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Old 12-30-2012, 06:00 PM   #1
tyfernandez
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Hi,

I'm in the planning phase of my electric build. I'm planning on using 2 120v 2000w elements. I'm planning on following this diagram and adding another element to it.


My electrical knowledge is limited but I believe I understand the diagram. My question is on the contactor. Is is really only there because the switch in the diagram cannot handle the 20a load? Basically if you had a switch that could handle the 20a load would you need a contactor?

I'm hoping to use the Auber 1 Din box for my enclosure but I'm thinking it's going to be very cramped with 2 SSRs, PID, 2 Heatsinks and all the other components.

Thanks,
Ty

 
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Old 12-30-2012, 08:51 PM   #2
stlbeer
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The contactor is there so that when it's disengaged the power to the element is fully off. SSR's can and do fail. When they fail it's in the closed position allowing the full amount of power drawn to run through, regardless of the control circuit. Therefore, if you need to cut the power, you can disengage the contactor without turning off the entire panel. It's really a safety feature. The cost is less than $10 for the part.
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Old 12-31-2012, 12:39 AM   #3
tyfernandez
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I do see that point, but wouldn't a switch in between the element and SSR do the exact same thing sans contactor? Like this diagram.


 
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Old 12-31-2012, 02:12 AM   #4
P-J
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Just a note: The diagram was drawn to the specific plan that was requested. I drew the diagram to fit that request. The need (want) was to use a Auber Instruments illuminated push button switch. I made the diagram to fit that desired design.

You most certainly could use a toggle switch instead. That is up to you for your planned panel.

Please keep in mind that when I make a diagram, it is for a specific detailed plan for a member.

You are more than welcome to do it your way.

P-J

 
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Old 12-31-2012, 03:03 AM   #5
tyfernandez
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PJ that confirmed what I had thought. I do like the look and function of the illuminated switch but haven't had any luck finding ones that could handle 20A. I'll have to think about which route I want to go.

Thanks a ton, I wouldn't even dream of making a control panel without all these diagrams to get ideas from and this forum.

Ty

 
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Old 12-31-2012, 04:58 PM   #6
stlbeer
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You can find toggle switches of the needed ampacity at Grainger. However, they most likely will cost more than the 10a illuminated push button and a contactor from Auber.
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Old 12-31-2012, 06:27 PM   #7
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As was said, it's a matter of preference. I wanted to keep my high-amp loaded runs as short as possible, so I used a contactor and a switch - plus it kept in theme with the rest of my panel. I have seen panels on here with a hefty 30A DPST switch, and they will do the exact same thing - as long as you have something that breaks the circuit between the SSR and the element, you have an extra (I'd say minimally required) level of safety over just relying on the SSR.
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Old 12-31-2012, 07:47 PM   #8
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Just to add to the above, you could use a switch in the above 20a/120v plans like this. They're under $10.


For a 240v system, NKK makes some high capacity switches that are rated at 30amps/250v. The DPDT version is only about $23. Its just a matter of what you like and feel more comfortable with.

ETA: Digikey and Mouser seem to have the best prices on these switches from what I've found.

Reason: added info

 
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Old 12-31-2012, 11:42 PM   #9
tyfernandez
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Cost isn't the issue for me yet, it's more of a space issue. I think I'm going to have to go without contactors if I'm dead set on using the Auber enclosure. It just doesn't seem like it has the space for a PID, 2 SSRs, 2 heatsinks, 2 contactors and all the wiring and switches.

One last idea before I give up and start planning again. Without using a contactor could I put a DC illuminated switch in between the SSR and PID instead of the SSR and element? I remember reading that somewhere on here but can't find the post anymore.

Thanks,
Ty

 
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