Heaters; Supply Air Heater; Electric Heater Overheat Protection; Cooling Of Electric Heaters - Salda MCB Technical Manual

5.36. HEATERS

5.36.1. SUPPLY AIR HEATER

The heater additionally pre-heats the supply air when the heat exchanger power is insufficient. It is controlled by means of a PID controller based
on the temperature indicated in the system and based on data of the supply air temperature sensor. One supplied air heater can be connected
to this system. It may be either electric or water heater. PID controller coefficients are set in the adjuster environment window ADJUSTER › PID
CONTROLLERS ADJUSTING.
Possible options of supplied air heaters in this system:
› Supplied air heater is not used;
› Electric heater is controlled by 0..10VDC signal;
› Electric heater is controlled by On/Off signal. PWM control interval in seconds is set to control it;
› Water heater.
Types of heaters are indicated in the service environment window SERVICE › HEATERS. Also it is possible to swap connection of the pre-heater and
heater protections and control signals.

5.36.2. ELECTRIC HEATER OVERHEAT PROTECTION

The electrical heater can have two protections: automatic and manual. The automatic protection automatically deactivates when the heaterhas
cooled down, and the manual protection should be deactivated by pressing the switch on the heater.
The automatic protection is checked at all times, while the manual protection is checked only when the heater is activated.
When the automatic protection is activated, the heater and its power circuit are disconnected, a message is shown and cooling is ensured by an
increased air flow. The automatic protection is eliminated automatically. The fan speed is controlled according to the supply air temperature, i.e.
if the supply air temperature drops below the minimum, the fan speed is reduced. When the manual protection is activated, the heater and its
power circuit are disconnected, a warning is shown and the indicated action is performed. According to the factory settings, blowing is carried out
a the full capacity in order to ensure the maximum cooling of the heater because there is a probability that the manual protection may be blocked
and leave it operating. Certainly, if it is activated properly, when blowing at the full capacity in winter, the supply air temperature falls rapidly to the
critical level and the system is shut down in any case.
The protection is configured in the window SERVICE › HEATERS of the service environment.

5.36.3. COOLING OF ELECTRIC HEATERS

If the used electric heater and the system wants to shut down the fan, the heaters are switched off and they are cooled down by blowing for an
indicated time period. A user is notified of heater cooling. Time is indicated in the service environment section SERVICE › HEATERS › ELECTRICAL
HEATERS COOLING. The fan speed is controlled according to the supply air temperature.

5.36.4. WATER HEATER FROST PROTECTION

The protection is always active, because the heater uncontrolled by this automation can be switched on in the supply air duct. The minimum al-
lowable supply air and return water temperature is indicated. If any of them drops below the indicated temperature or the thermostat is activated,
the unit is shut down and warning is displayed. The heating drive opens 100%.
This function also protects the heater against cold air when starting up the system in winter. Prior to switching on the fans the heater is allowed to
operate for the indicated time period at 100 %.
Always in winter (even in Stand-by mode) the minimum 20 °C return water temperature is maintained, moreover the circulation pump is always
rotating and the damper is not fully closed (stays ajar at least 5 %).
Protection is configured in the service environment section SERVICE › HEATERS › HYDRONIC HEATERS PROTECTION.

5.36.5. PROTECTION OF WATER HEATER CIRCULATION PUMPS

Circulation pumps of the water heater and pre-heater must be always on during the entire winter. In summer they are switched on for 30 minutes
for preventive check at indicated time intervals.
Circulation pump signals are also monitored. If a failure is reported, the circulation pump is switched off. The fault is cancelled manually. You can
specify whether to stop ventilation or only to display the message.
Protection is configured in the service environment section SERVICE › HEATERS › HYDRONIC HEATERS PROTECTION.

5.36.6. OUTDOOR AIR PRE-HEATER

Outdoor pre-heaters are controlled based on frost protection. The water pre-heater, as the same type heater, is pre-heated before system start-
up. In winter the circulation pumps are always rotating, and in summer they are switched on for 5 minutes for preventive check at indicated time
intervals.
Possible options of outdoor heaters:
› Supply air pre-heater is not used;
› Electric pre-heater is controlled by 0..10 VDC signal;
› Electric pre-heater is controlled by ON/OFF signal. PWM control interval in seconds is set to control it;
› Water pre-heater.
Types of pre-heaters are indicated in the service environment window SERVICE › HEATERS.
16 | EN MCB_miniMCB v2019.1