Danfoss AVTQ DN 15 (code no. 003L7015) is a flow-compensated self-acting thermostatic temperature controller designed primarily for district heating systems with plate heat exchangers for instantaneous domestic hot water preparation. The controller prevents the heat exchanger from overheating when no hot water is being drawn off by rapidly shutting off the heat supply. The domestic hot water temperature can be individually set within the range of 45–60 °C.

Function

The AVTQ controller consists of a thermostatic actuator with a diaphragm element, a main valve and a control (pilot) valve. The thermostatic actuator with diaphragm element and the main valve are installed on the primary side (district heating side), while the pilot valve is located on the secondary side (domestic hot water side). The diaphragm is connected to the pilot valve by capillary tubes.

When hot water is drawn off, the flow through the pilot valve creates a differential pressure which, via the diaphragm element, raises the temperature level from standby operation (approximately 40 °C) to the set operating temperature. This causes the main valve on the primary side to open and heat to be supplied to the exchanger. As soon as the temperature reaches the set value, the main valve closes. Standby operation prevents the district heating pipework from cooling down.

The controller is installed exclusively in the return pipe on the primary side of the heat exchanger. The pilot valve is installed in the supply pipe on the secondary side. The sensor can be installed in any position.

Features

• Flow-compensated self-acting operation – no external power supply or control electronics required
• Pressure-controlled opening/closing when hot water draw-off starts/stops
• Stepless adjustment of the operating temperature within the range of 45–60 °C
• Permanent standby temperature of approximately 40 °C (protects district heating pipework against cooling down)
• Suitable for plate heat exchangers with an output of up to 75 kW
• Installation in the return pipe on the primary side