Thread: workshops and off grid power

Tony, I am not off grid but have a sister who is. Most of their power is provided by a large bank of batteries charged by wind and solar. However, for large power consuming items she has to fire up the generator. Power hungry items can be plugged into any suitable power point. Having said that I believe that there are two circuits in the house and shed - 12V and 240V. The generator sits across both circuits. Good luck.

Originally Posted by Tonto

looking at a block of land and would need to be off grid. Now for you guys that are already there how do you run your sheds and woodwork machinery .

a largish generator -- but get ready for the sticker shock

just remember that nothing in a typical house has the current draw of the machinery and tools in the shed and some of your tools will require "clean" power.

then you need to decide if you're investing in a 3 phase generator, which might be desirable if you're putting air con in the house.

I suggest you determine how you will cook, generate hot water, heat and cool the house before settling on a generator as the house load might be able to act as a balancing load for the shed.

First thing to consider is building yourself a passive solar house, then for a shed and house power you'll probably need a power system that has an inverter capacity of 7.5 kva minimum.
We have a 48 volt system which flows through a 7.5 kva inverter. In the house we run the usual mod cons, in the shed I can run a bandsaw, disc-belt sander, wood lathe, planer/thicknesser, tormec waterwheel, drill press and assorted power tools. I do have a 10 kva generator for emergencies.
We run our system on solar and mini hydro, so during a drought coupled with bushfire smoke(bugger all sun) we use the generator to keep the batteries happy
PS. It's worth mentioning that one of the first things to fail in a bushfire is the power grid add to that one of the most common causes of bushfires(apart from lightning strikes and arsonists) are fallen power lines and neglected power poles

On the required size of generator, SuperBunny is building himself a new house in Tasmania.
He's off grid.
He's found that an 8kVA generator is not large enough to start his (single phase?) table saw. I'm not sure where he's currently at with his power issues, but THINK he might need a 15kVA unit to power his shed. Don't forget that along with a particular machine, you will most likely be running a DC which draws around 10 Amps once it's running.

Yes, motors and generators are quite problematic. The start current on a motor can easily overload the gen set. It has to be waaay over speked.

John

Tonto, don't rely on gensets or generators. Set up your off grid power system to suit your needs, only use your generator as insurance/backup in an emergency.

Originally Posted by HUON

Tonto, don't rely on gensets or generators. Set up your off grid power system to suit your needs, only use your generator as insurance/backup in an emergency.

agree
what I was trying to convey is that a set-up similar to yours -- 7.5kVA -- might be way too small to run a table saw, let alone power a dusty running at the same time.

The largest machine I run is a 2hp alongside a 1hp dust extractor, so yes you are limited to smaller machinery. The set up for 3 phase would be a fair bit larger than my set up.

A 1HP DC (~350 CFM) is hardly worth running as it does not have a hope of capturing fine dust at source so the majority of the dust ends up filling your shed.
If you are off grid, chances are you a well away from neighbours so in that case I would put the 1HP into force ventilation rather than a DC.
A 1/4HP squirrel cage fan can move 1200 CFM provided it is unrestricted and a 1/3rd HP can move 1600 CFM. It depends how big your shed is but 2 x 1/3HP fans will be far better than the 1HP DC.

Thanks for knowledge and advice, may have been put on back burner stupid land agents putting the scubby noses in when not required.

Well i can tell you what i have done. ive been off grid now for 5 years.
I run a 48v system
Ive got 24 x 2v batteries at 1600AH ( Lead acid )
I run a Latronics inverter 7.5kva
I run 3.75kw of solar panels.
My system supplies all the power i need for about 10.5 months of the year.
In the 6 weeks in the middle of the year i run my back up generator to keep my batteries topped up.
If you only skim the top off the batteries and dont let them get right down you will get a longer life out of them,
I also have a 35kva three phase generator which is run by a 3 cyclinder lister disel engine. very very reliable. dont buy any of the cheap chinese rubbish generators they dont last and can be a real pain.
my generator doesnt really get touched for about 10 months of the year and it starts first time every time at the push of a button.
My generator is wired to run in three single phases to supply my house etc. the latronics inverter has a pass through which takes power from the genny and makes it clean and feeds the house disconnecting from the battery bank. The next phase runs my charger and the third phase i have wired to hibay lihts just to put a load on it.
If i want three phase for equipment in the shed i just flick a couple of breakers and three phase is available

I did have a little generator(chinese ebay brand) but it blew up when i tried to use my inverter welder which required more power than you would believe to get it fired up.

Any questions just ask. only too happy to help

Regards
Allan

Originally Posted by swiftden

Well i can tell you what i have done. ive been off grid now for 5 years.
I run a 48v system
Ive got 24 x 2v batteries at 1600AH ( Lead acid )
I run a Latronics inverter 7.5kva
I run 3.75kw of solar panels.
My system supplies all the power i need for about 10.5 months of the year.
In the 6 weeks in the middle of the year i run my back up generator to keep my batteries topped up.
If you only skim the top off the batteries and dont let them get right down you will get a longer life out of them,
I also have a 35kva three phase generator which is run by a 3 cyclinder lister disel engine. very very reliable. dont buy any of the cheap chinese rubbish generators they dont last and can be a real pain.
my generator doesnt really get touched for about 10 months of the year and it starts first time every time at the push of a button.
My generator is wired to run in three single phases to supply my house etc. the latronics inverter has a pass through which takes power from the genny and makes it clean and feeds the house disconnecting from the battery bank. The next phase runs my charger and the third phase i have wired to hibay lihts just to put a load on it.
If i want three phase for equipment in the shed i just flick a couple of breakers and three phase is available

I did have a little generator(chinese ebay brand) but it blew up when i tried to use my inverter welder which required more power than you would believe to get it fired up.

Any questions just ask. only too happy to help

Regards
Allan

Just off topic a litte bit but can i ask if you add more panels would that help in the darker months or would you still need to run the genset?

Allan, what's the economy like on the genset ie. litres per hour?

Of course more panels would help but it reaches a point where you need to weigh up the cost factor of doing so. Also a generator that is run regularly is more reliable. no good it sitting there never being used as when you really need it it wont work. I also have mine set up as three individual stands of ten panels(1.25kw) each with their own controller so if one fails i still have 2/3rds running. its a bit of a fail safe. My stands were built to have an additional 5 panels on each but ive never gone there. Cost for diesel each year is minimal. It was going to cost me $65,000 + to get mains and that was only if two neighbour allowed a pole on their properties. I got my system installed for $45,000 and i dont get a bill each month .