Components And Their Function - Rheem 70103 Service Instructions Manual

Components and their Function

Timer: An electronic device which allows the user to program the BWU operating times
and/or sleep mode function. Refer to page 14 for more information on timer operation. 701
& 702 Series have a 24 hr / 7day programmable timer. 703 series have an Eco function,
refer to page 20 for Eco Sleep timer operation.
Heating Unit (Element): A tubular device containing an electric resistance element that
converts electrical energy to heat which is utilised to heat water. The standard boiling
water element rating is 1.8kW for 3L models, 2.4kW for 5 – 15L models, 3.6kW for 25L
models and 4.6kW for 40L models. The boiling water element also has a dry well which
houses the boiling water thermistor. The boiling water element in 3 – 15L models has an
inbuilt E.C.O. (see below).
E.C.O. (Energy Cut Out):
Also known as O.T.C. (Over Temperature Cut-out)
The boiling water element in 3 – 15L models has an inbuilt single pole E.C.O. which will
open circuit the element at 105ºC. The 25-40L models have a stand-alone, dual pole
E.C.O., inline between the control board and the element which will open circuit the
element at 110ºC. The E.C.O.'s will not reset automatically but may be manually reset
once temperatures have fallen to a safe level.
Control Board: The control board interprets signals from the timer and boiling water
thermistor and controls operation of the BWU.
Boiling Water Thermistor: is a sensor which is used to detect the water tank
temperature. The sensor is fitted into a pocket (dry well type) located in the boiling water
element assembly, and plugs into the control board where its output is monitored. The
resistance value of the boiling thermistor will change according to the water temperature
detected.
Inlet Solenoid Valve: An electro-mechanical device utilised to shut off the inlet water
supply to the BWU. Inlet solenoid valve operation is controlled by the low
and high level probes via the control board.
The flow regulator located in the inlet of the valve has a series of holes
which reduces the flow rate to 0.5 litres/ minute (3L - 10L models), or 2.5
litres/minute (15L - 40L models) to prevent turbulence within the boiling
water tank which would otherwise affect stratification.
Control Board Relay: The control board relay provides protection in the
case of an element triac short circuit. If an element triac short circuit is
detected by the control board, the element relay will de-energise which will prevent the
element triac from operating.
Level Probe: A device designed to detect the water level of the boiling water tank. The
level probe contains two probes; a low level probe and a high level probe. A circuit is
created when the water touches both the tank and the probe. This circuit is detected by the
control board.
23
TM063 701, 702 & 703 Series Boiling Water Unit Service Instructions
Revision D: Feb 2017
Service. All printed copies not bearing this statement in RED are deemed "uncontrolled"
This document is stored and maintained electronically by