ampacity ratings versus inductive ratings

ganutenator

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Join Date
May 2002
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kansas
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can double the ampacity of the wago relays to 16 amps non inductive by going w/ single pole vs double w/ same base.

Regarding signs in a car wash.

New car washes are going w/ led's so not a problem.

Old ones have these signs that are horrible inductive loads.

How does one figure out the right relay for inductive loads?
 
If you use a freewheeling diode or other surge suppression does it still matter?

We used to use both sets of relay contacts thinking it would halve the wear on each set and double the life of the relay, but that proved to be false (wasn't using surge suppression, switching both 24VDC and 120V DC solenoids on a HPU).

Releco makes some relays with a magnetic arc snuffer which take the abuse of switching the solenoid loads without surge suppression. Their documentation has curves for different cos phi loads which will help you get a handle on wear vs. inductiveness vs. amperage
 
ganutenator,

putting 2 contacts in series or parallel will not double the current.
look at the ac ratings as already mentioned.

I thought the same thing and ended up having to use a contactor.

james

WAGO lists the relay at 16A.

Only if you get the single pole one.

I don't understand the magic.

Low profile w/ insertion tool.

Easy to screw up pins is only drawback I see. That and the double pole and single pole look identical.

Relays are sufficient for job.

I was just wondering about the inductive thing because of something the engineer brought up at work.
 
And If I can get away w/ the double pole for this project, that will be ideal.

As I could run the light and the solenoid off the same relay, hence saving outputs.

I'll be back w/ more details.
 
I may have misunderstood your original post.

if you want to use a multiple pole relay for a solenoid and light that's ok.
I thought you were wanting to increase the amp capacity by putting them in series or parallel. While the math would look to support this, the actual problem is in the contacts and the mechanical part of the relay itself: their ability to make/break the arc.

james
 
If your load is inductive, the switching current is going to be 5-6x the continuous current. That's why you will see inductive ratings that are significantly lower than the "thermal current" ratings of relays. So on your Wago relays, that 16A rating is the thermal current rating, which is just the maximum continuous rating that they can handle, NOT the switching duty, unless the load is PURELY resistive, which is now very rare. Anything that involves a power supply now, such as an LED driver, is an inductive load and you must use the inductive switching ratings of the devices in the circuits. There is no "cheat" that is valid, the result of trying to get around the issue is usually welded contacts.

As others mentioned, the solution is to use the small cheap relay as an "interposing relay" to drive a larger one, like a contactor, that has a true inductive load switching duty rating.
 

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