controlling high AC load ~3-5KW

Hello,

What relay would you recommend for controlling resistive ac loads of 3-5KW - 220V environment

Thanks for sharing,

Guy

Hi, Usually large optically-isolated Solid State Relays are used.

Example HERE:

DISCLAIMER: Mentioned stuff from my own shop...

Or a dirty great relay called a contactor..... and to drive that you'll need a small SSR.

regards Allan

Opto-triac driving a large triac? Its only a resistive load (or is it lighting? Tungsten lighting is not resistive like heating elements, there are large surge currents). 5kW at 220V is 25A or so, not uber-massive.

Hi, Usually large optically-isolated Solid State Relays are used.

Example HERE:

DISCLAIMER: Mentioned stuff from my own shop...

Thanks, With a 1.6V drop this would make @4KW ~(4000/220)*1.6=28W. This is pretty high and it must be cumbersome with the heatsink(?)

allanhurst:
Or a dirty great relay called a contactor… and to drive that you’ll need a small SSR.

regards
Allan

you mean with 220VAC control voltage? Any specific recommendation? A part you worked with?

There are loads of suppliers for these devices - any large electrical wholesaler will carry a variety. They're used for large ac motors and similar nasty loads. They often have 3-phase contact sets.

I have used them, and if correctly rated have found them very reliable.

And yes, they generally do have a 220-240 volt coil, so a small SSR would be necessary to drive them from a logic source.

regards

Allan.

Thanks Allan, i found these devices in din rail mount modules, 16 and 20A, 220v coil. Ill look into them and report here my finding Guy

  • They sometimes also have an extra small contact set for mains-level logic. Can be useful.

regards

Allan

allanhurst: - They sometimes also have an extra small contact set for mains-level logic. Can be useful.

regards

Allan

Found this thing with 220V, ~3VA command consumption. Can you point me one with logic commande?

Thanks for your time Guy

Try ebay etc for ssr - choose one which will accept 5v input at less than 20mA.

Or you could use an opto triac such as the MOC302.

Note the contactor you referenced is only rated at 3kW - if you want to control 5kW suggest you get a bigger one.

The 25A is the steady state current it can carry, not accounting for high inrush currents.

regards

Allan

Yes I was thinking of driving the 220V commande with a zero cross moc (the3063) and a triac as the 3063 output driver is limited to 150mW dissipation 150mA. I should not have inrush current: my loads are the resistor of a water heater rated at 2.5KW or of a bathroom resistive radiator rated at 1.8KW, each with it's own command. Yet I was thinking that with a logic command contactor life should be easier

bought this thing. Will play with it and report here