Unvented Installation - Lochinvar CHA 100 G CE Installation, Commissioning, User & Maintenance Instructions

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2.4.4
2.4.5
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Working principle of the water heater
However, if the chimney is not drawing sufficiently (for example, due to a
blockage in the chimney), the flue gases will 'reflux' and flow back past the flue
gas thermostat sensor. The sensor will then detect an excessive temperature
and the flue gas thermostat will open. The demand will cease, and the burner
control will immediately stop the heating cycle. The flue gas thermostat will also
lock out. It must be manually reset before the appliance can resume operation .
Flame probe
To ensure that no gas can flow when there is no combustion, the water heater
is fitted with a flame probe (21). The burner control uses the ionisation-detecting
properties of this probe for flame detection. The burner control closes the gas
valve the instant it determines that there is a gas flow but no flame is present.
Safety of the installation
In addition to the appliance's standard built-in safety monitoring, the appliance
must also be protected by an expansion vessel, expansion valve, pressure
reducing valve, non-return valve and a T&P valve.
The use of an expansion vessel, expansion valve and/or pressure reducing
valve depends on the type of installation: unvented or vented.

Unvented installation

With an unvented installation, an expansion valve valve and expansion vessel
prevent the buildup of excessive pressure in the tank. This prevents damage
being caused to the enamelled coating (in the appliance) or to the tank. A non-
return valve prevents excessive pressure buildup in the water supply system.
This valve also prevents water from flowing backwards from the tank into the
cold water supply system. The pressure reducing valve protects the installation
against an excessively high water supply pressure (> 8 bar). These components
are fitted to the cold water pipe
Vented installation
With vented installation, excess pressure is taken up by the open cold water
head tank. The head height of the 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
into the cold water tank.
T&P valve
A T&P valve is only mandatory in an unvented installation. However, the
supplier 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 (3.7.3 "Hot water side").
gis
(3.6 "Vented water connections").
(3.6.3 "Hot water side"), which opens
Instruction manual CHA