ᐅ Which electrical cable / underground cable is suitable for an 80-meter service connection?

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

I’m not an electrician. However, there are tables that show the cross-sectional areas. Any electrician should be able to show you these.

It is similar for us.
A 5x50mm² (with sufficient oversizing) cable was installed.
In Berlin, 4-core cables are no longer used.

A&S Bau schrieb:

Hello everyone,

Here is the situation:
The utility company will install a NAYY-J 4x50 cable, approximately 10 meters (33 feet) on our property into a handover cabinet.
From there, we need to organize the rest of the connection to the house ourselves.
The house is another 70-80 meters (230-262 feet) away. (The house will be built in the third row)
The power requirement is 30 kVA.
We have received different opinions and different quotes from electricians.
We were advised to definitely use a copper cable.

Electrician 1 recommends at least an NYCWY 4x50 SM35 cable. Due to the length of 70-80 meters (230-262 feet), he actually suggests 4x70, because otherwise there could be a voltage drop and the 30 kVA might not be guaranteed.

Electrician 2 recommends NYCWY 4x35 SM16. According to him, this would be completely sufficient.

Who is correct, E1 or E2? What would you recommend?

Thank you in advance,
Müller

The meter will probably be installed in the handover cabinet?

There will always be some voltage drop, unless the electrician is suggesting a superconducting cable?! The question is only how much it will be: If I calculate for 70 meters (230 feet) of copper cable, the voltage drop is approximately

for 35 mm² (0.054 in²)
0.45% @ 10 kW per phase

for 50 mm² (0.078 in²)
0.31% @ 10 kW per phase

As a comparison— you will hardly reach the full 30 kW load, even with an electric car and/or photovoltaic feed-in.

You would already lose around 3 kWh per 1000 kWh with the thicker cable. The difference in losses is about 1.5 per thousand or 1.4 kWh per 1000 kWh consumption more. This is the worst case at maximum load. If you require less power, these percentages decrease proportionally and the difference becomes even smaller! If you are laying cable over such a long distance anyway, I would rather use a slightly larger duct (KG pipe) for the cable and pull a thin additional cable alongside— in case you want to install another service later on, you a) have a nice empty conduit and b) a pulling aid, saving you thousands of dollars and the need to repave your driveway or re-dig your garden. Better to have it and not need it with such a heavy main supply... 😉

Hello. I can respond here as an electrician since we have a similar situation.

The actual line loss is rather negligible here, at least for cross-sections larger than 25mm² (0.04 square inches) up to 100m (328 feet).

What matters is where the meter is installed. I assume it will be inside the house. According to the Low Voltage Connection Ordinance (NAV), the voltage drop between the house connection point (handover point from the utility company) and the meter must not exceed 0.5%. For your 30kVA connection, a 50A fuse will probably be installed at the house connection.

To comply with the 0.5% voltage drop, you would theoretically need to install a copper cable with a cross-section of 95mm² (0.15 square inches) for 70-80m (230-262 feet).

These are the regulations. In practice, in my opinion, this is completely oversized, especially since it might be difficult to connect 95mm² anyway, as the terminals are usually not that large. I would try to go with 70mm² (0.11 square inches) or 50mm² (0.08 square inches). Ultimately, your electrician must confirm to the utility company that the regulations have been followed. If electrician 1 uses 50mm², then it should not be your concern. Option 2 with 35mm² (0.05 square inches) would be too small for the cable length in my opinion.

What surprises me is the cable type. It is absolutely fine to install a 4-core cable and split it into 5 cores right after entering the house, if the utility company delivers a 4-core cable at the handover box (as you wrote). An NYY-J 4x50mm² (4 cores, 50mm² each) cable would be the right choice here, as it is also cheaper than NYCWY. However, this also depends on the utility company. They usually have connection examples on their websites, so it’s best to check there.

Thank you for the responses.

@ Poramyco: If I understood my energy supplier correctly, the electricity meter is located in the handover cabinet and not inside the house.
Electrician 1 also referred to the 0.5% voltage drop and therefore offered the 4x70 cable.
The utility company will install a NAYY-J 4x50 cable, not NYY-J 4x50 (as you wrote),
so it is an aluminum cable, according to what I found on Google.

So is E1 definitely the right choice?

Now a general question for better understanding:
What exactly is the difference between 4x35 SM16 and 4x70 SM32?
And why do you say that inside the house it should be split into 5-core?

Thank you!