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Garage Wiring, Coffee Roasting, Voltage Drop and Solar

Fultonius
Hi Folks,


I do a little coffee roasting. It's a 1300w machine, with a 230v heater element (40 Ohm - upgraded from a 240 / 44 ohm version). When running, it's drawing 5 amps and the voltage is dropping to 221v (around 229v before connecting).


Annoyingly, this means long roasting times in summer, and very long in winter! (not ideal)


So, here's my dilemma. I'm trying to consider the effects of voltage rise if I have batteries and an inverter. Obviously, I could get a variable output 1.5kw pure sine inverter and run it islanded. I have 7 x 16 ah 12v batteries redirected from going to the scrappies, which would have plenty juice to run this. I've been thinking for a while about putting a few solar panels on the roof and that's where it gets complicated.


Obviously the wiring from the house to the garage (at the bottom of the garden, so maybe 30m of wire) is a bit underspecced for what I need. Upgrading this would give me more chance of getting the correct voltage, and would probably make sense if I plan to put any "unused" power back to the grid. If the panels/inverter were grid-tied, what voltage would I end up with in the garage while running the roaster? My assumption is the amps will flow from the inverter to the roaster, and the grid will not have any effect? However, that's where my concern is - if my local voltage is higher, will that then default to pushing back to the grid and pull my voltage down?
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    Fultonius:

    Obviously the wiring from the house to the garage (at the bottom of the garden, so maybe 30m of wire) is a bit underspecced for what I need. Upgrading this would give me more chance of getting the correct voltage, and would probably make sense if I plan to put any "unused" power back to the grid. If the panels/inverter were grid-tied, what voltage would I end up with in the garage while running the roaster? My assumption is the amps will flow from the inverter to the roaster, and the grid will not have any effect? However, that's where my concern is - if my local voltage is higher, will that then default to pushing back to the grid and pull my voltage down?


    I'm not sure that last sentence makes any sense.  While the solar panels are generating, it will always pull up the voltage at the shed.  That could be either because the inverter is pushing current out to the grid (so the volt drop goes the other way), or at least reducing the volt drop because it will take some of the load and reduce the amount of volt drop.

    Bear in mind that solar panels only work well when it's sunny, and when the sun is shining directly onto them.  They do generate on cloudy days, and from indirect sunlight, but it will be a lot less.

    It generally isn't recommended to do a solar install at the end of a long cable.  You end up losing a significant amount of power warming up an underground cable, rather than doing anything useful with it.


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    Fultonius:

    Obviously the wiring from the house to the garage (at the bottom of the garden, so maybe 30m of wire) is a bit underspecced for what I need. Upgrading this would give me more chance of getting the correct voltage, and would probably make sense if I plan to put any "unused" power back to the grid. If the panels/inverter were grid-tied, what voltage would I end up with in the garage while running the roaster? My assumption is the amps will flow from the inverter to the roaster, and the grid will not have any effect? However, that's where my concern is - if my local voltage is higher, will that then default to pushing back to the grid and pull my voltage down?


    I'm not sure that last sentence makes any sense.  While the solar panels are generating, it will always pull up the voltage at the shed.  That could be either because the inverter is pushing current out to the grid (so the volt drop goes the other way), or at least reducing the volt drop because it will take some of the load and reduce the amount of volt drop.

    Bear in mind that solar panels only work well when it's sunny, and when the sun is shining directly onto them.  They do generate on cloudy days, and from indirect sunlight, but it will be a lot less.

    It generally isn't recommended to do a solar install at the end of a long cable.  You end up losing a significant amount of power warming up an underground cable, rather than doing anything useful with it.


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