually with the advent of more emphasis on proper SCCR ratings, this (non-fused disconnect type combo starters) is tending to go by the wayside now. Most NF disconnects are not rated very high for SSCR without the fuses and not series rated with breakers. So if you can only use them down stream of another fused disconnect, that makes them either pointless, or only applicable for use where you have a fused switchboard feeder, which are less and less popular. I do not know of any distributors that still stock them even if their manufacturer still offers them, then when you go to buy one you discover that you not only have to wait to get it, but it is no cheaper than a fused version or an MCP version. I just ran into that issue recently, went with the MCP version combo starter because it was on the shelf AND less expensive than the NF version!
 
iceworm said:
Hummm ... didn't know that. I don't think I have ever seen a combination starter that did not have OCP ahead of the contactor - fuses, TM, mag-only.

Code issues aside, that does not sound like good design. What is the short circuit protection?

ice
Click to expand...

david luchini said:
The short circuit protection is the branch circuit breaker supplying the circuit.
Click to expand...

kwired said:
May not be something convenient for most applications you run into, but they are out there. If you already have branch circuit protection, why do you need such protection a second time?
Click to expand...

That would be true.

So an appliction might be a QOB panel with a bunch of 3p CBs each feeding a separate stand alone combination starter - the starter having a non fused disconnect to provide the disconnect insight of the controller?

ice
 
iceworm said:
That would be true.

So an appliction might be a QOB panel with a bunch of 3p CBs each feeding a separate stand alone combination starter - the starter having a non fused disconnect to provide the disconnect insight of the controller?

ice
Click to expand...
Exactly one scenario I have going on a project right now. Not a QOB, but close enough comparison, my install is EDB breakers instead of QOB's, and I need a disconnect either within site of the controller or within site of the motor. We chose to place combination starter within site of the motor in this case as controls are only needed at the motor location in this application so it is breaker at start of branch circuit - combination starter - motor. Pretty simple install.

Available fault current can be something you need to pay attention to as has been mentioned, especially for a non fused switch that has circuit breaker for overcurrent protection ahead of it.
 
ptonsparky said:
For us, a non-fused disc does not require the working space a fused unit would. As long as the door opens 90deg we are good. Check with your inspector before installation.
Click to expand...
True for a disconnect only, throw a motor starter in the same cabinet and you have something that may require service or adjustment while energized.
 
Status
Not open for further replies.
Top