Home Office Design

It has previously been mentioned that some or maybe many domestic dwellings will have a home office or study which is also used as a home office. Note for taxation purposes a room should not be dedicated as an office, if it is then it attracts council tax at a different rate to the rest of the dwelling and any waste generated in that office has to be disposed of by utilising a commercial waste disposal company not the council domestic waste disposal services, which are included in the domestic council tax. Put a television in the 'office' and it becomes an office/entertainment room and council tax is due at the domestic rate.

The electrical services for a home office should follow the general principles laid down previously however there needs to be some additional considerations, where the work done in the office is computer based and a failure of the electricity supply may cause loss of income a UPS system should be given serious consideration. There are a number of types of UPS the cheapest are the standby type which has the normal supply connected to the load via a transfer switch which upon failure of the normal supply transfers the load to a battery inverter system, the problem with this type is that until the supply fails it will not be known if the transfer switch and inverter system are working, there is also a delay in power being switched from the normal supply to the standby supply. There are variations on the standby type however everyone suffers from the change-over delay. The best and needless to say most expensive is the double conversion type where the normal supply is converted to dc which is used to charge the battery and to supply the inverter which converts the dc to mains voltage ac, with this type a failure of the normal supply will cause a seamless transfer to the battery supply.

If it is determined that a UPS is required the question of it's capacity and size and how to integrate the unit into the distribution system has to be considered. Before the capacity can be determined there is the question of what is to be supplied by the UPS? The obvious answer is the computer and it's associated screen, great, but what about the modem, routers and switches that form the pathway to the internet and do you need the lighting in the office to be supported. The reality is that a computer and it's screen will have a load of approximately 750VA, a modem 10VA, router 12VA, switch 20VA and printer up to 800VA, then there are the auxiliary services such as the lighting that load will be dependant on the number and types of luminaires, at this stage a 60VA load should be assumed; this gives a total load of 1652VA if the printer is to be included or 852VA if it is not. It would be prudent to request of the client whether other equipment and appliances should be fed from the UPS those items should be added to the 'office' load to determine the UPS output. Once the output level has been determined the next step is to determine the autonomy, the support time, of the UPS; most UPSs can accomodate different battery sizes to suit the required autonomy, however as the autonomy time increases so does the battery cost. The output and autonomy can now be determined and thus the cost, next options should be considered, for example should all the lighting circuits be fed via the UPS, should the television system be fed via the UPS, should the central heating system be fed via the UPS etc. Having determined the revised load the cost can be finalised.

If the consumer unit is a three phase MCB board, although configured for a single phase supply, then phase L1 can be used to feed the non-UPS supported fixed appliance supplies, phase L2 can be for the non-UPS supported socket outlets and lights and phase L3 for the UPS supported fixed appliances, socket outlets and lights.