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First you need to please understand that I am a truck driver, I lift heavy things and have a smaller brain pan than you good readers. Aka; not an intellectual that understands elictrickery.

While on the road 2,000 km from home for an extended period, the wife needed a generator for back-up power to our home during a particularly stormy season. She bought one that is a petroleum fuelled 12 kVA large enough to run all household and sheddy items - with the 12 kVA thingy detail. However, she is as un-smart as me and purchased a 32 A 2nd-handgenerator instead of 10 A (which is what Australian households are).

So without pointing fingies at her further, my question is:

Can a 32 A generator be converted to output 10 A somehow or do I just scrap the generator in the back of the shed and source another one?

Have a nice day, thanks for reading.

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    \$\begingroup\$ The 32 amps rating is the maximum it can supply, not what it will supply. \$\endgroup\$
    – DKNguyen
    Jun 11, 2020 at 1:40
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    \$\begingroup\$ The generator can supply UP TO 32 amps, but it will only deliver what the load (your house? 10 amp sounds really low for a whole house!) wants. \$\endgroup\$ Jun 11, 2020 at 1:46
  • \$\begingroup\$ Hey thank you for the answers. It gets tricky though, I've tried plugging it to the house and it just keeps tripping the breaker... So I am stumped \$\endgroup\$
    – Roadeater
    Jun 11, 2020 at 2:07
  • \$\begingroup\$ This is a question for Home Improvement, not Electrical Engineering. \$\endgroup\$
    – The Photon
    Jun 11, 2020 at 2:44
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    \$\begingroup\$ DO NOT CONNECT YOUR GENERATOR TO YOUR HOUSEHOLD WIRING WITHOUT A TRANSFER SWITCH. Doing so is gonna be super illegal for sure pretty much everywhere in the industrialized world. Why? Because you'll potentially be pushing voltage out into the neighborhood and possibly kill a lineman. \$\endgroup\$
    – Kyle B
    Jun 11, 2020 at 3:38

3 Answers 3

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At a guess, you have a household trunk circuit breaker (usually about 200A) connected to municipal power lines through a transformer (often pole-mounted in a cylindrical can).

Each branch circuit in the house has a (10A ?) circuit breaker, and feeds the normal outlets. The trunk (200A) feeds all those branches.

It is possible that you are 'plugging' the 32A generator into a branch circuit, which (naturally) will blow the branch circuit breaker if the total household power use exceeds 10A. That's what branch circuit breakers do.

Instead, you want to use a transfer switch, which (1) disconnects the municipal power lines and transformer from your house, and (2) connects the 32A generator to the same wiring trunk that those power lines drove. That, too, may blow a circuit breaker (there's one in the generator), unless enough house circuits are disabled so that only a few appliances will run concurrently (presumably, including a refrigerator and a lamp and a clock).

While having a trunk power capacity of 32A is limiting, it ought not to be unlivable. The local fire safety codes will apply (probably a professional should make the connections), unless you're willing to bypass the house wiring and just plug a few appliances through extension cords into the generator.

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No need for a conversion. The rating in the generator is the maximum power delivery capacity. A 32A 110v generator will be able to run 35, 100w bulb total 3500 w.

P = V * A

If the voltage requirement is same then you are good to go with this generator.

Edit 1:

Illustration :

enter image description here]

power rating of 32A 110v generator = 3.52 kVA

Assuming a simple connection ignoring the existing power-line setup, and inductive loads at home like motor and fan.

The generator has a main switch or tripper. The rating on this tripper will be 32 A as it is the maximum capacity. If the house hold equipment draws more current than the max rated value it will trip. e.g. In my earlier bulb example if I connect a 100w heater to the generator the total power drawn by my household equipment is 3500w + 100w = 3600w which is higher than the max rating of the generator, to safeguard the coil in the generator the tripper will break the circuit.

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  • \$\begingroup\$ @Roadeater the tripping of breaker is may be due to some short circuit at the output of the breaker or some heavy household equipment. I updated the answer with an image \$\endgroup\$ Jun 12, 2020 at 5:23
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Mechanical power = torque * RPM

Electric power = Voltage * Current

Combustion engine powered electric generators, just as most power supplies in general use, provide a certain nominal output voltage (within some small margin). The generators actually have an automatic throttle on the gas / diesel / air intake that aims to keep a somewhat constant RPM under varying load, and something very similar (even easier) happens in the dynamo/alternator part.

Think about the diesel engine in your truck. That comes with some maximum horsepower, but it's not running at that HP all the time - rather, you have your gas pedal, and maybe even better, you have "cruise control". That's a pretty good description of what the generator does.

Depending on how many consuming devices you attach, they will draw some current (that's where the Ampers come into play) - and the generator will try to satisfy their total current draft, while maintaining the nominal output voltage. Apart from the RPM/torque/throttle regulation in the combustion engine, the dynamo or alternator also works that way: the mechanical load (input) on the shaft depends on how much electric output you draw from it. = If there's no electric current draft, the combustion engine just throttles its torque, and the output voltage does not exceed the nominal level.

It's like pressure vs current in the water tap.

Note that the mains electricity is AC = "Alternating Current". Means that the voltage (and, yes, current) switches polarity around 0 Volts, and does this 50 or 60 times per second. Which means that it is super-stupid to just connect your generator in parallel with the public AC power distribution - first and foremost because the two sources of AC power will not be phase-aligned (if they ever end up both up and running at the same time). Very likely, your public power plant will try to "pull up" exactly while your generator is trying to "pull down". That's going to trip any circuit breaker :-) This alone can be circumvented by wiring your generator to the house in such a way that the two power sources will never be present both at the same time, so that you do not need to solve for phase alignment at all. That's the transfer switch others have been talking about. A double-throw switch that "breaks before it makes".

Note that... while your mains distribution has a black-out, it's still not appropriate to wire your generator straight parallel to that (or worse yet, just plug it into a wall socket somewhere, to power your whole house) because the cascade of mains circuit breakers likely stays ON/closed, meaning that you'd be trying to power your whole street using your generator. The whole street under a black-out is quite a hefty load on your nimble generator = that definitely will trip a circuit breaker, too :-)

It gets more complicated than that. Your house probably has 3-phase input. If you have 3-phase motors in the house, you either need a 3-phase generator to cater for them, or you have to avoid powering such motors from a single-phase generator. A three-phase motor, powered by a single phase supply, will burn.

So you have some options as to how to go about it. Plug things directly into the generator - possibly what your wife can dare to do on her own (though a bit of local educated help might initially be appropriate). Or try to integrate a permanent generator-based backup into your house, in some form, that will keep your fridge / freezer and minimal lighting up and running, while not harming any 3-phase motors (if that's a risk). Not exactly rocket science, but still - any mod to the house wiring will require a professional. Electricity bites.

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