Identifying wiring issues in older buildings
Many flats and houses in the region still run on an installation built for two lamps and a radio. We show you how to read the condition of your system and when a renovation is really due.
The most important signs at a glance
In our assessments of older buildings in Rendsburg, the same five findings come up again and again — they can usually already be read off at the meter cabinet and the sockets.
Five findings that call for an inspection
- The meter cabinet contains rotary fuses with a porcelain head instead of circuit breakers for switching.
- There is no residual current device (RCD) — or just one for the entire flat.
- Sockets without an earth contact: two round holes without the side metal clips.
- Only one or two sockets per room, with power strips and extension cords used as a permanent solution.
- Switches and covers are yellowed, brittle or cracked; cables with a fabric or rubber sheath.
Age of the installation and typical construction periods
The year the house was built says less than the year the wiring was installed: many systems were extended once in the 1970s and have not been touched since.
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Before 1960: fabric cabling and classic earthing
Cables with a fabric or rubber sheath, often just two conductors without a protective earth. Sockets without an earth contact are the norm. A system from this period no longer meets current standards and is usually replaced completely.
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1960 to 1980: rotary fuses and little reserve
A meter cabinet with screw-out fuses, two to four circuits for the whole flat, residual current protection at most in the bathroom. Here, a staged renovation is often worthwhile: starting with the distribution board, then room by room.
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1980 to 2000: circuit breakers, but thin distribution
Circuit breakers are present, and usually a protective earth too. A typical weakness is the number of circuits and sockets — the kitchen and workspace are too sparsely supplied for today's appliances.
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From 2000: usually sound, often expandable
Residual current devices and sufficient circuits are standard. Instead of a renovation, this is usually about extensions: a wallbox, solar power, additional circuits, or an inspection of the existing system.
Signs in detail
Two places reveal the condition of a system fastest: the meter cabinet in the hallway or basement, and the sockets in the living area. You can look at both without any tools.
At the meter cabinet
- Rotary fuses with a porcelain or ceramic head that you have to turn to switch off — an indication of a distribution board built before 1980.
- No residual current device: if the wide switch with a test button is missing, nothing will trip in the event of a fault current through the body.
- Only two to four circuits for the entire flat — the cooker, washing machine and kettle then run, in effect, on the same line.
- Open terminals, a wooden board instead of a distribution box, or missing covers: live parts are exposed to touch.
- No current circuit diagram and no labelling of the fuses — in the event of a fault, you're left searching in the dark.
- No spare capacity in the distribution board: extensions for a wallbox or solar power cannot be added.
In the rooms
- Two sockets per room or fewer, plus permanently plugged-in power strips and extension cords under carpets.
- Sockets without an earth contact, recognisable by the missing metal clips above and below the socket rim.
- Brittle or yellowed switches that crack or wobble when pressed, or whose cover is cracked.
- Warm sockets or switches, brown discolouration at the edge, or a burning smell near the socket.
- Flickering lights when a larger appliance starts up — a sign of overloaded or overly long cables.
- A fuse trips repeatedly when the same appliance is switched on; if it is permanently bypassed, that is an acute risk.
- No protective earth in the bathroom, even though a washing machine or fan heater is run there.
- Lamp connections with only two conductors, often found in ceilings of living and bedrooms.
The fuse protects the cable, not you
A fuse element trips when the cable gets too hot. But if current flows through a person instead, it stays too low for that. Only a residual current device closes this gap — which is why a renovation of an older installation almost always starts at the distribution board for us.
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How we check the existing system
Whether an old building's electrical installation is still sound isn't decided at the fuse box alone. That's why we work in four steps: inspect, measure, document in writing, and only then renovate.
In an apartment, the inspection usually takes one to three hours; for multi-family houses, we schedule separate time slots for each residential unit.
We open distribution boards and individual sockets to see what is actually installed: conductor cross-sections, insulation, terminal points, fuse links instead of circuit breakers, missing protective earth conductors, classic neutral earthing (Nullung). We also note later additions from previous years, which are often the real weak point.
Using an installation tester, we measure insulation resistance, loop impedance and the continuity of the protective earth conductor, and trigger any existing residual current devices (RCDs) under controlled conditions. The measurement shows whether a cable is merely old or already electrically compromised — which is the decisive difference when it comes to cost.
You receive the results in writing, sorted by urgency: defects posing immediate danger, defects with a deadline, and recommended upgrades. This allows refurbishment work to be spread over several years and tenant changes, rather than having to tackle everything at once.
We usually refurbish section by section: first the meter cabinet and main supply line, then the circuits for kitchen and bathroom, followed by the living areas. Within each section, the power is generally only off for a few hours at a time, and the flat is usable again by evening.
Cost
What determines the effort involved
Two flats of the same size can differ significantly in refurbishment effort. It's rarely the floor area that's decisive, but the condition of the wiring routes. These are the points we look at during the survey, before we write a quote.
- Conduits already in place: If new cables can simply be pulled through, there's no need for chasing — the single biggest cost item in any renovation.
- Condition of the meter cabinet: If the meter cabinet needs to be brought up to today's standard, registration with the grid operator is also required.
- Number of circuits: Older flats often have just two to four circuits; today we calculate kitchen, bathroom and appliances separately.
- Occupied or vacant: In vacant flats we can work faster, without dust-protection walls and daily tidying up.
- Listed status and stucco: Surfaces worth preserving call for surface-mounted solutions or cable routing in the floor.
- Accessibility of the distribution board: If the sub-distribution board is in the hallway rather than behind a built-in cupboard, this shortens every future intervention.
- Preparation on your part: Clear access to walls, cupboards moved back, keys for the cellar and attic — this saves a measurable amount of working time.
- Desired extensions: We plan network sockets, outdoor sockets or a supply line for the wallbox in at the same time.
Unsure about the state of your electrics?
We'll take a look at your installation on site and explain what it shows.