Stockmore Street - Regulations and loading
This week the Carma UK Electrical Services Team have been back at our ongoing project at Stockmore Street.
The current stage of the project is completed the first fix of a full rewire of the existing property and extension of the wiring system to accommodate the new built space.
A snap shot of regulations to consider.
As they have no kitchen going in until a later date, the team have been future proofing for that date. Sockets and switches have been put in to regulation height of 450mm minimum for sockets and 120mm to the top of the switches. This is to aid people with disabilities. This is part of the building regulation requirements for all installations in the UK. There are 12 parts to the building regs that apply the electrical work. Part A-R. Part P is probably the most recognised as this is what is used to notify building control when any notifiable work has been carried out e.g. the installation of a new circuit, replacement of a consumer unit and any work in a special location (mainly bathrooms). Part M of the building relates to access to and use of buildings. This is where heights of sockets and switches also consumer units applies. Also on a rewire like this part A structure has implications related to depths of chases in walls, size of holes and notches in floor and roof joists.
a. Maximum diameter of hole should be 0.25 x joist width
b. Holes on centre line in a zone between 0.25 and 0.4 x span
c. Maximum depth of notch should be 0.125 x joist depth
d. Notches on top in a zone between 0.07 x 0.25 x span
e. Holes in same joist should be at least 3 diameters apart
All these regulations need to be considered through an installation which is why it is important to have work carried out by a qualified electrician.
Air Source Heat Pumps and circuit loading.
As with many projects there are often changes that occur on site as a project develops and the space is realised for the client. Changes to an electrical design on site requires careful thinking and planning regarding new cable routes, switch positions, overall cable lengths and loading and implications for the distribution board along with the mains supply to the property.
More and more projects and clients are opting to upgrade their central heating system replacing traditional gas boilers with Air Source Heat Pumps. These heat pumps add an additional high load to the electricity supply to the property. A major consideration clients should be made aware of before opting to pursue this route is will adding the new load increase the required capacity of the mains supply beyond that installed.
For example, most UK single dwellings have a single phase power supply with a 100amp rating. This means should the property draw more electricity (current) that 100amps, the fuse will begin to burn and fail to protect the mains supply cable. Often adding an air source heat pump to an existing property will exceed this supply rating.
The options that must then be considered are as follows:
1 – Keep a gas boiler. This will not increase the load on your property, and may provide enough spare capacity to add a modest electrical car charger when the opportunity arises.
2 – Review the entire electrical system within the property, and see if any circuits can be safely down rated to a lower current rating in the hope this will leave enough capacity for the additional air source heat pump.
3 – Upgrade your single phase supply to the property and consumer unit to a three phase supply. Often domestic 3 phase supplies will have a maximum current rating of 300amps or 3x the previous capacity.
There are of course cost implications for any of these options with option 3 likely being the most expensive, but perhaps the best approach long term. Often the cost amounts to £5-10k as a minimum which you have to weigh against your long term heating bill savings and the impact on the environment.