Understanding Maximum switching power and Relays

I just bought these

and was looking at a datasheet i found online JQC-3F datasheet & applicatoin notes - Datasheet Archive
the first one there was particularly confusing to me

Ill admit I am a software developer and am still learning a great deal about how these things work though I have pretty decent fundamentals. One thing that I am having trouble understanding is Maximum Switching Power

I assume this is the maximum amount of energy the load can consume. Is this correct? I find two different datasheets for this thing one listing 120Watts and another 210Watts. This is confusing to me because I assumed the writing saying I can consume

10A at 120V , lets assume im only powering incandescents so i have a power factor of 1 then that means I would have a power of 1200 watts 6 times the switching power. So I am obviously wrong in my understanding somewhere here and if anyone could offer some advice or a resource to check out I would greatly appreciate it.

Also does anyoen recommend a relay that can handle 15A at 125V?

Mechanical relays are very unreliable, and their load switching capability depends a great deal on the type of load you intend to switch. For example when initially switched on, incandescent bulbs draw a very large current (5-10 times the steady state value) and when switched off, motors produce "inductive kicks" that destroy relay contacts very quickly. What exactly do you want to switch?

Solid state relays are much more reliable and surplus electronics outlets usually have good deals. Below is link to one that can handle anything you would want to throw at it http://www.allelectronics.com/make-a-store/item/SRLY-50/50-AMP-SOLID-STATE-RELAY/1.html Or look at this list: http://www.electronicsurplus.com/LeftNav/Relays/SolidState.cat

Hey I want to control a wall socket with it and I want to try and put some high load thigns on it (a table saw, a very powerful computer)

I see what you mean about the Sold states. I spoke to some people about what the maximum switching power is and its the amount the load can be disipating when the relay is activated (otherwise it can damage the relay, it can arch, someting i can visualize but that I don't actually understand).

so the SSR are really pricey and I am looking to make quite a few of these (I want to retrofit my house with them)

I saw this Buy Packard C230B, Contactor 2 Pole 30 Amps 120 Coil Voltage on HVACBRAIN.com and get the best price.

so I am learning about contactors, 120V is not a problem to supply it since it will be on the wall but I will need someting lke a small relay to activate it so that the arduino can ocntrol it.

I hear that for a contactor you want to control it using an ssr not a mechanical (how to switch contactors? - General Electronics - Arduino Forum)

so I am starting to realize that I am toying in dangerous waters and really need to be better informed before I undertake this... I am used to working with small currents and only dc voltage. I feel a bit lost though because I don't know where to start researching. I am going to go read my old electronics book as a refresher though!

I didn't mention but the reason the contactor plus ssr thing would replace the just ssr is because the combo of them comes out to 5 dollars vs 25 dollars for that ssr.

Wow I just looked at the dimensions of that contactor. I guess its cheap because its freaking enormous :).

ok I hadnt looked very hard for the ssr there are some pretty cheap ones


thanks so much for turning me onto these!

Also does anyoen recommend a relay that can handle 15A at 125V?

A Bosch automotive relay can handle it; about 6 months or so ago I repaired a commercial waffle-cone maker iron that originally had an Omron 12VDC coil relay, which switched 120VAC to the heating elements of the iron (controlled by a microcontroller device). The relay had burnt out, and it needed to be fixed -immediately- and I couldn't get the replacement part (not for a few days - and this was being used by a local ice-cream shop).

So I went down to O'reilly auto parts and picked up an "auxilary" 12VDC relay (40 amps) - Bosch style (common in automotive relays). Worked perfectly, and still being used every single day to pump out waffle cones. If it ever does fail, the case is all steel, so nothing will catch fire easily. Heck, the old relay was somewhat charred when it burned out...

Now, granted, this was being used to control a resistive heating element, so the contacts are somewhat "buffered" - if you plan to use something like this to control a motor or solenoid - or similar - look into "relay contact snubber" circuits (which will help preserve the contacts).

You want to control an outlet with a "table saw" and "a powerful computer" ?

For what purpose ? Do you intend to interrupt these devices when they are running ?

If you are just looking for a method of remotely turning off the power to your shed to stop people from playing with your toys, you could do that with a relay, because when you are opening or closing the relay, the load would not normally be on.

If you are doing this to invent your own kind of electrical safety protection scheme, then don't, leave that to the experts.