Contactor or switch the relay signal?

[GoeHaarden]

So, I'm trying to rebuild/upgrade my RIMS panel and have a few questions...

1. Is there any disadvantage or safety concerns with using a switch to enable/disable an element via the DC signal to the relay? Instead of using the switch to control a contactor on the AC side? I'd like to get rid of the contactor if possible as it takes up a rather large amount of space.

2. If the above is possible, would I still be able to use these (www.auberins.com) illuminated push button switches and have the light work? I'm thinking I could run a separate 120v line to light it and then run the dc signal to the other posts? Maybe it's not that simple, but I'm hoping someone could shed some light on my idea...

Thanks!

 

[swimIan]

If your element is 120v you’d put your light after the 120v line leaves your ssr.

 

[swimIan]

Might still want a switch for 120 to the element.

 

[GoeHaarden]

If your element is 120v you’d put your light after the 120v line leaves your ssr.

Sorry, I guess I should have specified. Yes, it's a 120v/2000w element.

Might still want a switch for 120 to the element.

That's what I'm asking. Do I have to put a switch for on/off control of the element on the 120v side? My initial design was to use the illuminated switch to control a contactor which will in turn enable/disable the element regardless of SSR output. As an added safety in case the SSR junks out.

I'd like to get rid of the contactor, and just use a switch to DC signal from the PID to the SSR. Ah hah, now that I've read this out loud I realize that this wouldn't disable the SSR output if it sticks. Correct?

 

[swimIan]

The switch you linked won’t do your element. You need a switch rated at 16.667 amps. I’d do 20 to be safe.

I use a 30a dpdt switch in mine and it works great. I think it got it online from grainger.

 

[swimIan]

The switch wound need to be before the ssr to disable if it got stuck.

 

[GoeHaarden]

The switch you linked won’t do your element. You need a switch rated at 16.667 amps. I’d do 20 to be safe.

I understand, and I wasn't going to use the switch in line of the element. Hence the contactor...

 

[swimIan]

I understand, and I wasn't going to use the switch in line of the element. Hence the contactor...

If you get a higher rated switch, you can ditch the contractor.

 

[GoeHaarden]

I suppose I could do that, but I havent been able to find many 20a panel switches..

Do you have any links?

 

[golfindia]

I switch the relay and SSR signals in all of my stuff, and just use one contactor at the front of everything 240, 120 whatever. I'm sure this would make a lot of folks here scream in terror, but it has always worked fine for me. Way I see it, I'm eliminating a lot of other places a possible problem could arise.

 

[doug293cz]

Yes there is a safety concern with not having a contactor/switch on the AC feed to the SSR/element. SSR's typically fail in the on mode, so cutting off the DC control signal to the SSR will not shut off the AC voltage. You want an mechanical disconnect on the AC before the element. Also, SSR's are current switches, and can have a few mA of leakage current, which is enough to give you a good shock (but shouldn't be lethal.) I prefer the switch/contactor on the supply side of the SSR, as that cuts the AC to more of the wiring in the panel than a switch on the load side of the SSR.

For 120V you only need a single pole, single throw contactor/relay. You should be able to find 20A SPST relays significantly smaller than double pole 240V contactors.

Brew on

 

[GoeHaarden]

give you a good shock (but shouldn't be lethal.

LOL. I prefer to not ride the lightning if at all possible. Yeah, after thinking about what I was trying to achieve I realized that it wasn't possible safely. Thanks for the info. I'll guess I'll stick with a contactor and look for a 20A SPST. Do you recommend any online sources for a good one?

Also, if I'm using a terminal to split up the incoming power lines I only have to use 12 gauge wire for element (~16ish Amps) connections? Correct?

 

[doug293cz]

If you reduce the wire size for things other than the element, then you should add fuses to the hot lines where the size reduction takes place.

Auber sells a smaller form factor power relay that should work, but there are lots of other possibilities as well. The Auber unit is SPDT, so you would use the COM and NO terminals for your application.

Brew on

 

[GoeHaarden]

If you reduce the wire size for things other than the element, then you should add fuses to the hot lines where the size reduction takes place.

Auber sells a smaller form factor power relay that should work, but there are lots of other possibilities as well. The Auber unit is SPDT, so you would use the COM and NO terminals for your application.

That looks exactly like the one I was just looking at on amazon with prime shipping. https://www.amazon.com

The fuses would be to just prevent additional current leak through the smaller wires? Is it safer to just use 12g for all the wiring?

 

[doug293cz]

The fuses are to prevent overheating of the smaller wires in the case of a short somewhere. Overheated wires can cause fires.

Yes it is safe to use 12AWG wire everywhere, but finer wire is much easier to work with.

Brew on

 

[GoeHaarden]

The fuses are to prevent overheating of the smaller wires in the case of a short somewhere. Overheated wires can cause fires.

Yes it is safe to use 12AWG wire everywhere, but finer wire is much easier to work with.

Brew on

Thanks for your help. Ill keep it 12AWG throughout.

 

[doug293cz]

That looks exactly like the one I was just looking at on amazon with prime shipping. https://www.amazon.com

The Amazon one is equivalent to the Auber unit.

Brew on

 

[GoeHaarden]

Cool. Just ordered it. That should help free up a little space from the bigger contactor I have...