9
♦
Charging the heating system
When charging the heating system, the boiler shall be unplugged from the mains by disconnecting the main
circuit breaker. The charge pressure with a cold system should be between 1 and 1.5 bar. The system shall be
charged slowly so that air bubbles can be released through the vent valves. In accordance with
CSN 07 7401
,
water used for the first charge as well as for any re-fill must be clear, colourless, without suspended substances,
oil and chemically aggressive ingredients, it must not be acidic (pH must not be lower than 7) and have minimal
carbonate hardness (max. 3.5 mval/l). When treating the water in relation to its hardness, only approved agents
shall be used.
Should these requirements not be fulfilled, the warranty shall not apply to any damaged
components!
♦
Selection of regulation and control features
The boiler comes with basic control and safety features as indicated in the following wiring diagrams. The
THERM ELN boiler is able to control its output automatically. It is fitted with its own PID regulation which
prevents the boiler from overheating beyond the temperature setpoint. For example, when the heating water
temperature is set to 80
°
C, regular electric boilers tend to overheat up to the temperature of 96
°
C, while the
THERM ELN boiler heats up to the max. temperature of approx. 84ºC.
In any case, it is economical as well as recommended that the electric boiler be controlled by a subordinate
regulator - room thermostat. Such regulators are not included in the delivery of the boiler! For control based on
the room temperature, Thermona delivers and recommends a wide range of room thermostats: e.g. PT 22, CMR
707, CMT 727 (wireless design) etc.
♦
Connecting the room thermostat
The room thermostat (switch contact only) shall be connected directly to the screw terminal PT on the boiler
automatic control system. Voltage on the left terminal is +24 Vss, on the right one there is the measurement
input. 3 to 5 mA current passes through the contact when connected.
3-phase jumper
