Lister Engines > Lister Based Generators
Circuit Breakers
guest23:
I have a 6/1 with a 5kw generator which is mounted on a trailer. It does not have any circtui protection. Has anyone put breakers on theirs? The generator is currently wired for 115 volts. Should I leave it at that or wire it for 230 volts?
Doug:
I would go out and buy a fused disconnect and some time delay fuses. You'll have to decide for yourself of you want a 120 or 240 volt connection. Fused switches are a little cheaper and unlike CBs they aren't as sensitive to vibration. Fuses are cheap and reliable they only fail one way (they blow obviously) where as CBs tend to be more expensive and more sensitive to heat and vibration.
I have an industrial 30 amp fused disconnect for my genset in the making for the generator itself and small laod center that will be mounted inside that house. This is an Ontario rule to have a local disconect, but when you think about it its not a bad idea for any remote aplication where your load and your generator are not within line of sight and easy reach.
Doug
Don't forget grounding!!!!!!!
You will need to ground common wire in your set to make the system safe. Again code requirements may differ in your state or province but a good rule of thumb is a #6 green wire joined at the white common wire in your disconnect and ground bus to a suitabe plate electrode or ground rod with no splices or joints.
Over current protection, grounding and bonding are the most important steps you will take with the project
solarguy:
You should make provisions for circuit breakers unless you like fires, electrocution, general mayhem and so on...
The 120V vs ~220V question is more complicated.
If you wire it so that you have a single 120V output, you can crank the entire 3kw (contiuous load) or the entire 5kw (peak load) into a single big load, eg a decent table saw that runs on 120V or a 120V water pump, or some combination. The other advantage is that you don't have to worry about balancing the loads on two separate circuits (or "legs"). The big drawback is that you can't run ANYTHING on 220V.
The other option is to wire it for 120/230 with two separate "legs". You get 120V on each leg, and 230V between the two legs since they run opposite phase. The big disadvantage is that each circuit or leg will only be able to push 1500 watts continuous or 2,500 watts peak, and you have to pay attention to balancing the loads so they are approximately equal between the two legs.
On the other hand, the fact that you have "oversized" the generator for the horsepower you have, allows you to cheat a little. In reality, you could probably push 2,500 watts through one leg of the generator, but the gen won't specially like it and will probably make funny noises since it's unbalanced that way.
Hope that helps!
troy
trigzy:
Hi,
I'm with Doug on this one - if it's mounted on a trailer, or anything that vibrates excessivley, go with the fuses. Breakers offer alot of advantages with differnt trip curves, resetability etc. and if they can be isolated from the vibration, I would prefer them.
Grounding / Bonding systems like this is a major issue that even most residental/industrial electricians wont understand fully, so you should check with your local authority, and/or someone who installs generators for a living. I wont even start to cover it becuase of all the "ifs" and "whatever you do don't ........"'s that vary in each circumstance.
Now; for my safety warning. I'll amplify the scenario to make it more obvious what can happen:
Lets say you have a 10kW Listeriod, and you've hooked it up to a 20kW gen head. So you go ahead and put fuses on it rated for the 20kW output of your alternator. Here's where you run into problems: You dead-short the output, but because your listeroid only makes 10kW, the power out of your gen-head wont go much above 10kW. Let's even say it goes up to 15kW in a dead short, that is still not enough to to blow your fuses, and your wiring/load burns up and starts a fire.
So, always make sure that whatever fuse/breaker size you choose, that it's appropriate for the generator as well as the prime mover, and that the generator and the prime mover together can provide enough energy to trip the protection in a reasonable amount of time.
Of course, with a 6HP engine (~4.5kw) and a 5kW gen head, this isn't much of an issue, but I thought I'd mention it for those with bigger setups.
Steve
guest23:
Looks like I will go with the fuse idea. Would 40 amps be about right? I will keep it wired for 115 volts to keep the load balanced. I will put in a ground rod with some sort of clamp that can be easily removed so I can move the generator if needed. Here in the country we don't wory about inspectors or codes, but I do not want to cut corners to make anything unsafe.
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