LMartin57
Member
- Location
- Valrico, Florida USA
what part of the code should I refer to when using instant trip breakers on motor application.
motor rated breakers
- Thread starter LMartin57
- Start date
- Status
Pay particular attention to 430.52(C)(3).
(3) Instantaneous Trip Circuit Breaker. An instantaneous trip circuit breaker shall be used only if adjustable and if part of a listed combination motor controller having coordinated motor overload and short-circuit and ground-fault protection in each conductor, and the setting is adjusted to no more than the value specified in Table 430.52.
(3) Instantaneous Trip Circuit Breaker. An instantaneous trip circuit breaker shall be used only if adjustable and if part of a listed combination motor controller having coordinated motor overload and short-circuit and ground-fault protection in each conductor, and the setting is adjusted to no more than the value specified in Table 430.52.
Last edited:
You type as bad as I do.
sec 430 :ashamed1::slaphead:
- Location
- Massachusetts
I agree with Gus, this is most important An instantaneous trip circuit breaker shall be used only if adjustable and if part of a listed combination motor controller.
You cannot install one in a panel.
Yes, because they have no thermal overload protection. As a side note the rating on the end of the toggle is important to note as the 150a MCPs and below that I am familiar with have solenoids that are current sensitive that can be fried should they be subjected to more current than theory can handle. When the current passes through the solenoid it is the device that creates a magnetic field that pulls a due ice that trips the MCP. The adjustment on the MCP changes the gap thus changing the mag pickup.
So it is extremely important to never exceed the rating of the MCP because you will destroy the solenoid element.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
sure you can, as long as you install it as part of a listed combination. what you can't do is make up your own combinations of parts. the combination itself has to be listed.
many people believe erroneously that they have to be in some kind of enclosure, and the whole combination starter and enclosure is what has to be listed. that is just not so. It can be sold in one, but that is not a requirement to be a UL listed combination starter. I think this myth got started maybe because a NEMA combination starter is an assembly that does by definition include the enclosure.
Last edited:
- Location
- Massachusetts
I do not see it as a myth I see as applying the code section as written
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
where in the code does it require the thing to be in an enclosure to be a listed assembly?
- Location
- Massachusetts
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
so all the UL listed assemblies that include an MCP that are not sold in an enclosure are not code legal? is that your contention?
and who said anything about a panelboard?
- Location
- Massachusetts
Nope, I never said any such thing.
I did.
To which you replied
So you leave me entirely confused.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Time to split hairs.
Yes they can be installed in panels (Square D ones are available in I-Line construction), however they cannot be installed as branch circuit protective devices (e.g. when the load conductors leave the panel). So, if the panel also contained the motor starter (e.g. think custom enclosure), the installation might be compliant.
- Location
- Massachusetts
Time to split hairs.
Yes they can be installed in panels (Square D ones are available in I-Line construction), however they cannot be installed as branch circuit protective devices (e.g. when the load conductors leave the panel). So, if the panel also contained the motor starter (e.g. think custom enclosure), the installation might be compliant.
Might, maybe, and certainly not field installed by a construction electrician like myself.
From the OPs profile.
Engineers, making the simple complicated since the beginning of time.
Before anyone gets upset I am joking, I have much respect for engineers and what they do. It is just that we often speak different languages.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Regarding combination starter ratings, to be listed a combination of short circuit tests are done in an enclosure. Basically any failure which occurs must be contained within the enclosure as I recall. The rating of the combination motor starter is affixed inside the enclosure and not the , contactor, OLR or their mounting base. As such A combination starter without an enclosure would not be available with a UL liable since it hasn't been supplied with an enclosure.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I would never call a panelboard a panel. its a panelboard.
to me a panel is a control panel.
I agree it would be difficult (at best) to comply with the various restrictions if the MCP was installed in a panelboard.
to me a panel is a control panel.
I agree it would be difficult (at best) to comply with the various restrictions if the MCP was installed in a panelboard.
LMartin57
Member
- Location
- Valrico, Florida USA
Instantaneous Trip Circuit Breaker
Instantaneous Trip Circuit Breaker
Recently I had problem with a instantaneous trip breaker in a new installation. The panel come with a 35 amp breaker which was to feed a VFD controlling a blower with a 10 hp motor, 208 volts 3 phase, wire size #8. The problem was if you put the VFD in manual the breaker would trip upon start up. According to NEC 430.52 how would you calculate the correct breaker size.
Instantaneous Trip Circuit Breaker
Recently I had problem with a instantaneous trip breaker in a new installation. The panel come with a 35 amp breaker which was to feed a VFD controlling a blower with a 10 hp motor, 208 volts 3 phase, wire size #8. The problem was if you put the VFD in manual the breaker would trip upon start up. According to NEC 430.52 how would you calculate the correct breaker size.
Just curious, is the MCP a part of a UL listed motor controller? Being that I just don't want to get the cart before the horse addressing a nuisance tripping MCP that is not part of a listed assembly would be aiding and abetting a misapplication.
- Status