Suggestions for a grid tie inverter with limiter

[minghidsf]

Hi, I'm building my own system from scratch and currently have 8x Trina 295w solar panels sitting in the garage.
The specs are Vmp=32.5v, Imp=9.08A, Voc=39.6v, Isc=9.68A, Max fuse=20A.

I was looking at getting 2x Ecoworthy 1kw units (22-65v) and attach 3 panels in parallel to each of the two phases.
However decided I need something larger and future proof like a 3kw inverter on each phase along with a battery backup capable in the future.
So I figured the Growatt at https://watts247.com/product/2-x-spf-3000tl-lvm-48p/ would be ideal.

I'm just not sure if I would be able to somehow attach a limiter clamp in the breaker panel with this inverter. Reached out to Ian and he replied "These inverters do not backfeed. So no worries". I replied saying how does the inverter know not to push excess amps out to the meter and he said "This is internal, you can either enable or disable grid feedback. Your meter will not spin backwards, ever, not designed to do that. The worst that can happen is to stop it". My understanding of the limiting function is there needs to be a clamp that goes around the hot lead in the breaker box to measure the current flowing in. Am I missing something?

 

[gnubie]

It depends on the design of the unit. Some simply can't back feed due to design, the load is 100% carried by the inverter or 100% carried by the mains (grid). At no time is the inverter output connected to the mains. If you ever exceed the capabilities of the inverter the unit switches to mains temporarily etc. Many can take mains and solar power and provide them to the inverter stage at the same time to run the load in some sort of sharing basis.

Grid tie inverters are a different story of course and are designed to always provide current to the mains and potentially will 'spin the meter backwards'.

From the blurb for your particular inverter, it falls into the first camp.

5-in-1 unit. (Not Grid Tied – no feedback, only Grid assist – the load gets switch over to grid when all else fails)

There are many variations on the theme so it is entirely possible to find an inverter that will contradict any single statement.

 

[minghidsf]

Damm. this sounds like it could get complicated quickly haha and yes the design needed would be a grid assist I think. I currently have an Emporia Vue energy meter with two clamps measuring roughly 900w min power consumption (600w on one phase & 300w on the other). My target goal with this system is to cancel that minimum 900w 24x7. I'm in zip code 18064, so sun hours is apparently 4.2 which means I need to generate approx 6kwh and store the excess energy somewhere (yes batteries are expensive and probably an additional complication but this would be an interesting challenge). Am I correct in that I need 6kw of panels for this? Thanks in advance.

 

[gnubie]

That's roughly right, but maybe the wrong units. For that 4.2 hours you'd need to be producing about 6kW continously, storing the unused watts in a pretty good battery for later use. If you haven't take a look at the insolation maps in the FAQ section of the forum. They'll give you an idea of how much power a given array will produce daily. Sun angle and line of sight through the atmosphere has an effect on the actual power coming out of the array, so there's more than just hours to consider there. You may need quite a bit more than 6kW of panels to null that 900W draw across 24 hours.

 

[minghidsf]

Thank you. I'll check out more on it.