Part P Consumer Unit Replacement

Question 1

Why was consumer unit replacement made notifiable work under Part P?

Accepted Answer

Because a consumer unit is the main protection and control device for the entire installation, and incorrect replacement could leave the whole property unsafe

Answer

Because it requires planning permission

Answer

Because only the electricity supplier can replace consumer units

Answer

Because consumer units must be approved by the local authority

Question 2

What does BS 7671 18th Edition require all new domestic consumer units to be made from?

Accepted Answer

Non-combustible material (metal enclosures)

Answer

Plastic (to prevent shock hazard)

Answer

Any material rated to 850°C

Answer

Any material if the consumer unit is less than 100 A

Question 3

When replacing a consumer unit, what additional work is required under current regulations?

Accepted Answer

The existing installation must be inspected and tested; the earthing and bonding must be verified (and upgraded if deficient); an EIC must be issued

Answer

No additional work is required beyond fitting the new consumer unit

Answer

Only the new consumer unit needs to be tested, not the existing installation

Answer

The entire installation must be rewired before a new consumer unit can be fitted

Question 4

What type of consumer unit is now considered best practice for new domestic installations?

Accepted Answer

A fully RCBO-equipped consumer unit (one RCBO per circuit) or a consumer unit with at least two RCDs (split-load) protecting all circuits

Answer

A rewirable fuse board with no RCDs

Answer

A single-RCD consumer unit with all circuits on one RCD

Answer

A consumer unit with only MCBs and no RCDs

Question 5

What is the purpose of the main switch in a new consumer unit?

Accepted Answer

To provide a means of isolating the entire installation from the supply for maintenance and emergency isolation

Answer

To control all RCDs simultaneously

Answer

To protect the installation from overloads

Answer

To control the electricity supply to the meter

Question 6

What is the typical rated current for the main switch in a single-phase domestic consumer unit?

Accepted Answer

100 A

Answer

32 A

Answer

63 A

Answer

230 A