How do you derate multiple solar wires conduit? The wire will have 26.32 amps. 1.25 (80% rule) x 1.25 (solar source/cloud edge effect) = 1.56. If there are more than three current carrying conductors in a conduit? Does the multiple conductor derate get added to that or is it included already? 1.25 x 1.25 x 1.25 ≈1.95. Does that mean my 26.32 amp load (26.32 * 1.95 = 51.324) can't be on 8 awg wire (using 75C° rating). In cabin that will not be inspected but I still want to do it right. Thanks
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Derating 3+ solar source wires inconduit
- Thread starter Jet
- Start date
The wiring question though is running to a Electrodacus DSSR50 there will be another wire with two solar panels also connected to the DSSR50. The DSSR50 output will be connected to a load of 1200 watts at 36V. The wire should only see half of that. So the why are amperage would be approximately 17. I'm sure 8awg is good then.
zanydroid
Solar Wizard
You multiply all derated together (might have to take some reciprocals)
You start derate from 90C unless the conductors are going through junction box or raceway not rated for 90C. And then you take the min of 75C column and derate answer, assuming all terminations are 75C or better
You start derate from 90C unless the conductors are going through junction box or raceway not rated for 90C. And then you take the min of 75C column and derate answer, assuming all terminations are 75C or better
zanydroid
Solar Wizard
Since #8 has 55A 90C ampacity I think you squeak just under. But, do you also have to do an ambient temperature derate?
Do you qualify for the 24” conduit nipple rule? (For short conduits)
Do you qualify for the 24” conduit nipple rule? (For short conduits)
The conduit is longer than 24 in. There are 8 awg wires carrying positive current. Sets of two wires are combined in a charge controller thing. Together the sets are powering a 1200 watt heating element. 1200/36 = 33.33 amps. As there are two wires per controller, each wire should only be carrying 17 amps. I forgot it's only half the current.
In the conduit there are 4 other 6AWG positive wires. 1 each of the 6 awg 8 awg wires are connected together at a bus bar outside the cabin. The 6 awg wires Go to a charge controller for charging the battery and the AWG wires. Go to the charge controller for heat diversion.
I use the 6AWG so I didn't have to have fuses before the charge controller. As the 75C wire could be protected by the 63 amp breaker after the charge controller. The 8 awg wires will have 30 amp fuses just in case. As they could potentially connected to two charging sources, the battery and the solar panels. The charge controller is designed not to back feed though but I did that as a safety precaution.
I don't know how to ambient temperature derate. The distribution blocks, fuses and charge controller are rated 75C and up. The wire is THWN-2 copper.
In the conduit there are 4 other 6AWG positive wires. 1 each of the 6 awg 8 awg wires are connected together at a bus bar outside the cabin. The 6 awg wires Go to a charge controller for charging the battery and the AWG wires. Go to the charge controller for heat diversion.
I use the 6AWG so I didn't have to have fuses before the charge controller. As the 75C wire could be protected by the 63 amp breaker after the charge controller. The 8 awg wires will have 30 amp fuses just in case. As they could potentially connected to two charging sources, the battery and the solar panels. The charge controller is designed not to back feed though but I did that as a safety precaution.
I don't know how to ambient temperature derate. The distribution blocks, fuses and charge controller are rated 75C and up. The wire is THWN-2 copper.
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zanydroid
Solar Wizard
Ambient temperature I believe is based on ASHRAE table or your guesstimate of how hot that part of your building is
There are some exceptions like NEC has rules for locations (EG rooftop) that have specific ambient temp rating adjustment. In which case you have less leeway to guess, you use what the man tells you.
+ vs - vs grounded vs ungrounded conductor is irrelevant, it's all about the ampacity sent through the conductors.
You have to derate all conductors - the #6 and the #8 - and verify that things are OK. 63A sounds like too large of OCPD for #6 after derating for number of CCC but I didn't do the math.
I don't know whether you need to factor in 17A or 34A for that parallel wiring (and #8 may not be eligible for parallel wiring on a single circuit -- https://www.electricallicenserenewa...ation-Courses/NEC-Content.php?sectionID=297.0).
I think I've gone as far as I can get with only a text description.
There are some exceptions like NEC has rules for locations (EG rooftop) that have specific ambient temp rating adjustment. In which case you have less leeway to guess, you use what the man tells you.
+ vs - vs grounded vs ungrounded conductor is irrelevant, it's all about the ampacity sent through the conductors.
You have to derate all conductors - the #6 and the #8 - and verify that things are OK. 63A sounds like too large of OCPD for #6 after derating for number of CCC but I didn't do the math.
I don't know whether you need to factor in 17A or 34A for that parallel wiring (and #8 may not be eligible for parallel wiring on a single circuit -- https://www.electricallicenserenewa...ation-Courses/NEC-Content.php?sectionID=297.0).
I think I've gone as far as I can get with only a text description.
It's not really parallel wiring. I don't know what to call it. The controller has two sets of MOSFETs and diode connected to each wire but one output. They're not really the same circuit.Ambient temperature I believe is based on ASHRAE table or your guesstimate of how hot that part of your building is
There are some exceptions like NEC has rules for locations (EG rooftop) that have specific ambient temp rating adjustment. In which case you have less leeway to guess, you use what the man tells you.
+ vs - vs grounded vs ungrounded conductor is irrelevant, it's all about the ampacity sent through the conductors.
You have to derate all conductors - the #6 and the #8 - and verify that things are OK. 63A sounds like too large of OCPD for #6 after derating for number of CCC but I didn't do the math.
I don't know whether you need to factor in 17A or 34A for that parallel wiring (and #8 may not be eligible for parallel wiring on a single circuit -- https://www.electricallicenserenewa...ation-Courses/NEC-Content.php?sectionID=297.0).
I think I've gone as far as I can get with only a text description.
Thanks for your help. The 6 awg wire doesn't have any circuit protection. I was going to use #4 or #6 wire between the 63 amp DC mini breakers and the charge controllers. The 6 awg wires in the conduits only have 26.32 amps each and connect to separate isolated inputs on the charge controller. Do I need fuses on those wires too? I could put 40 or 45 amp fuse.Ambient temperature I believe is based on ASHRAE table or your guesstimate of how hot that part of your building is
There are some exceptions like NEC has rules for locations (EG rooftop) that have specific ambient temp rating adjustment. In which case you have less leeway to guess, you use what the man tells you.
+ vs - vs grounded vs ungrounded conductor is irrelevant, it's all about the ampacity sent through the conductors.
You have to derate all conductors - the #6 and the #8 - and verify that things are OK. 63A sounds like too large of OCPD for #6 after derating for number of CCC but I didn't do the math.
I don't know whether you need to factor in 17A or 34A for that parallel wiring (and #8 may not be eligible for parallel wiring on a single circuit -- https://www.electricallicenserenewa...ation-Courses/NEC-Content.php?sectionID=297.0).
I think I've gone as far as I can get with only a text description.
I have a 175 amp class T fuse on the main charging cable (2/0 cable). Then two 63 amp breakers and one 45 in a combiner box. Those go to three charge controllers. 6 awg wire goes to din rail power distribution blocks used as bus bars. Where 10 awg wire connects (protected with 25 amp midget fuses). I was hoping I wouldn't need more fuses.
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zanydroid
Solar Wizard
This kind of system is not something I've designed in detail (which makes it even harder for me to advise when I have to construct a visualization based on my limited experience). I would recommend finding some manufacturer diagrams (doesn't have to be your brand) and following those.
You probably only need fuses on things that with potential to take the hit from a battery.
Conceptually, OCPD are needed on any conductor that does not have inherently current limited sources on both sides.
Practically, wiring diagrams/NEC codebook.
You probably only need fuses on things that with potential to take the hit from a battery.
Conceptually, OCPD are needed on any conductor that does not have inherently current limited sources on both sides.
Practically, wiring diagrams/NEC codebook.
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