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Topic Title: New three phase supply, old single phase generator
Topic Summary: Dairy farm.
Created On: 04 September 2013 10:56 PM
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 04 September 2013 10:56 PM
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KENNYROGERS

Posts: 3
Joined: 04 September 2013

Would be grateful for suggestions on this one. Farm and two houses currently on single phase with changeover switch to single phase generator. New three phase supply being installed to take 50Kw PV system. Do we need a new three phase generator or is there a manual changeover switch that can go from three to single phase? Thanks
 04 September 2013 11:08 PM
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peteTLM

Posts: 3152
Joined: 31 March 2005

Assuming the farm and the 2 houses are all on the same phase, leave them on the existing arrangement, and let the new 3 phase connect to the PV, albeit with 1 phase interconnected to the existing farm/ houses/ via generator change over.

Not very elegant having a 3 phase supply available with 3 installations hanging of just the single phase.

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Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 04 September 2013 11:28 PM
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Legh

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Joined: 17 December 2004

Wouldn't this be the classic time for an upgrade and put each installation on a different phase?. But then, i suppose, it all depends on the finances available.

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 05 September 2013 08:55 AM
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davezawadi

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Joined: 26 June 2002

I would leave it all as it is, there is little need to change as you have a 50kVA supply (at least!). Unless you have electric heating, the maximum demand is unlikely to be more than 20kVA worst case. Is the old generator in good condition? I would just give it a good service, new brushes in the alternator (if fitted), a full load test for 24 hours and a full test of its overtemp, oil pressure etc. systems.
I can supply this if required, where are you?

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David
CEng etc, don't ask, its a result not a question!
 05 September 2013 01:23 PM
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ectophile

Posts: 546
Joined: 17 September 2001

If you want to go the changeover switch route, then if you can source a three-phase changeover switch (3 or 4 pole, as required), then there's no reason you couldn't connect the single phase of the generator to all three phases on the generator side of the three-phase switch.

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S P Barker BSc PhD MIET
 05 September 2013 06:51 PM
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AncientMariner

Posts: 517
Joined: 14 December 2004

Before everyone gets too excited, with the existing single phase arrangement how many meters are there? ie Does the farm and the two houses all get their supply via a single (single phase) meter for the total load, or does each property have its own Electricity Company meter?

(I'm thinking here on how the three properties all manage to switch over to a single generator.)

Cheers!

Clive

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Clive S Carver GCGI IEng MIET
 05 September 2013 10:08 PM
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davezawadi

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Good question Clive.
Are you still at sea or now shore bound?

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David
CEng etc, don't ask, its a result not a question!
 05 September 2013 10:32 PM
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AncientMariner

Posts: 517
Joined: 14 December 2004

Originally posted by: davezawadi

Are you still at sea or now shore bound?


I was made a good offer and therefore took early retirement in 2002.
(My photo left is circa 1985ish)

I'm of farming stock, hence my interest in this one - we had 3 x single phase meters for milking and corn grinding, with a separate single phase meter for the house and outbuildings.

I'm currently a County Councillor in Flintshire. Google my name as below and you will find me.

Cheers!

Clive

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Clive S Carver GCGI IEng MIET
 07 September 2013 12:43 PM
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KENNYROGERS

Posts: 3
Joined: 04 September 2013

Well thanks fellas for all your suggestions, the farm and two houses are all on the one smartmeter at the moment. That is coming out and a new three phase import / export going in. Now planning to have houses and farm on seperate phases, in to three phase changeover switch to panel, then as suggested strapping the three phases on the generator side of switch to supply single phase to the farm and houses while isolating the three phase panel and PV system.Appreciate your thoughts.

KR
 07 September 2013 02:52 PM
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weirdbeard

Posts: 1535
Joined: 26 September 2011

Hi kenny, just a thought, but if theres pv, I know if the grid fails the inverter must shut down, but is there any reason not to have the pv on-line when the generator is running, ie the grid is down?
 07 September 2013 04:50 PM
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Fm

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The pv needs to detect the grid, to export.
 07 September 2013 06:23 PM
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KENNYROGERS

Posts: 3
Joined: 04 September 2013

Thought about that one, the inverters are three phase and probably wouldnt start up. Also we dont want to feed the grid if there are faults on it. My main concern would be balancing the loads from the farm and two houses. When the cows are milking there will be a large load on one phase!
 08 September 2013 07:57 AM
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aligarjon

Posts: 2834
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Does this mean that you will have to manually shut down the PV if the generator is on ? or is there a way it can distinguish between the grid and an alternative supply ?

Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 09 September 2013 10:17 AM
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AJJewsbury

Posts: 11462
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Does this mean that you will have to manually shut down the PV if the generator is on

Probably easier just to connect it upstream (grid side) of the change-over switch.

- Andy.
 09 September 2013 08:47 PM
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slittle

Posts: 3510
Joined: 22 November 2007

I'd certainly connect it grid side of the changeover switch as generators and PV don't tend to like each other.

A large poultry farm that I look after when their own sparks is away had PV installed by one of the "double glazing type firms" They took the PV supply from the nearest DB.

The generator was less than impressed when it started after a power failure, took load and then saw the PV trying to push back at it ! It dumped the load and shut down almost resulting in major losses.

Stu
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