Grid tie micro-inverters WITHOUT power company inspection/approval

[zanydroid]

One simple way to use microinverter without zero export is to tag them into an air conditioner circuit, connecting based on current flow threshold. And size the inverter to be under the lowest power setting of the AC. That should be very hard to detect. It’s strictly speaking not code compliant to have it directly on the device branch circuit and ideally you would scale the wire/OCPD accordingly. You could also connect it to an adjacent branch.

 

[kevin93]

It wouldn't benefit him. The old meters worked similar to a non directional CT or a clamp on amp meter. They just measure current flowing. No matter which direction.
This is why the old grid-tied systems required two meters. It was the only way to know what came or went.

The traditional electromechanical meter has both a voltage coil and a current coil. The rotation of the meter depends upon the integral of the instantaneous product of the two measurements. This is so it correctly records true power not just KVA and also takes correct account of voltage variations.

Those meters do rotate backwards when exporting power. My brother in the UK still has one of those meters and gets paid for exported energy.

There are various ways that the power companies can prevent reverse rotation that have been implemented to avoid that and there is even more flexibility with electronic meters but in general they all have the capability to detect the direction of power flow.

kw

 

[timselectric]

I have no experience with the meters used overseas.
Only the ones used in my local area of the US.
And they did not spin backwards.
But I will concede that it's possible that other meters used elsewhere could.

 

[glandpuck]

Why not just buy my Outback Radian inverter listed on this site, set to DO NOT SELL and just AC couple your micro inverters and you are all set!

 

[pollenface]

Stay away from grid tie inverters unless they can be setup for zero-export or you already have a bidirectional meter and buyback scheme in place.

Otherwise you are just painting a target on your back.

 

[glandpuck]

Stay away from grid tie inverters unless they can be setup for zero-export or you already have a bidirectional meter and buyback scheme in place.

Otherwise you are just painting a target on your back.

Your comments don't apply to Outback Radian inverters.

 

[timselectric]

Your comments don't apply to Outback Radian inverters.

It applies to all grid-tied systems.
They have to see some export, before they know to control it. Some can be set to always import a set amount. And adjust accordingly to that. but, there's always a chance of not being fast enough. And allowing some to slip through.
The only way to guarantee zero export is to disconnect from the grid.

 

[pollenface]

Your comments don't apply to Outback Radian inverters.

Correct.

My comments were for the OP.

Not you.

 

[hwy17]

It wouldn't benefit him. The old meters worked similar to a non directional CT or a clamp on amp meter. They just measure current flowing. No matter which direction.
This is why the old grid-tied systems required two meters. It was the only way to know what came or went.

I just don't believe that's universally true. This utility ran all analog meters at the time and solar customers would get their meter swapped with a non detent analog meter so that it could turn backwards. So some analogs definitely can. But I'm still working on my understanding of the mechanisms.

That was of course the origin of net metering policy in the first place, it was the only way a single analog meter could meter solar at all.

If you're gonna say that some forms of analog would and some wouldn't and that you're sure the non solar customers would have got a form that read positive in both directions I can't totally dispute that. But you can't totally assert that either.

 

[1201]

It applies to all grid-tied systems.
They have to see some export, before they know to control it. Some can be set to always import a set amount. And adjust accordingly to that. but, there's always a chance of not being fast enough. And allowing some to slip through.
The only way to guarantee zero export is to disconnect from the grid.

There are some hybrid systems that will disconnect from the grid and still allow a grid tie inverter to feed a backup loads panel

 

[zanydroid]

There are some hybrid systems that will disconnect from the grid and still allow a grid tie inverter to feed a backup loads panel

These are also pretty expensive at present. I don’t think there’s any below $4000. Well, maybe $1500+500 for a multi plus and some really good autotransformer fu. I guess two multiples is $3000 and cuts out the AT.

By comparison you could put the money into a 10K inverter and batteries and end up farther ahead with a DC system

 

[zanydroid]

It applies to all grid-tied systems.
They have to see some export, before they know to control it. Some can be set to always import a set amount. And adjust accordingly to that. but, there's always a chance of not being fast enough. And allowing some to slip through.
The only way to guarantee zero export is to disconnect from the grid.

You can also somewhat guarantee with an appropriately set minimum consumption. Which is the same technique as the one I posed for interlocking it to a circuit with known draw

 

[hwy17]

Double conversion with Charger > Battery > Inverter guarantees zero export.

That's what I landed on, not out of paranoia about milliseconds of export but out of dissatisfaction with Schneider's logic. And the true zero export is a nice bonus.

 

[timselectric]

I just don't believe that's universally true. This utility ran all analog meters at the time and solar customers would get their meter swapped with a non detent analog meter so that it could turn backwards. So some analogs definitely can. But I'm still working on my understanding of the mechanisms.

That was of course the origin of net metering policy in the first place, it was the only way a single analog meter could meter solar at all.

If you're gonna say that some forms of analog would and some wouldn't and that you're sure the non solar customers would have got a form that read positive in both directions I can't totally dispute that. But you can't totally assert that either.

All that I can say is that I personally flipped meters to disprove the myth in my area. But I shouldn't have assumed that all meters were the same. And before bidirectional smart meters were introduced (again, in my area) two meters were required for a grid-tied system. Because of that reason.

 

[hwy17]

And before bidirectional smart meters were introduced (again, in my area) two meters were required for a grid-tied system. Because of that reason.

Sounds like your area was smart and didn't fall for net metering in the first place.

 

[timselectric]

There are some hybrid systems that will disconnect from the grid and still allow a grid tie inverter to feed a backup loads panel

Yes, a hybrid can disconnect. But if you want to go that route. It's a lot cheaper to go off grid with grid backup.
Most people who need to use micro inverters. Are trying to gain battery backup. And still use their already installed grid-tied system. And in this case, they should already have an agreement in place.

 

[timselectric]

You can also somewhat guarantee with an appropriately set minimum consumption. Which is the same technique as the one I posed for interlocking it to a circuit with known draw

Yes
The easiest way is to connect the micro inverters to the load side of the contactor in a central air outside unit. This way they are only connected when it's running. Then, you should never worry about exporting. (Assuming that the compressor never fails)

 

[zanydroid]

Double conversion with Charger > Battery > Inverter guarantees zero export.

That's what I landed on, not out of paranoia about milliseconds of export but out of dissatisfaction with Schneider's logic. And the true zero export is a nice bonus.

What was so bad about schneider’s logic that you were willing to pay an extra 10% efficiency penalty?

 

[timselectric]

Sounds like your area was smart and didn't fall for net metering in the first place.

We've had net metering for several years.
And I believe that it was a pretty favorable credit.
But I still called it a suckers bet.

 

[zanydroid]

Yes
The easiest way is to connect the micro inverters to the load side of the contactor in a central air outside unit. This way they are only connected when it's running. Then, you should never worry about exporting. (Assuming that the compressor never fails)

Sure, that’s the classic approach

Problem is it’s not super compatible with inverter systems, I think the contactor is buried pretty deep, and they have many power levels. Mine has 50W for blower and 1kW for minimum cooling/heating stage. So if I were to set this up I would configure a current trip threshold at say 1A, and a combination of grid tie inverter of 900W output.