Velux TFF 200 Directions For Use Manual page 8

SECTION I: TANK INSTALLATION
Typical discharge pipe arrangement
Safety device
(eg. temperature relief value).
500 mm maximum
300 mm minimum
Metal discharge pipe (D2) from tundish, with
continuous fall.
See Building Regulation G3 section 3.9d i-iv,
Tabel 4 and worked example.
2.3.1 Sizing of copper discharge pipe 'D2' for common temperature relief valve outlet sizes
Valve Minimum size of
outlet size discharge pipe D1*
G½ 15 mm
G¾ 22 mm
G1 28 mm
8 VELUX
Metal discharge pipe (D1) from temperature relief
valve to tundish.
Tundish
Minimum size of Maximum resistance allowed,
discharge pipe expressed as a length of straight
D2* from tundish pipe (ei. no elbows or bends)
22 mm
28 mm
35 mm
28 mm
35 mm
42 mm
35 mm
42 mm
54 mm
Discharge below fixed grating
(Building Regulation G3 section
3.9d gives alternative points of
discharge).
Resistance created by
up to 9 m
up to 18 m
up to 27 m
up to 9 m
up to 18 m
up to 27 m
up to 9 m
up to 18 m
up to 27 m
Fixed louvred grating
Trapped gully
each elbow or bend
0.8 m
1.0 m
1.4 m
1.0 m
1.4 m
1.7 m
1.4 m
1.7 m
2.3 m