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With the recent weather events a number of the members here have been contributing information about how their machines have been keeping the lights on. That is awesome. It makes me smile to read about this equipment improving the lives of their owners.
One thing everyone needs to be aware of when using the gauges and especially the % load gauge is this - gauges lie. The load gauge REALLY LIES. It can lead you to believe you generator is not loaded as much as it is. In case you don't want to read everything below the simple message here is do not rely on the load meter alone to determine that everything on your generator is fine. Get a clamp on amp meter and use it to better manage the load on your machine.
The reason is simple, the load meter is calibrated assuming for a power factor of 0.8. If you look at the gauge itself you'll see written on its face something like PF = 0.8.
If you are interested in what power factor is there are a number of really good tutorials on the web that will bore you with math we've all long forgotten. If you don't care so much for the math there is the cliff notes version..
Not all electrical loads are the same. Resistance loads (oven, incandescent lamps, and dryer) are considered "perfect consumers" they use POWER (Volts * Amps) exactly as the simplest version of the formula for power says it will. Awesome, nice and simple. PF = 1.
Motors, computers, and CFL/LED lights are not perfect consumers of power. These loads can have a PF < 0.7. In this case the basic formula for power can't be use to calculate load on your generator. More complicated measurements and math are necessary.
So.. What does this mean in regards to our generators load meter? The load meter circuit on the generators is very simple. More like the basic formula for power (V * A) kind of simple. It can't tell if the power being consumed is being consumed perfectly (PF = 1) or imperfectly (PF < 1). Since it can't tell the difference the designers make an assumption. They calibrate the system to what they think will be the average PF of the loads being attached to the generator. In this case 0.8.
The problem this causes is if your loads have a PF of 1 the load meter will read 20% low. If the PF of your loads is 0.7 the load meter will read 12.5% high. The only time the meter is correct (assuming its correct to start with) is when the PF = 0.8. Which will be practically never.
Ok. For most of us the PF of the average of all the stuff in our houses should be between 0.87 and 0.93. That means the error in the meter will be ~8% @ a PF of 0.87 and ~14% @ a PF of 0.93. Once you factor any additional error from the effects of time and usage, your load meter could be seriously lying to you.
This is why its important (in my opinion) to have a clamp on amp meter so you can measure the voltage and current directly. You can take some measurements to determine how truthful your load meter is.
This turned into a lot more than I wanted when I started typing. Hopefully the info is helpful. If anyone would like to discuss more about PF I'm happy to chat about it.
One thing everyone needs to be aware of when using the gauges and especially the % load gauge is this - gauges lie. The load gauge REALLY LIES. It can lead you to believe you generator is not loaded as much as it is. In case you don't want to read everything below the simple message here is do not rely on the load meter alone to determine that everything on your generator is fine. Get a clamp on amp meter and use it to better manage the load on your machine.
The reason is simple, the load meter is calibrated assuming for a power factor of 0.8. If you look at the gauge itself you'll see written on its face something like PF = 0.8.
If you are interested in what power factor is there are a number of really good tutorials on the web that will bore you with math we've all long forgotten. If you don't care so much for the math there is the cliff notes version..
Not all electrical loads are the same. Resistance loads (oven, incandescent lamps, and dryer) are considered "perfect consumers" they use POWER (Volts * Amps) exactly as the simplest version of the formula for power says it will. Awesome, nice and simple. PF = 1.
Motors, computers, and CFL/LED lights are not perfect consumers of power. These loads can have a PF < 0.7. In this case the basic formula for power can't be use to calculate load on your generator. More complicated measurements and math are necessary.
So.. What does this mean in regards to our generators load meter? The load meter circuit on the generators is very simple. More like the basic formula for power (V * A) kind of simple. It can't tell if the power being consumed is being consumed perfectly (PF = 1) or imperfectly (PF < 1). Since it can't tell the difference the designers make an assumption. They calibrate the system to what they think will be the average PF of the loads being attached to the generator. In this case 0.8.
The problem this causes is if your loads have a PF of 1 the load meter will read 20% low. If the PF of your loads is 0.7 the load meter will read 12.5% high. The only time the meter is correct (assuming its correct to start with) is when the PF = 0.8. Which will be practically never.
Ok. For most of us the PF of the average of all the stuff in our houses should be between 0.87 and 0.93. That means the error in the meter will be ~8% @ a PF of 0.87 and ~14% @ a PF of 0.93. Once you factor any additional error from the effects of time and usage, your load meter could be seriously lying to you.
This is why its important (in my opinion) to have a clamp on amp meter so you can measure the voltage and current directly. You can take some measurements to determine how truthful your load meter is.
This turned into a lot more than I wanted when I started typing. Hopefully the info is helpful. If anyone would like to discuss more about PF I'm happy to chat about it.
