we installed a pv solar system for a customer, but his meter is speeding up instead of running backwards like all the other systems. what could cause this?
Hey Jared, frustrating problem you have there isn’t it? Let’s narrow the field a bit. I assume you have an array of some size connected to a grid tie inverter. There are two possibilities here. One, your system is actually pulling power in from the grid when it should be going out. Two, the meter installed on the house is a newer type, which in some cases looks like the old electric-mechanical ones we grew up with, but differs in how the logic inside works. Here is a simple test you can do. Go to the house at a time when you have good midday sun. Have the homeowner turn off all nonessential loads. This will put your system in a state where it should be producing enough power to feed the home and the grid simultaneously. Now examine the meter and see which direction and how fast it is spinning. It should be spinning in a direction that indicates power feeding out to the grid. You won’t know which way is which yet, but you will in a minute. Next, have someone turn off the inverter, so that you know no power is feeding back onto the grid, and examine the meter while this is done. If the meter spins faster, but in the same direction, all is well, it means the home was using more power than the array was providing, but deactivating it increased the amount of grid power the house needed to keep running. In this case I would suspect the home has some unknown load someplace, such as an attic fan running continuously, or a well pump with a bad check valve, and so forth. If the meter slows down when you turn off the solar, than it means one of two things. First, that your solar system is actually drawing a load someplace. Without seeing the system you installed I couldn’t begin to guess where the problem might be. I would suspect the inverter or AC wiring from the inverter to the house. Second, that the meter on the house is a new type that only runs in one direction, and it sees the extra power from the grid as more load power.
The third thing that could happen is the meter reverses direction when the solar is turned off. This indicates that the system is working well also, but the homeowner simply is using additional power someplace after hours.
As a side note, after doing this test by turning the inverter on and off, try also turning off the AC feed from the house to the inverter while it is running and see if the results are the same. If you get a different result, it might indicate that the solar array is in fine shape, but the AC wiring to the inverter or the inverter itself are suspect.
I’m wondering, you said, "We" installed this array, are you a solar installer for a living? If so you might put in a call to the inverter manufacturers tech support and throw this at them, if problems like this have occured before with their product, they usually know about it.
Good luck Jared, and take care, Rudydoo
Hey Jared, frustrating problem you have there isn’t it? Let’s narrow the field a bit. I assume you have an array of some size connected to a grid tie inverter. There are two possibilities here. One, your system is actually pulling power in from the grid when it should be going out. Two, the meter installed on the house is a newer type, which in some cases looks like the old electric-mechanical ones we grew up with, but differs in how the logic inside works. Here is a simple test you can do. Go to the house at a time when you have good midday sun. Have the homeowner turn off all nonessential loads. This will put your system in a state where it should be producing enough power to feed the home and the grid simultaneously. Now examine the meter and see which direction and how fast it is spinning. It should be spinning in a direction that indicates power feeding out to the grid. You won’t know which way is which yet, but you will in a minute. Next, have someone turn off the inverter, so that you know no power is feeding back onto the grid, and examine the meter while this is done. If the meter spins faster, but in the same direction, all is well, it means the home was using more power than the array was providing, but deactivating it increased the amount of grid power the house needed to keep running. In this case I would suspect the home has some unknown load someplace, such as an attic fan running continuously, or a well pump with a bad check valve, and so forth. If the meter slows down when you turn off the solar, than it means one of two things. First, that your solar system is actually drawing a load someplace. Without seeing the system you installed I couldn’t begin to guess where the problem might be. I would suspect the inverter or AC wiring from the inverter to the house. Second, that the meter on the house is a new type that only runs in one direction, and it sees the extra power from the grid as more load power.
The third thing that could happen is the meter reverses direction when the solar is turned off. This indicates that the system is working well also, but the homeowner simply is using additional power someplace after hours.
As a side note, after doing this test by turning the inverter on and off, try also turning off the AC feed from the house to the inverter while it is running and see if the results are the same. If you get a different result, it might indicate that the solar array is in fine shape, but the AC wiring to the inverter or the inverter itself are suspect.
I’m wondering, you said, "We" installed this array, are you a solar installer for a living? If so you might put in a call to the inverter manufacturers tech support and throw this at them, if problems like this have occured before with their product, they usually know about it.
Good luck Jared, and take care, Rudydoo
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Rudydoo has made a very good explanation but the reversal of direction when the inverter is disconnected does not mean there is an after hour load as the spin direction and rate of spin is only indicative of current power draw but it does indicate that the PV array is producing more power than the house is consuming at the time hence disconnecting the PV array changes the direction of power flow from to the grid to from the grid. This is the ideal situation as it means you have enough surplus power to sell power to the grid during the day to counter what you buy back over night. Note that if your power provider allows for net metering where you are allowed to sell power back to them then you want to see this reversal of direction but if your power provider does not allow you to sell power to the grid then you don’t want to see a reversal in direction and would need a smaller array.
I think the questioner is implying that the direction that the meter spins is the same with and without the PV array but is faster with the array. This means something in the system is consuming power not producing power or is miswired somehow or the meter is incapable of distinguishing direction of power flow thereby requiring a second meter to be installed (some power companies has a second meter as a requirement for net metering). Check to see if the inverter output is synchronized to the grid, if it isn’t then you would be consuming power rather than producing power. Also if that’s the case, something is getting really hot and could start a fire. That’s why it can’t just be an inverter, it has to be a grid tie in inverter that can synchronize itself to the grid. If it is a grid tie in inverter, it may be that the phase locked loop that is synchronizing the frequencies is somehow giving you a phase difference between the grid and the inverter, as the grid is much more powerful than the inverter, this would mean power is going through the inverter. I would need to know more details about the inverter such as is it triac based, is it passive or active snubber circuitry, or how does it synchronize, to comment further.
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some meters that the utility company have installed cannot spin backwards, so any excess electricity that is pumped into the grid increased the rate at which the meter is already spinning causing a higher bill. Basically you will have to force the utility company to replace the meter and or replace it yourself and send them the bill. there shoudl be some herbage about this in the Net Metering agreement between the home owner and the utility company.
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It is possible that the customer just stopped being good about energy usage. I know my family has gotten a little lazy about energy conservation since we got out panels.
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The inverter should indicate how much power is being put into the customer’s wiring. If you see a value that’s below expectations, it’s worth double checking the wiring. I’ve seen cases where one string of panels was accidentally wired in a loop, or not connected to the inverter.
The claim that the meter is speeding up is suspicious. You can check this by flipping open the breaker connecting the inverter to the mains while watching the meter. Do it when it’s sunny out. You might even do this with the customer watching. If the meter slows down when you disconnect the solar system in this manner, then something is broken or not hooked up right.
In the more likely event that the meter speeds up when you disconnect the solar system, then it’s just a coincidence that the customer is drawing more power. With their permission, you can help them isolate where that power is being drawn. Maybe a lot of people in the house/building decided to run space heaters in the cooler weather. If you cannot find the culprit by a walk-through, then you could always (again, with their permission), start opening breakers until you find out which circuit is drawing a large amount of power.
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