ᐅ Which electrical cable / underground cable is suitable for an 80-meter service connection?
Created on: 6 Apr 2022 10:24
A
A&S Bau
Hello everyone,
Here is the situation:
The utility company will install a NAYY-J 4x50 cable, approximately 10 meters (33 feet) onto our property into a distribution cabinet.
From there, we have to organize the rest of the connection to the house ourselves.
The house is still about 70-80 meters (230-260 feet) away. (The house will be built on the third plot.)
The power requirement is 30 kVA.
We have received different statements and various quotes from electricians.
We were advised to definitely use a copper cable.
Electrician 1 recommends at least a NYCWY 4x50 SM35 cable. However, due to the length of 70-80 meters (230-260 feet), he actually suggests using 4x70, because otherwise there could be a voltage drop and the 30 kVA might not be fully guaranteed.
Electrician 2 recommends NYCWY 4x35 SM16, which he says would be completely sufficient.
Is Electrician 1 or Electrician 2 correct? What would you recommend?
Thank you in advance,
Müller
Here is the situation:
The utility company will install a NAYY-J 4x50 cable, approximately 10 meters (33 feet) onto our property into a distribution cabinet.
From there, we have to organize the rest of the connection to the house ourselves.
The house is still about 70-80 meters (230-260 feet) away. (The house will be built on the third plot.)
The power requirement is 30 kVA.
We have received different statements and various quotes from electricians.
We were advised to definitely use a copper cable.
Electrician 1 recommends at least a NYCWY 4x50 SM35 cable. However, due to the length of 70-80 meters (230-260 feet), he actually suggests using 4x70, because otherwise there could be a voltage drop and the 30 kVA might not be fully guaranteed.
Electrician 2 recommends NYCWY 4x35 SM16, which he says would be completely sufficient.
Is Electrician 1 or Electrician 2 correct? What would you recommend?
Thank you in advance,
Müller
Okay. If the meter is installed inside the distribution cabinet, the situation is a bit different. In this case, the maximum voltage drop allowed is 3% up to the last light fixture and 5% up to the socket outlet. Then, the 70mm² (approximately 140 circular mils) cable is definitely oversized. I can recalculate that tomorrow.
Up to the cabinet, the utility company installs its cable, and you have no influence on the cable type or the cross-section. Usually, they use NAYY cables (correct, these are aluminum) because they are more cost-effective. From the cabinet onward, copper cables are generally used (NYY).
The difference between the two cable types is as follows:
4x35/16 means 4 cores each with 35mm² (approximately 69 circular mils) plus an outer braid with a cross-section of 16mm² (approximately 31 circular mils).
4x70/35 means 4 cores each with 70mm² (approximately 137 circular mils) plus an outer braid with a cross-section of 35mm² (approximately 69 circular mils).
The outer braid acts like a fifth conductor, woven around the other four cores and reduced in cross-section. This can be used because in some five-core applications, the protective earth conductor (PE) can be reduced in cross-section.
As mentioned, in my opinion, this is not necessary because the fifth conductor can be completely omitted up to the main distribution panel. Inside the house, however, five-core wiring must be used as stated. This is necessary so that protective devices such as residual current devices (RCDs) can function properly.
Up to the cabinet, the utility company installs its cable, and you have no influence on the cable type or the cross-section. Usually, they use NAYY cables (correct, these are aluminum) because they are more cost-effective. From the cabinet onward, copper cables are generally used (NYY).
The difference between the two cable types is as follows:
4x35/16 means 4 cores each with 35mm² (approximately 69 circular mils) plus an outer braid with a cross-section of 16mm² (approximately 31 circular mils).
4x70/35 means 4 cores each with 70mm² (approximately 137 circular mils) plus an outer braid with a cross-section of 35mm² (approximately 69 circular mils).
The outer braid acts like a fifth conductor, woven around the other four cores and reduced in cross-section. This can be used because in some five-core applications, the protective earth conductor (PE) can be reduced in cross-section.
As mentioned, in my opinion, this is not necessary because the fifth conductor can be completely omitted up to the main distribution panel. Inside the house, however, five-core wiring must be used as stated. This is necessary so that protective devices such as residual current devices (RCDs) can function properly.
P
Peter Pohlmann7 Apr 2022 12:57I am not an electrician.
In general, I would recommend running a 5 x 10mm² (5 x 0.02 inch²) copper cable into the house from the connection point, regardless of any tables or standard recommendations.
Right next to it, install two empty conduits. Times change. I also installed 5 x 10mm² (5 x 0.02 inch²) cables throughout my property, including other buildings. Especially considering photovoltaics, electric vehicles, heat pumps, and so on, I believe this cross-section ensures you are completely future-proof.
This is of course oversized, but it allows for higher loads in the future. That way, you won’t have to replace the cable with a thicker one in 20 years.
I would also install a large-diameter PVC pipe (such as a KG pipe) from the distribution box to the house to leave enough space for future cables, wallbox chargers, etc.
You never know what kind of devices we will have 10 or 20 years from now.
In general, I would recommend running a 5 x 10mm² (5 x 0.02 inch²) copper cable into the house from the connection point, regardless of any tables or standard recommendations.
Right next to it, install two empty conduits. Times change. I also installed 5 x 10mm² (5 x 0.02 inch²) cables throughout my property, including other buildings. Especially considering photovoltaics, electric vehicles, heat pumps, and so on, I believe this cross-section ensures you are completely future-proof.
This is of course oversized, but it allows for higher loads in the future. That way, you won’t have to replace the cable with a thicker one in 20 years.
I would also install a large-diameter PVC pipe (such as a KG pipe) from the distribution box to the house to leave enough space for future cables, wallbox chargers, etc.
You never know what kind of devices we will have 10 or 20 years from now.
Peter Pohlmann schrieb:
I have also installed 5 x 10 m² (square meters) everywhere in my place as well as in the other buildings. 5 x 10 m² (square meters) = 50 m² (square meters) cross-section?! 🙄
That’s roughly an 8 m (26 ft) diameter – sounds more like a tunnel boring machine you’ve brought in. You’re right, with that you could potentially run not just one electric car but an entire dual-track subway line 😉
*dodges and runs away*
P
Peter Pohlmann7 Apr 2022 13:39Hmm, the cable wasn’t that thick after all.
Yes, the "m" obviously doesn’t belong there. Good catch! That earns an extra point!
Yes, the "m" obviously doesn’t belong there. Good catch! That earns an extra point!
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