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| Accidentally grounded live wire from UPS line |
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| cmosfxx:
Hello everyone, So... yeah, for the first time in my life I did something really stupid allow me to say. :palm: I was trying to take some measurements when I accidentally shorted live wire to ground for a split second by touching a metallic object between these two wires coming straight from the UPS line (APC SMART SMC) UPS was NOT in battery mode at that time. The fuse in the circuit breaker for that room (25A 240v) popped, nothing else actually tripped. (there is a 10A A/C unit on the same line) UPS switched to battery mode and all equipment kept working like normal. Now I'm wondering, 1. Why the RCD didn't trip. Is the breaker really faster than the RCD on short circuit situations? 2. Why the overload breaker on the UPS didn't trip ether 3. There is no short circuit protection on APC UPS? Shouldn't the UPS switch off to protect its self? 4. Is the UPS ok now or there is a hidden damage somewhere? I have already contacted APC about the incident and they told me if the UPS is working fine and there are no errors then it's fine but you know, something tells me it isn't right. Any thoughts would be appreciated. |
| thm_w:
To verify, you shorted the output of the UPS from live to earth? If you want proper RCD protection you'll need to put one on the output of the UPS right? Because if its running off of the battery your supply RCD is not connected at all. The overload breaker on the UPS would be a very slow thermal overload and would take a while to trip. |
| james_s:
I see no reason for a GFCI (RCD) on the output of a UPS, are you going to use your computer while in the bath? Outside next to the pool? It wouldn't make sense to plug electric gardening tools or work lights into a UPS. The circuit breaker for the room may indeed be faster than the RCD in the case of a large overload like that. |
| thm_w:
--- Quote from: james_s on August 03, 2021, 09:52:33 pm ---I see no reason for a GFCI (RCD) on the output of a UPS, are you going to use your computer while in the bath? Outside next to the pool? It wouldn't make sense to plug electric gardening tools or work lights into a UPS. The circuit breaker for the room may indeed be faster than the RCD in the case of a large overload like that. --- End quote --- Considering the whole reason for this thread was OP was playing with live wiring, the RCD could have some value. |
| james_s:
Well, there is that. You can't protect a person from every conceivable edge case though, IMHO it's better to just not play with live wiring. |
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