Electrical Earthing properties

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glenick
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Electrical Earthing properties

Post by glenick » Tue Feb 06, 2018 5:04 pm

I hear a lot from people about electrical problems in properties, including modems being blown, fuseboards tripping etc etc
Does anyone know of a solution to this?
do some houses have an 'earthing strip' from the roof down to earth and what about the power inlet which is sometimes away from house?
how can this be protected?
any help would be great,
thanks

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zorbas2
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Re: Electrical Earthing properties

Post by zorbas2 » Wed Feb 07, 2018 9:20 am

I do not know a lot but regarding the lightning it is very often not a direct hit. If a lightning hits in between power supply and telephone cable (maybe some 100 meters away) an induction can occur which can cause very high voltages in the power and/or the telephone line.
There is reliable protection which can be installed right behind the electricity meter - but quite expensive. And that does not help the telephone line...
That's all I know...
Stephan Bartholomä
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glenick
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Re: Electrical Earthing properties

Post by glenick » Wed Feb 07, 2018 2:35 pm

thanks Stephen,
regards
Glenn

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timmillea
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Re: Electrical Earthing properties

Post by timmillea » Fri Feb 09, 2018 5:35 pm

Do not confuse a lightening conductor with electrical earthing on a domestic wiring circuit!

The former is a heavy, metal conductor running from above the highest part of the building directly, on the outside of the building, into the ground and is designed to carry a lightning strike safely to earth in locally high and exposed places (the classic case is the highest building in a village).

The latter is intended to reduce the risk of electrical shock from electrical items with metal parts and casings in case of an internal electrical fault. Electrical 'earth' is created locally ideally with a dedicated long ground spike (literally a metal spike in the ground) under or very near the building but at a very minimum by connecting to a non-insulated, metal mains water pipe where it enters the building. All metal plumbing, the earth conductors of all cables and hence the earths of all appliances are connected together via the consumer unit to local earth.

It should therefore be obvious that a lightning conductor is never connected to the earth of a domestic wiring installation - all electrical and electronic goods would be destroyed and possibly the inhabitants electrocuted instantly should there be a lightning strike!

From my experience in Stoupa, almost all electrical issues have been caused by low mains voltage, often 15-30V below the nominal 230V. This wreaks havoc with appliances and power supplies for delicate electronic equipment not designed to cope with such a low mains voltage.

When it comes to electronics, look for 'universal voltage' power supplies, i.e. 110v-240V, or even replace existing PSUs for modems etc. with such rated PSUs (ensuring same output voltage, polarity and plug type/size). Very few domestic appliances will be rated for anything other than the nominal local voltage so it really is just a question of luck as to whether they will be happy with the low voltage or not. I have lost two microwaves to low mains voltage and I have given up on them for now.

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splitbulb
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Re: Electrical Earthing properties

Post by splitbulb » Sun Feb 11, 2018 11:03 am

Thanks for that Tim, fascinating and informative.

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Re: Electrical Earthing properties

Post by aloni » Mon Feb 12, 2018 2:35 pm

Useful info Tim. The electrical circuit in our house seems to get overloaded quite easily - for example it trips if the oven and iron are both on. Is that because of low mains voltage?

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Re: Electrical Earthing properties

Post by timmillea » Tue Feb 13, 2018 9:46 pm

Aloni, it is hard to say.

What exactly trips? Is it the individual breaker for that circuit, e.g. 15A, 30A etc. or is it the main breaker? The latter, if a modern RCD (residual current device) would indicate an earth problem. If it is an individual breaker, then the oven and iron together simply exceed the current rating for that circuit. You may find that another socket in the house is on another circuit and the iron could be plugged in there. From my stage lighting days, I learned to 'upgrade' the breaker (to a higher current rating) knowing that I would not exceed the design current for very long - e.g. like ironing!

Having said that, when I installed an RCD in my house the washing machine, electric immersion heater and microwave all, separately, caused it to trip. I could only put that down to low voltage. RCDs are sensitive. It was replaced by a more conventional main breaker.

Hope this helps,

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The Real Stoupaman
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Re: Electrical Earthing properties

Post by The Real Stoupaman » Wed Feb 14, 2018 6:47 pm

The voltage would have to drop dramatically to cause these problems!

For example, an appliance that is rated at 2kW (2,000 watts) at 240v uses 8.33 amps.
If the voltage reduces to say 200v the amperage will increase to 10 amps - hardly a problem. Plus appliances are designed to operate at various voltages within the 'normal' 200/240v
To have any effect on the MCB, the voltage would have to drop heavily, which doesn't really happen. For example again, IF it dropped to say 150v (which it won't!) the same appliance would then take 13.33 amps.

The oven would have to be on full capacity ie all rings on full, plus the oven itself on full, and other appliances also on full. This may trip a 15A MCB but all of this is very irregular (plus the oven should be on its own separate, larger sized MCB anyway)

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