TECHNICAL 35
Hot water cylinder ( HWC ) installations explained using SANS 10254 ( Part 4 )
By
Patrick Gordon - Calafrica
The temperature pressure and safety valve are next under the magnifying glass in Patrick ’ s hot water cylinder series .
The next item in the water supply to the hot water cylinder ( HWC ) is the temperature and pressure safety valve ( TP & S ).
All HWCs must include a TP & S valve . In most HWC installations , it is very straight forward as to where the TP & S valve must be fitted on the cylinder . Where it becomes a bit more complicated is when it is a dual HWC – i . e ., it can be installed either horizontally or vertically .
On these cylinders , the one connection point is on the opposite side of the cylinder to the cold-water inlet ( A ), and the other is on the rounding of the HWC also on the side that is furthest away from the cold-water inlet ( B ).
SANS 10252 / 1 2018 : 6.6.1.6 Any temperature and pressure safety valve shall be installed within the top 20 % of water in the container , and not lower than 150mm from the top of the container . The thermal probe shall be situated in the zone of highest temperature .
Images supplied by Patrick Gordon
Another point that we should remember is that the hot-water outlet must always be at the highest point of the installation to ensure that no air can be trapped in the cylinder . If we look at the picture above , the TP & S and hot-water connections are correctly fitted .
However , if the HWC was installed in a vertical position , the hot-water connection would change to point A , and the TP & S will be at point B .
Remember that the discharge pipe from the TP & S valve must be metallic and may not be made from any other material .
If you have enjoyed this article , look out for the next article where we will discuss how the TP & S valve works .
For any further information on this topic please contact the writer : PA
If the reasoning behind the positions of the connections is understood , you will be able to connect the HWC correctly no matter what the connection configuration of that specific unit looks like . You will also be able to identify any non-compliant cylinders that do not have the correct connection configuration .
“ The hot water outlet must always be at the highest point of the installation .”
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July 2024 Volume 30 I Number 5 www . plumbingafrica . co . za