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Forum Index : Electronics : Using one phase of 3-phase?

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domwild
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Joined: 16/12/2005
Location: Australia
Posts: 873

Posted: 07:24am 29 Dec 2011

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Hi,

Assuming I can find out which one phase of my 3-phase house supply is supplying ONLY my solar/electric H/W system, would it be possible to use the existing home wiring to heat my water during the strong Easterlies at night?

Please do not panic as I am not going to attempt to kill myself. The question is what sort of other sinks the 3 phases are generally connected to. There will be no cooking at night and it is only the fridges and freezers I have to worry about and I would not want to use the mill to drive them anyway.

From the little that I know there are four wires running for 200 m, one neutral and three active for the three phases. Each active combined with the common neutral yields 240VAC.

Now please stop laughing at my hare-brained suggestion: Assuming there is a "dead" active available at night and it would be dead because it would be disconnected from the supply temporarily (and by a relay installed by a licensed electrician), could the common neutral and the now "dead" active be used for the AC connection to the mill? Worse: Perhaps even for DC from the mill with the common as the negative??

More to the point: I will have a 36VDC system, how many watts would the mill have to produce and not stall to heat water with a common 48VDC heating element? 200 m house supply for 36VDC looks like a bad idea, too due to excessive resistance.

My 50l Braemar electric storage system has a single phase heating element, which probably draws more than one kilowatt, with a single rotor F&P do I have a chance to heat the water? The UPS is a 1,500W model and would be used as an inverter for the AC supply. The mill would be charging 3 x 12V batteries and the H/W system would be the dump load. This is the dream.

Laying a new cable to the H/W system would a problem.

Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up.

Winston Churchill

sjh7132
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Joined: 27/12/2011
Location: United States
Posts: 13

Posted: 03:53pm 29 Dec 2011

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I'm not sure what the codes are like down there, but here in the US, a licensed electrician would / could never wire something like that. Having your feed half hooked to the grid and half hooked to your mill just sounds like a bad idea. One problem is the two sources would not be in the correct phase relationship.

How about put the relay on a set of outlets instead? Then those outlets would be 100% on one source or the other.

Maybe I misunderstood what you were suggesting?

Steve

domwild
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Joined: 16/12/2005
Location: Australia
Posts: 873

Posted: 10:33am 06 Jan 2012

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Thanks for reply. Just trying to save myself a 600 foot wiring run with this crazy idea and during the day the normal 3-phase supply would be reestablished.

I suspect two phases go already into the stove/oven and therefore to find a phase solely dedicated to the H/W system must be an illusion anyway.

Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up.

Winston Churchill

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