Protection for the solar heating system, 2gis – A.O. Smith 30 User Manual
Page 18
Working principle of the appliance
18
Instruction manual SGS
2
gis
2.5.2
Vented installation
With a vented installation, excess pressure is taken up by the open cold water
head tank. The height of the head tank determines the working pressure in the
water heater, which may not exceed 8 bar. The installation must also be fitted
with a vent pipe from the hot water pipe, that opens into the cold water tank.
Ideally, the vent pipe should discharge into a separate tundish/drain or
otherwise to the open cold water head tank. The water heater should also be
fitted on the hot water side with a stop valve
.
2.5.3
T&P valve
A T&P valve is only mandatory in an unvented installation. However, A.O. Smith
also recommends the use of a T&P valve in vented installations.
A T&P (Temperature and Pressure Relief) valve monitors the pressure in the
tank and the water temperature at the top of the tank. If the pressure in the tank
becomes excessive (> 10 bar) or the water temperature is too high (> 97°C), the
valve will open. The hot water can now flow out of the tank. Because the
appliance is under water supply pressure, cold water will automatically flow into
the tank. The valve remains open until the unsafe situation has been rectified.
The appliance is fitted standard with a connecting point for a T&P
valve
.
2.6
Protection for the
solar heating system
2.6.1
Drain-back tank
The solar heating system may optionally be equipped with a drain-back tank.
The tank fills itself with the heating fluid when there is no heat demand. This
avoids overheating of the solar heating system. The high insulation factor of the
tank also protects the system from freezing of the fluid. The use of the drain-
back tank also serves to extend the useful life of the fluid.
The presence of a drain-back tank is set
(12.8.1 "Setting the drain-back tank")
during the installation. Refer to the solar heating system manual for more
details.
2.6.2
Fluid temperature
The heat exchanger of the solar heating system may be filled with glycol. If the
temperature of the heating fluid is too high, a signal is sent to the controller of
the solar collector and the pump of the solar collector is switched off. This signal
is passed to the controller by temperature sensor S
1
.
At present, no heating fluids other than glycol are supported. The heating fluid
type is set
(12.8.2 "Setting the heating fluid type in the solar heating system")
during installation.
Temperature protection for solar heating system
Protection
Description
Maximum temperature S
1
, if solar
heating system is filled with
glycol:
- S
1
> 130°C
The pump of the solar heating system
switches off when the temperature of the
heating fluid at S
1
exceeds the maximum
value. The solar heating system enters
error mode. The error is also visible on the
display of the SGS appliance