October 10, 20223 yr I have a few questions on conduit for DC cables. 1. Must conduit be metal or plastic? 2. Do you need to use conduit in ceiling spaces? 3. Can you use plastic trunking instead of conduit for interior surface cables?
October 28, 20223 yr Apparently if run is > 50m then one must use metal conduit. In ceiling spaces its probably a good idea to use metal... For short runs inside the house plastic trunking is good.
October 28, 20223 yr On 2022/10/10 at 2:16 PM, Chris_S said: I have a few questions on conduit for DC cables. 1. Must conduit be metal or plastic? 2. Do you need to use conduit in ceiling spaces? 3. Can you use plastic trunking instead of conduit for interior surface cables? I've got metal conduit (pipe) from where the cables come through the tiles into the roof space all the down into the circuit breaker / lightning protector box in my garage. Plastic trunking from from that box to the inverter.
October 29, 20223 yr Author 8 hours ago, wolfandy said: I've got metal conduit (pipe) from where the cables come through the tiles into the roof space all the down into the circuit breaker / lightning protector box in my garage. Plastic trunking from from that box to the inverter. What's the advantages of using metal in the ceiling space over pvc? I have about 25m to run in the ceiling that's quite a bit of pipe.
October 29, 20223 yr The Sans for PV is not out yet. For electrical the PVC is fine. But you can also just use flat twin cable as that can be used in a ceiling. Be mindful of Volt drop when you choose a cable. but no rule or law stating pipe must be used. Appropriate cable is fine. almost every single new build and extension is down with the flat twin cable chucked in the roof. Clients don't want to pay for pipe and time and then happy for the cable to be chucked accross the roof. Albeit as neat as possible but again Clients budget dictates what they get. Fair warning is given and they almost always choose to sling it haha. Anyway that was a small rant but yes flat twin cable in the roof is fine. Metal or PVC is also fine. Be mindful of the size of PVC as there needs to be sufficient space in the pipe for heating etc.
October 29, 20223 yr The questions to ask are the following: That 50m run as mentioned, is it 50m + or - or is it 25m + &-... Under the solar panels is that considered adequate protection from the elements? Why do they specify metal trunking? PV DC cable is quite specialist type of cable. There is a lot of UV protection that is added & this cable will sit on your roof for a long time, thorough many summers & winters, basically any part of cable that will sit in the sun, needs this extra protection. Now when you have this said cable neatly wrapped under the solar panels & or its inside your roof that becomes an idea of wire safety. The inverters these days are going to higher & higher Voltages. These wires especially if they make physical contact with each or are not adequately protected, makes for a good amount of potential energy that needs to go somewhere. The plastic conduit can protect an AC cable from a few sparks. DC cables cause a very high temperature type of welding to take place. DC at high voltage or even at low voltages like 48V with our lithium batteries is a whole other science. I have shorted a Lithium 3.2V cell. The Screw driver was melted at the tip & such is the evidence of the potential energy that is available. I can only share my opinion & that is that the DC side of my solar installations is the part that I focus on with high attention to detail for the reasons stated above. Don't skimp on the DC side, it could cost you a lot in the long term. That cable must be future proofed, 25 odd years is the life span of a Solar panel. Don't neglect the cables, they serve a vital role & care should be taken to avoid a future problems.
October 29, 20223 yr Author 22 minutes ago, Steve87 said: The questions to ask are the following: That 50m run as mentioned, is it 50m + or - or is it 25m + &-... Under the solar panels is that considered adequate protection from the elements? Why do they specify metal trunking? PV DC cable is quite specialist type of cable. There is a lot of UV protection that is added & this cable will sit on your roof for a long time, thorough many summers & winters, basically any part of cable that will sit in the sun, needs this extra protection. Now when you have this said cable neatly wrapped under the solar panels & or its inside your roof that becomes an idea of wire safety. The inverters these days are going to higher & higher Voltages. These wires especially if they make physical contact with each or are not adequately protected, makes for a good amount of potential energy that needs to go somewhere. The plastic conduit can protect an AC cable from a few sparks. DC cables cause a very high temperature type of welding to take place. DC at high voltage or even at low voltages like 48V with our lithium batteries is a whole other science. I have shorted a Lithium 3.2V cell. The Screw driver was melted at the tip & such is the evidence of the potential energy that is available. I can only share my opinion & that is that the DC side of my solar installations is the part that I focus on with high attention to detail for the reasons stated above. Don't skimp on the DC side, it could cost you a lot in the long term. That cable must be future proofed, 25 odd years is the life span of a Solar panel. Don't neglect the cables, they serve a vital role & care should be taken to avoid a future problems. In this case if my inverter is 25m from my panels must I use a breaker box in the ceiling where the panels enter the roof or is a dc DB box at the inverter sufficient?
October 29, 20223 yr The one at the Solar plant is more than sufficient. The idea of having two comes into mind when you have a massive solar farm & the operator is far away from the inverter & can safely isolate himself from the PV Array.
October 29, 20223 yr Author 7 minutes ago, Steve87 said: The one at the Solar plant is more than sufficient. The idea of having two comes into mind when you have a massive solar farm & the operator is far away from the inverter & can safely isolate himself from the PV Array. You mean the one at the inverter is sufficient?
October 29, 20223 yr 2 minutes ago, Chris_S said: You mean the one at the inverter is sufficient? Yes
October 29, 20223 yr This video will show you the dangers first hand as to why they specify metal conduit. This is the High voltage Solar PV inverters, so that would include all of the modern machines. (Sunsynk, Deye, Kodak, Infinisolar) The new Infinisolar has dual MPPTs that can handle 1kV strings as I think does the Sunsynk 16kW if I am not mistaken. That level of PV energy is very dynamic. Don't skimp on the DC combiners, Surge protectors, Cabling as well as switch gear. If you do it's not very forgiving like AC connections. Edited October 29, 20223 yr by Steve87
October 29, 20223 yr Author 51 minutes ago, Steve87 said: This video will show you the dangers first hand as to why they specify metal conduit. This is the High voltage Solar PV inverters, so that would include all of the modern machines. (Sunsynk, Deye, Kodak, Infinisolar) The new Infinisolar has dual MPPTs that can handle 1kV strings as I think does the Sunsynk 16kW if I am not mistaken. That level of PV energy is very dynamic. Don't skimp on the DC combiners, Surge protectors, Cabling as well as switch gear. If you do it's not very forgiving like AC connections. Metal it will be 🔥😩
October 29, 20223 yr 1 hour ago, Chris_S said: Metal it will be 🔥😩 The video is talking about switching, you need proper DC isolators and rule of thumb, do not switch off/ON any circuit while under load. You will definitely get arcing. You can not get that arcing on a solid cable that is running from one point to the next. we have high voltage DC cables running in open cable trays and no issue
October 29, 20223 yr Author 4 minutes ago, hoohloc said: The video is talking about switching, you need proper DC isolators and rule of thumb, do not switch off/ON any circuit while under load. You will definitely get arcing. You can not get that arcing on a solid cable that is running from one point to the next. we have high voltage DC cables running in open cable trays and no issue I have seen chewed wires in my ceiling before
October 29, 20223 yr 5 minutes ago, Chris_S said: I have seen chewed wires in my ceiling before it must have been rats, then steel conduits will still not help you because they can just go straight to your PV panels and chew the wires there. The point is that you can run High voltage cables in cable trays, plastic conduit, steel conduit or plastic trunking if you want and still have a safe installation Edited October 29, 20223 yr by hoohloc spelling
October 29, 20223 yr 1 minute ago, hoohloc said: it must have been rats, then steel conduits will still not help you because they can just go straight to your PV panels and chew the wires there. The point is that you can run High voltage cables in cable trays, plastic conduit, steel conduit or plastic trunking if you want and still have a safe installation I would use steel conduits if I was going to run my cables outside of the building, only to protect them against the elements
October 3, 20232 yr Hallo everyone. I am in the process of obtaining a COC for my solar installation, and the one person I have spoken to, insists that the positive(+) and negative(-) DC cables running from the panels to the combiner box must be in separate conduits, and that + and - cannot run in the same conduit as I currently have. Now I have read though all conduit requirements pertaining to solar, and I have not come across this requirement in any document, unless I have missed it. Can someone more knowledgeable than this beancounter please shed some light on this issue and provide me with accurate information.
October 3, 20232 yr DC cables running from the panels to the combiner box must be in separate conduits, and that + and - cannot run in the same conduit as I currently have. He's got it the wrong way round. They must run in the same conduit, and if you have multiple strings in the same conduit then you need to tie the conductors of each string together at regular intervals for easy identification. From SANS 10142-1 2021, under the "Additional requirements for photovoltaic installations", page 237:
October 4, 20232 yr He's got it the wrong way round. They must run in the same conduit, and if you have multiple strings in the same conduit then you need to tie the conductors of each string together at regular intervals for easy identification. From SANS 10142-1 2021, under the "Additional requirements for photovoltaic installations", page 237: Thanks for this info!
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