Solve : Home Electrics / RCD Protection / Fusebox?

1.	Solve : Home Electrics / RCD Protection / Fusebox?
Answer» I have a device that needs to run 24/7. It takes two power supplies in case one fails - then it continues running from the other power supply, uninterrupted. The problem is, recently one power supply DID fail - but it tripped the RCD unit at the main fuse box. So it knocked out power to the other power supply, as well as several rooms, totally defeating the reason for having two power supplies I decided the solution would be to buy two plug-in RCD adapters, so I could plug each power supply directly into its own RCD. So if there was a fault with one of the power supplies, the worst it could do is trip the RCD that it was directly plugged into, and the fault would go no further - crucially it would not trip the RCD at the main fuse box. The theory was great, and I tested it with the known faulty power supply, but unfortunately nobody had told electricity about my theory, so it decided to do its own thing - again it tripped the RCD unit at the main fuse box! Again, everything went quiet and very dark Another solution would be to run a new circuit directly to the fuse box and avoiding the RCD protective device there, just connecting directly the Live, Neutral and Earth, and the only protection being the two RCDs that the power supplies are plugged into. However, this solution would be unacceptable simply because the cable will look too much of a mess - let alone be dangerous running permanently exposed in areas of traffic, and crucially if someone accidentally broke it - there's no RCD protection at that end! Can anyone think of REAL solution? Thanks.What is a RCD? Your local electrical codes may put limits on what you can do. If this is really a commercial operation, then you should treat it as an industrial application and talk to you local utility company. For home and office applications that require less than abo0ut 10,000 watts the solution is a UPS. uninterruptible power supply Present your problem to the people who make UPS units. They have heard your story bedsore and have a solution. Big industrial users of electrical power invest in special equipment that delivers power full time. Examples are TV stations, Airports and Hospitals. Quote from: Geek-9pm on July 20, 2014, 12:06:58 AM What is a RCD? Residual Current Device - (RCD) the name in Britspeak countries. In the USA & Canada, Ground Fault Circuit Interrupter (GFCI), Ground Fault Interrupter (GFI) or an Appliance Leakage Current Interrupter (ALCI). Often combined with overload protection in one device. The poster's use of British spellings on other posts and here, the "live, neutral, earth" names, suggests a British or British Commonwealth location. Geek's point about legal/wiring code issues is a good one, and here: Quote Another solution would be to run a new circuit directly to the fuse box ...of course you meant "pay for a qualified electrician to run a new circuit..." and issue the relevant paperwork, to avoid legal issues and possible insurance cover problems. If you are in Britain, this applies in a home, let alone a workplace. I'd add a UPS dedicated to each power supply of the redundant power supply server setup. Also would have an electrician come in and give you a non-RCD power feed for this server setup according to code. Generally they can install a special outlet such as a orange colored outlet that is for non-RCD power going back to breaker box with a standard breaker in the panel that wont trip unless there is an overload condition. With other outlets white or beige, this orange one would stand out as the special outlet for the setup that must stay live with just overload protection.Whats the device that needs on 24/7 ? ?Thanks for the replies. Yes this is a UK installation. In addition to what Salmon Trout correctly pointed out, RCD = Ground Fault Circuit Interrupter (GFCI), the following terms might also help (if not please ignore): Earth = ground Power supply = AC/DC Adapter I think DaveLembke's suggestion is the closest, but twin UPS systems would be a large expensive compared to the RCD devices I originally wanted to use (search for eBay item #130909849440 if you want to see this simple and cheap type of RCD device). Twin UPS would also be a work-around to a problem which should really have a simpler solution. We rarely have power outages here, so I don't need UPS for the purpose of power outages. By the way, any electrical work I would do myself. It's legal here in the UK (I already rewired the whole building, DESIGNED and installed a gas central heating system and installed the gas boiler, I only needed a qualified plumber to test and connect the last pipe from boiler to gas supply). But I've SINCE renovated all the rooms and really don't want to install a new circuit just to solve this technical problem. I've seen something called an RCBO which is similar to an RCD but also includes overcurrent protection (for example, eBay item #261537206838). If I bought two RCBO switches, and connected each power supply unit to one of them, then when there is a fault - what item would trip first, the RCBO or the RCD at the main fuse box? I think I just need to understand why the RCD furthest away tripped first. Is it something to do with that RCD being closest to the earth rod (this is the metal rod that GOES into the ground next to the main fuse box)? Or is there a millisecond rating for such devices, and the fastest device trips first?On further investigation, it seems to be a matter of timing. I FOUND an article where a similar problem was discussed, with RCD units used in series. All RCD units were rated 30ma (like mine are) and the most popular solution was to replace the 30ma RCD at the main fusebox with a 100ma time-delayed RCD, and then have each circuit protected by its own 30ma RCD or RCBO device. This ensures discrimination and prevents the whole installation being knocked out. In my fusebox I actually have 2 x 30ma RCD units. So I plan to replace these with 2 x 100ma rated RCD units. I can build a small sub-fusebox locally next to my device, reuse the 2 x 30ma RCD units by installing them inside it, to feed the two power supplies. So this should be a very cheap fix, just the cost of 2 x 100ma RCD units and a small bare fusebox enclosure, all of which I can get pretty cheaply 'used' off the Bay. Well again, this is all theory. Once I've installed and tested it, I will post an update to confirm if it actually worked

Answer»

I have a device that needs to run 24/7. It takes two power supplies in case one fails - then it continues running from the other power supply, uninterrupted.

The problem is, recently one power supply DID fail - but it tripped the RCD unit at the main fuse box. So it knocked out power to the other power supply, as well as several rooms, totally defeating the reason for having two power supplies

I decided the solution would be to buy two plug-in RCD adapters, so I could plug each power supply directly into its own RCD. So if there was a fault with one of the power supplies, the worst it could do is trip the RCD that it was directly plugged into, and the fault would go no further - crucially it would not trip the RCD at the main fuse box. The theory was great, and I tested it with the known faulty power supply, but unfortunately nobody had told electricity about my theory, so it decided to do its own thing - again it tripped the RCD unit at the main fuse box! Again, everything went quiet and very dark

Another solution would be to run a new circuit directly to the fuse box and avoiding the RCD protective device there, just connecting directly the Live, Neutral and Earth, and the only protection being the two RCDs that the power supplies are plugged into. However, this solution would be unacceptable simply because the cable will look too much of a mess - let alone be dangerous running permanently exposed in areas of traffic, and crucially if someone accidentally broke it - there's no RCD protection at that end!

Can anyone think of REAL solution?

Thanks.What is a RCD?
Your local electrical codes may put limits on what you can do. If this is really a commercial operation, then you should treat it as an industrial application and talk to you local utility company.

For home and office applications that require less than abo0ut 10,000 watts the solution is a UPS.
uninterruptible power supply
Present your problem to the people who make UPS units. They have heard your story bedsore and have a solution.

Big industrial users of electrical power invest in special equipment that delivers power full time. Examples are TV stations, Airports and Hospitals. Quote from: Geek-9pm on July 20, 2014, 12:06:58 AM

What is a RCD?

Residual Current Device - (RCD) the name in Britspeak countries. In the USA & Canada, Ground Fault Circuit Interrupter (GFCI), Ground Fault Interrupter (GFI) or an Appliance Leakage Current Interrupter (ALCI). Often combined with overload protection in one device.

The poster's use of British spellings on other posts and here, the "live, neutral, earth" names, suggests a British or British Commonwealth location. Geek's point about legal/wiring code issues is a good one, and here:

Quote

Another solution would be to run a new circuit directly to the fuse box

...of course you meant "pay for a qualified electrician to run a new circuit..." and issue the relevant paperwork, to avoid legal issues and possible insurance cover problems. If you are in Britain, this applies in a home, let alone a workplace.

I'd add a UPS dedicated to each power supply of the redundant power supply server setup. Also would have an electrician come in and give you a non-RCD power feed for this server setup according to code. Generally they can install a special outlet such as a orange colored outlet that is for non-RCD power going back to breaker box with a standard breaker in the panel that wont trip unless there is an overload condition. With other outlets white or beige, this orange one would stand out as the special outlet for the setup that must stay live with just overload protection.Whats the device that needs on 24/7 ? ?Thanks for the replies.

Yes this is a UK installation. In addition to what Salmon Trout correctly pointed out, RCD = Ground Fault Circuit Interrupter (GFCI), the following terms might also help (if not please ignore):

Earth = ground
Power supply = AC/DC Adapter

I think DaveLembke's suggestion is the closest, but twin UPS systems would be a large expensive compared to the RCD devices I originally wanted to use (search for eBay item #130909849440 if you want to see this simple and cheap type of RCD device). Twin UPS would also be a work-around to a problem which should really have a simpler solution. We rarely have power outages here, so I don't need UPS for the purpose of power outages.

By the way, any electrical work I would do myself. It's legal here in the UK (I already rewired the whole building, DESIGNED and installed a gas central heating system and installed the gas boiler, I only needed a qualified plumber to test and connect the last pipe from boiler to gas supply). But I've SINCE renovated all the rooms and really don't want to install a new circuit just to solve this technical problem.

I've seen something called an RCBO which is similar to an RCD but also includes overcurrent protection (for example, eBay item #261537206838). If I bought two RCBO switches, and connected each power supply unit to one of them, then when there is a fault - what item would trip first, the RCBO or the RCD at the main fuse box?

I think I just need to understand why the RCD furthest away tripped first. Is it something to do with that RCD being closest to the earth rod (this is the metal rod that GOES into the ground next to the main fuse box)? Or is there a millisecond rating for such devices, and the fastest device trips first?On further investigation, it seems to be a matter of timing. I FOUND an article where a similar problem was discussed, with RCD units used in series. All RCD units were rated 30ma (like mine are) and the most popular solution was to replace the 30ma RCD at the main fusebox with a 100ma time-delayed RCD, and then have each circuit protected by its own 30ma RCD or RCBO device. This ensures discrimination and prevents the whole installation being knocked out.

In my fusebox I actually have 2 x 30ma RCD units. So I plan to replace these with 2 x 100ma rated RCD units. I can build a small sub-fusebox locally next to my device, reuse the 2 x 30ma RCD units by installing them inside it, to feed the two power supplies. So this should be a very cheap fix, just the cost of 2 x 100ma RCD units and a small bare fusebox enclosure, all of which I can get pretty cheaply 'used' off the Bay.

Well again, this is all theory. Once I've installed and tested it, I will post an update to confirm if it actually worked

Solve : Home Electrics / RCD Protection / Fusebox?

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