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Author Topic: AC generator grid tie  (Read 12076 times)
fifthwheel
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« Reply #15 on: August 21, 2015, 10:48:26 AM »

Morning all just a quick question if I were to install a 4kw ground array in the garden would I have to go to the house to connect? I ask as I have a supply running from the house into an out building. If I could feed this it would save digging up block paving and a lot of work. Also would it be ok to run DC from the panels to the inverter in the building or would the inverter have to be close to the array in a cabinet and run AC across the lawn. thanks john.
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Ted
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« Reply #16 on: August 21, 2015, 11:41:18 AM »

It depends on the distance from shed to house and what size cable has been used and what the present fuse/MCB size is. The recommendation is to have no more than 1% voltage drop on AC from where the inverter is installed back to the mains incomer in the house and no more than 3% volt drop on the DC cables. This governs the size of cables that need to be used. If the cable is too small the inverter will power off often as the voltage varies from what it is designed to handle and you will lose any generation.

Locating the inverter close to the panels for short DC/long AC - this can be done either way, but, again, it is recommended to keep the DC cable lengths shorter.

An MCS installer has to follow the guidelines in the MCS PV Guide when designing your system, which covers all this and more:
http://www.microgenerationcertification.org/images/PV%20Book%20ELECTRONIC.pdf
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fifthwheel
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« Reply #17 on: August 21, 2015, 12:14:48 PM »

Thank you, appreciate your reply, I have just started to read the document I will have a few more questions no doubt. regards john.
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fifthwheel
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« Reply #18 on: August 25, 2015, 05:38:39 PM »

The shed is around 25m from the house, it looks like 2.5 twin and earth from the consumer unit to the house wall. From there it goes underground if I remember rightly this cable is armoured to the shed. Not sure about the size of the trip but this could be changed. If the solar panels fed the shed and from there to the house would it present a problem monitoring the total usage and solar output?
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Ivan
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« Reply #19 on: August 28, 2015, 10:29:13 PM »

You might need to worry more about AC voltage drop. I suspect you'd probably be ok, as long as your voltage is in-spec, but you'd find your inverters would trip out if your voltage is high. You can find voltage drop calculators online - work out the voltage drop, and add it to your highest 'normal' daytime voltage. If this is under the over-voltage cutout spec for the inverter, then everything will be ok.

If you have long DC cables, you'll have voltage losses and therefore power losses, but it shouldn't have any effect on the inverter function.

If I remember correctly, AC household wiring is often sized for 5% losses - which is actually rather a lot!! If you were wiring a house from scratch, you might well choose to oversize the cables beyond the regulations.
« Last Edit: August 28, 2015, 10:32:09 PM by Ivan » Logged

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