Is it normal for this relay to arc like this the original one shows a burn out mark and why do you think this is happening
Hi Freddyy75,
Welcome to the community!
It’s not normal but it does happen.
Could you please share the part number of the failed relay?
Also it would be helpful to know what kind of voltages are involved on your load side and the kind of load, are there motors/inductive load wired up to this?
Is that one picture showing the relay glowing?
Freddy yousfan
Lisa administration
| Kristof_2649 DigiKey Employee
August 24 |
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Hi Freddyy75,
Welcome to the community!
It’s not normal but it does happen.
Could you please share the part number of the failed relay?
OZ-SS-109LM1F
Also it would be helpful to know what kind of voltages are involved on your load side and the kind of load, are there motors/inductive load wired up to this?
240 40 amp oven
Is that one picture showing the relay glowing?
Yes
Greetings,
That’s not “normal” operation, but a pretty common result to see when a relay fails. A similar product with clear cover is pictured below to give an idea of how such things are built internally. The power-handling contacts are at right in the below image, which appears flipped horizontally relative to the glowy/burny end of the relay shown in the first two images posted above, with the third above image looking like a photo of an adjacent similar relay showing a part number .
Long story short, an arc occurs whenever a set of mechanical contacts switching a significant amount of power opens. A normally-functioning relay depends on the contacts separating rapidly enough to extinguish that arc before it heats things up enough to cause damage.
As a relay wears, various factors can cause that separation to not happen rapidly enough, so that the normal switching arc fails to extinguish until some outside factor interrupts the current flow, or the contacts burn away enough that the gap opens. The latter case is pretty common, because the load that the relay was driving is still there, limiting current flow and preventing standard circuit breakers or fuses from detecting and interrupting the fault.
It’s because of phenomena like this that there are regulations regarding the fire retardant properties of electronic components and materials.
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An additional point: If that relay is truly switching a 40A load, it would seem to be significantly underrated for the job, as it is only rated for 16A.
It’s driving a 3600w oven element so with ohms law calculator sits drawing 0.2 amps at 240 v
Freddy yousfan
Lisa administration
Quick calculation
Power = Current x Voltage
3600W = Current X 240V
3600W/240V = 15A, which is pretty close to this relay’s maximum.
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I see not very good at this I plugged in numbers in ohms law
Funny thing is that I replaced the original relays with the same exact ones you think it’s not sufficient ?
Freddy yousfan
Lisa administration
Do not mean to argue, but if you plug 200mA into Ohms Law in the other direction,
240V multiplied by 0.2A = is 48Watts.
Running a relay somewhat close to it’s absolute maximum is going to decrease it’s life expectancy.
No your right like I said I’m new at this
Freddy yousfan
Lisa administration
Thank you everyone for your help and input support ….I really appreciate it !
Freddy yousfan
Lisa administration
I checked our inventory for a relay that might have the same footprint with a higher current carrying capability, unfortunately I didn’t find anything.
Thank you, but I think that I was a little bit paranoid because I think it’s normal that there’s a tiny spark for a millisecond when the contacts take place
Freddy yousfan
Lisa administration
By the numbers it looks like this oven design is marginal with a 16A relay used for a 15A circuit.
You can assume the replacement will last just about as long as the original part. So whether or not the design is marginal depends on the how long it took for this relay to fail.
If the oven lasted 2 times the warranty length before failing then the design was just right from corporate profit standpoint.
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