Diversity
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Diversity in this context is all about how one establishes the maximum demand for an electrical installation or an electrical circuit. The guidelines shown here are some of those as presented in the On Site Guide. Note however that these are just that - guidelines. They are based on statistical probabilities and typical usage. As a circuit or installation designer you may choose to make less flexible assessments of current demand based on your knowledge of the actual installation.
Note also that the figures presented here are for domestic properties only.
Allowances at point of use
When assessing the current demand at a point of use, the following guidelines can be used:
| Point of use / appliance | Current demand to be assumed |
|---|---|
| Other Socket outlets (i.e. not 2A or 13A) | Rated current of the socket |
| 2A Sockets | at least 0.5A |
| Lighting outlet | actual rating of lamp or 100W (whichever is greater) per lamp holder. For circuits supplying only discharge lighting, then use 100% of the total load including any control gear and any reactive/harmonic currents. If the Power factor of the lighting units is unknown, then use the VA rating times 1.8 |
| Shaver socket, bell transformer,
electric clock point, or any appliance under 5 VA |
May be neglected for the purposes of assessment. |
| Cooking appliance | 10A of total load plus 30% or remainder. Add additional 5A if cooker point socket is fitted. |
| All other fixed equipment | Use nominal current as specified on the appliance ratings plate. |
Allowances for Diversity
| Purpose of circuit | Diversity applicable (domestic) | Notes |
|---|---|---|
| Lighting | 66% of total current | |
| Heating and Power | 100% of total demand up to 10A, + 50% of the remainder. | Where space heating is connected to a general purpose power circuit. |
| Cooking appliances | 100% of total demand up to 10A, + 30% of the remainder. | Add a further 5A if a socket is fitted to the cooker point. |
| Water heaters (instant) | 100% of first appliance, 100% of second, and 25% of any remaining appliances. | |
| Water heaters (storage) | No diversity allowable | |
| Under floor heating | No diversity allowable | |
| Storage Heaters | No diversity allowable | |
| Standard Circuits | 100% of current demand of largest circuit. + 40% of demand for every other circuit. | These are standard final circuits as described in appendix 8 of the OSG |