Dantherm HPP-iw Series, Owners & Installation Manual, Page: 17 / 308

17 1007332 ISSUE 5
Electrolytic corrosion will occur when dissimilar metals
that are in contact with each other create a potential
difference between themselves. Sometimes separated
by a conductive substance known as an electrolyte, the
dissimilar metals will create a small voltage (potential
difference) that allows the ions of one material to pass
to the other.
Just like a battery, ions will pass from the most positive
material to the more negative material.
Anything more than 0.3 volts can cause the most
positive material to degrade.
A swimming pool with its associated equipment
can create this effect. The pool water being an ideal
electrolyte and components of the filtration circuit,
heating system, steps, lights etc providing the dissimilar
metals needed to complete the circuit.
Whilst these small voltages are rarely a safety threat,
they can create premature failure through corrosion.
Not dissimilar to corrosion through oxidation, electrolytic
corrosion can cause complete failure of a metallic
material in a very short period of time.
In order to prevent this type of corrosion all metallic
components in contact with swimming pool water
should be bonded together using 10mm² bonding
cable. This includes non-electrical items such as metal
filters, pump strainer boxes, heat exchangers, steps
and handrails. It is highly recommended that bonding
be retrofitted to existing pools, which may not be
protected by this system.
All electrical work to be carried out in accordance with
l.E.E.regulations, latest issue, or local codes of practice
as applicable.
The machine should be installed in accordance with
EMC2004/108/EC.
Always isolate the main power supply before removing
machine covers.
The machine power supply must incorporate the
following. Fuses or motor type circuit breakers (aM
Fuse / MCB type C) to specified rating (see datasheet).
When using a fuse, H.R.C. fuses are recommended. An
isolator which disconnects all poles must be must fitted
within 2m and in line of sight of the heat pump. The
isolator must have a minimum of 3mm air gap when
turned off.
All units must be correctly earthed/grounded and its
own separate type RCD earth leakage trip installed
which protects the machine only. See data sheet for
the correct type.
The following limits of operation must not be exceeded.
Failure to provide the necessary voltages will invalidate
the warranty. This voltage must be available at the heat
pump whilst running. The voltage must not drop below
the above figures when starting the compressor.
Minimum Maximum
Voltage
Single phase machines
207V 253V
Three-phase machines 360V 440V
Cycle frequency (50Hz) 47.5Hz 52.5Hz
3�6 ELECTROLYTIC CORROSION IN SWIMMING
POOLS 3�7 ELECTRIC WIRING AND SUPPLY