Contactor Ratings

[IAmSparkytus!]

Afternoon all,

If a contactor has a rated operational current of 40A but a maximum power rating of 6kW, will this be acceptable to switch an air con unit (recommended fuse size 32A, max running amps 13A) MCB?

Thanks.

 

[Darkwood]

You need the AC3 rating of the contactor at the voltage you're using, this will be listed in the contactor info, are you using 3ph 400v here or 230 single?

When you are given an amp rating on a contactor it usually denotes it switching and load ability with a resistive load not inductive.

 

[IAmSparkytus!]

Single.

Yes thats what I thought. Find a lot of the ratings I'm looking for to be in kW or HP as well. Any reason for this?

 

[Darkwood]

Depends where they are been advertised too and what the market is they are aiming for, both inductive and resistive ratings are often given on the contactor, if you are in a motor control section while looking them up you tend to see the KW rating, if you're in a heating section you may be given the amps and then there are wholesalers who simply don't know their products and supply the wrong info for the section they put them in, luckily most reputable companies provide downloads to the product specs'.

 

[Lucien Nunes]

NEMA in the USA uses hp ratings to size contactors to motors, just as they still use imperial measuring units for things that we have long since switched to metric.