Power Module Help

The most common reason for a CMD power module to stop working is that the fuse has ‘blown’ in the socket.

Fuses can blow for numerous reasons which are triggered when an appliance draws an excessive current. Some examples of this include mismatched loads, short circuits, device failure and overloading. The fuse blows to prevent damage in the appliance such as overheating or even a fire.

CMD manufacture products that are designed to meet the requirements of British Standard BS 6396:2008 Electrical Systems in office furniture and education furniture. In order to meet this standard CMD’s power modules have individual fused sockets, rated at either 3.15 or 5 amps.

Purpose of the fuse

The individual fusing of power sockets is a safety feature of CMD’s power modules, which is a deliberate weak link in a circuit which will blow if the connected device draws too much current. CMD use Bussmann Anti-Surge fuses as most equipment requires a higher current for a short time on start-up and these anti-surge fuses will withstand short term surges greater than their current rating. The fuses are manufactured in compliance with BS EN 60127-2.

Changing the Fuse

The fuse is accessible from the fuse drawer on the front of the socket fascia (see below).

The correct fuse to use is; Cooper Bussmann 5 x 20mm Time-Delay, Ceramic Tube Fuses S505 Series either;

  • 3.15 Amp (S505-3.15-R)
  • 5 Amp (S505-5-R)

CMDs power modules DO NOT USE GLASS TYPE FUSES. Installing glass type fuses will stop the power module from functioning correctly and potentially cause damage to the power module.

The fuse rating required can be seen on the front of the fuse drawer. These fuses can be purchased directly from CMD or an electrical wholesaler.

How to replace a fuse

Why do my fuses keep blowing?

CMD’s power modules meet the requirements of BS 6396:2008 and are designed to power office equipment with some exclusions such as laser printers, laminators and photocopiers.

The table below shows the typical current ratings of common equipment that may be used in an office environment. Items highlighted in green are suitable to be plugged into a CMD power module. Items highlighted in red are typical sources of fuses blowing as they are drawing more current.

These devices should not be plugged into CMD power modules.

Equipment (Amp rating)

  • Computer Monitor (<0.5A)
  • Desktop computer (3.0A)
  • 60W Desk lamp (<0.5A)
  • Laptop Charger (<0.5A)
  • Mobile phone charger (<0.5A)

Equipment (Amp rating)

  • Vacuum cleaner (9A)
  • Electric radiator (8.5A)
  • Kettle (13A)
  • Toaster (9A)
  • Hair dryer (10A)

Source: Electrical Safety First

The two tables above are a selection of equipment which can and cannot be plugged in to a CMD power module. This, however is by no means a comprehensive list. For each 230 Watts, a 1 Amp current is drawn. Under BS 6396:2008 Electrical Systems in office furniture and education furniture, any electrical item that requires more than 5 Amps must be connected directly to its own 13 Amp wall socket.


We manufactures a range of office power solutions to meet your requirements, and our sales team are able to assist in helping you choose the right solution. Give us a call on 01709 829511 or email us to find out how we can help.

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