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I think Joe's example is not one the average HO should follow... Although Joe may have an average home, as a member of this forum he is not the average HO...
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I really wanted to push it for the purposes of testing. At one point, I was reading a total of 50.6 amps on one leg, and 46.9 on the other leg with stable Hz. Had my wife turn on her 1,850 watt hairdryer and only then did the genny shut down on overload and Hz drop (50A genny breaker didn't trip).
On many gen sets over-load and under freq are optional items...

Thermal overload isn't going to do a very good job of preventing generator overload- the trip curves on those breakers are just far too lenient; I wouldn't expect a 12kW to put out 24kW long enough to trip! In cases like this, the generator really aught to have an electronic relay designed to trip before the engine stalls. Or maybe it's just not a big deal on engines this small, and at least saves on fuel if the engine just dies vice running unloaded...

I might be unique here in that I've only ever worked with the BIG gensets, 200kW, 400kW, 3MW etc, and we always have current transformers, PLC logic and servo-breakers with the luxury of sophisticated programming of the switchboards to do whatever we want. When you're talking about emergency power, sizing to avoid overload isn't just good practice, it's absolutely essential. What sort of brains do these small ATSs have? Is it just an atmel chip, a few lines of code on an EEPROM and a 2P contactor? That doesn't generally allow for reactive droop and closed transition back to utility power, does it?

On the big gennies, they're always rated for overload, and include internal protections to shut down if things are too out of whack for the engine to maintain proper rpm. I can go up to the panel on any of these and set what frequencies are acceptable, maximum current levels, etc, and adjust the trip settings on my breakers to match it. In-rush on startup is usually the worst; if the breakers can be timed to come back on one at a time, or not come back on at all if the generator is overloaded, it can allow a marginally sized generator to power a load it might otherwise stall or trip on. I can see how that might be cost probititive to a homeowner...

I'll just stick with my little manual-start 3.6kW that I bought a few years ago but have thankfully never had to use [Linked Image] It'll keep the fridge, TVs and lights on, and even run the A/C if I'm expedient with my load-shedding. As this forum shows up in a google search that laymen might find, I won't mention how I plug it in...



[This message has been edited by SteveFehr (edited 11-14-2006).]