buy or fabricate

[paulengr]

I can see some not thinking proper overload protection is necessarily worth it with general purpose motor of maybe 5 hp or less, especially if you have an application that would seldom have mechanical overloading. Those motors are low enough cost and some places may have spare motors in stock for replacements where necessary and might see them as expendible. Even having overload protection but not setting it properly may not really save you much. Sure you may have less shut down on small overloads, but allowing to run at a little higher loading still is going to lessen winding life over time. Having proper protection and paying attention to what is going on when it does trip maybe would lead one to realize they have undersized equipment to begin with (for what they are demanding it to do anyway). This not only lessens motor life but possibly other driven components over time as well.

Are you kidding me? A Klixon thermal switch is a couple bucks. That’s why you see thermal switches used in small motors. The RC manual motor starters are a game changer though. The starter becomes just two parts.

 

[tortuga]

Not to mention, I doubt you are going to have your home-brews listed by UL, and that may be a requirement either for your jurisdiction or your customer.

Keep in mind there is no requirement in the NEC (article 409) for industrial control panels to be listed.

 

[kwired]

Are you kidding me? A Klixon thermal switch is a couple bucks. That’s why you see thermal switches used in small motors. The RC manual motor starters are a game changer though. The starter becomes just two parts.

I didn't say that was how I felt, I said I can see some thinking this way.

I also seem to end up working around people that want anything that trips and interrupts an operation bypassed, don't want the trouble. Hard to convince some of them it is tripping because something is not in normal ranges and it will probably eventually lead to other problems, including motor failure. Some common small motors they don't seem to care. Larger motors they may not care until they replace it, then they might consider looking into what may be causing tripping, but some them they figure they need to increase motor size since they are replacing it anyway, but don't consider that they also likely needed to replace gearbox or other driven components with larger ones if they truly need more power.

 

[ptonsparky]

I didn't say that was how I felt, I said I can see some thinking this way.

I also seem to end up working around people that want anything that trips and interrupts an operation bypassed, don't want the trouble. Hard to convince some of them it is tripping because something is not in normal ranges and it will probably eventually lead to other problems, including motor failure. Some common small motors they don't seem to care. Larger motors they may not care until they replace it, then they might consider looking into what may be causing tripping, but some them they figure they need to increase motor size since they are replacing it anyway, but don't consider that they also likely needed to replace gearbox or other driven components with larger ones if they truly need more power.

So true.

We did a pretty good sized grain handling system for a farmer a few years ago. All the bells and whistles. I was there defeating the PL:C interlocks (toggling HMI buttons) as his mechanic was struggling with the results of those bypasses. Owner wanted it to run until something(s) broke. Why they could take the time to figure out the 3 or 4 monitors in the combine or tractors and not even try at the storage bins still has me shaking my head.

WTH, I got paid.

 

[Jraef]

Keep in mind there is no requirement in the NEC (article 409) for industrial control panels to be listed.

Not directly, but indirectly, it works out that way. Article 409 requires that the ICP be labeled for the SCCR, and the way to get an SCCR is to list the panel through an NRTL (someone like UL).

409.110(4)
Short-circuit current rating of the industrial control
panel based on one of the following:
a. Short-circuit current rating of a listed and labeled
assembly
b. Short-circuit current rating established utilizing an
approved method
Informational Note: ANSI/UL 508, Standard for Industrial
Control Panels, Supplement SB, is an example of an
approved method.

 

[paulengr]

Keep in mind there is no requirement in the NEC (article 409) for industrial control panels to be listed.

That’s a grey area and why 508A and 507 exists. If it’s not Listed the components must be, and installed per Listing: You quickly run into thermal issues among others.

If you just want manual control hard to beat an MMS. Adding a contactor in a box makes it full control but limited HP. Putting an IEC contactor in a fused 30/60 A disconnect with a thermal switch in series gets way up in HP.. I’ve seen attempts at shoehorning in overloads. By that point the combination starters look really good. ICPs are for stuffing a lube pump, fan, and duplex pump controller in the same box. When you go down the road of multiple full starters that’s when the labor savings in MCCs adds up quickly. When it gets ridiculous is when someone wants controls built into an MCC with like two starters...paying a ton for the MCC but getting no value.

 

[tortuga]

There is no gray area other than the AHJ, Approved is defined in article 100 as "Acceptable to the authority having jurisdiction."
I am no expert in building these, I work more on the installation side which means pleasing the AHJ.

I just go over it with the AHJ and provide them copies of the standards (508A or IEC or whatever).

Been doing that for years.
Its up to your AHJ and customer of course.

 

[kwired]

So true.

We did a pretty good sized grain handling system for a farmer a few years ago. All the bells and whistles. I was there defeating the PL:C interlocks (toggling HMI buttons) as his mechanic was struggling with the results of those bypasses. Owner wanted it to run until something(s) broke. Why they could take the time to figure out the 3 or 4 monitors in the combine or tractors and not even try at the storage bins still has me shaking my head.

WTH, I got paid.

But needing a crane to come out so a repair can be done to something at top of the leg doesn't cost anything, so why have any limit switches on anything or any motor overloads?
Few years back, brand new leg I connected a panel meter so they can tell how loaded the leg motor is, owner comes out while we are unloading a truck and we were running near full load rated amps and he looks at the stream of flow out of the truck and says "we need to be able to unload faster than that". I wanted to say "then you should have gotten a leg with higher capacity rating".

I'm sure he probably agreed on a certain bushel per hour rating when selecting equipment.