1. A boiler or an appliance must comply with the useful efficiency requirements—
(a)at rated output (that is operating at rated output Pn expressed in kW, at an average boiler-water temperature of 70 degrees C); and
(b)at part load (that is operating at 30 per cent part load, at an average boiler-water temperature which varies according to the type of boiler),
set out in the table in paragraph 2.
2. The table referred to in paragraph 1—
| Type of Boiler | Range of power output | Efficiency at rated output | Efficiency at part load | ||
|---|---|---|---|---|---|
(1) Including a condensing boiler using liquid fuels | |||||
(2) Temperature of boiler water supply | |||||
| kW | Average boiler-water temperature expressed in degrees C | Efficiency requirement expressed in percent | Average boiler-water temperature expressed in degrees C | Efficiency requirement expressed in per cent | |
| Standard | 4 to 400 | 70 | Greater than or equal to 84+2 log Pn | Greater than or equal to 50 | Greater than or equal to 80 + 3 log Pn |
| Low temperature(1) | 4 to 400 | 70 | Greater than or equal to 87.5+1.5 log Pn | 40 | Greater than or equal to 87.5 + 1.5 log Pn |
| Gas condensing | 4 to 400 | 70 | Greater than or equal to 91 + 1 log Pn | 30(2) | Greater than or equal to 97 + 1 log Pn |
3. A boiler or an appliance with a dual function of—
(a)heating premises; and
(b)providing sanitary hot water,
must comply with paragraph 1 to the extent of the heating function only.
4. A boiler which is—
(a)a back-boiler; or
(b)a boiler designed to be installed in the living space,
must be treated as a standard boiler but its efficiency at rated output and part load may be 4 per cent less than shown in the table in paragraph 2.