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Old 06-05-16, 10:04 AM   #21
MEMPHIS91
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Good to know they are much cheaper than I thought.
Steve what do you mean by they are silent to my power company? We have smart meters, and they are older, meaning not as smart as they want us to believe they are. lol
I don't have a 220V line anywhere near where my panels are. That was the beauty of the cheap 110v setup.

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Old 06-05-16, 04:21 PM   #22
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Memphis,

God help me for what I am going to say . . . .

"Silent to the grid" means the electric utility will not know if you connect up. I am not professionally telling you this, but you can simply buy the Enphase M250 or M215 (< $100) and just hook it up to a 240 V plug (dryer, or at the panel). One microinverter for each PV panel.

You plug in each PV panel into the Enphase microinverter that makes 240 V AC, 60 Hz. This then feeds a trunk line that has other similar inverters connected to it. The trunk line then terminates at a 240 V panel or plug.

What wattage panels do you have? If they are less than 270 watts, go with the cheap Enphase M215. If more than 270, go with the M250. The M215 puts out 215 watts, the M250 puts out 250 watts.

So long that you do not over produce, meaning that the bill would be less than zero, there is no way the utility can tell you are on "their" grid.

The advantage of the Enphase system is that, if it looses 240 V power, it shuts down in msec. This means that the solar PV system cannot back feed the local grid and zap an unsuspecting lineman in the event he/she is doing repairs on what they think is a "dead
line.

I REALLY like Enphase for the simplicity, ease of use, safety and cost. String inverters (Sunny boy, etc) mean you are snaking high voltage DC across the roof. No so with Enphase. Then 97% efficiency and 25 year full replacement warrantee. What is there not to like?

I can hear you chuckling as you hook this up . . . . . .


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Old 06-07-16, 07:12 AM   #23
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Steve, awesome you just confirmed what I need to know.
What about some of the cases I have heard where people where getting charged for the power going through the meter? Like the meter couldn't tell what way the power was going and not only charged them what what they used, but charged them for the power they sent to the grid?
Is my smart meter going to know the difference? It's awesome that they will not know, but if I end up with a higher bill, it is not so awesome. lol

I need to do some serious rewiring to get 240v to where I'm at. So in the mean time I'll just do it with a cheap grid tie from ebay. I found one used for $40. Then when I get the time to get things right I buy the enphase.
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Old 06-07-16, 08:25 AM   #24
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Ok, the theory goes like this: say you connect a 250 watt panel up to your eBay inverter. You then connect the eBay inverter to a wall receptacle with a standard lamp cord (3 pin wired correctly). When the sun shines brightly, the panel sources its 250 watt rated power to the inverter. The inverter transforms the power at 95 percent efficiency into the 120 VAC wall socket. This 237 W of power then feeds back to the electrical panel and is seen by all the outlets on that leg of your 220 V service. As long as everything in the house on that leg is using at least 237 W, none of the generated power will make it to the meter. If the leg is using more than 237 W, you will still have power flowing in from the pole.

However, if all of the equipment on that leg is consuming less than 237 W, you will have the remaining generated power trying to flow back to the pole. Most smart meters can detect this reverse current flow. Old school power meters don't care, they will turn backwards during this condition. With an old school meter, and an observant meter reader, the only time this condition can be detected is if it is happening when the meter is being read. Smart meters are programmed to do the power utility's bidding. Some power companies are more forgiving (or lazy) than others and do not worry about these events. Then again, some power utilities are very anal about things and have their meters log these events, set flags or alarms, etc. Either way, if your power company is using smart meters, power balance between legs and reverse current events can be detected. You never know how your provider is going to respond.

With the same panel feeding both legs of your service (240 VAC), the generated power is distributed to the whole panel, so you have a much higher chance of having something online consuming power before it can reach the meter. The inverter usually runs more efficiently also, due to the reduced current.
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Old 06-07-16, 08:40 AM   #25
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Memphis,

Here is the way to test your meter. You hook up your panels. I think you said they were 800 watts total with microinverters. I don't like the eBay inverters as they simply do not last. I wish I had a dime for every cheap inverter I have replaced with an EnPhase one.

Anyway - hook it up to your main circuit panel with a 240 V 20 A double breaker (standard like you are hooking up a 240 V stove, water heater, clothes dryer, etc). Turn this breaker off.

Go look at your meter. It should be turning or have a digital display that "looks" like a meter turning. I am assuming that there are some electrical loads in the house running ('fridge, water heater compressor, etc).

While you are looking at the meter, have someone turn off ALL breakers to house distributed wiring - this will mean flipping many circuit breakers to the off position. Leave the main breaker in the panel ON.

The meter should immediately stop "turning".

Now, turn on the circuit breaker ONLY to the PV panels (I am assuming it is sunny outside). Watch what the meter does. I am about 95% confidant that it will now turn "backwards" - even if a smart meter.

Turn on all your other circuit breakers, rejoice and break out a brewski (or two)



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Old 06-07-16, 08:51 AM   #26
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Jeff and Memphis,

Note that a 250 watt panel is rated at very narrow lab conditions. This is the STC value. In the field, we use PTC - which is about 90% of the STC. So, a 250 watt panel will only put out maximum about 225 watts.

Then the microinverter converts the DC into 240 V, 60 Hz AC with about a 90-97% efficiency. Lets assume it is an Enphase and it is 97%.

The net you get out is now 97% of the PTC 225 watts or now about 218 watts.

The vast majority of solar installers will quote STC (lab) ratings and will not tell customers that their net is some 85-88% of that.

The nice thing with an Enphase system is that you can monitor each microinverter and also your total system (DC amps and voltage in, AC voltage, current and power out, microinverter temperature, etc.) with a computer of cell phone app. Makes trouble shooting a snap.


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Old 06-07-16, 09:16 AM   #27
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What Steve said. The generic inverters are ok for experimental use or proof of concept, but I wouldn't trust them to be reliable for a more permanent installation. Like Steve said about power panel ratings, the builders tend to inflate their specs also. The cheaper they cost, the closer to the absolute maximum the specs are. I have let the smoke out of some of these units at half of their rated power, doing nothing unusual with them. Luckily, most of them use the same basic circuit and semiconductors to do the work, and parts are pretty cheap to repair them. Most of the more durable and reliable units are filled with epoxy or resin, so if they die they are not easy to repair. But then again, they don't usually die.
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Old 06-07-16, 10:07 AM   #28
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Jeff, yes this is what I was thinking as well, several articles I've read say about the same thing. Good thing is I have a lot running on the same leg my panels will be on. But I will start looking for a way to do a enphase unit.

Steve, thank you, I promise as soon as I get it wired correctly will go to a quality enphase unit.
What gives you the 95% confidence? When all the articles are saying the opposite? I'm willing to give it a try but a little more info would sure make me feel better about it.
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Old 06-07-16, 01:48 PM   #29
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Memphis,

I too have seen the articles, but a lot of people want to make this difficult. It is not hard to test your meter.

It is hard to understand, why people make a big deal of this. Perhaps it is just the few outliers that report problems where the 95% where it works fine simply don't report a problem - as there are no problems (or very few).

If the meter does not operate correctly, your utility is REQUIRED to put in one that will make distributed generation work. And at no charge to you.

But they will then want to inspect the system, etc.

I see the Enphase M215 now at ~ $105 each (see renvu.com). I don't know the size of your panels. Sometimes hooking up a couple small ones (100 watt panels) in parallel works to get the total wattage up to 200 watts or so. Then one M215 can easily work for that pair. Some (many) panels have blocking diodes that allow this to work.

Here is one solution. Buy one M215 microinverter. They are on eBay used as people are swapping them out for the M250 or S280. But do not pay more than $105 as you can get a new one with the 25 year full, non prorated guarantee for that. I see a lot of them on eBay for $99. Not worth it as $5 more gets you a new one.

I can help you wire up the connector so you don't have to buy the Enphase trunk cable. It is just a four conductor system (two 120 legs, a neutral and a ground). You just cut off their connector and wire nut it up.

I don't have any spare M215's around, but I think pinball does. See if you can "rent it" from him. But you will need to buy a trunk connector ($9) to test as he won't want you cutting his connector off!


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Old 06-07-16, 03:56 PM   #30
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Gotcha, well I hooked everything up, the test is under way right now. Either the dot by the dot will come on (not good) or the dot will go off(very very good). I'll update soon, its cloudy and I'm only push 200 watts to the grid.

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