Phase convertor, blower & contactor issue

[dubliner]

I have my RPC running sweet but occasionally the contactor between the RPC & the the 15hp FPZ blower trips and shuts the blower off. I have zero knowlege of contactor blocks. There is a small dial with 0 to 55 on it beside a test & reset button, but the blower has both run & kicked off with the dial set at 0 & 55, so was wondering if the contactors go bad? or what else might be going on? any ideas I'd appreciate - I have a job waiting on the bloody thing, grrrr!

[bcondon]

Neville,

I am digging in my brain by a whole bunch of years when I worked as an electrician.

I have never seen a contactor block go bad.

Many of the contactor blocks have heaters or thermal cutouts in them.
You could be running them too hot (the wrong thermal cutout for the load
as on many contactors, you purchase them separately as an addition or option) The dial I presume to be some form of timer... This is necessary for the starting of motors that tend to pull 300% of the normal running current during starting (which was why you could not use regular glass or cartridge fuses but had to use specific ones for motor starts)

It sounds to me that the block has a cutout that is not capable to handle the load.

Questions...-1- does it "always" shutdown when set to a low number and rarely when set on a high number? (I am asking if there is any correlation?)

and -2- does it shutdown during the starting cycle of the motor or completely at random times?

Can you send the brand and model number as I can then look for it on the internet or MSC..

Thanks
Bob Condon