So how bad are string inverters vs microinverters?

**Mike90250** · 03-25-2022, 01:56 AM

without my sitting through yet another mindless fool tube episode, what do they say that is so mindblowing ?

**nomadh** · 03-25-2022, 05:20 PM

Originally posted by Mike90250

without my sitting through yet another mindless fool tube episode, what do they say that is so mindblowing ?

He did a side by side comparison and even with some extreme shading there wasn't more than 2 to 3% difference. He does a good job with some graphs and worth the watch.

**Mike 134** · 03-25-2022, 06:00 PM

His testing did disprove the idea that one module shaded would drop the entire string down to its level. Since in my case I need to have rapid shutdown up at the module level might as well get optimizers.

**nomadh** · 03-26-2022, 01:43 AM

Originally posted by Mike 134

His testing did disprove the idea that one module shaded would drop the entire string down to its level. Since in my case I need to have rapid shutdown up at the module level might as well get optimizers.

I've been hearing a bit about this. What's the issue? Isn't a string inverter shut down fast enough?

**Mike 134** · 03-26-2022, 08:53 AM

Originally posted by nomadh

I've been hearing a bit about this. What's the issue? Isn't a string inverter shut down fast enough?

If you don't do the shutdown at the panel level then the wires under the panels can have 300-400 DC volts on them. A mis-swing with an axe while trying to save someone life or property venting the roof could cut those wires endangering the firefighter even more than climbing up onto a burning building's roof.

**SunEagle** · 03-26-2022, 08:56 AM

Originally posted by nomadh

I've been hearing a bit about this. What's the issue? Isn't a string inverter shut down fast enough?

The Fire Departments have found that breaking the roof with a "live" solar array can be dangerous so the NEC has included the requirement of a shut down feature that kills the voltage within a few feet of the panel system.. As long as the voltage is below 50VDC then the First responders shouldn't be electrocuted if they cut into a "live" wire.

**nomadh** · 03-26-2022, 08:00 PM

Originally posted by SunEagle

The Fire Departments have found that breaking the roof with a "live" solar array can be dangerous so the NEC has included the requirement of a shut down feature that kills the voltage within a few feet of the panel system.. As long as the voltage is below 50VDC then the First responders shouldn't be electrocuted if they cut into a "live" wire.

So now we are looking to outlaw string inverters? Has a firefighter ever been electrocuted this way before?

**Mike 134** · 03-26-2022, 08:10 PM

Originally posted by nomadh

So now we are looking to outlaw string inverters? Has a firefighter ever been electrocuted this way before?

Not at all but do need to add an additional piece at each solar module so that the voltage is limited to only what one module puts out. As to a firefighter getting hurt? Whether one has or not the code is being proactive to prevent it. After working 40 years hands on with electricity I can assure you codes are there for a valid reason, getting a rule into the NEC is not something done casually.

**SunEagle** · 03-26-2022, 10:45 PM

Originally posted by nomadh

So now we are looking to outlaw string inverters? Has a firefighter ever been electrocuted this way before?

Actually yes there have been some injuries due to energized solar arrays that fire fighters have tried to remove to save the building that was on fire. So I never said that string inverters are outlawed only that you now need to include "shutdown" equipment to adhere to the latest NEC which all AHJ's read and then determine what it means. So if you don't like what is now the rule then don't perform a DIY install or follow the rules.

**oregon_phil** · 03-27-2022, 10:35 PM

Originally posted by Mike 134

His testing did disprove the idea that one module shaded would drop the entire string down to its level. Since in my case I need to have rapid shutdown up at the module level might as well get optimizers.

It should be noted that the YouTube author used 120 cell half cut solar panels which can be much more shade tolerant than standard 60 cell panels. That being said, I have an SMA string inverter with TIGO optimizers on 60 cell solar panels and am very satisfied with my set up. I too needed rapid shutdown so why not just get optimizers.

**solar pete** · 03-29-2022, 03:12 AM

Originally posted by nomadh

From all the things I've heard for years this really blew my mind.
I can rest easy now with my sma and won't bother to fixate on getting a tigos on that shaded corner.

https://youtu.be/UQ9Szhl1ceQ

String Inverters rock

**J.P.M.** · 03-29-2022, 09:46 AM

Originally posted by solar pete

String Inverters rock

Pete: I agree, or at least I will until my string inverter craps out and there's no string inverter replacement to take the power from my 8+ yr. old Sunpower panels.

Legacy/Rebuilt string inverters are getting scarce. Any suggestions ?

**nomadh** · 03-29-2022, 03:33 PM

Originally posted by oregon_phil

It should be noted that the YouTube author used 120 cell half cut solar panels which can be much more shade tolerant than standard 60 cell panels. That being said, I have an SMA string inverter with TIGO optimizers on 60 cell solar panels and am very satisfied with my set up. I too needed rapid shutdown so why not just get optimizers.

I wanted to add a few tigos to my system for shading and calling 5 places it seems no one even understands what I'm taking about . I was wondering if tigo went out of biz. Was it swallowed up by Smi?

about the 120 cell panels, so was he scamming to do that? You think using 60 cell would have been much worse?

**nomadh** · 03-29-2022, 03:38 PM

Originally posted by SunEagle

Actually yes there have been some injuries due to energized solar arrays that fire fighters have tried to remove to save the building that was on fire. So I never said that string inverters are outlawed only that you now need to include "shutdown" equipment to adhere to the latest NEC which all AHJ's read and then determine what it means. So if you don't like what is now the rule then don't perform a DIY install or follow the rules.

the big advantage of the string inverter was cheaper and simpler, no electronics on the roof. If you need a module at each panel then you killed the string inverter market. In fact if someone wanted to do something like it it is in fact illegal you need what used to be a simple string inverter plus another 29 or 30 electronic breakable doodads on you roof causing problems.

So how bad are string inverters vs microinverters?

So how bad are string inverters vs microinverters?

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