D) Using The Internal Relay - Conrad FHT 8W Bedienungsanleitung

d) Using the internal relay

The relay in the "FHT 8W" is switched constantly depending on heating demand.
If no heating is required. the relay is in rest mode, i.e. the contacts are connected as per the following
switching diagram and as shown in the circuitboard markings. If there is heating demand, the relay
activates.
KL2
REL1
The relay has gold-plated contacts which are resistant against buildup of deposits and which allow
long-term stable switching of the low voltages which are present in many control inputs.
The maximum loading of the relay is limited to 8A.
If a mains supplied device is to be directly switched then a suitable fuse must be
included in the wiring. In many applications this internal fuse will already be installed
in the heating system.
For higher loads then 8A, a relay with corresponding capacity or switching protection
must be used.
Basically there are different ways to connect the heating demand relay to the heating system. The best
option is definitely determined by the corresponding switching procedure. Many modern boiler
controls have freely configurable inputs which allow the use of a switching selection unit, for example,
in holiday homes. This input should be programmed such that the heating system is switched to
"standby mode" when there is no heating demand.
Another option is to let the "FHT 8W" control the remote control or room thermostat inputs.
This type of input is present on nearly all boiler controls, even older models. If there is no heating
demand, the system is switched from nominal operation to heat reducing operation.
In addition the relay can, of course, also be directly inserted at the circulation pump intake. This is
however an imperfect solution as the boiler continues to heat water, but the heat is not transported
through the system. On the one hand this does not make full use of the energy-saving potential of the
device, on the other the boiler control may end up registering malfunction due to the fact that the heat
is not being transported away.
Further information on the switching configuration is available in the handbook or installation
instructions for the boiler control. If in doubt you should consult a heating systems expert!
Heating demand
Not present
Present
Internal relay
31