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15.0 SHOWER – RELAY CONTROL FOR AMPTEC
BOILERS.
Limitations on electrical supply
Where there is an electric shower and an electric flow boiler installed, the electrical supply may be overloaded
if both units are operating at the same time. To prevent this condition a simple switch over relay box must
be added.
Connections: - The coil of the relay is connected across the switched supply to the electric shower. The
‘normally closed’ contact of the relay is connected into the control line of the electric flow boiler. The relay
does not switch the high current to the boiler, only the control signals.
Operation: - When the shower is switched on, the relay is activated breaking the control signal to the boiler,
and hence shutting it down in a controlled manner, thereby preventing overload on the mains electrical
supply. After showering the boiler will restart.
Electric showers are normally run for short periods at a time and therefore shutting down the heating during
these times should not cause any discomfort.
Note, this is only required if there is doubt with regard to supply limitations and an electric shower that
heats the water at the same time as the Amptec boiler is used. It is not required with power showers which
only pump the water.
A suitable relay unit is available from Heatrae Sadia, part number 95 970 134. This relay unit is also suitable
for other applications where there is a high load demand to be shared with the boiler.
Other relay units containing 2 or 3 relays are also available from Heatrae Sadia.
FIGURE 22 : SHOWER RELAY CONTROL
-
N
R
N
L
PULL SWITCH
2 AMP FUSE
SHOWER OR OTHER
HIGH LOAD
DEVICE
HEATRAE SADIA
PART NUMBER
95 970 134
AMPTEC BOILER
SUPPLY
BOILER CONTROL
SIGNAL
NORMALLY CLOSED
CONTACT (240V)
COIL
240V
50/60HZ
A1
A2
11
12
14
N L
