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khamill2000
Bronze Member
Looks exactly the same, however the HF one is cheaper with shipping for me.
Generator PTO Generator
- Thread starter khamill2000
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Looks exactly the same, however the HF one is cheaper with shipping for me.
Iplayfarmer
Super Member
That would work for solar, because most solar set-ups are still connected to the grid, and you are just trying to offset your usage. With a back-up generator the real number you need to work with would be the peak usage instead of average usage.
As an example, my last power bill says I used 1260 Kwh. The bill covers 31 days, so that's 744 hours or 1.69 Kilowatts per hour. I'm very doubtfull that even a 2 kw generator would come close to powering my house. I have a well, an electric water heater, an electric oven, and an electric dryer, not to mention all the lights, computers, refrigerator, etc.
Last time I pushed the numbers to see what I needed for a backup generator, I came up with 6 kw minimum, and that would require some power management tactics like only running one 220 volt appliance at a time (dryer, water heater, oven). I think I'd need a 10 kw to run the house like we normally do.
It would be interesting to take a poll here where we all put in our calculation based on the power bill vs. our calculation based on one of the more popular generator wattage calculators and see if we come up with a consistent conversion factor.
JB4310
Super Member
I agree, it's all about power management. unless you really don't want to know, and spend well over $20,000. for a auto stand by system that a Doctor I recently worked for had installed, and guess what the first time the power went out it didn't kick in, when he called them they told him to go down the basement and push the reset button on the refrigerator sized control box!
The hourly average over a months time is just that, average, and worthless for calculating what size gen you would need. as it's taking into account the over night periods when nothing is on.
If you really wanted to run everything at once with a gen then you need to know peek demand and you'd have to do like you said and turn every possible load on for some set period of time and do the math using the numbers off the meter.
I think it would be easier to walk thru the house and add up all the possible loads, it would be tricky figuring those 3X start surges of motors using the meter method, I would think.
JB.
The hourly average over a months time is just that, average, and worthless for calculating what size gen you would need. as it's taking into account the over night periods when nothing is on.
If you really wanted to run everything at once with a gen then you need to know peek demand and you'd have to do like you said and turn every possible load on for some set period of time and do the math using the numbers off the meter.
I think it would be easier to walk thru the house and add up all the possible loads, it would be tricky figuring those 3X start surges of motors using the meter method, I would think.
JB.
RonMar
Elite Member
That is the problem with using the electric bill. All those night time hours when you are asleep, all the lights are off and the meter is barely moving, drive the overall average down.
As for reading your mechanical power meter, it is way easy. This info from Wikipedia:
The amount of energy represented by one revolution of the disc is denoted by the symbol Kh which is given in units of watt-hours per revolution. The value 7.2 is commonly seen. Using the value of Kh, one can determine their power consumption at any given time by timing the disc with a stopwatch. If the time in seconds taken by the disc to complete one revolution is t, then the power in watts(P)= 3600 X KH Divided by "t".
For example, if Kh = 7.2, and one revolution took place in 14.4 seconds, the power is 1800 watts. This method can be used to determine the power consumption of household devices by switching them on one by one.
I tried this and it seems to work pretty well. 3600 represents the number of seconds in an hour. This is similar to the formula I use for checking a speedometer. 3600 divided by the number of seconds required to cover a measured mile = speed in MPH. The value for Kh should be on the face of The meter somewhere. Mine was 7.2. Just time the wheel thru one complete revolution. and use this number to divide 3600 X Kh...
As for reading your mechanical power meter, it is way easy. This info from Wikipedia:
The amount of energy represented by one revolution of the disc is denoted by the symbol Kh which is given in units of watt-hours per revolution. The value 7.2 is commonly seen. Using the value of Kh, one can determine their power consumption at any given time by timing the disc with a stopwatch. If the time in seconds taken by the disc to complete one revolution is t, then the power in watts(P)= 3600 X KH Divided by "t".
For example, if Kh = 7.2, and one revolution took place in 14.4 seconds, the power is 1800 watts. This method can be used to determine the power consumption of household devices by switching them on one by one.
I tried this and it seems to work pretty well. 3600 represents the number of seconds in an hour. This is similar to the formula I use for checking a speedometer. 3600 divided by the number of seconds required to cover a measured mile = speed in MPH. The value for Kh should be on the face of The meter somewhere. Mine was 7.2. Just time the wheel thru one complete revolution. and use this number to divide 3600 X Kh...
Travelover
Elite Member
I've got a Kill A Watt meter that I bought on Amazon that does a good job of measuring surge and running amperage for 110 volt appliances. It also tells you the frequency, which is useful for when the generator is running..
Amazon.com: P3 International P4400 Kill A Watt Electricity Usage Monitor: Electronics
Amazon.com: P3 International P4400 Kill A Watt Electricity Usage Monitor: Electronics
The trouble with taking the ratings of all the appliances off of the rating plates is that they are maximum ratings, so you will end up over-sizing your generator a bit compared to what the appliances will actually draw. Of course, if you want to guarantee you have enough juice to run all of the appliances, simply adding up the plate ratings would be sure to accomplish that.
Don't forget any lighting circuits you might want. Easy enough to add up the wattage of all the bulbs in the light fixtures.
Timing and then doing the math on the electric meter is the cheapest way to measure your actual power consumption - the power company has already purchased and installed a perfectly good and certified accurate meter!
The same time the meter trick can be used for setting the fuel rate of gas appliances - adjust the pressure regulator until timing the gas meter says you are burning the right number of BTU's per hour that the ap[pliance is rated for.
If you use a clamp-on meter, be sure to measure both branches - most of your 110v stuff could all be on one branch.
Here in MN, one of the top concerns is having enough juice to run heating equipment. One of the things I did to mitigate that concern is that I have a couple of gas fire places that run without any electricity. They can keep the house warm enough for a long time if necessary. If I lose gas supply, that would be a whole different story.
- Rick
Don't forget any lighting circuits you might want. Easy enough to add up the wattage of all the bulbs in the light fixtures.
Timing and then doing the math on the electric meter is the cheapest way to measure your actual power consumption - the power company has already purchased and installed a perfectly good and certified accurate meter!
The same time the meter trick can be used for setting the fuel rate of gas appliances - adjust the pressure regulator until timing the gas meter says you are burning the right number of BTU's per hour that the ap[pliance is rated for.
If you use a clamp-on meter, be sure to measure both branches - most of your 110v stuff could all be on one branch.
Here in MN, one of the top concerns is having enough juice to run heating equipment. One of the things I did to mitigate that concern is that I have a couple of gas fire places that run without any electricity. They can keep the house warm enough for a long time if necessary. If I lose gas supply, that would be a whole different story.
- Rick
Iplayfarmer
Super Member
Right. I can get by without a clothes dryer or an oven for a day or so if needed to save me a few thousand dollars on a full size generator. My biggest concern is the well pump, a few lights, and maybe the furnace fan. I have a gas fireplace that runs without electricity, but it heats a lot better if the fans can run.
I would think that the most accurate determination of needs (vs. wants) would be to run essential appliances that you deem necessary in the event of a power outage. Run them for a set time and use the meter trick to check the wattage. Get a generator sized to meet the need.
As for surge, aren't most generators built to handle a surge? Most generators I've seen have a rated watts and a surge watts spec.
JB4310
Super Member
I went with the 10kw so in our household of 5, I could use the oven OR the dryer in an extended outage, but I definitely don't need to use both at the same time.
"As for surge, aren't most generators built to handle a surge? Most generators I've seen have a rated watts and a surge watts spec."
I guess that's true but I think they take great liberty in the surge ratings, the manufacturer of mine states surge rating of 2 times the reg constant output, but mine had a good deal of trouble starting a large air compressor, had to let most of the air out first, don't remember exactly what the amp rating was but I was thinking the gen should start this easily.
As far as timing the meter, anytime you start using letters in math equations, like in that wykpedia account, it's time for someone to bring me home!
"As for surge, aren't most generators built to handle a surge? Most generators I've seen have a rated watts and a surge watts spec."
I guess that's true but I think they take great liberty in the surge ratings, the manufacturer of mine states surge rating of 2 times the reg constant output, but mine had a good deal of trouble starting a large air compressor, had to let most of the air out first, don't remember exactly what the amp rating was but I was thinking the gen should start this easily.
As far as timing the meter, anytime you start using letters in math equations, like in that wykpedia account, it's time for someone to bring me home!
John47
Silver Member
My survey WAS for a complete solar generator, too far from mains for a connection.
I've done two complete surveys some years back. No backup, total solar.
When I lived in California, my standby generator only just handled the well pump on startup with nothing else running. Made the old Briggs and scrapiron grunt a bit!
Iplayfarmer
Super Member
Did you have a battery bank?