Water Temperature Protection; Flue Gas Outlet Cut-Out; Ionisation Pin; Safety Of The Installation - State Water Heaters SCE 80-115 Installation, User And Service Manual

2
2.4.1
Table 2.1 Temperature protection
Protection
Frost thermostat
Maximum thermostat
Safety thermostat
2.4.2
2.4.3
2.5 Safety of the
installation
2.5.1
16
Operating the appliance

Water temperature protection

The burner controller uses the frost, maximum and safety thermostat to monitor
three temperatures that are important in terms of safety.
Description
If the frost thermostat sensor y measures a temperature of 20°C or lower, the
appliance's warm-up cycle is started. See paragraph
the appliance'.
If the maximum thermostat sensor q measures a temperature, which is higher
than 84°C, the maximum thermostat opens. The heat demand ends and the
burner control stops the warm-up cycle until the maximum thermostat closes
again. Immediately the burner control resets the appliance and re-starts the
warm-up cycle. Maximum protection serves to prevent overheating and/or
excessive scaling in the appliance.
If the safety thermostat sensor p measures a temperature, which is higher
than 93°C, the safety thermostat opens. The heat demand ends and the
burner control immediately stops the warm-up cycle. A lock out fault occurs on
the burner control. This has to be manually reset before the appliance can be
put back into operation.

Flue gas outlet cut-out

The flue gases are drawn outside via the draught diverter b and the flue gas
outlet a. To prevent the flue gases from getting into the installation room, the
outlet for it is monitored by a so-called thermal reflux safety (T.R.S.) feature. For
this purpose a flue gas thermostat sensor m complete with flue gas
thermostat n is fitted in the draught diverter. Under normal circumstances this
sensor measures the ambient temperature. However, if it is not drawing
sufficiently (for example, due to a blocked chimney), the flue gases will 'return'
and flow back past the flue gas thermostat sensor. The sensor then measures
an excessive temperature and the flue gas thermostat opens. The heat demand
ends and the burner control immediately stops the warm-up cycle. A lock out
fault occurs on the flue gas thermostat. This has to be manually reset before the
appliance can be put back into operation.

Ionisation pin

To prevent gas flowing when there is no combustion, an ionization pin B is fitted.
The burner controller uses this pin for flame detection by measuring ionisation.
The burner controller immediately cuts off the gasflow as soon as it determines
that gas is flowing but there is no flame.
In addition to the standard safety monitoring of the appliance, the appliance
must also be protected by an expension vessel, pressure overflow valve, non-
return valve and a T&P valve.
Use of an expension vessel, a pressure overflow valve and/or a pressure
reduction valve depends on the type of installation: unvented or vented.

Unvented installation (sealed)

With an unvented installation, a pressure overflow valve and expension vessel
prevent excessive pressure in the tank. This prevents damage from occurring
to the enamelled coating (in the appliance) or to the tank. A non-return valve
prevents excessive pressure in the water supply system. This valve also
prevents water from flowing from the tank into the water supply system. The
pressure reduction valve protects the installation against an excessively high
water supply pressure (> 8 bar). These components are fitted to the cold water
pipe. See paragraph '3.6.1 Cold water
gis
Table 2.1
'2.3 Warm-up cycle of
side'.
Instruction Manual SCE