To correctly size your first stage module, you will need to identify both the potential number of dwellings and the maximum heat input, also known as ‘full load’, to each. We suggest the following heat input guidelines:

Table 1:

Based on the heat input guidelines provided, it is possible to calculate the maximum number of each type of property on full load which can be serviced by a first stage module of a given capacity:

Table 2:

As it is unlikely that all properties will be on full load at the same time, the following diversity factors can be applied:

Table 3:

If you have thirty holiday caravans, for example, it is reasonable to assume for the purposes of sizing your first stage module that only 21 (30 x 70%) will be on full load at any one time. Using table 2, 21 holiday caravans can be serviced by a 5m Btu/hr first stage module.