What is Derating? Inside Our Industry- Redline Electric & Solar
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- Опубликовано: 28 сен 2021
- What is Derating? Inside Our Industry- Redline Electric & Solar
Joshua and Marcus discuss what it means to derate an electrical panel for solar. This question is asked by many clients and in this video, we explain!
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Please watch: "Who Would Do This? Episode 29 - Inside Our Industry"
• Who Would Do This? Epi...
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Have a question? Leave us a comment!
Great video!! Just curious, when you backfeed solar into the main service. How can that work with two different services being combined? Wouldn’t that blow up from being back fed?
Like having an interlock on a main panel for a generator, so two different sources can’t be on at the same time. I’m confused, Thanks.
@@mcarroll598 the solar inverter synchronizes the frequency and the output voltage to match its connected grid. I haven't worked with a generator smart enough to do that yet🤷♂️. Rapid shutdown technology turns the inverters off when the utility goes down to keep the solar from back feeding. Hope this helps!
@@Redline-Electric-Solar appreciated it man thanks!!
Why derate to 175 from 200?
What formula allows this specific reduction in amperage?
Shouldn’t we de rate to 150?
You derate for the appropriate amount needed for your solar backfeed.
This is the best most understandable explanation of this NEC rule I've heard so far. Thanks guys! 😀
Thanks! 💪
Good stuff guys. This was very helpful, thank you!
Thank you, Ray!
Crossing my fingers this comment gets noticed, even on a video from 2 years ago.
As simply as I can ask it, (assuming I meet all code requirements, 2020 here in Utah) are inverters (that you are familiar with at least) able to have a supply side splice between the overcurrent device and the panel, that runs through a 60 amp breaker into the inverter "Grid" connection side of the inverter (again 63 amp breaker in the inverter to protect this connection) and then use the 'load' connection on the inverter, sending grid passthrough power, + battery, + DC solar panels (63 amp breaker on the inverter) to backfeed into the main panel?
I can see a couple of limitations I can see. It's a Sol Ark 8k, so a total of 63w max output, between the grid passthrough, solar production, and battery. If the grid goes down, we are down to just over 30 amps max. That can easily overload what the inverter can push, without using the internal limiter.
That said:
1: I can 1: limit the max output of the inverter to prevent damage to it.
2: We are planning on installing a Leviton panel, and I intend to use smart breakers that will trip off branch circuits when the power goes out, to control the essential loads vs load that can be turned off or if things get over loaded.
3: I'd prefer to have a single loadcenter, not two.
Context and backstory, if it is helpful. The solar install company (name withheld until I hire an experienced code inspector to do a 3rd party inspection and documentation) installed the inverter and battery and solar panels on to the existing 200 amp service at my parents’ house. (I just moved in next door and only recently discovered the problems) they choose to take the entire 200 amp service, through a the 60 amp breaker, giving them a grand total of 63 amps for their entire service. Including the grid pass through. And didn't mention that fact. When they installed it. And we need to upgrade some items, including adding wo mini splits. Ant that just won’t work.
Some of the problems and violations existed before they showed up. For example, it's a Zinsco panel, and as near as I can tell, it was installed in the 60s. It's using (all but one) original Zinsco breaker from all those years ago. It's now a subpannel, with neutrals and grounds all mixed up. Some concerning spots on the bus bars, but I’ve seen worse, thank god.
On their side of mistakes, for example, when the 3/0 copper wire coming into the house (feeder not service, fun fact, there are no service entrance conductors) was not long enough to reach to second panel they installed to pipe the gid power out to the inverter, they just used some Polaris lugs (smart move) to splice on some extra conductor to reach the extra distance. Why the thought it would be a good idea to connect the 3/0 from the 200 amp service disconnect into 4AWG aluminum, I have no idea. Sections 220 and 310.12(C) They introduced code violations left and right some large, mostly small. But very very unprofessional.
Thanks for making it to the end. I'd love to know if it's save to back feed into the same panel (at the bottom) where I am splicing into the grid or supply side of that same panel board, provided I am able to control essential and nonsensical loads without the use of a sub panel.
Thanks!
Hey, Yummy! Did the original installer have a permit? If so, they should have an engineered plan set that shows what they did and why. I am happy to discuss this with you.
@@Redline-Electric-Solar Thanks Joshua! I really appreciate the chance to get a second set of eyeballs on this. It was permitted. They should be safely stored away for future needs... now if only I remembered the exact filing cabinet :P
Bad joke aside, give me a day or so, and I'll shoot you an email.
Thanks again sir!
MANY THANKS FROM INDIA
amazing info...
Glad you liked it
This was great. Very informative
Thank you so much!
It was a Great Great Great Video BoOYa
Video very helpful, especially moving 25a from main to solar in comment. Derating seemed to say larger wire not good, smaller OK.
Question - inverter AC out of 48a x 1.25=60a 60a breaker OK or use 70a?
48a x 1.25=60a. 60amp breaker is perfect!
@@Redline-Electric-Solar Thanks, working my back through the videos.
Don’t forget a “solar ready” panel busbar rating in a 200Amp service panel is rated for 225A. Giving you 70A of potential solar back feed instead of the normal 40A without needing to do a Derate. Derating a solar ready panel to 150A would give you up to 120A of solar back feed which is how they should come. 200A panel, 225A busbar, 150A main breaker is optimal for residential needs.
Excellent explanation! But in my case the 200 amp breaker was derated to 150 amps.
Must have been a pretty big system💪👍😎
What Joshua said🙌😎
Great vid guys! Question, city says my setup doesn’t comply with the 120% rule. Solar w/batter backup with 125amp sub panel. The main is ge 200amp with a 200amp bus, I have a 70amp back feed Solar breaker and left a 50amp ac breaker in main also. What would be the correction? Thanks ahead
If you have a 200amp panel, using the 120% rule you would only be able to have a 40amp solar back feed breaker, unless you derate the main breaker to 170amp (200X1.2=240-70=170) however, a 150amp breaker would be the most common step down past 175a. If you have both the solar (70) and the battery (50?) you would need to derate further. Do you have a critical loads panel and a Transfer switch?
So how does the breaker code for main at the top and the solar breaker all the way at the bottom work on a panel that feeds the busbar from the middle?
Still furthest spot from the breaker. In either direction. Top or bottom, you pick!
Great video, How do I find out what my Bus rating is for my panel ? Thank you
This will be on the label. Or you can search the part number of your panel with the manufacturer 👍
What if the meter main was base on the house load and now the breaker is getting derating will possible create a tripping problem? Just wonder.
There is always a possibility for the main breaker to trip. However, the load calculations on a home are done so as to keep this far away as possible to allow for this derate to occur. NEC allows a load study calculation based on 72hr or 30day. As long as you stick to those calculations you are fine per NEC. However, yes, you may need to upgrade to a larger service if you cannot work under those parameters.
Do you have to derate for continuous load on solar feed? Example. 15000 watt solar inveter. 15000÷240 = 62.5 amps. 65 amp breaker or 62.5 x 1.25 = 78.125 amps or 80 amp breaker?
Thanks, Gordy
80amp:
690.9 Overcurrent Protection.
(B) Device Ratings.
Overcurrent devices used in PV source circuits shall be listed for use in PV systems. Electronic devices that are listed to prevent backfeed current in PV system dc circuits shall be permitted to prevent overcurrent of conductors on the PV array side of the device. Overcurrent devices, where required, shall be rated in accordance with one of the following and permitted to be rounded up to the next higher standard size in accordance with 240.4(B):
(1)
Overcurrent devices shall be rated not less than 125 percent of the maximum currents calculated in 690.8(A).
(2)
An assembly, together with its overcurrent device(s), that is listed for continuous operation at 100 percent of its rating shall be permitted to be used at 100 percent of its rating.
How does the panel service load calculation play into the derating?
We take load calculations into consideration when sizing the system. When working with our engineers we see if a derate is possible or if we need to provide a panel upgrade.
I have a friend who works for a solar company. I myself am an Electrician and have workers on solar systems but via my contractor. But he’s needs help with d rating systems. So he’s asking for my help. How much should I charge including materials?
The breaker cost and how many hours it takes you to do the work. You may want to add costs for permits if you need to get the utility involved. We've seen derating costs range from $500-1500
What about a line side tap for solar? What are your guys thoughts on that
We answered your question in our next episode here: ruclips.net/video/TVazwjYz4aA/видео.html
Have you ever de-rated 125amp panel to 100amp for 6.0kw solar system?
If your panel is 125amp buss rating you would be able to go 120% = 150amp total. Then derate to 100amp = 50amp total available backfeed breaker from solar. That should be plenty for what you're looking to do😎👍
Awsome video. I am looking at going solar and have a 125A panel. Do I need to upgrade. My vendor is recommending a subpanel to save money. What do you think?
Interesting...
Your amperage rating has nothing to do with the need for a sub-panel. If you're out of breaker space you may need a sub-panel. If you need more amperage the sub-panel will not help. You would need to upgrade to a larger service. Are you in Arizona?
@@Redline-Electric-Solar No, I am in CA. They said a subpanel $900 (probably as you said out of space) and derating main breaker $700. I am trying to get the app in before the new net metering rules on Apr 15th (SDG&E ripping us off)
Yeah, they are trying to fight against Solar!
I'm not sure if those are good prices as I'm not in your market. But they're in line with a few scenarios we see.
@@Redline-Electric-Solar Thanks for the reply. Last question. I'm more interested in how limited I am with this scenario of my existing 125A panel without doing a new panel upgrade. How would you handle this situation and solar system size recommendation.
125amp is small for us as in Arizona we have large cooling loads in the summer. And if you're derating, to 100?, That may or may not leave room for growth. We would probably suggest you upgrade to a 200amp panel with a 225amp buss rating and 30-60 circuit capacity depending on what you might go in the future. i.e. pool, hot tub, welder, etc...
is there disadvantage of derating? will it cause more breaker tripping and resetting?
The only disadvantage I see is you are losing 25-50amps of maximum capabilities, however, typical home peak loads rarely exceed half of the service rating to the home. If you derated your 200amp main breaker to 175amp or 150amp, this will be your new "limit"... make sense? If not we can shoot a video to help! Thanks!
@@Redline-Electric-Solar Thanks for reply. It does make sense. After derating from 200A to 175A, can we still add EV charging to the same panel?
@@gillybabi5642 in most cases absolutely 🙌
@@Redline-Electric-Solar Our panel is SU2040M200F and the breakers are all used up with 3 tandem breakers already in place. Is this still okay to derate by adding a fourth tandem to free up a breaker slot? Or, is it better to upgrade to a larger bus or larger amp panel? If side-tap, the 120% rule to 200A of main panel still applies, correct?
@@gillybabi5642 great question! Your panel is a 20space 40circuit, which is designed to be filled with all tandem breakers if needed 🙌😎👍
20% is 'wiggle room'.......is there a clearer/better way to state the (physics)?
Not sure what you mean. This is based on the NEC requirements
Nice.. you made a 3 min explanation take 15 min
You're welcome 😎💪😜
Brands with no available spare parts should be replaced.
Why not mention Nuisances tripping? . It is a factor in Derating.
We derate based on the NEC per the ocpd based on interior output.