Redring DC3810 - Manual (Page 7)

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WORKED EXAMPLE:
The example below is for a G1/2 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 1
• Maximum resistance allowed for a straight length of 22mm copper discharge pipe (D2) from a
G1/2 temperature relief valve is 9.0m.
• Subtract the resistance for 4 No. 22mm elbows at 0.8m each = 3.2m
• Therefore the maximum 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 G1/2 temperature
relief valve equates to 18m.
• Subtract the resistance for 4 No. 28mm elbows at 1.0m each = 4.0m
• Therefore the maximum permitted length equates to 14m.
• As the actual length is 7m, a 28mm (D2) copper pipe will be satisfactory
HOT WATER OUTLETS
Dynamic pressure always drops across a system when more than one outlet is opened.
The unit has a working pressure of 3 bar.
Good system design should take this into consideration & pipe sizing should be in line with current
good practice.
In hard water areas a reduced operating temperature will help to prevent premature scaling.
EXPANSION VESSEL
The vessel (supplied loose) screws onto the top of the unit. It is sized appropriately and includes
some allowance for pipework. Check the charge is at 3.0 bar before commissioning.
The expansion vessel can also be fitted remotely between the unit and the check valve on the cold
supply or by adaptor to the top female fitting on the cylinder.
PRIMARY CIRCUITS
The maximum primary pressure is 3.5 bar.
The boiler must have a mechanical high-limit thermostat.
Solid fuel boilers cannot be used
If the primary circuit is sealed, an additional expansion vessel must be fitted.
If a secondary circuit is connected an additional expansion vessel may be required.
INSTALLATION
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