Definite purpose contactor for RPC use?

[Trunk Monkey]

I searched this forum and saw several mentions of definite purpose contactors but most references were for replacement queries as opposed to design considerations.

Is there anything one should look for in a DP contactor for RPC use? I'm pretty new to a lot of this and I'm in the beginning stages of collecting the parts to build my RPC. I've seen a lot of the options available on Amazon and the prices seem reasonable but I'd like to have 20hp eventually and a new 70+ amp Asian made contactor is still kind of spendy relative to the numerous used likely non-Asian made DP contactors available on eBay and FB Marketplace (most seem to be HVAC units originally).

So far I've found that 3 pole contactors seem to be more common and usually cheaper than 1p options.

For an appropriate contactor do I need to consider anything beyond:
1) min. voltage rating (240 in my case)
2) current rating (min. 68 maps in my case)
3) contactor is of normally open design (Google states that DPC's are almost exclusively normally open designs)
4) Coil/switch voltage is appropriate for design (240V would be the most practical for my use)
As an example, something like this Honeywell part could likely be had for $50 on eBay (120v coil in this one though). ebay also currently has a 75 amp Furnas DPC for $20 shipped.

Thoughts?

 

[memphisjed]

brand new, 50 hp rated weg, https://www.automationdirect.com/ad...etic_contactors/iec_contactors/cwb65-11-30v24

buying used is good for some things, contactors- risk/reward value is just not there imo.

 

[jim rozen]

Yo probably want to have one with an aux. hold-in contact so the power contactors drop out in the event of power loss to the system. If a 3 phase contactor, the unused contact can be used for this.

 

[rons]

The contactor in the picture appears to have a coil for 110Vac.

You can buy contactors that have connection points for auxiliary switches. For a start/stop switch that is easy to do.

You don't have to buy a contactor for high voltage. I use 24Vac coils and 24Vac indicator lights.

If you want to protect your idler motor the contactor would have a overload block. This thing can be from a different
brand of contactor. But it looks better if the same brand is used.

You can use the third set of points for a drop-out stop. I use the third set for the generated leg from the idler motor.