ᐅ Temporary construction power: What type of cable is sufficient?

Hello,

we need to cover a distance of 40-50m (131-164 feet) to reach our plot. An early temporary power connection is not feasible timing-wise, so we have to pull a cable. Now I am wondering whether 5x16mm² (5x0.63 inch²) is sufficient or if it must be 5x25mm² (5x0.98 inch²). I have browsed various sites but am still not quite sure.

For construction, we require 1x63A and 2x32A.

Thank you very much

It was similar for us: for 50 meters (about 165 feet) plus two bends, totaling around 80 meters (about 260 feet), the general contractor planned to use 5x16mm² cables.

A friend who is an electrical engineer recalculated.

For our single-family house, including a sauna, electric stove, large cooktop, heat pump, electric car preparation, washing machine, dryer, and dishwasher, the calculated voltage drop was too high (allowed up to 2%). His recommendation, with some safety margin, was 5x35mm². When comparing cable prices, we ultimately decided on 5x50mm².

That might seem a lot today, but it could be different in 20 years.

Ok thanks, but for us, the temporary setup is really only for the construction power, not for the operation of the house. The line will be laid underground by then. We need about 12-16 weeks for this temporary solution :/

Our contact person was the electrician from the general contractor, who decides what is necessary.
If you have to pay for both the construction power cable and the house cable,
I would only get the latter and then have it rewired.

Nida35a schrieb:

It was similar for us: for 50m (164 feet) and two corners (a total of about 80m (262 feet)) the general contractor planned 5x16mm2 cables. A friend who is an electrical engineer recalculated. In our single-family house with a sauna, electric stove, large cooktop, heat pump, EV charging preparation, washing machine, dryer, and dishwasher, the calculated voltage drop was too high (allowed 2%). His recommendation was 5x35mm2 for a margin, but when comparing cable prices, we decided on 5x50mm2.

That sounds like an unrealistic desk engineer trying to apply their textbook knowledge here. Reality and practice diverge drastically at the moment when in your household all the stove burners, oven, dryer, dishwasher, sauna are running simultaneously, the heat pump operates at full load, and the electric car is charging.

In that case, the calculated voltage drop is too high? And for that, you’re installing a bigger cable?

This is honestly the worst nonsense I’ve read in a long time. I hope you deduct the extra cable costs from the engineer’s birthday gift budget. I hope he lives long enough to compensate for this unnecessary expense on your side.

Bauenaberwie schrieb:

To bridge the 40-50m (130-164 feet) distance to our plot.

Now I’m wondering if 5x16mm² (5x0.021 square inches) is sufficient or if it has to be 5x25mm² (5x0.039 square inches).

We need 1x63A and 2x32A for the construction site.

Now, back to your question:
It’s not possible to answer with the information provided.
I assume the construction site requires 63A and 2x32A connections for the temporary power distribution.
However, you shouldn’t assume that all connections will continuously be loaded at their maximum capacity. (This was the mistake the electrical engineer made in the example above.)
The real question is what equipment will be operated. For example, if you have a crane, it will get a 32A connection by itself. But usually, the crane only rarely draws the full rated current—only when lifting a heavy concrete bucket or similar and simultaneously rotating and moving. Even then, it typically draws about 25A rather than 32A.
The same applies to all other connected devices. Very few will run at full load continuously.
You need to consider what you really need on your construction site and be a bit realistic when assessing the load.

Example:
Crane: 25A (not continuous)
Screed pump: 55A (only for certain periods on site, but runs for an extended time)
Multiple drying units with 4A each = 12A continuous
Hand tools, circular saws, and other small devices add another 5A.

In total, that’s 25A + 55A + 12A + 5A = 97A, roughly 100A.
Because these loads won’t all operate simultaneously, you can assume a maximum load of about 80A. This already covers the extreme case of crane and screed pump running at the same time.

If the cable is not buried underground, a 5x16mm² (5x0.021 square inches) cable is sufficient. It can handle a continuous load of 85A, and the crane will not run continuously anyway.
For comparison: a 25mm² (0.039 square inches) cable under the same installation conditions can carry about 110A, which you typically won’t need for a normal construction site.

If I were you, I would lay two cables of 5x6mm² (5x0.009 square inches) each. This is generally cheaper than a 16mm² cable and can carry a total of 92A.

For the installation, of course, a friendly and competent electrician will assist you.