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Old 12-08-2012, 06:30 PM   #1
jdowling
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Default Quick question about contactor rating meanings

As a bit of background - I'm in the middle of planning out a parts list for a 50A control panel (upgrading from a smaller 120VAC toolbox build I have currently).

I'm trying to figure out which parts to use for the contactors. I'm aiming to use 2x 50A contactors: 1 for main power on/off and one for elements on/off (2x 4500W elements on the same control circuit for the option of 30+ gallon batches).

I was looking at this: 40A contactor from auber instruments.

It says:

Quote:
Full Load AMPS 40A, 120-600VAC
Resistive SMPS Rating 50A, 120-600VAC
I don't know enough about electrical terminology to know if that means it's rated for 40A or 50A for control panel main power control. I did some searching on google to try to find out what "AMPS" versus "SMPS" means but came up empty handed.

Looking at Grainger I see that essentially all their contactors that are 40A are rated for 40A Inductive load and 50A resistive load. As near as I can tell the control panel is resistive load so it seems like a 40A contactor would be rated appropriately for the use.

I was hoping someone could either validate that my conclusion is correct & I can use this contactor or tell me that I'm totally wrong before I order it .

Thanks!


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Old 12-08-2012, 06:50 PM   #2
grandequeso
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Resistive = heating element. inductive = motors, compressors.



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Old 12-08-2012, 06:55 PM   #3
jdowling
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So the control panel will have some of each (37.5A resistive and 2 pumps worth of inductive).

I suppose that means that I should really aim for 50A inductive rating?

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Old 12-08-2012, 07:09 PM   #4
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Eh, those pumps don't draw much at all. I doubt you could go wrong either way. Steer clear of used contactors. Its usually the coils that wear out rather than the contacts. The contactors should last a very long time in a clean environment and very short duty cycle like a brew panel.

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Old 12-13-2012, 05:10 PM   #5
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If you look at where "s" and "a" are on your keyboard, I'd be willing to bet $10 that "SMPS" is simply a typo of "AMPS".



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