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Thread: RCDs and old machines
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10th Jan 2019, 09:38 AM #16Intermediate Member
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The nuisance trip from RCD's can occur frequently. One solution is a time delayed RCD. These RCD's cost substantially more than your common RCD, but allow a small time when connected for the caps to charge in the RCD before they allow normal operation. They then behave exactly the same as a normal 30mA RCD.
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10th Jan 2019, 09:51 AM #17Senior Member
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Not all vfd's trip rcd's. I have some Mitsubishi inverters that are fine, and some SEW's that are not.
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10th Jan 2019, 02:19 PM #18Diamond Member
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What is causing them to trip though? Could just be something as simple as a setting.
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10th Jan 2019, 04:33 PM #19
I would have thought that ANY earth leakage from ANY piece of electrical equipment is an issue that should be resolved.
Cheers.
Vernon.
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Bite off more than you can chew and then chew like crazy.
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10th Jan 2019, 11:07 PM #20
The geckos in my shed get inside the gpo's and obviously short the switches. Until recently it was not a problem,
With a second freezer in there now, I have to check the RCDs every morning otherwise I may have a freezer full of bad meat.
The ants do a good good job of removing the zapped geckos but I do wonder can the switched gpo,s be sealed up without any detriment to them?
The odd thing is that it does not happen inside the house. We don't see geckos inside the house. Maybe they don't like the aircon.
Grahame
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10th Jan 2019, 11:49 PM #21Intermediate Member
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The vfd's can cause the RCD's to trip through a couple of different means. Either by the charging of the internal capacitor bank or some vfd's contain filter circuit to minimise electrical noise on the circuit it is attached to. Neither of these occurrences can harm the operator, just creates an imbalance in the active/neutral lines and trips the rcd.
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11th Jan 2019, 12:48 AM #22Member: Blue and white apron brigade
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Yes they can be sealed.
Many years ago (pre RCD days) I was having breakfast when one of the 20A (non-RCD) house circuits tripped.
After some fruitless investigations inside the house I remembered that the same circuit also went down to the shed and when I threw open the shed door I was hit with the smell of acrid smoke and saw one of the GPOs under the window was smouldering and looking like it was about to catch fire.
What I worked out happened was ants had setup a nest inside the GPO.
This was pre-dust serious collection days and the GPO was also partially buried in sawdust which I guess made it nice and warm inside the GPO.
During a storm in the night, a small amount of rain had blown in under a window and entered the GPO such that the mix of water, fine sawdust and ant juice (formic acid) shorted the inside of the GPO.
So although the power was off the GPO and sawdust around it was still smouldering and developing into a proper fire - luckily some of the sawdust was also damp from the rain.
The inside of the GPO got hot enough to melt the insulation around the wires so they had touched each other causing the breaker to open.
That's when I decided to have RCDs adde to the house circuits, installed a sealed window in the shed and it became a driver to get some proper dust collection going.
An RCD would have switched the circuit off much earlier but just in case I also installed a fire alarm.
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11th Jan 2019, 09:52 AM #23Cheers.
Vernon.
__________________________________________________
Bite off more than you can chew and then chew like crazy.
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12th Jan 2019, 05:25 PM #24Intermediate Member
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The fault is not a problem with the device.It is just caused by certain devices in normal operation.As long as that is what is causig the RCD to trip and not another wiring problem. Ideally it would not happen, and there is a solution, the time delayed RCD's, but not many people would like to pay for them. A three phase 32 amp rcd/breaker delay combo is ~$400 just for the part. It is actually not a bad thing if you do get the tripping. It makes you operate the RCD, this ensures that the trip mechanism is actually working and not stuck.
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25th Jan 2019, 09:08 AM #25Most Valued Member
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The only issues I've had with old machines that would have been an issue for an RCD is two of them used earth as neutral.
Other than that the only issue I've had is if I turn off my compressor at the GPO the RCD trips, though if I let it turn itself off or use the switch on the compressor its fine. I assume the compressor has a double pole switch, but have never looked into it.
What brands of VSD cause nuisance tripping? I would like to be sure not to buy one.
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