Thermal magnetic and MCP

[adamscb]

Hi all,

Here is my understanding of the differences between a thermal magnetic and MCP circuit breaker: thermal magnetic breakers have both short circuit and overload protection built-in, while motor-circuit protectors only have short-circuit protection built-in; the overload protection must be provided by external means. Is this correct?

Also, how would I tell which breakers are thermal magnetic and which are MCP's, based only on looking at pictures (besides writing down the part number and looking them up online)? i.e. any distinguishing physical characteristics?

Thanks

 

[Jraef]

Hi all,

Here is my understanding of the differences between a thermal magnetic and MCP circuit breaker: thermal magnetic breakers have both short circuit and overload protection built-in, while motor-circuit protectors only have short-circuit protection built-in; the overload protection must be provided by external means. Is this correct?

Also, how would I tell which breakers are thermal magnetic and which are MCP's, based only on looking at pictures (besides writing down the part number and looking them up online)? i.e. any distinguishing physical characteristics?

Thanks

#1, an MCP can ONLY be used as part of a FACTORY assembled combination motor starter, there is NO OTHER valid use for them. So if you are looking at a switchboard or panelboard, there is zero chance of it being an MCP, unless someone screwed up.

Then if you ARE looking inside of a FACTORY assembled combination motor starter, there is a HIGH likelihood that it IS an MCP, because the thermal trip elements would be redundant to the OL relay, so the mfr doesn't waste the money paying for them.

Lastly, if you are unsure and cannot tell by the catalog number, look for a UL bug; MCP breakers are NOT able to be UL listed, they are only UL Recognized because they cannot be used stand-alone, they are a component of a larger assembly that then must be tested AGAIN, so you would see the backward "UR" instead of the UL with the circle around it.


UL Listing mark = Thermal Mag breaker.


UL Recognized Component mark = MCP