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Topic Title: Economy 7 time switch.
Topic Summary: Isolation
Created On: 07 October 2012 06:55 PM
Status: Post and Reply
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 07 October 2012 06:55 PM
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Wessex

Posts: 58
Joined: 26 June 2009

I am currently looking into providing an auxiliary generated supply through a 3 position change over switch.
My concern is the meter operator's economy 7 time switch connected to the meter. The time switch appears tobe operating control gear fed from tails before the time switch. I would be taking the metered supply to the change over switch. When the aux supply is selected this could lead to two sources of supply in the control gear enclosure.
A solution would be to use a four pole change over switch to isolate the time clock output given the single phase supply. Alternitively if I could reliably ensure isolation between control and power circuits and put a sign on the enclosure indicating it contains two sources of supply, would this be exceptable.
Your thoughts please.
 07 October 2012 07:27 PM
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weirdbeard

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Hi wessex, could you describe in more detail what is being controlled by what in the existing installation, ie is there a 24hour supply to the standard circuits board and a separately switched supply to a heating only board for instance?
 07 October 2012 07:54 PM
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Wessex

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Joined: 26 June 2009

Yes exactly that. Outgoing from the metering unit there are a pair of tails going to DB. Also outgoing from the meter are what appear tobe two double insulated cables of about 4mm2 to the time clock right next to it. There are then two cables from time switch going to the enclosure containing the control gear providing the supplies for the economy 7. There are also meter tails going to the enclosure coming from before the time clock.

Edited: 07 October 2012 at 08:02 PM by Wessex
 07 October 2012 08:14 PM
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weirdbeard

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Ok then, just to make this clear you have a single phase supply? You have a DB with the standard 24 hour supply, and you have a separately switched DB that feeds the off peak heating circuits? - is your generator going to supply both DB's?
 07 October 2012 08:42 PM
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Wessex

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Single phase supply and at the time of writing the post I would have said yes to providing for both supplies, but I don't have to provide a backup for the economy 7. The meter could still be live making the time switch live and also at times it's output. Perhaps another option is not to provide a backup supply for the the economy 7 control gear and its distribution.
 07 October 2012 08:49 PM
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weirdbeard

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I guess a key factor then is what size is the proposed generator? if its got to provide power to heating it might need to be pretty hefty, if its only for lighting and general power there could be a heck of a difference in size?
 07 October 2012 09:08 PM
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Wessex

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True, but my main concern was that I would end two supplies in one enclosure. Now with your help I realize that I don't have to provide a supply for the economy 7. At the end of the day if there is no metered supply there would be no time switch control. Thanks for your help
 07 October 2012 09:29 PM
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weirdbeard

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TBQH, not sure what I did but if it helped then what the hey!
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