Would a relay fail on or off?

Basic / Standard Reef Angel hardware
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YuppiWanna
Posts: 29
Joined: Sun Apr 17, 2011 6:46 pm

Would a relay fail on or off?

Post by YuppiWanna »

If one of our relays were to fail, are they designed to fail in the ON or OFF state? Has there ever been a report of a relay failing in the ON state?
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rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: Would a relay fail on or off?

Post by rimai »

They will stick in the "on" position.
The reason they fail is due to large inrush current, which causes the relay contacts to arc when they are turning on. This arc generates heat which melts the contact together.
Yes, there has been reports of them sticking before.
Roberto.
YuppiWanna
Posts: 29
Joined: Sun Apr 17, 2011 6:46 pm

Re: Would a relay fail on or off?

Post by YuppiWanna »

Are they rated for 10 amps? Have you noticed a trend of which device(s) have caused said problems?

I'm concerned about my ATO pump sticking on so I'll probably gonna add an independent float/relay setup to sit between the relay box and the pump--something similar to what I have for my DT to kill the return pump if it ever started to overflow.
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rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: Would a relay fail on or off?

Post by rimai »

Very unlikely.
Pumps don't have the internal electronics to cause such insrush current.
You will only find problems when driving MH ballasts or LED drivers that have large capacitos inside that needs to be charged at once. A discharged capacitor draws as much current as if it was a shortage.
Roberto.
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