Generator wiring options
OffGridiot
Registered Users Posts: 10 ✭✭
Hey all. I’m in the market for a new generator to replace the Honda 3000 watt inverter generator I’ve been using to charge my batteries for the last decade and a half. It’s done a somewhat adequate job for the most part but there have been times when it has come up short, and it’s getting pretty long in the tooth at this point. I’m thinking a diesel replacement in the 5 to 7 kW range is in the cards. I want it to either be the variable speed inverter style, or steady 1800 rpm type, and my budget will most likely mean shopping for a used unit. My question(s) is (are) mainly about circuitry to my MagnaSine 4024 inverter/charger. I understand that there is a capacity for ‘pass through’ juice beyond the 29 VAC charging current that the charger half of my inverter will process, enabling me to power other household loads while charging the batteries.
So, it seems that most generators I’ve been considering have breakers rated for around 30 amps. Being rated as 6 or 7 kW, I assume (from reading online data sheets) that this either means there are two 120 volt circuits around that capacity, or one 240 volt circuit at that amp rating to arrive at a total wattage output rating of the machine. My MagnaSine won’t accept 240 volts, and using only one 120 volt circuit @ 30 amps takes care of my battery charging needs but leaves virtually nothing for ‘pass through’ household loads.
Do the series/parallel rules used to make battery banks of different voltages apply to AC power as well? Could I (or a qualified electrician) combine two 30 amp, 120 VAC circuits in a parallel manner to (safely) create one 60 amp circuit? Or would it make sense to run one 30 amp circuit to each of the two AC input terminals in the inverter (I’m not certain if these separate inputs can be used simultaneously, or if they are only to be used one at a time, for convenient source-switching purposes)?
I’ve got my eye on an Onan Cummins 7.5 kW unit that’s almost brand new, and about half the price I’d have to pay retail from a dealer. And there are plenty of 6 kW light plants available on Kijiji at relatively reasonable prices. Opinions on these choices are also welcome.
I’ve got my eye on an Onan Cummins 7.5 kW unit that’s almost brand new, and about half the price I’d have to pay retail from a dealer. And there are plenty of 6 kW light plants available on Kijiji at relatively reasonable prices. Opinions on these choices are also welcome.
Thank you.
Bruce
Comments
This changes from 240V 30A to 120V 60A ( or whatever size the genset is )
I don't know of any variable speed, diesel, inverter gensets. Diesel is pretty much going to be a
a conventional alternator . Double check you can get Full Power at 120v from it
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
Most of the time you can rewire the two 120vac output windings in parallel.
You have to get the phase polarity correct. To do this from all four wires disconnected, ohm out to find out which two sets of wires go to each separate winding.
You have to be careful about field winding pickoff power. Sometimes they mix it up with output winding connections near socket panel. Most generators have their own separate stator windings for field rotor power so should not be an issue.
Pick two wires, one from each separate winding and connect them together. Run gen and check voltage across two open end wires. If you get near zero AC voltage you got them in parallel for 120v. If you get near 240vac you have them connected in series and need to disconnect your first guess and swap with other end of same winding. Repeat test to check you get near zero AC on two open wires and you should now be able to connect the two open wires together.
Largest AC socket for 120vac is 30 amps. If generator is greater then 4kw you should change to higher amperage socket. You could also use two of the sockets keeping to their current limit for each or use half a 240vac 50 amp sockets. Don't just parallel the two original L1,L2 240vac socket outputs.
The Magnasine or any other hybrid inverter is limited on pass through current to what their connect relay is rated for.
If you can't get the power you need at 120V, you can use a step-down transformer, 240V - 120V
If you want long life, look for 1800RPM generators
https://www.electricgeneratorsdirect.com/power/1800-rpm-generators.html
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
Only thing I don't like about them is diesel engines that run at 3600 rpm. I don't believe they have the long term reliability of a normal 1800 rpm diesel.
I think they come in 3000watt 5000watt and 10000watt
they seam to be selling for 3 to 5k for low hours unit .
I use the Honda , it sips fuel any way and cost 1000 bucks .