Growatt SPF 12000T DVM MPV vs 2x EG4 6500EX-48

[WYtreasure]

I apologize I am new to this forum and it may not be my place to say anything about solar. I have the EG4 inverters and batteries and I am in California, off grid. but I have noticed what that there is a lot of talk about pros and cons of having combiner box's or not. And that has to do with savings but there may not be any. the NEC has said more than 3 load carrying conductors in a conduit has to be D-rated. my system has no combiner box's. I have 8 PV coming down. Which D-rates the load capability to 70% of the wires rated load.
load. Just something to think about I have been looking to find if conduit size, may makes a difference and I have unable to find that information. So if you can go up in conduit size which costs more money. It's possible it's just a trade off larger conduit or combiner boxes.

Welcome to the party Dave A. You can say whatever you want about solar (within reason), I do and sometimes it makes sense.
Kornbread is right, lots of questions. NorCal, SoCal, coast, mountains or downtown LA?

I use a fused combiner box to turn off the PV DC before it enters the house. It's also another line of defense in my attempt to keep lightning out of the expensive electronics.

Here are a couple of threads which may help with terminology.

Commonly used Forum Acronyms & Abbreviations

Solar is befuddling enough! Why use acronyms? Well, we're lazy typists.... :LOL: xSyP - e.g., 2S2P, shorthand for how many cells in Series (S) and Parallel (P). A - Amperes or amps. A measure of current. See warning. AC - Air Conditioning, sometimes A/C. AC - Alternating Current, a waveform...

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Impress your friends by using correct units and abbreviations

The following are common units and their abbreviations. Note that unit abbreviations are case-sensitive. While some units can be understood when written incorrectly, some have a completely different meaning if the wrong case is used. Avoid any possible confusion or ambiguity and use the correct...

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[Dave A]

NFC (310.15(C)(1) Adjustment Factors for More Than Three Current-Carrying Conductors.) the problem I'm having I cannot find if changing conduit size changes the NFC adjustment factor that they have set forth in 301.15 the reason I was asking if anyone new in my case my strings are at maximum for the EG4 inverters (4140w per string)(42v per panel)(10.86 amp)two strings per inverter four wires. I have two inverters which would
be eight wires in conduit.70% reduction on 10awg THHN drops the load capacity from 30 amps down to 9 amps which makes my system not legal using their formula. To me it looks like I need to run two lengths of conduit four wires the reduction percentage on four wires is 20% which would make me legal. My comments were only had to do with cost savings and I think if you don't think about the conduit you're fine but if you add that factor in it's not much of a cost savings at least it seems so to me. Again I apologize it's not my place to tell people how to save money it just looked like to me some things that cost a lot of money were being overlooked like conduit.
just another note it doesn't matter whether you do direct burial or conduit their adjustment factoring is the same.

 

[Kornbread]

How many panels in a series for what Voc to the inverter?

 

[timselectric]

It's not always combiner box, versus conduit.
Usually the combiner box discussion is combiner box or branch connectors. As long as the amperage is below say 25a, Branch connectors win. And in my opinion the next option would be MC4 fuse holders and a junction box. (Which is what I have chosen) I don't need a fancy expensive combiner box.

 

[ColtB45]

70% reduction on 10awg THHN drops the load capacity from 30 amps down to 9 amps which makes my system not legal using their formula.

I think you're off a bit there. it's not a 70% reduction, but reduced to 70%. Put simply, subtract 30%, not 70%.

7-9 current-carrying conductors in a raceway would be derated to 70% of their capacity. So take their normal capacity and multiply it by 0.7. For 10AWG that's 21 amps, not 9.

 

[Clifton]

There will be a large surge load (3 ton HVAC with soft-start kit [LRA can get as high as 60A @ 240V]). Today I am able to run the entire house with a 8KW genset and start the HVAC about half the time. Obviously there is some load management when on genset (we wont run the electric dryer, water heater, or oven at the same time) but otherwise it works.

You'll have no problem with a 3 ton. I'm running a soft start on a 3.5 ton a/c. 22A per leg on start up. It can start with other loads running or not, no problem with the 6500's. I cannot start the 2.5 ton on my garage without a soft start, it shuts every thing down.

 

[Kornbread]

I think you're off a bit there. it's not a 70% reduction, but reduced to 70%. Put simply, subtract 30%, not 70%.

7-9 current-carrying conductors in a raceway would be derated to 70% of their capacity. So take their normal capacity and multiply it by 0.7. For 10AWG that's 21 amps, not 9.

Glad someone else is doing the math. IIRC, the derating is considering 40% free space in the conductor.

 

[ColtB45]

You'll have no problem with a 3 ton. I'm running a soft start on a 3.5 ton a/c. 22A per leg on start up. It can start with other loads running or not, no problem with the 6500's. I cannot start the 2.5 ton on my garage without a soft start, it shuts every thing down.

What is the LRA on your 3 & 2.5 ton? My soft-start isn't magical and gets me ~50% off LRA.

 

[timselectric]

My soft start cut my start up by 70%.
These things are a game changer.

 

[ColtB45]

My soft start cut my start up by 70%.
These things are a game changer.

Which soft start did you go with?

 

[timselectric]

Which soft start did you go with?

MicroAir
My start up surge went from 39a to 12a.

 

[Dave A]

ColtB45 sorry if my comment misled lead anyone. the mistake is probably mine. it is a 30% reduction with the number of conductors (8) leaving the load capability at 70% of the original 30 A which makes it 9 A. And with 4 conductors it will be a 20% reduction and load capability. If you feel that I have made a mistake look it up for yourself it is quite possible I am misunderstanding this but this was the NEC's 2020 changes that are now coming into effect. NFC (310.15(C)(1) Adjustment Factors. My original question was if someone happened to know if conduit size would change there NFC (310.15(C)(1) Adjustment Factors. Because this is a heat rated factor I don't know. but someone asked if it was a DC load would it make a difference I don't know and that is a very good question.

 

[Dave A]

Timeselectric you're correct my math sucks, I think I need to go back to school you're correct 21A that's great that puts me just fine preciate the help Timeselectric

 

[ColtB45]

ColtB45 sorry if my comment misled lead anyone. the mistake is probably mine. it is a 30% reduction with the number of conductors (8) leaving the load capability at 70% of the original 30 A which makes it 9 A. And with 4 conductors it will be a 20% reduction and load capability. If you feel that I have made a mistake look it up for yourself it is quite possible I am misunderstanding this but this was the NEC's 2020 changes that are now coming into effect. NFC (310.15(C)(1) Adjustment Factors. My original question was if someone happened to know if conduit size would change there NFC (310.15(C)(1) Adjustment Factors. Because this is a heat rated factor I don't know. but someone asked if it was a DC load would it make a difference I don't know and that is a very good question.

No need for apologies.? We're all here to help and get help. I just don't want you to have to spend more on larger conductors, conduit, materials, etc. But, your still off ?
70% of 30 is 21.

 

[Clifton]

What is the LRA on your 3 & 2.5 ton? My soft-start isn't magical and gets me ~50% off LRA.

My 3.5 ton LRA's are 95. I don't know about the 2.5 ton. I don't need it as much so haven't bothered checking to see, just left it on utility.

 

[Browse]

One thing I found out about soft starters is that they are not as effective at reducing inrush current on systems that use a TXV instead of a piston. I confirmed this with a Micro-Air engineer after only witnessing a 40% current drop on my 4-ton system. People who are getting >70% inrush reductions have pistons to regulate refrigerant pressure.

 

[shopman]

One thing I found out about soft starters is that they are not as effective at reducing inrush current on systems that use a TXV instead of a piston. I confirmed this with a Micro-Air engineer after only witnessing a 40% current drop on my 4-ton system. People who are getting >70% inrush reductions have pistons to regulate refrigerant pressure.

That would only apply to systems with a hard shutoff TXV where high pressure is maintained between the compressor and TXV when in an off state. Not all systems use a hard shutoff TXV. I just installed a Micro-air unit on my system with a hard shutoff TXV and it cut the inrush current in half from 42 amps to 19.

 

[Shinzul]

Wow, that's amazing - glad I stumbled across this thread! That soft starter kit seems like a game changer for reducing the max current surge due to HVAC...