19
Worked example of discharge pipe sizing
The example on page 18 is for a G½ Temperature Relief Valve with a discharge pipe (D2) having 4 No. elbows and length of 7m from the
tundish to the point of discharge.
From Table 5:
Maximum resistance allowed for a straight length of 22mm copper discharge pipe (D2) from a G
1
/
2
Temperature Relief Valve is 9m.
Subtract the resistance for 4 No. 22mm elbows at 0.8m each = 3.2m
Therefore the permitted length equates to: 5.8m
5.8m is less than the actual length of 7m therefore calculate the next largest size.
Maximum resistance allowed for a straight length of 28mm pipe (D2) from a G
1
/
2
Temperature Relief Valve equates to 18m.
Subtract the resistance of 4 No. 28mm elbows at 1m each = 4m
Therefore the maximum permitted length equates to: 14m
As the actual length is 7m, a 28mm (D2) copper pipe will be satisfactory.
INDIRECT MODEL
Boiler Selection
The MEGAFLO Eco Indirect models are suitable for use with most gas or oil fired boilers compatible with unvented systems i.e. fitted with a
temperature control thermostat and thermal cut-out. If in doubt consult the boiler manufacturer. Solid fuel boilers or any other boiler in which
the energy input is not under effective thermostatic control, unless additional and appropriate safety measures are installed, SHOULD NOT
be used. The boiler used can either be a sealed system or open vented type, maximum primary circuit pressure 3 bar. The primary flow from
the boiler MUST be pumped. Gravity circulation will not work due to the special design of the primary heat exchanger. It is recommended
that an air bleed point or automatic air vent is incorporated in the primary return pipework close to the MEGAFLO Eco unit. The boiler flow
temperature should usually be set to 82ºC (maximum flow temperature to primary heat exchanger 88ºC). The boiler cannot be vented through
the MEGAFLO Eco unit.
Indirect Thermal Cut-Out And 2-Port Motorised Valve
To comply with Building Regulations, and to prevent the MEGAFLO Eco from overheating the 2-port motorised valve supplied MUST be fitted
to the primary flow to the indirect coil (see Figure 11 below).
Figure 11 - Primary connections to indirect units
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