5V 40A DPDT relay?

[treefort]

Hi everyone. I want to turn on my sauna from inside the house and the plan is to use a couple pics and wireless modules.

It is a 240VAC 40A sauna, and it appears as though most, if not all saunas have the 40A going through the 60 minute mechanical timer which I need to connect in parallel with to turn it on/off.

What is the best way to have my mcu switch the power?

Thanks alot!

 

[Diver300]

You need a big solid state relay. Something like this Digi-Key - CC1082-ND (Manufacturer - D2450-10) and a heatsink.

 

[treefort]

Thanks for the reply Diver. I was looking at those, but I need something to switch 2 hots and those are only spst. Unless I am missing something?

 

[Diver300]

Just use two.

A smaller solid state relay driving a conventional DPST relay might be a lot cheaper.

 

[treefort]

That sounds good. I have a conventional 5V relay I could use to switch a DPST relay. But, in case I don't have the required power or space available, would you be able to recommend a good solid state relay for use with mcus?

 

[treefort]

I ended up ordering a couple 40A spst solid state relays and heatsinks off eBay for $15 each. Thanks again for you help Diver.

 

[Sceadwian]

Don't forget to determine their required power dissipation and add an appropriate heat sink, they generally do NOT have protection circuitry built in, so if you don't do the calculations properly you'll have nothing but smoke on your hands. The heat sinks on a 40amp relay are going to have to be very large.

 

[treefort]

Here are the ones I bought. Hopefully they calculated the heatsinks properly for 40A max.

**broken link removed**

Edit: I think I am going to have to watch the temps and if need be try screwing some computer fans on the heatsink to assist in cooling. I read that ssr' cannot work in above 50 deg C.

 

[Diver300]

Those are DC output relays. They probably won't work on AC.

Sorry to be the bearer of bad tidings.

 

[Sceadwian]

Yep, sorry treefort but what Diver said is correct. Those relays will not work with AC power. If the purchase has already gone through you're pretty much stuck with them.

 

[tcmtech]

You are not lost yet!
I have a whole box of odd used take off 480 VAC 50 amp commercial SSR units with extra external snubbers that came off of a bunch of machines that had large heaters on them. They have the standard 3 -32 VDC control inputs as well and should be the same base mounting hole spacings as your DC units so they would be a direct drop in. If you dont mind them being used and of an odd brand.
They are Electromatic RA4850-D12 but they cross reference to the Crydom A48 series parts from what I have found. Digi-Key Some of the take offs where that exact Crydom part but I have used those already.

I would happily trade you 4 of them for your two big DC units.

You pay shipping of course.

$10 a piece for anyone else that wants some being I have at least 10 more I will part with without complaint and probably more if I looked since I had around 50 at one time.

PM me if interested.

 

[treefort]

Whew, I was kind of scared there for a second. I was looking at different relays and attached the wrong link. Here are the relays I bought.

**broken link removed**

and the heatsinks.

**broken link removed**

 

[Sceadwian]

Applicable to a rectangle single phase SSR on which the actual load current is no more than 15A.

You're probably under heatsinking. Here comes the smoke!

 

[treefort]

Lol..I was going to strap on some fans and see if I could manage that way..but thankfully tcmtech is helping me out with a couple of properly sized heatsinks he has available!

Saves me a lot of grief...I am really trying not to use contactors.

 

[Sceadwian]

Thanks to tcmtech then.

 

[treefort]

Thnx to you Sceadwian. Much appreciated. +rep (with the little rep I have)

 

[tcmtech]

Lol..I was going to strap on some fans and see if I could manage that way..but thankfully tcmtech is helping me out with a couple of properly sized heatsinks he has available!

Some days its good to have too much 'stuff'! You never know when you may meet someone who has too little 'stuff' and needs more 'stuff'.

And as many here can attest to I am almost always full of 'stuff" and more than willing to spread it around at every chance I can get!

 

[Sceadwian]

I'm not going near anything you just said with a 10 foot pole... 20 foot if I can help it. Radiation and biohazard suit minimum.

 

[specie]

Why not use a regular spst relay to control the coil of an appropriate contactor ?

 

[treefort]

I am trying to avoid EMI.