A quick code concern

Shawn-H

The question is in Arizona is it legal (up to code) to run both AC and DC lines through the same piece of conduit?

I built a new generator house and need to run the lines from outside passed my solar panels and into my utility room. As I pass my solar panels I want to tie in to my inch and a half conduit. Instead of running a whole new line of conduit does anybody see any issues with this.

SolarPowered

NEVER

Seperate conduit runs.

DC side requires labelling

Shawn-H

Damn..... ok thank you.

Ethan Brush

Shawn-H wrote: »

The question is in Arizona is it legal (up to code) to run both AC and DC lines through the same piece of conduit?

I built a new generator house and need to run the lines from outside passed my solar panels and into my utility room. As I pass my solar panels I want to tie in to my inch and a half conduit. Instead of running a whole new line of conduit does anybody see any issues with this.

Although there is no general restriction for "AC and DC" to be in the same raceway, NEC 690.4(B) requires conductors of photovoltaic source and output circuits to not be in the same raceway as conductors of "other systems". However I would personally have no problem with this if it didnt need to be "up to code".

SolarPowered

Ethan Brush wrote: »

Although there is no general restriction for "AC and DC" to be in the same raceway, NEC 690.4(B) requires conductors of photovoltaic source and output circuits to not be in the same raceway as conductors of "other systems". However I would personally have no problem with this if it didnt need to be "up to code".

You should have a problem with it because DC circuits use seperate over current protection from AC over current protection.

The concept is that solar does not shut off, so it uses a combiner with overcurrent protection devices. AC Line side does not operate in the same nature as DC current.

The only way to avoid all these circumstances" not so complicated problems", is if you want one conduit run, design/build for micro inverters, if it is not off grid, or hybrid. Micro inverters simplify everything, and don't even require an ac disconnect.

In the event an electrical fire occurs/happens combining in one channel between the 2 parts of 1 system the voltage can well exceed 600V potential. That is the purpose of the separation, because of voltage, not whether or not the over current reacts to amperage. Most breakers can operate well above a 600V threshhold.

Ethan Brush

SolarPowered wrote: »

You should have a problem with it because DC circuits use seperate over current protection from AC over current protection.

The concept is that solar does not shut off, so it uses a combiner with overcurrent protection devices. AC Line side does not operate in the same nature as DC current.

The only way to avoid all these circumstances" not so complicated problems", is if you want one conduit run, design/build for micro inverters, if it is not off grid, or hybrid. Micro inverters simplify everything, and don't even require an ac disconnect.

In the event an electrical fire occurs/happens combining in one channel between the 2 parts of 1 system the voltage can well exceed 600V potential. That is the purpose of the separation, because of voltage, not whether or not the over current reacts to amperage. Most breakers can operate well above a 600V threshhold.

Well first to clarify, What I meant was I would have no trouble doing so at my own house, and I dont see any safety issue with folks doing this where they build and maintain their own electrical systems and they dont need NEC compliance. When I am working in a professional capacity, I strictly follow codes regardless of whether it is getting inspected or not.....

I do not agree with your assessment of the reason for this requirement. I dont see a voltage issue as long as all conductors are rated for the highest voltage encountered, and pretty much all conductors are 600v rated these days. Now if you had a 1000v Pv system supplying 1 KV PV wire mixed with some 600V THHN then of course that would not be kosher. I guess it is theoretically possible for positive and negative of two different strings to fault resulting in a "string" of 1200V, but that seems pretty far fetched and I just dont think the CMP was thinking of that scenario and if they were they should have taken "PV output circuit" out of the requirement.

Regarding current I see no problem here either as it is common to have a feeder protected at hundreds of amps to be in the same raceway as a 20 amp branch circuit.

I assume the reason for the requirement is because the PV conductors will essentially never be dead (until the new rapid shutdown becomes common) and its a safety issue for people working on the system and thinking they "turned the breakers off". But who really knows, the CMP's frequently come up with code requirements that dont follow logic and reason

SolarPowered

Ethan Brush wrote: »

I do not agree with your assessment of the reason for this requirement. I dont see a voltage issue as long as all conductors are rated for the highest voltage encountered, and pretty much all conductors are 600v rated these days. Now if you had a 1000v Pv system supplying 1 KV PV wire mixed with some 600V THHN then of course that would not be kosher. I guess it is theoretically possible for positive and negative of two different strings to fault resulting in a "string" of 1200V, but that seems pretty far fetched and I just dont think the CMP was thinking of that scenario and if they were they should have taken "PV output circuit" out of the requirement.


I assume the reason for the requirement is because the PV conductors will essentially never be dead (until the new rapid shutdown becomes common) and its a safety issue for people working on the system and thinking they "turned the breakers off". But who really knows, the CMP's frequently come up with code requirements that dont follow logic and reason

This is in regards to how inverters operate.

Hypothetically the DC end you can have a string operating at 580V

AC end will operate at 240V

Combining one end from the other exceeds the 600V maximum.

There are 2 different cycles and types of linear, and non linear electricity, which can pose conductors to melt long before over current reacts and shuts down one end or the other of inverter. Even if EGC is installed in error such as teh bakersfield macy's fire that was in solar pro magazine, and that issue was a DC side only issue, and EGC/GEC bonding issues that weren't compliant with code.

This is why "string" inverters are required to have a GEC, which in the case of micro its just EGC out, because micro's are both AFCI, and GFCI protected for EGC out, there is no GEC conductor or bare copper past the point of micro.

How its been explained to me by the engineers.There are 2 different streams of voltage occuring at different rates. Putting both sets of conductor in 1 run does pose the potential for Arch. Or atleast that is how the engineers have explained it to me in laymens terms.

As of now only micro inverters meet the requirements for NEC rapid shut down and that is probably because the DC run is under 3', and there are 2 forms of protection at the point of inverter. I don't at any time see this actually happening with string inverters on a commercial, or residential level, mostly because of both DC and AC conductor lengths that are required, and the means of combining.

According to how string inverters do operate under frequency conditions requiring frequency to generate power for grid, string inverters should and do meet rapid shut down. I believe there is just to much complication with code language why string inverters havent been identified as the switching mechanism for rapid shut down. If that were the case.

Yes than I would agree with you 100% that both dc and AC side could share a common conduit/channel.

Ethan Brush

SolarPowered wrote: »

This is in regards to how inverters operate.

Hypothetically the DC end you can have a string operating at 580V

AC end will operate at 240V

Combining one end from the other exceeds the 600V maximum.

In a non isolating inverter, it is my understanding that one leg of the DC side and one leg of the AC side will be at nearly the same potential at a given moment in time - the voltages cant "combine" . In a isolating inverter, there is isolation between the two sides so there is theoretically zero voltage between conductors of both sides. Sure a high impedance meter will read voltage from capacitive coupling but I cant think of a scenario where those would add to more than the highest voltage on one side. There is no such requirement to keep conductors of "normal" separately derived systems (transformers) separated, even if one of the derived systems is ungrounded, so I am just not buying any of this as a plausible scenario.

There are 2 different cycles and types of linear, and non linear electricity, which can pose conductors to melt long before over current reacts and shuts down one end or the other of inverter.

?? Non linear loads can be an issue in three phase 4 wire systems as harmonics can add on the neutral conductor resulting in as much as 1.73 times the phase current. I dont see what this has to do with anything in this thread.

Even if EGC is installed in error such as teh bakersfield macy's fire that was in solar pro magazine, and that issue was a DC side only issue, and EGC/GEC bonding issues that weren't compliant with code.

I read that article some time ago. I dont really remember the details well enough to talk about it. My recollection that it was a combination of some poor workmanship and the "blind spot" of the GFP system. Regardless, I dont see the connection of this to the topics in this thread??

This is why "string" inverters are required to have a GEC, which in the case of micro its just EGC out, because micro's are both AFCI, and GFCI protected for EGC out, there is no GEC conductor or bare copper past the point of micro.

An isolating inverter has a GEC because it is essentially a separately derived system and if you want to ground it (the system and/or the electrical parts} then you need a GEC by definition. Its just like a transformer - it gets a grounding electrode conductor to ground the new system. Non isolating inverters dont need a GEC because the DC side is "still grounded" through the non isolating inverter.

As of now only micro inverters meet the requirements for NEC rapid shut down and that is probably because the DC run is under 3', and there are 2 forms of protection at the point of inverter. I don't at any time see this actually happening with string inverters on a commercial, or residential level, mostly because of both DC and AC conductor lengths that are required, and the means of combining.

According to how string inverters do operate under frequency conditions requiring frequency to generate power for grid, string inverters should and do meet rapid shut down. I believe there is just to much complication with code language why string inverters havent been identified as the switching mechanism for rapid shut down. If that were the case.

I would say that Any GTI - micro or not - meets the rapid shut down requirement due to their anti-islanding scheme. Just with non micros, they have to be located no more than 5 feet inside a building or 10 feet from the array. There is no language in the NEC "identifying" or not certain types of inverters as meeting/not meeting the 690.12 requirements. Maybe your jurisdiction as adopted some language saying such.

SolarPowered

Ethan Brush wrote: »

?? Non linear loads can be an issue in three phase 4 wire systems as harmonics can add on the neutral conductor resulting in as much as 1.73 times the phase current. I dont see what this has to do with anything in this thread.

DC side of system has the potential for Arching as a linear load. Voltage can literally jump onto non linear voltage, coming in from the grid

Ethan Brush wrote: »

I read that article some time ago. I dont really remember the details well enough to talk about it. My recollection that it was a combination of some poor workmanship and the "blind spot" of the GFP system. Regardless, I dont see the connection of this to the topics in this thread??

The connection of this topic is that it was a point of failure on the DC end side of the system which caused the fire. If by chance both DC and AC sides were to be within the same race way then the ac side as well would of been prone to that fire bypassing the GFP of inverter. Separation is to prevent the "cross contamination" of the 2 parts of the system in case one part or both parts of the system fail. In either regards to lack of understanding code, incompetence of installation in the case of the bakersfield fire (which we come to find out really only required a GEC conductor within the raceway), and for what ever reason why it did not happen, well that is definitely an installer error. Code is made to have fail safes, checks and balances as additional preventative measures so when, or (if) part of a system is bound to fail regardless of competence of installation, the additional safe guards allow for shut down at one, or both parts of either DC or AC side of system, to prevent additional problems (such as fires spreading to other locations such as inverter pad/switch gear rooms, etc).

Ethan Brush wrote: »

I would say that Any GTI - micro or not - meets the rapid shut down requirement due to their anti-islanding scheme.

We are both in agreement. I believe it is more so how jurisdictions interpret the language.

Shawn-H

You guys got completely off topic I was not talking about terminating them in the same location I was simply talking about running the wires next to each other so I could get them in the house protected from the Sun weather and vehicle traffic my DC would still terminate at my charge controllers and the AC would continue on to the Outback for backup and charging I'm simply talking about running the wires next to each other in the same conduit. I am completely off grid and we are talking about a generator not grid power. None of this "has to" be up to code but I would like it to be in case I sell the home someday

SolarPowered

They need seperate raceways. DC has to be identified with labeling.

We weren't talking about termination,

This was about seperate raceways, grounding, and how it affects the solar system.

If by chance your system is under 10amps on both DC and AC side, you could disregard seperate chase way/conduits as NEC doesn't recognize over current protection under 10amps of current.

Shawn-H

Ok thank you. I'll run them separately as I'm supposed to.

t00ls

conduit ....raceway...2 different things

conduit you cannot open , a raceway you can

I was sure you could have both ac and dc in the same raceway......but not conduit

Ethan Brush

t00ls said:

conduit ....raceway...2 different things

conduit you cannot open , a raceway you can

I was sure you could have both ac and dc in the same raceway......but not conduit

It has nothing to do with AC vs DC.  Here is the applicable code section:

NEC 690.4(B) Conductors of different systems.  Photovoltaic source circuits and photovoltaic output circuits shall not be contained in the same raceway, cable tray, cable, outlet box, junction box, or similar fitting as feeders or branch circuits of other systems, unless the conductors of the different systems are separated by a partition or are connected together.

inetdog

I see a lot of casual declarations about what the NEC says (which is OK as long as quoted correctly) as well as why it says that (much harder to justify since the Code Making Panels (CMPs) do not always document their motivations, just the resulting code.

The reason for the separation is NOT that the two systems have different OverCurrent Protection Devices (OCPD) nor that the voltages can add because they are out of phase and might arc nor that they come from different sources.
The NEC has several major provisions about not sharing:

1. Power limited circuitry (Class 2 and Class 3) cannot share a raceway with power wiring probably because a short to the Power Limited circuit could cause severe problems before any OCPD tripped.
2. Service wires (effectively having no OCPD since POCO sizes their primary side OCPD to protect their wiring and system integrity, not the secondary wiring (you) cannot be combined with building wiring with OCPD just because the service wires are inherently dangerous and are not even allowed inside the building except for limited distances. Any fault to feeder or branch wiring could cause a fire in the branch wiring or equipment.
3. Solar PV input and output circuits, because the Code says so. Period. That is all you need to understand.

Sharing a conduit and sharing a raceway are both prohibited by 3.
You can run them through the same weatherproof entrance into a building as long as that entry is not part of a raceway system.

Shawn-H

Thank you so much

Dave Angelini

And keep in mind that the NEC is the minimum requirement.  It can always be done better!

westbranch

inetdog said:

3. Solar PV input and output circuits, because the Code says so. Period. That is all you need to understand.

Sharing a conduit and sharing a raceway are both prohibited by 3.
You can run them through the same weatherproof entrance into a building as long as that entry is not part of a raceway system.

Point 3 has me thinking about the input and output from my Classic 150 where the 2 types (input & output) of wire are all passing through a conduit connecting the Classic and the Epanel....??  does it apply there also?

Dave Angelini

westbranch said:

inetdog said:

3. Solar PV input and output circuits, because the Code says so. Period. That is all you need to understand.

Sharing a conduit and sharing a raceway are both prohibited by 3.
You can run them through the same weatherproof entrance into a building as long as that entry is not part of a raceway system.

Point 3 has me thinking about the input and output from my Classic 150 where the 2 types (input & output) of wire are all passing through a conduit connecting the Classic and the Epanel....??  does it apply there also?

I would be concerned if it was high voltage DC (400 VDC) near your low voltage DC.
 Normal wiring separation, good insulation, and wiring practices. The gear is UL listed right and you are using it per Midnite docs?
People combine  low voltage solar in/out in one conduit all the time like the Outback and Schneider manuals show.
 On the XW system with a 400 vdc solar charger everything is the way I would want it, and it is UL listed

vtmaps

westbranch said:

Point 3 has me thinking about the input and output from my Classic 150 where the 2 types (input & output) of wire are all passing through a conduit connecting the Classic and the Epanel....??  does it apply there also?

The input to your classic is a cable from combiner to ePanel, and ultimately another cable through conduit to the Classic.  By the time it goes through that conduit to the Classic, it has been through circuit breakers.  Circuit breakers are considered a device, I think, so it's not really your PV output going into the Classic...  your PV output goes to a circuit breaker. 

I'm not really sure how contorted the logic is, but this came up in another thread about parallel cables. 

Generally speaking, parallel cables are NOT permitted.  (NEC does allow parallel cables, in some narrow circumstances).   Inetdog pointed out that if you have circuit breakers in each of the 'parallel' cables, then technically they are not parallel, because they are connected to a device (the circuit breaker), not to each other.

--vtMaps

Ethan Brush

westbranch said:

inetdog said:

3. Solar PV input and output circuits, because the Code says so. Period. That is all you need to understand.

Sharing a conduit and sharing a raceway are both prohibited by 3.
You can run them through the same weatherproof entrance into a building as long as that entry is not part of a raceway system.

Point 3 has me thinking about the input and output from my Classic 150 where the 2 types (input & output) of wire are all passing through a conduit connecting the Classic and the Epanel....??  does it apply there also?

I dont see any issue as long as both conductors are rated for the highest voltage encountered.  I would consider both the input and output from a charge controller to be "Photovoltaic output circcuit conductors" (look at the NEC definition) so they can be in the same raceway.

Shawn-H

I can tell you and Snowflake Arizona it's unacceptable you must run them separately. At least for the midnight solar classic 150 or 150 light. And this is because one set of conductors is rated for 60 amps and the other for 90. I was supposed to separate them into two separate one inch conduit.

westbranch

Shawn, have you go the max in/out V and A plus a picture or 2 of that setup in action?

Ethan Brush

Shawn-H said:

I can tell you and Snowflake Arizona it's unacceptable you must run them separately. At least for the midnight solar classic 150 or 150 light. And this is because one set of conductors is rated for 60 amps and the other for 90. I was supposed to separate them into two separate one inch conduit.

Not sure who is telling you that but it makes no sense.  Absolutely no restriction on putting conductors of different ampacity in the same raceway

inetdog

Ethan Brush said:

Shawn-H said:

I can tell you and Snowflake Arizona it's unacceptable you must run them separately. At least for the midnight solar classic 150 or 150 light. And this is because one set of conductors is rated for 60 amps and the other for 90. I was supposed to separate them into two separate one inch conduit.

Not sure who is telling you that but it makes no sense.  Absolutely no restriction on putting conductors of different ampacity in the same raceway

+1
The closest solid provision in the NEC is that service wires (which have NO overcurrent protection to speak of) must not share a raceway with protected wires. The idea is that you do not want any possibility of the unlimited service wires getting shorted to the protected wires.