# watt meter for a generator



## smabon (Sep 15, 2009)

Last winter during a power outage after an ice storm that knocked the electricity out of 8 days I got a generator.  The generator is rated for around 5000 watts.  My question is, is there any type of meter that I can attach to the generator to tell me how many watts that I am using.  Is there something that I can plug in to the generator and then plug my power cord that came with the generator into.  During the aftermath of the storm I had no idea how much of the generator I was using.  I thing that I was only using a fraction of the possible output of the generator.  Any input would be helpful.  And as always, money is tight and the cheapest solution would be best.  Thanks for your time.


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## WES999 (Sep 15, 2009)

How about a cheap clamp on amp meter, you can get them for around $10 at Harbor tools.
Multiply the amps times voltage to get watts, should be close enough.


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## BrotherBart (Sep 15, 2009)

I use the Kill-A-Watt. Not only does it tell you if you are near capacity but it is good for adjusting engine speed to the ideal output voltage.

http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU


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## smabon (Sep 15, 2009)

BrotherBart said:
			
		

> I use the Kill-A-Watt. Not only does it tell you if you are near capacity but it is good for adjusting engine speed to the ideal output voltage.
> 
> http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU



I thought of that but I want to use the large cord that came with the generator that has the twist and lock plug style on the end that connects to the generator.


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## LLigetfa (Sep 15, 2009)

WES999 said:
			
		

> How about a cheap clamp on amp meter, you can get them for around $10 at Harbor tools.
> Multiply the amps times voltage to get watts, should be close enough.


+1


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## nshif (Sep 15, 2009)

Pro DIY said:
			
		

> BrotherBart said:
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Is it a 240 volt twist loc that splits into mutiple 120 volt legs? if so just plug the killawatt into the legs one at a time and add them togather. Depending on what you are powering your load may change over time as things cycle on and off ( refer, freezer, lites on/off, etc ) are you trying to run your entire house?. If so 5kw is barely enough and you might even overload it with a good load. I run a 7.5 kw and can overload it if im not careful, although I am also running a 240 volt well pump from it.


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## Highbeam (Sep 15, 2009)

Boo, I run the whole house with a 3500 watt genset. You just need to manage your needs, especially the automatic ones. For instance, shut off the water heater, well pump, and hot tub if your genset isn't big enough to run all of them at once.

Tough to measure what's happening inside a 4 wire twistlok cable. A clamp on ammeter might spaz out when there are different loads on each of the hot legs.


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## BrotherBart (Sep 15, 2009)

And since a Kill-A-Watt is only rated at 15 amps smoke would be coming out of it pretty soon.


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## nshif (Sep 15, 2009)

Highbeam said:
			
		

> Boo, I run the whole house with a 3500 watt genset. You just need to manage your needs, especially the automatic ones. For instance, shut off the water heater, well pump, and hot tub if your genset isn't big enough to run all of them at once.
> 
> Tough to measure what's happening inside a 4 wire twistlok cable. A clamp on ammeter might spaz out when there are different loads on each of the hot legs.



Hot water is on demand propane, no elec. no hot tub. And many times my power is off for 5-7 days in a bad storm. I need the well,Im not going to go without water for a week, and if i allow the pressure tank to drop below 20 psi I have to go out there and manually restart it, not fun in 4 feet of snow. My " automatics " are refer, freezer, and well. other then that I run the tv, pc, and a few lights. Things I have to watch are the micro, coffee maker, and other kitchen items (deep fryer )
Ive only overloaded the gen once and it just stalled the engine, but still not a good thing.
Its not un common for this this to happen 3-4 times a winter and maybe in the sumer if there is a local wildfire. needless to say if thats the case I need the well


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## nshif (Sep 15, 2009)

BrotherBart said:
			
		

> And since a Kill-A-Watt is only rated at 15 amps smoke would be coming out of it pretty soon.


If its like the cable that came with my Generac the 4 splits are 120v/15amp each


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## seige101 (Sep 16, 2009)

Check out this http://www.reliancecontrols.com/ProductDetail.aspx?WP1250

I think thats what you are looking for. I am assuming you are using a transfer switch or a separate gen panel or the like. 

Or this one would work
http://www.reliancecontrols.com/ProductDetail.aspx?MB125

Been a while since i put one in but they were reasonable. Handy for balancing your loads and seeing peak/startup watts


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## fbelec (Sep 16, 2009)

hey nshif don't use your computer on the gen unless it's a laptop or your running a ups. the surging of the gen will take out electronic circuits. last storm i blew out my police scanner and a phone machine. 
the only way you'll get a proper reading from a clamp on style amp probe is running one wire at a time. and i don't mean cable wire i mean the black out of the white and black wires in a 115 volt circuit. or the red out of the white and red wires. if you put a amp probe across a cable it will say 0 amps even tho you know your running the microwave that takes about 12 to 14 amps.
i run a 5000 watt gen that is two 115 volt circuits each at 20 amps thats it's max for each leg. so your 5000 watt gen has 2, 115 volt 20 amp circuits. or 1, 20 amp 240 volt circuit. so if your well pump is 240 volts at ten amps your taking 10 amps from each of the 115 volt circuits to start before you add in anything else.


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## rustynut (Sep 16, 2009)

their are charts out there that tell you approximately what an item draws
start up info and running info for those that pull a bit more when starting
have a look around the web
you should be able to find something that can put you in the ballpark by adding them up
unless you are just wanting an actual meter
rn


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## Stevebass4 (Sep 17, 2009)

fbelec said:
			
		

> hey nshif don't use your computer on the gen unless it's a laptop or your running a ups. the surging of the gen will take out electronic circuits. .



that is unless your genset is a honda - they put out clean power  

my plan if need be is just to plug in a surge protector and then what i am using into it – then again haven’t lost power since I bought a generator


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## nshif (Sep 17, 2009)

Stevebass4 said:
			
		

> fbelec said:
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I have a filter ( fixes the sine wave problem) and a surge protecter installed. Been running this setup for 5 years and no problems.


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## fbelec (Sep 17, 2009)

that's good you got a filter. but the problem is voltage variation and frequency variation. i'm not sure if your filter can smooth out the voltage and freq. the ups does. surge suppressors only job is to keep a eye on voltage spikes. if they are not grounded they don't work. if it's clamping voltage is at 200 volts everything below goes thru. if a 400 volt spike trys to come in it send the voltage above 200 to ground. a good sign that your surge suppressor took a hit is that the circuit that it on blows the circuit breaker. then you reset it and it works fine. alot of the spikes that can come thru happen so fast you wouldn't even see it happen. never mind the cheap one's, but some of the good surge protector clamping voltage is 180 to 200 volts. just think of the transformer in the power supply. at 120 volts that transformer is giving you about 15 volts for the regulator to do it's thing. now stuff 200 volts into that same transformer and you get 25. if your regulator holds out your ok but if it doesn't, bye bye. and surge protectors can only take so many hits before they stop protecting. if your surge protector does not have a light saying that it's still protecting you should replace it once a year. i've had people give me a hard time about they have the best surge protector available so they are not worried. they seem to think that if the line voltage drops down to 90 volts they should be ok. that's not how a surge suppressor works. if it worked that way it would have a battery.

sorry i was long winded but i have this conversation with customers all the time.


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## Gooserider (Sep 17, 2009)

Note that there are two different types of UPS units, one offers excellent protection against just about any kind of power glitch, the other isn't much better than a power strip surge protector...

The better units use isolation that essentially keeps the UPS circuitry working all the time - the UPS makes DC that charges the battery and drives the UPS output circuitry that makes AC for the powered hardware.  This type of unit totally isolates the protected equipment from the wall outlet, such that any power problem has to get through the entire UPS to cause a problem.  Short of a direct lightning strike that isn't very likely, though something could fry the UPS itself...

The lower quality units work on a "pass through" basis - The AC comes in and splits - part drives the battery charger, the rest goes through the control circuit and straight to the not-so-protected equipment.  The control circuit monitors the AC and switches in the UPS inverter if needed, but doesn't normally do much more than minimal conditioning beyond whatever benefit you get from the filtering provided by the transformer...  Thus a major power glitch will reach whatever is plugged into it...

It can be hard to tell what sort of unit a given UPS is, but often the difference is between a larger heavy duty "server-room" quality unit, vs. the light weight units they sell for short bucks in the discount store.

Gooserider


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## fbelec (Sep 17, 2009)

i've seen those cheaper units. they look like a glorified surge strip. and i don't think the battery is replaceable. bottom line here is be careful using electronics on a generator.


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## jebatty (Sep 19, 2009)

It might be a good idea to put in a transfer switch, not only for safety, but also for power management. Most of these have watt meters that show the draw on each leg of the 240v circuit. That also allows you to better balance your load between the two legs, which increases gen efficiency and eases the work load. 

My 220V well pump works fine off the 5000W generator.


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## LLigetfa (Sep 19, 2009)

At work I have many UPSs some of which also have natural gas backup generators behind them.  It takes a good UPS to accept genset power and it takes a good genset to satisfy the UPS.  We have annual scheduled power outages in the mill and every year they rent gensets expecting the UPSs to work with them.  They almost never do and so they often bypass the UPS to power my edge network and computer equipment.  They typically fry about 5 computers on every outage.

We typically lose that many on unscheduled power outages too even though there are no gensets involved.  There are often massive surges as the power fails and again as the power comes back on.  All my important network and servers are behind quality UPSs and quality gensets.  Most production computers in the mill are protected by Sola ferro-resonant power conditioners. It's the unprotected stuff out on the edge that gets taken out.


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## Dune (Sep 19, 2009)

You could buy a meter socket and a single phase meter. Not super cheap, but acurate and not really that expensive if you really need to know.


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## basod (Sep 20, 2009)

being a power engineer by trade all suggestions would work except the clamp on meter, 2-phase power requires readings on both legs.  I don't know where you're located but most areas require by code a auto transfer switch (ATS).   The rating of your generator 5000w continuous or peak?  Manufactures rate in peak which would be inrush current (your genset slows down when somehing turns on and governor brings back speed) they all typically work under speed droop control.
Whatever you guys do to "hook up" you're gensets please open up your main disconnect and connect your leads on the secondary of that disconnect not into a receptacle.  Your power cord should be large enough to handle the full 5000w (5000/120=42A peak)  that 12gauge 100ft extension cord will probably leave burned streak in your yard
For those that haven't escaped the "Darwin Filter" don't run it in basement/garage or other enclosed area.
-Sorry for lecturing,
look around for an old meter base, you could wire the 2 phase through it to a separate breaker panel and monitor both phases continuosly.  Time to watch the Pats whup up on those J-E-T-S overated jets


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## velvetfoot (Sep 21, 2009)

BASOD said:
			
		

> Time to watch the Pats whup up on those J-E-T-S overated jets


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