Safety Of The Installation - A.O. Smith TWI 35-130 Instruction Manual

2
2.5

Safety of the installation

14
Operation of the device
Apart from the standard security of the device, the installation shall further be
protected using an expansion vessel, an expansion valve, a pressure reducing
valve, a non-return valve and a T&P valve.
The use of an expansion vessel, expansion valve and/or pressure reducing
valve is dependent on the type of installation: unvented or vented.
2.5.1 Unvented installation
With an unvented installation an expansion valve and an expansion vessel
avoid a too high pressure in the tank. This prevents damage to the tank.
A non-return valve avoids a too high pressure on the water piping. This valve
also avoids water from the tank fl owing into the water piping. The pressure
reducing valve protects the installation against a too high water piping pressure
(> 8 bars). The parts are mounted into the cold water system
side").
2.5.2 Vented installation
With a vented installation the open water tank absorbs the overpressure. The
height of the water tank determines the maximum operating pressure in the
tank. The maximum operating pressure is 8 bars. The installation shall also be
equipped with an expansion valve of the hot water piping that fl ows out into the
water tank. In the ideal situation this should fl ow out in a separate discharge
channel, otherwise in the open water tank. The device shall also have a stop
valve on the water side
2.5.3 T&P valve
A T&P valve is only obligatory with unvented installations. However, A.O.
Smith recommends using a T&P valve with vented installations as well. A
T&P valve (Temperature & Pressure valve) monitors the pressure in the tank
and the water temperature at the upper part of the tank. The valve will open
when the pressure in the tank becomes too high (> 10 bars) or when the water
temperature gets too high (> 97°C). The hot water can now fl ow out of the
tank. As the device is under water piping pressure, cold water will automatically
fl ow into the tank. The valve remains open until the unsafe situation has been
removed. The device typically has a connecting point for a T&P valve
"Hot water side").
(3.6.2 "Hot water side").
Instruction manual TWI 35-130 G/TWI 45-190 G
(3.6.1 "Cold water
(3.6.2