Rheem 874W27NF Service Manual page 11

Burner Manifold: The manifold consists of an aluminium die-casting sealed with a
press-formed steel plate and cork gasket. Cast galleries convey gas from the staging
solenoid valves to the injector orifices, which are machined into the side of the manifold that
faces the burner venturis.
Gas type connector - Removable electronic chip that programs the fuel type, product type
and model number.
Overheat Limiter - A plastic film that is wrapped around the combustion chamber and is
printed with a conductive path that is connected to the control system. In the event of
excessive temperature external to the heat exchanger, the conductive path will be broken
and the water heater will shut down.
Heat Exchanger – Consists of a number of finned copper tubes that cross the top of the
combustion chamber and absorb heat from the flue gases and transfer it to the water that is
passing through the tubes. There are nine copper tubes each with an outside diameter of
16mm and a wall thickness of 0.7mm. Each tube has 0.3mm thick copper fins.
Primary Flue - An exhaust hood, made from 0.6 mm thick stainless sheet steel, carries the
flue gases from the outlet of the combustion chamber to the flue way terminal.
Flue Way Terminal - An exhaust hood made from 0.5 mm thick stainless steel sheet that
projects through a slot in the upper part of the appliance front cover and directs the flue
gases horizontally away from the appliance.
Anti-Frost System - Electrical resistive heaters are activated by an ambient air sensing
thermostat to heat critical parts of the water system in the event of freezing conditions.
Heating Unit (Element) - A tubular device containing an electric resistance element that
converts electrical energy to heat. Standard rating is 500W.
Thermostat - A device, sensitive to temperature, which controls the supply of electrical
energy to the heating unit to maintain the heated water at the required temperature of 70ºC.
The thermostat incorporates an energy cut-off (ECO), which provides double pole
disconnection and requires manual operation to reset. The thermostat temperature setting is
not adjustable.
Temperature and Pressure Relief Valve (T&PR) - A valve designed to provide automatic
relief by discharging water in case of excessive temperature, pressure or both.
Auxiliary Hot Water Storage Tank - A 2.6L storage vessel that houses the heating unit,
thermostat and T&PR valve. The container is constructed of copper with no internal coatings
and is insulated with „fire retardant‟ expanded polystyrene foam (EPS).
Transfer Valve - A temperature actuated bypass valve that will bypass when inlet water
temperature is above the set temperature. The factory set temperature range is in the
vicinity of 42-46ºC. The transfer valve is not user adjustable.
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TM061 Rheem 27 Water Star Service Instructions – Issued: 11/10
REV A Issued 08/13
Service. All printed copies not bearing this statement in RED are deemed "uncontrolled"
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