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operation manual

Applications of the power distribution boxes

Our mobile power distribution boxes have been designed especially for use on construction sites, on stage and in the TV, film, and entertainment industries.

With an enclosure made from THERMOLENE® – an exceptionally rugged material – they are extremely reliable, even under harsh operating conditions, at extreme heat, heavy rain and prolonged full load.
THERMOLENE® stands for exceptional ruggedness. Rounded edges further increase the boxes’ resistance to harsh handling. The low thermal resistance of THERMOLENE® ensures optimum heat dissipation, allowing safe and reliable operation even at prolonged full load (see section “Ambient temperature”).
Extremely rugged, large cable clamps prevent supply cables being pulled out, even when a high force is applied. The solid rubber-encased steel handles are impossible to break or pull out. Some of the handles are incorporated in the enclosure.
The boxes are designed and manufactured in conformance with the Low Voltage Directive.
The normative documents are:
BS EN 61439-1        Low-voltage switchgear and control-gear assemblies. General rules    
BS EN 61439-4        Low-voltage switchgear and control-gear assemblies. Particular requirements for assemblies for construction sites (ACS)
Further applicable specifications are the provisions of the employers’ liability insurance association:
BS 7909:2008          Code of practice for temporary electrical systems for entertainment purposes
BS 7671                  Requirements for Electrical Installations

Inspection before each use

Before taking the equipment into operation, perform a visual inspection. Pay special attention to any damage of the protective covers for the SCPD (short-circuit protective devices), residual-current devices, sockets, and (if fitted) the connectors for control units, the connecting cable including anti-kink sleeve and the enclosure.
In your own interest, please replace any defective components immediately. Missing socket covers, for example, can lead to corrosion of the contacts, resulting in overheating of the contacts and consequently fusing of the insert. Defective components must be replaced with identical parts according to standard BS EN 61439-1. Repair work must then be carried out by electricians or under supervision and instruction of an electrician.
After a completed repair, check the electrical safety of the distribution box.
Any existing residual current devices must be tested for correct functioning by pressing the test button before each use or hire.
If a distribution box has been stored for a longer period, test the RCDs’ tripping times with a suitable tester before putting the box into operation again. The test instrument for testing the RCD should be capable of applying the full range of test current to an in-service accuracy as given in BS EN 61557-6.

Network configuration (type of earth connection)

Our mobile distribution boxes are generally laid out for a TN system.

PAT testing

Pat testing or portable appliance testing is an important part of any health & safety policy.
The Health & Safety Executive states that 25% of all reportable electrical accidents involve portable appliances. The Electricity at Work Regulations place a legal responsibility on employers, employees and self-employed persons to comply with the provisions of the regulations and take reasonably practicable steps to ensure that no danger results from the use of such equipment. This in effect requires the implementation of a systematic and regular program of maintenance, inspection and testing. The Health & Safety at Work Act (1974) places such an obligation in the following circumstances:
  • Where appliances are used by employees.
  • Where appliances are supplied or hired.
  • Where appliances are repaired or serviced.
The test intervals should be specified so that any likely faults can be identified on time. According to the „IEE Code of Practice for In-Service Inspection and Testing of Electrical Equipment“  the frequency of inspection and testing of portable equipment should be as follows (industrial use )


Formal visual inspection


every 3 month   (recorded)

Combined inspection
and testing

distribution boxes up to 18 kg

distribution boxes over 18kg

every 6 month   (recorded)  

every 12 month (recorded)  

Please note that all distribution boxes exceeding 18 KG are rated as movable equipment.

Ambient temperature, thermal load and load factor

The power distribution boxes are designed for operation under continuous load at an ambient temperature of 30 °C. Depending on the distribution boxes’ design, protection class and equipment level, it can reach an internal temperature of between 50 and 70 °C. To reduce the mutual magnetic interference of the MCBs and ensure optimum ventilation, we fit special filler pieces between the MCBs.

Load factor of the power outlet circuits

Due to the distribution boxes’ internal temperature, an outside temperature of 30 °C results in an average load factor of 0675 per circuit. In the worst case*, the rated currents for the individual power outlet circuits are:
(*worst case= ambient temperature over 35 °C, MCB/RCD fitted without filler pieces, with closed protective cover over MCB/RCD.

Load Factor

Rated current of connector

Rated current without and

with filler piece between MCBs

16 A

10.8 A

11.9 A

32 A

21.6 A

23.9 A

63 A

42.5 A

47 A

125 A

84.37 A


The ambient temperature limit of our distribution boxes is 45 °C. The rated diversity factor is 0.60. Please contact us if you intend to use your distribution box at higher temperatures. We will then determine the individual rated diversity factor.

Usage location – weather resistance:

Observe the protection classes on the nameplate. Distribution boxes with a protection class of less than IP44 must be used only in dry conditions.
Distribution boxes of series 11 and 12 with protection class IP44 must not be used with the side containing the power sockets facing upwards under damp or wet conditions or outdoors.
All other series can – unless the nameplate does not indicate a protection class less than IP44 – be used outdoors, also in adverse weather conditions. Note that the distribution boxes must not stand in puddles that are more than 20 mm deep.
To prevent the inner heating up further through sunlight, the distribution boxes should, where possible be placed in a shady location.
Do not place the distribution boxes with the fuse side directly against a wall, as this impairs heat dissipation from the built-in short-circuit protective devices (SCPD).
For distribution boxes mounted in flight cases, the same limitations regarding their usage location apply. Note, however, that the flight case is made of wood and may swell when exposed to moisture.
All distribution boxes can be used at an altitude of up to 2000 meters above sea level.
Our distribution boxes are designed for pollution degree 3 (industrial environments). They therefore fulfil also all requirements for pollution degrees 1 and 2.
Our distribution boxes are designed for EMC Environment B (public low-voltage mains supply).

Mechanical influences

Our distribution box housings are made from THERMOLENE®.
THERMOLENE® housings fulfill the requirements for the highest specified protection class IK10 (BS-EN 62262: impact energy of 5 kg at a drop from 400 mm height)

Insulation Test

BS 7671 requires that  insulation resistance is measured between all of the live conductors and between the live conductors and with the protective conductor connected to the earthing arrangement .
The electronic components of the mobile distribution boxes, such as phase indication lamps, measuring devices,
RCBOs (one space unit only), and pilot or indication lamps, can incur damage at test voltages => 500V and will falsify the reading. They must therefore be disconnected or the series-connected pico fuse removed.
The active conductors can be electrically connected with each other and tested against PE. In this case the electronic devices do not have to be disconnected.
Insulation resistance measurements are meaningful for the total circuit only when all switching elements in the circuit are closed.

Residual-current protection

All distribution box sockets of or with less than 32 A must be protected with residual current devices with a tripping current of no more than 30 mA.


Transient overvoltage can be the reason for malfunction of electronic components, such as measuring devices and electronic RCDs.
Transient overvoltage can be caused by:
● Electrostatic discharge
● Switching off especially inductive loads
● Lightning strike in the vicinity
● Switching operations in the power grid (surge, pulse rise times of several µs, pulse duration of several 10 µs)
By default our distribution boxes are not protected against transient overvoltage. Should defects on any installed instruments frequently occur or if the power outlet circuits are to be subsequently protected against transient overcurrents, most distribution boxes can simply be fitted with Class 2 overcurrent diverters. In this case, the varistors of the overcurrent diverters must be tested at regular intervals.

Occasional over voltages

Our distribution boxes tolerate short overvoltage (current impulses) of up to 1 kV.

Short-circuit rating

The short-circuit strength of our distribution boxes is:

Short-circuit strength

16–125 A

6–10 kA

160 A

16 kA

250–400 A

20 kA

In most cases, this short-circuit rating is sufficient for mobile distribution boxes.
When feeding distribution boxes from low-voltage transformers with very short cables to the main distribution box, a higher short-circuit current may flow. In this case the current limitation capability of the distribution box’s main fuse may not be sufficient. The short-circuit current must then be calculated under the actual operating conditions.

Transportation and storage

For transportation and storage the distribution boxes can be stacked. Make sure, however, that the protective covers of the built-in electrical protection devices, the covers of the fitted earth contacts and CEE sockets and any sockets for control units do not become damaged.Store the mains cable in such a way that it and its anti-kink sleeve cannot be kinked or trapped during transport. Also make sure that the plug is protected against damage.

Connection extension leads

To prevent thermal overload of the sockets, the connection leads of the connected consumers must have the legally specified cross-section.

Cross Section

16 A 3-pin

1.5 mm²

16 A 5-pin

2.5 mm²

32 A

6.0 mm²

63 A

16.0 mm²

125 A

Min. 35.0 mm2

At longer lengths and under unusual environmental conditions the reduction factors specified in the relevant IEE Wiring Regulations must be applied.

Passed-through sockets

The sockets of some of our power distribution boxes are protected with a rated current equal to the rated current of the input plug, and not with an SCPD (short-circuit protective device). When connecting two distribution boxes in series, make sure that the total supply cable lengths of the distribution boxes does not exceed the permissible supply cable length.

Warranty Conditions

The mobile distribution boxes are manufactured according to the applicable directives, standards and regulations.
As part of final inspection and testing, the required inspections and tests are performed on all distribution boxes and recorded. This ensures that all products are built to the same, high quality standard.
Should a supplied product not meet safety or quality requirements, we will repair or replace it free of charge under the legally applicable warranty conditions. Any fault must be reported immediately and no later than three days after receipt of the product.
The warranty applies only if the product is used for its intended purpose and under the specified operating conditions.

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