Thermalec ZENITH ZHR 96, Instruction Manual

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Zenith Range Instruction Manual
Page 4
Heater construction (cont’d...)
Thermalec® electric heaters are specifically designed for use with swimming pools and
spas. The base of the heater is a fusion epoxy coated cast iron vessel through which the
water from the swimming pool flows. The vessel is fitted with four safety pressure relief
valves, a drain valve and the water inlet and outlet nozzles and its base is designed to
support the heater on a flat, solid surface.
Overflow weirs are cast into the inside of the heater vessel at the inlet and outlet nozzles.
These ensure that the vessel is kept filled with water to a constant level at all times. A
baffle plate is suspended inside the heater across its width, downstream of the inlet weir.
A similar baffle plate is suspended upstream of the outlet weir. The top edges of each of
the cast weirs are slightly sloped. This patented combination of weirs and baffles is
designed to impart a spiral regime to the flow of water through the heater. It also
prevents the direct impingement of cold water directly on to the heating elements.
The inlet and outlet pipework are connected to the heater by uPVC solvent weld socket
stub flanges. These are attached to the inlet and outlet ports on the cast iron vessel by a
steel backing flange, ensuring that the uPVC socket can be replaced if ever that were
necessary.
The outer sheath metal of the spiral circular heating elements is in highly corrosion
resistant Incoloy 825. The heating elements are suspended inside the vessel from the
thick uPVC element holding plate that covers the top of the vessel and from which the
removable baffles are also suspended. The heating elements are fitted with their
smallest profiles facing the direction of flow. The terminal ends of each element pass
through glands in the element holding plate and into the heater control enclosure that is
fixed to the top of it. Two temperature pockets protrude into the vessel through the
element holding plate, one at the inlet end and the other at the outlet end. These contain
the probes of the control and safety over-temperature liquid-filled capillary type
thermostats, respectively. An additional pocket accommodates the probe for the pool
water temperature thermometer. The joint between the uPVC element holding plate and
the top flange of the cast iron vessel is made tight by a temperature resistant silicone
rubber gasket.
The powder coated steel heater control enclosure houses the electrical switchgear, the
power connection terminals and control components.
Mains circuit breakers are provided. They will interrupt the mains power supply should
any problems occur during the normal running of the heater. Power is supplied to the
elements through heavy duty contactors. An interlock relay is provided to ensure that no
mains power can be supplied to the heating elements if the interlock signal from the
main pool filter pump is absent.
The heating elements on Zenith models are organised in 3/4 banks. A time delay relay
engages the contactors in two separate stages to reduce electrical surge and avoid a
voltage drop when the heater switches on.