How can I see the watt draw from a generator?

4237 Views 20 Replies 5 Participants Last post by deeze, Jul 13, 2009

deeze

Discussion Starter · Jul 12, 2009

I have one of these (pic below) which shows how many watts my electrical devices use in Watts. Is there a similar device that would allow me to see how many watts my generator is using through the 240 plug?

It would be nice to just step out and read how hard my generator's working.

(For instance: If I was running several appliances... I could step out and see if I had enough free wattage to run my coffee maker)

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Yoyizit

· #2 · Jul 12, 2009

deeze said:
Is there a similar device that would allow me to see how many watts my generator is using through the 240 plug?

Assuming a constant ~240v just use a clamp-on ammeter and multiply the amps by 240. V x I is close enough to the wattage for this application.

How many watts is your gen. rated for?

dcopps

· #3 · Jul 12, 2009 (Edited)

I was looking into one of these for a standby generator

http://nooutage.com/RMK.HTM

I found another product that had a row of LED's to indicate amps but I can't find the link. It worked the same way.

Edit. The LED meter is also by the same company. Just follow the link

deeze

Discussion Starter · #4 · Jul 12, 2009

Yoyizit said:
Assuming a constant ~240v just use a clamp-on ammeter and multiply the amps by 240. V x I is close enough to the wattage for this application.

How many watts is your gen. rated for?

It's a portable 8000/13500 Briggs and Stratton

Here's a picture from a random web site:
http://www.electricgeneratorsdirect....0210/p887.html

deeze

Discussion Starter · #5 · Jul 12, 2009

dcopps said:
I was looking into one of these for a standby generator

http://nooutage.com/RMK.HTM

I found another product that had a row of LED's to indicate amps but I can't find the link. It worked the same way.

Edit. The LED meter is also by the same company. Just follow the link

WOW... this is fantastic dcopps! Could I just attach this to my generator breaker switch and install it in the wall right beside my electrical panel (in garage)? That would be 100% perfect!!!

Yoyizit

· #6 · Jul 12, 2009

deeze said:
It's a portable 8000/13500 Briggs and Stratton

Here's a picture from a random web site:
http://www.electricgeneratorsdirect....0210/p887.html

So your wattmeter needs to handle 33A to 56A, assuming 240v, and double this current at 120v.

deeze

Discussion Starter · #7 · Jul 12, 2009

Yoyizit said:
So your wattmeter needs to handle 33A to 56A, assuming 240v, and double this current at 120v.

Will this work: http://nooutage.com/RMK.HTM

Yoyizit

· #8 · Jul 12, 2009

deeze said:
Will this work: http://nooutage.com/RMK.HTM

Apparently, but the disclaimer about 10 kW, min., is puzzling.
This link is very short on specifics. Be careful. If you e-mail them with questions but they call you back with answers, be especially careful.

deeze

Discussion Starter · #9 · Jul 12, 2009

Yoyizit said:
Apparently, but the disclaimer about 10 kW, min., is puzzling.
This link is very short on specifics. Be careful. If you e-mail them with questions but they call you back with answers, be especially careful.

Brilliant thought. I can hear them now "put nothing in writing".

Are there similar devices out there? I've been Googleing around trying to find one with a better picture and more specs.

jerryh3

· #10 · Jul 12, 2009

deeze said:
Brilliant thought. I can hear them now "put nothing in writing".

Are there similar devices out there? I've been Googleing around trying to find one with a better picture and more specs.

Same principle:
http://www.theenergydetective.com/index.html

deeze

Discussion Starter · #11 · Jul 12, 2009

Yoyizit said:
Assuming a constant ~240v just use a clamp-on ammeter and multiply the amps by 240. V x I is close enough to the wattage for this application.

Okay, so I got everything set up today and the generator easily turned over my 4 ton variable speed ac system (it does have a KickStart or something installed on heat pump... not sure exactly what they called it... dampens the initial electric kick when it starts.). I could also run my refrigerator and 60" plasma at the same time... AWESOME!

I have everything in my entertainment center running to two power strips... one that has only my TV, Dish Receiver and DVI Switcher and then a second power strip that says "turn off while on generator". that kills the power to all the other unnecessary stuff like computer, security camera hub and other stuff.

ANYWAY, I hooked the amp meter to the black wire within my emergency disconnect (only place I could access it) BUT is just reading that one wire enough? Isn't the white wire hot too? I'm a little confused and uneducated in this area. However based on the math equation you gave me Yoyizit, the ac system running alone was drawing 16amps or 3,840watts. Small price to pay for central air in FL!

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Yoyizit

· #12 · Jul 12, 2009 (Edited)

Here's what inside of them
http://electronicdesign.com/Articles/ArticleID/6411/6411.html

Yes, 16A is plausible, yes, just the hot wire. The neutral wire has the same current in it unless you have problems. The current goes out on one wire and returns on the other.

10 cents/kwh in FL but 4600 Cooling Degree Days/yr in Miami. What do you pay for year round cooling in FL? If this 16A, 240v thing runs 8 hrs/day, it's ~$3/day.
But your engine/generator is maybe 20% efficient so depending on the price of gasoline you will be paying quite a bit more per kwh. 1 gal of gasoline converts to 38 kwh at 100% efficiency.

With your setup, you could post back with how long one pint of gasoline runs your HVAC system. . .

Not that I'm asking you to do this. . .

dcopps

· #13 · Jul 12, 2009

Seems the RMK watt meter offered by nooutage is made by gen/tran. The following link is the manufacture website.

http://www.gen-tran.com/eshop/10Browse.asp?Category=MTSOPT

The price on nooutage website has not been updated since 7/1/08 so it might be safer to get it direct from gen/tran

deeze

Discussion Starter · #14 · Jul 12, 2009

Are they both reliable sources?

The NoOuttage.com price (after shipping) is: $65.28
The Gen-Tran.com price (after shipping is: $81.75

$16.47 difference

Do you suppose I will receive the exact same product from either company?

dcopps

· #15 · Jul 12, 2009

That's a good question.

I would call nooutage and make sure the price is current.

I going to order mine from Gen/Tran (the manufact) just to be safe

deeze

Discussion Starter · #16 · Jul 13, 2009

Here's an interesting response I got from the technical guys at NoOuttage.com:

Thanks for the contacting NoOutage.com LLC. The RMK-15-F is designed for a maximum full scale load of 15,000 Watts. So at full load on your generator of 8,000 Watts you will be reading a little above half scale. And at typical running loads of half that you will be way down at one quarter scale. So, this meter will work but it won't read very accurately.

A better choice would be the electronic LED meter at this link with the appropriate CT...

http://www.nooutage.com/e140132-5.htm

Reply if you have further questions.

Gigs

· #17 · Jul 13, 2009

Yoyizit said:
Apparently, but the disclaimer about 10 kW, min., is puzzling.
This link is very short on specifics. Be careful. If you e-mail them with questions but they call you back with answers, be especially careful.

Almost surely it's just because you'll be wasting valuable scale real estate on wattages you'll never reach.

Just like any meter, you want to pick a full scale setting that gives you a reasonable range.

Edit: Oh I see they basically said the same thing, guess I was right.

Yoyizit

· #18 · Jul 13, 2009

Maybe somebody makes a power meter with a logarithmic scale (but the logging circuit tends to make them temperature sensitive).

deeze

Discussion Starter · #19 · Jul 13, 2009

These guys at NoOutage are very helpful and I feel as though they are definitely earning my business. Here is the latest email which clarifies a few things (at lest for me

This meter (referring to Powermeter PRO) actually senses current through the CT and displays percent of full load. That makes it easy for anyone to understand.
Full load through the L1430R outlet would be 30A x 240V = 7200W. So, if you order the 60/5 ratio CT the loading scale on the meter will display 100% load at 7200W. To get the maximum 8000W output through this 30A outlet you would have to overload the outlet slightly (not advisable).

I'm wondering if I could get a slightly larger unit with the understanding that the 8th LED is full power instead of 10 out of 10 (for example).

dcopps

· #20 · Jul 13, 2009

The Powermeter pro seems like a good unit. Go for it and tell us how it works.:thumbup:

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