I have a system where the current output exceeds what I am allowed to add to the 200A bus in the main panel, so I will be installing using taps. My AC output conductors run through a 60A fused disconnect, then to a gutter where I will make my taps. I was told by an engineer that the conductors from the load side of the fused disconnect to the gutter need to be run in RMC. Is RMC the only option I have here? I've been searching the code with no luck. Can someone clarify this for me?
Protection of tap conductors
- Thread starter csoc64
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
240.21(B)
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
It sounds like you are talking about a supply side connection, aka "line side tap." That is, the taps would be on the line side of the service disconnecting means. In that case, your new tap conductors are considered service entrance conductors, and must be run in RMC. (And your 60A fused disconnect is considered a service disconnecting means).
I don't believe 240.21(B) is relevant, unless the installation is more involved than you've implied, such as a tap between a main disconnect and a separate panel.
I don't believe 240.21(B) is relevant, unless the installation is more involved than you've implied, such as a tap between a main disconnect and a separate panel.
shortcircuit2
Senior Member
- Location
- South of Bawstin
Where in the code does it say RMC is to be used?
kwired
Electron manager
- Location
- NE Nebraska
Maybe you described this wrong, but if you have more than what is allowed in the panel you need another supply or a larger supply:?
If you are making taps the tap conductors must be protected from physical damage - most cases with a raceway. Requirements vary some between each of the tap rules. See 240.21(B) There are five subsections and each one mentions physical protection, but some are different than others.
In your case you are likely using the 10 foot tap rule or maybe even the 25 foot tap rule both require conductors to be in a raceway, the 25 foot rule includes the words "or by other approved means".
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Why would the load side of a fused disconnect need special protection? Maybe I am missing something here.
maybe it is not a tap at all.
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kwired
Electron manager
- Location
- NE Nebraska
Did you notice this is in the PV forum. I did not when I made my first reply, so that may change things some. Still not really sure just what the OP situation is though.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
What is the load side and what is the line side of a PV AC disco is a frequent source of confusion to folks in the trades who don't have experience dealing with solar. Although the current flow is from the inverter to the interconnect, the inverter is connected to the load side of the switch. If it is a fused disco the reason for this is obvious at a glance; when the switch is open the fuses must not be energized and when the switch is open the inverter cannot continue to energize the conductors on that side of the switch. The more general concept is that although the normal current flow is from inverter to interconnect, all the protection on the circuit is to protect against feeding a fault from the service side; the inverter is incapable of putting more current on the line than its rated maximum output (and hence the rated ampacity of the conductors) and will shut down if there is a fault.
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I did not notice that either. I am not real familiar with PV installations. In any case, exactly what the OP is trying to describe is pretty murky to me.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
My mistake, it doesn't say that.
Around here it is enforced that way for service risers. Maybe it is in our local code. I hadn't ever thought to check.
To the original poster: Look at 230.43. It allows several options besides RMC.
Also, to avoid confusion, try refer to the "utility side" or the "inverter side" of the switch, rather than line and load. The line side of the switch should be connected to the utility.
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jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
If I am reading the OP correctly, it is not a 240.21 tap. It is a supply side connection for a PV system as allowed by 230.40 Exception (5), 230.82(6) and 705.12(A). It is generally taken that Article 230 governs the installation between the tap and the disconnect.
Let's see if I can describe this better (if I knew how to insert a one line, this would be easier). Anyway, the conductors in question would be coming from the utility side of the fused disconnect. These conductors then go into a gutter, where they are combined with load side conductors from a newly installed main service disconnect breaker (required by POCO) and a set of feeders going back to the 200A main panel.
shortcircuit2
Senior Member
- Location
- South of Bawstin
Your description is quite confusing on what you are doing there.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
I agree with shortcircuit, confusing description. But I think I have doped out what you mean...
Starting from the utility...
The service conductors go to a new service disconnect.
The conductors on the load side of the new service disco are then tapped/split to feed both the existing 200A panel and the new 60A disco for the PV.
Did I get that right?
The new service disco should NOT be required, but as long as you are putting it in then this IS a 240.21(B) tap. Still, RMC should not be required. I wouldn't take the word of some 'engineer', I would ask the AHJ.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
did we decide it is a PV system? the new description from the OP clouds that even more.
Thanks for you patience. I am very new to PV installs, and dealing with conflicting advice is frustrating. You are correct in your interpretation of my description, so I think I'm finally clear on the tap issue. On the issue of the new service disco, I have been told, by those more knowledgeable than myself, that without the new service disco, the POCO would consider it a 260A service with the addition of the PV source.
shortcircuit2
Senior Member
- Location
- South of Bawstin
The set-up your describing will still have 60amp and 200amp feeding the bus of the 200amp panel. This does not comply with the 120% rule.
Just connect the solar as a supply side connection.
Just connect the solar as a supply side connection.
What exactly do you mean when you say "supply side connection"? How would that be wired?
BillK-AZ
Senior Member
- Location
- Mesa Arizona
View attachment 8893
A Supply Side connection of a PV system is a connection made between the Utility revenue meter and the existing load center (or in some cases a fused safety switch). The PV current does not flow through the existing load center. There are many items to consider such as if there is a suitable place to make the connection within the listing restraints of the service entrance. If you do not know what this requires, get help from someone with experience.
The attached is a simple diagram by John Wiles.
A Supply Side connection of a PV system is a connection made between the Utility revenue meter and the existing load center (or in some cases a fused safety switch). The PV current does not flow through the existing load center. There are many items to consider such as if there is a suitable place to make the connection within the listing restraints of the service entrance. If you do not know what this requires, get help from someone with experience.
The attached is a simple diagram by John Wiles.
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BillK-AZ
Senior Member
- Location
- Mesa Arizona
Sorry, I could not make the attachment work and this site limits one to 15 minutes with a posting edit.
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