How to size a Contactor?

[sheriffadam]

I've got a 7kW Cooling, 2.6kW Electrical Single Phase aircon unit here I'm working on in a 'project'

I want to control the unit via a contactor, there's a thermostat/microprocessor control switching between the aircon and a fan for cooling.

But I don't know what size contactor I need? The unit is connected to a 20Amp MCB, the closest contactor I've found is 18Amps, the next biggest is 25? Will either be ok?

Thanks! :p

[install monkey]

2.6kw condenser will pull no more than 13amp.
startup if non inverter will be about 5 times this.25amp contactor will cope with the inrush better,an 18amp is still sufficient,reommend fitting links to use more than 1 pole to split the load ie 6.5a per pole

[sheriffadam]

Thanks!
Where you mention 'links' is this where I'd get a 3 Pole N/O contactor and daisy chain the inputs together with a short piece of wire or a pressed metal link such as this: https://eb.automation.siemens.com/goos/catalog/Pages/Templates/Collateral.axd?method=product&mlfb=3TX7680-0D&region=IN

I think an 18Amp unit has already been ordered, think it might be a 3pole one, but with some 4MM cable linking 3 contacts would be better than having nothing right?

My internet research of googling images and reading here is coming together now! Cheers!

[install monkey]

yes link l1 to l2 and l3 inputs then on the bottom of the contactor link l1 to l2 to l3 on the outputs then ur only using 4.3amp per pole-dont use the 4th pole-usually for a crankcase heater

[sheriffadam]

Sweet as a nut mate, thanks a lot!