TECHNICAL
87
SANS 10254 and under-
counter water heaters
The problem facing many installers is how to get hot water to
isolated terminal points. This is especially so where you need to
eliminate long dead legs.
By Patrick Gordon
The current solution is to use a small under-basin/sink
geyser. The problem that faces the installer is how to
install the unit in compliance with SANS 10254. Why
would this be a problem?
SANS 10254 requires that all pressurised hot water
vessels be installed with five basic ancillaries: 1) T&P
safety valve; 2) Pressure reducing valve; 3) Expansion
relief valve; and 4) Two vacuum breakers. Anybody that
has ever installed one of these units will know that it
is virtually impossible to do so. It is however possible
to install it according to SANS 10254 as an open-vent
system. This means that at all times the internal pressure
in the heater will be open to vent to the atmosphere. This
can only be achieved by using a specially designed mixer
or connection convention.
a mixing control valve unit of a type shown in
Figures 1 and 2.
NOTE 2: The drip tray is not required for over-basin
(such as a sink or bath) installations.
NOTE 3: The cold water supply connection between