Just got my new STXR online this month (took advantage of the GC-1000 upgrade plan).

I currently have 4 strings on my roof: two strings of AstroPower AP-110s, one string of AP-120s, and one string of Kyocera KC-120s. I've done a little on-line research and it seems that the slight mismatches in the rated output of these panels isn't a problem when combining the strings, and probably doesn't have much of a negative impact to MPPT either. The tricky part is that my KC-120 string is on the side of my house (SE) where it mostly contributes power during the morning hours, whereas the rest of the strings are mounted on the front of my house (SSW) where they get most of their sun during the peak of the day. I'm wondering if I need to install additional diodes to protect the "less active" strings? Are there any other downsides to combining strings that are experiencing fairly different lighting?

I'm planning to sell my PV generation via green certificates. In order to do that I need to install a utility-grade meter to measure the STXR output. Thus starts a small saga. I had my electrician install a meter. He used the Schlumberger Centron C1S digital meter. One of the first nights my system was running I went down to check on the meter before going to bed. I noticed a slight hum coming from the STXR. I stood watching the C1S carefully and used a stopwatch. That's when I learned that the STXR consumes about 5 watts -- all night. During this time the C1S meter's simulated spinning dial slowly spins forwards, adding the "leak" wh to the meter instead of subtracting! I'm wondering if anybody out there can recommend a utility-grade digital "net metering" meter that is easy to obtain that will correctly account for the leak?

Which brings me to the 5 watt leak (which Guppy has mentioned perviously). Are there any plans to use a relay (as in the Sunny Boy I think?) to disconnect from the mains at night to avoid the leak? I wouldn't mind 1 watt, but for a smaller PV system like mine 5 watts is less like a drip drop and more like a slow trickle. (Besides, it just seems wrong somehow. (shrug))

Thanks for any insights you can provide
Bill in Rhode Island

No Diodes are needed , the ambient light is enough to keep the cells not getting direct light from sinking power from the array in direct light



Standard Mechanical meter , you can get them from a zillion palces , I paid 25 buck for mine. The meter you have does'nt do bi-derction/net metering and it is standard anit-theft to read postive in both directions in almost ALL if the electronic meters , of course there are ones that do bi-direction , not sure what the manufacturing/part numbers are in the 300-400 dollar price range (or so I've read)

I thought the Suntie Lifetime total would quailify for getting generation totals , It approved by the CA programs for that function ..



I doubt Xantrex will invest any further r&d dollars into the Sunite , It's five years old now and my guess it will be replaced at some point with a more state-of-the art design

But even at 5 wHrs , your talking 22 kHr / YEAR , or about 2 buck's worth of grid power





I am also looking into this , but I'm not to happy with the 100.00 sign up fee ... My dual 2900 watt systems might bring in 200-400 dollars /year , but I havent seen in writing yet if its 2 cents or 5 cent a kWhr credit

For your system , You may never generate enough kHr's to pay for the meter/electrican/signup fee ... whats you calculated payout/payback ?

Thanks for the info re: mixed strings. I had just enough EE training to know about circuits with fixed current/voltage sources. An MPPT inverter and PV definitely doesn't quite qualify!

I had asked my contact here in RI about selling PV power. He checked and with my system at the time -- an AE GC-1000 with its AM-100 meter -- I'd need to add a utility-grade meter. I haven't double-checked with him to see if the built-in STXR life-time count is okay. Would be great if it were! I just went downstairs to compare the meter readings. The meter has been connected since the STXR was installed. Right now the Schlumberger meter reads 59kWh, while the lifetime meter on the STXR says 61.0kWh. Sounds like the values are within expected tolerences?

Although, since the system has been running for 15 days, and since the Schlumberger meter seems to be advancing during the night, I'd had expected that meter to read about 900 Wh higher than the STXR meter. It's reading from 1 kWh to possibly as much as 1.99 kWh lower than the STXR meter. Seems a little odd.

My contact says that right now I'd get 6 cents per kWh. I haven't re-read the paperwork but I don't believe there was a sign-up fee of any sort. That means that the only outlay is the new meter. I'll have to check again since you mentioned you have a sign-up fee in your area. For once, maybe "too good to be true" is actually true!

Sunny days to all of you!
Bill

I'd like to know where one can get 6 cents kWr ! , can you please post the details and the firm handling the green tag sales ?

I just got off the phone with Erich. This program is only good for customers in New England. People's Power & Light, a Rhode Island based company, consolidates the PV energy readings from its customers and sells the total to the New England Power Pool.

The New England Power Pool regulations insist that the customers' meters meet the appropriate ANSI meter standards. I don't happen to know the specific standard numbers. Erich is going to try to find that information for me. Do you know if the STXR's meter meets any ANSI metering standards?

Here is the contact information for PP&L:


Erich confirmed that there is no membership fee!

I had edited my previous post to add the current meter readings. Do those seem right? The more I think about it, the more I think that the external meter reading should be higher than the STXR, not lower. Must be too much pollen between my ears.

Bill

The Sunties Lifetime would include test time at the factory ... Thats why its higher ...