The amount of the circulating water in the system decreases and the pressure of the system increases respectively when the thermostatic valves are choked. In this case needs the pressure of the circulation pump to be reduced to the nominal value. For this the frequency control rotation adjustment system is used. The pressure difference is adjusted by rotation since the quotation is ?p=n2. The DAF SPEED Series DFR device is a comfortable to use, high standard automation panel with an integrated frequency convertor unit, developed for the control and automation of systems with a single or with multiple pumps. It is possible with the DFR panel to optimize the operation of any type of pumps or pump groups, used at heating, cooling and sanitary installations, by subjecting them to automation pursuant to the plumbing and environment conditions and thus to achieve, along with a comfortable operation, energy savings in a considerable extent.
The DFR control panel is not only a frequency convertor device.
It contains within its entity along with the frequency convertor device many electronic and electromechanic equipments like electronic contactors in order to prevent noise generation at motors and harmful voltage increases at coils, motor thermic preventing and interference ignoring filters, digital regulation electronics, menu control display, necessary fuse and transformer groups for main power and auxillary circuits. Successful results can be achieved at the control and automation of particularly the pumps used at heating-cooling installations thanks to that.
The FR device controls the hydraulic power transmitted to the system by changing the rotation speed of the pump (flow rate = Q and pumping height ?P=H). It adjust the pump power in a set option on the panel by subjecting it to regulation based on definite values. The power control at the pumps is basically the rotation speed control of the pump performed by changing the voltage frequency. The flow rate Q, pumping height H (?P) and the power consumed by the pump from the mains among the operating parameters of the pump is directly dependent on the rotation speed n of the pump. How the operating parameters of the pump depend on the voltage frequency is indicated with numeric values in the table below. Within the scope of a standard delivery controls the FR device the rotation speed of the pump in a range between the nominal rotation speed and 40% thereof. The control range can be decreased down to 30% upon special request. But the widening of the control range is rarely able to be applied due to reasons like the loss of the hydraulic stability of the installation, insufficient cooling of the electrical motors and deterioration of the hydrodynamic balance of the pump at low rotation speeds.