Normal Short CIrcuit Protection

[Jandr]

Good day!

120V AC line with load rated @ .18Hp Actuator Motor, 1Phase, 3a FLA. It is of very small HP rating and low FLA, operating intermittently as draft fan vane actuator, would Miniature CB be suitable as motor and line protection?
Any suggestions/discussions?
Any particular model and brand that caters this rating?

Thank you very much!

 

[JuanBC]

Hi Jandr,

Are you referring to the Short-Circuit Withstand Capability of the circuit breaker?

JBC
.......
"The more I read, the more I acquire, the more certain I am that I know nothing"

 

[LionelHutz]

A standard 15A lighting panel breaker would meet the code requirements in North America.

If you want to go beyond that, pretty much any supplemental protector could be used and MANY companies sell those breakers in sizes under 15A. That type of protector (breaker) is commonly DIN rail mounted and is listed under UL1077. For a 3A motor something around 5A to 6A should work.

 

[xnuke]

Supplemental protectors can only be used inside equipment to protect internals, or where branch circuit protection is already provided or not necessary. A basic rule I follow is if wiring leaves equipment carrying line voltage power to another device, I provide UL 489 branch circuit protection.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[wroggent]

miniature circuit breakers built to UL 489 are available

 

[GroovyGuy]

Hi JAndr,
What about O/L protection? A standard 15A panelboard type CB is OK for S/C protection, but does not provide any O/L protection?
Does the motor have integral O/L protection? IF not why not use a manual motor-starter, per the following link?

http://raise.rockwellautomation.com...ents.asp?CID=8018CE5652524321ABCFCF732895178F

GG



"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

 

[Jandr]

Thanks for all the inputs. Will check and give you feedback.

 

[jraef]

...draft fan vane actuator...

Typically these don't have built-in thermal protection and don't need to because they are for such short duty cycles and use what's called an "impedance protected motor".

Assuming, because it is 120V that this is North America somewhere, 120V will come from a single pole circuit breaker or fuse. So as long as you run wire rated for the rating of that CB, for example #14 for a 15A breaker, you don't need further circuit protection for a vane actuator. See NEC Article 430.42(A), because these devices typically fall under 430.32(B).


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[HCBFlash]

Agree with jraef. It essentially has its own protection.

If this actuator is particularly crucial it should be protected by sensing it's position and tripping an alarm if it is not in the proper position(s) within an appropriate time of its actuation/deactivation.

.

(Me,,,wrong? ...aw, just fine-tuning my sarcasm!)

 

[Jandr]

It does have stall, overtorque and over-travel protection. That's why I only intend to put 7.5A D-curve (250% of full-load current) Trip Breaker as redundant protection since it will be operating intermittently or this is over the needed protection? Thoughts?

Thank you!

 

[jraef]

Nobody is going to stop you from OVER protecting it. But also understand that the CONVENTIONAL way this is done would NOT have that added protection. So let's say some day in the future the vane ceases to work and someone calls an HVAC contractor. He will likely NOT think to look for a separate circuit protective device since that's not the way it is done. So he may assume the vane motor is defective, replace it, see that it still doesn't work, test the circuit, find it is dead, test the feeder breaker, see that it's live, then have to start tracing the wires, only to find your tripped circuit breaker... 3 hours later! He will curse you and your progeny.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[Jandr]

Haha got it clearly Jraef. Thanks!