Is there a power-strip like device for use with portable generators that turns off outlets when other outlets are using a certain number of watts?
Like you'd want to turn off the refrigerator while the sump pump cycles, to keep the total watts under say 2000; but mostly the refrigerator stays on.
You can easily build your own if you're handy with electrical modules. You won't have to build any circuit boards because the parts are available off the shelf. You can use a current sensor and relay module manufactured by Functional Devices, Inc which are sold at many HVAC supply houses like Johnstone Supply.
other related:
If you had a transfer switch it would be alot safer on the equipment, a cheap one wont do what you want but will have 2 watt meters so you know the load and can balance it. They are cheap and easy to install many are prewired. Generac has one prewired with exterior baox cables plugs tec for about 300, I got mine free at Lowes with a cheap gen.
Generator load management is a bit more complicated than that and simply dropping lower priority loads when higher priority ones come on won't work properly and could potentially damage items.
A proper load management setup needs a controller with some smarts, and monitoring connections to things like sump pump switches, thermostats, etc. so that it can tell when an item needs to run, even though it is not currently powered. This type of control just isn't practical on a small scale where the cost of the control would exceed the cost of a larger generator.
Of course it is. It's nothing but a logic setup. a = on, x = off etc. Simple current monitoring or even clamps.
yes but you do NOT want to turn off power to the fridge and then turn it back on a few seconds later... the compressor will not be able to re-start when the pressure is already built up in the system... it will cycle on overload for a few minutes until the pressure dies down. That is OK it won't BREAK anything right away but it does stress the overload switch and compressor and is not the best thing to do for long term.
Mark
Mark wrote: ...
... So what's a 555 timer cost???
The general idea isn't difficult to implement w/ anybody who's got some Radio Shack-type skills and interest.
It's probably there are some moderately inexpensive devices readily available altho I've not done any looking. Undoubtedly there will be info on the alternate-energy and living-off-grid and generator groups...
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Nope, the end result of such simplicity will just be an intermittently overloaded generator, devices damaged by short cycling, floods because the sump pump didn't get enough run time, etc. Proper load management requires the smarts along with sensing to hold off providing power to item Y until item X has completed it's cycle.
Simplest would be to attach a 120 Volt NC (Normally Closed = ON) relay to the compressor's two electrical feed wires. When the compressor is running, the relay is activated and its contacts are open (=Off). When the compressor has stopped, the relay closes and lets the sump pump, e.g., run.
What you are seek> Is there a power-strip like device for use with portable
2,000 freaking watts! Geez! A very simple automatic switch can do the trick for the guy. A current sensor, a timer and a relay could make up a simple load control for the man's generator to drop the refrigerator when the sump pump kicks in. No micro-controller or fancy PLC needed. If it involved 10,000 to 150,000 watts or more, I could understand the need for more finesse. For a generator I can pick up with one hand, nope, nope, nope.
TDD
Have you ever heard of an anti short cycle timer. It's a little module available at the same HVAC supply house as the other parts. The things are very inexpensive and I install them on AC units all the time. It would be easy to add it to the setup. Do I have to design the darn thing now?
TDD
Christ! Just a simple anti short cycle timer in the mix would do the trick. No big complicated control setup needed. Ever heard of relay logic? Nothing complicated needed for the application.
TDD
Bull.
With a generator as small as 2KW, the generator will probably stall before you can shed the new load, and even if it doesn't it will bog down badly causing low voltage and low frequency issues. If it's an inverter based unit like an EU2000i it will just go into protect mode and you will loose output until you manually stop and restart the generator.
You think it sounds simple, but you've clearly never done load management, nor have you thought through the details of the problem. With a generator that small, the OPs safest and simplest solution is to swap power cords around manually.
Relay logic as you noted in another post would be a bloody mess for this since you have to know the load of each of the controlled outputs and determine the allowable combinations that will not overload the generator.
Good Lord, you're making it more complicated than it needs to be. I could do it quite simply with all off the shelf inexpensive timers and relays. I have had a smidgen of experience with little Cats and tiny little 16 cylinder EMD generators putting out a minuscule 4,160 volts and enough current to melt the proverbial crowbar. Don't over engineer the golly gosh darn thingy itty bitty generator, it's not an APU on the space shuttle. I guess all those 5 to 40kw generators I've installed and maintained for homes and business have left me with a substantial dearth of knowledge when it comes to electrical systems. Should I walk you through the simple steps that would address all your dire concerns for blowing up the itty bitty power plant? Of course, the simplest thing is as you say is to switch cords but if he's anything like all of us lazy humans who love to take advantage of existing technology for the sake of convenience, he wants something automatic.
TDD
Whoop-dee-doo, you still haven't covered the actual issues, particularly with the probability of an inverter based generator give the OPs mention of 2KW, and the fact that as soon as the new load came online the inverter would trip out on overload before your relay could shed other loads.
What inverter based generator? The guy has a itty bitty generator sitting on top of an inverter? That's a heck of a silly thing to place a generator on top of. GEEZ!
TDD
You apparently don't understand a logic chart; or you wouldn't say that. x & y are NOT equipment; they are states. And simple to work out.
You're making it even more obvious what you don't know. Because you don't know how to do something is no reason for you to attack others who might be on the right track. Your concepts of how relays can work is in bad need of help also. When you have nothing worthwhile to say, that's what you should say: Nothing.
Why not post a schematic somewhere for him? A pic's worth a thousand words ... or more. Unless, as your antagonistic and childish approach is showing, you're nothing but a kiddie bag of hot air.
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