right relay for water heater

I want to turn on water heater on and off using relay but I do not know which relay I should pick provided the Voltage input is 230 volt AC only and wattage is 2.0 kW

2000W/230V = 8.7A?
Here are a bunch of 240VAC, 10A relays.
What coil voltage do you want to use?
http://www.digikey.com/products/en/relays/power-relays-over-2-amps/188?k=relay&k=&pkeyword=relay&pv1410=2&FV=fff40010%2Cfff80367%2Cffe000bc%2Ca8c0007%2C160c0050%2C1f140000&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

There are ratings for both the coil (input) and contacts (output).

Power (Watts) is Voltage x Current so the contacts need to be rated for at least 230VAC and at least 9 Amps. i.e. Contact ratings are "maximum" ratings, so it's OK to use 400V or 30A relay.

If you use a regular electro-mechanical relay you'll need an appropriate voltage source and driver circuit to drive the coil. Or, you can get relay boards with the driver circuit already built-in. (Coil ratings are "exact"... A 12V coil should be driven by 12V, and it will then draw the rated current... The power supply for the coil can be capable of supplying higher current.)

If you use a solid state relay (which doesn't actually have a coil) you can find one that can be driven directly by 5V/low-current from an Arduino I/O pin.

...Is that a small water heater? 2kW "feels" a little low to me. A toaster or hair dryer is usually 1-1.5kW and I would expect a water heater to require a lot more energy.

The standard used to be 60w per gallon so a 30 gallon hws would have 1.8kw element. Thats 125 litre metric. 60 gallon or 250 litre was 3.6kw. The exception was quick recovery systems in pubs or cafes and the like.

Hi,
OK we know 9 Amps at 230V and a nice resistive load.

This would work but marginal.

This is rated 30 amps.

This is even better and easy to use. Need to attach to some metal / heatsink. I have one running a 3000W kiln element as we speak..

DISCLAIMER: Mentioned stuff from my own shop...

terryking228:
Hi,
OK we know 9 Amps at 230V and a nice resistive load.

This would work but marginal.

This is rated 30 amps.

This is even better and easy to use. Need to attach to some metal / heatsink. I have one running a 3000W kiln element as we speak..

DISCLAIMER: Mentioned stuff from my own shop...

I think I will go with the second one, but listed on amazon .

Thanks

seaurchin:
I think I will go with the second one, but listed on amazon .

Ha! Take that, Terry! :slight_smile:

Ha! Take that, Terry! :slight_smile:

Hey, I'm 100% fine with wherever someone can find what they want. I even send some to Amazon/Ebay. I make money on selling 500 relay boards or 4000 temperature sensors to equipment manufacturers. But I really like the $15 orders to some kid in Bangladesh after 3 emails asking questions... :slight_smile: