FAQ – Frequently asked questions

An IR accessory was mentioned in connection with the FL 1 series of the fume cupboard control system. How does it work?

The fume cupboard’s presence detector functions as an IR transmitter/receiver, monitoring whether an employee is present in its monitoring area. If it detects a person in its area, the fume cupboard control system uses the preset value 1 (e.g. 0.5 m/s) as the fume cupboard sash opening air flow. If it does not detect movement, the preset value 2 (e.g. 0.3 m/s) is used as the set air flow. The amount of exhaust air is therefore smaller if the employee is not present. In practice, in addition to saving energy, this especially improves the adequacy of the extraction power of the old ductwork or fan for other fume cupboards, i.e. the “kick” of the fan is available for the fume cupboards that are being worked on.

Are your products CE approved?

Our products have been tested and meet the requirements of the directives that apply to them. In terms of electromagnetic compatibility, all components of FL systems meet the requirements of the EMC directive (2004/108/EC) and additionally the requirements of the low voltage directive (2006/95/EC).

In addition, we belong to the SELT producer community, through which we handle the collection, recycling and scrap processing of electrical and electronic equipment.

Can the control system be connected to building automation?

Yes, depending on the controller, it can be connected with the current, voltage and relay messages listed below.

The output message from the fume cupboard controller FHR 210 is:

• Sash status information (5 V)
• Alarm mode (interchangeable tip relay)
• Alarm mode (5 V)
• Air volume in the fume cupboard (0 – 20 mA)
• Area of the fume cupboard sash opening (0 – 20 mA)

The output message from the room controller FHS 122 is:

• Alarm for fume cupboard (interchangeable tip relay)
• Total exhaust air volume (0 – 10 V)
• Total exhaust air volume (0 – 20 mA)
• Total supply air volume (0 – 20 mA)
• Universal exhaust air dampers alarm (5 V)
• Supply air damper alarm (5 V)

The output message from the room controller SAR 410 is:

• One of the following from the change tip relay:
  • Low flow in exhaust air
  • Low flow supply air
  • Low zone pressure
  • Low room pressure
  • High room pressure
  • Communication error
  • Service alert
  • High air volume (room)

• Total exhaust air volume (0 – 20 mA)
• Total supply air volume (0 – 20 mA )
• Fault alarm for data transmission (5 V)
• Exhaust air damper alarm (5 V)
• Supply air damper alarm (5 V)
• On the add-on card, the above information to the Modbus RTU bus
• In addition, from the FHR 310 alarm relay:
  • Maintenance alarm from the fume cupboard
  • Flow alarm from the fume cupboard
• With additional card FHR 310 additional relay:
  • Status information about presence
  • Status information about the status of the fume cupboard (on/off)

The fume cupboard alarm FL 101 has two 1-pin change-over relays (60 VDC / 1A) for indicating the alarm state or for controlling the fan/damper.

The RPCS room pressure regulator has two 1-pin changeover relays (60 VDC / 1A) for indicating the alarm status (pressure alarm/door alarm) and an output message about the measured pressure (0/2 – 10 V, option 0/4 – 20 mA).

Does the measurement of the extraction air volume of the fume cupboard require protective distances?

It is not required, because the exhaust air duct does not have a measuring device that gets dirty and requires protective distances. The air volume is determined by an air flow sensor installed on the wall of the fume cupboard and a position sensor that measures the position of the sash. With this arrangement, the response time of the control system is short, because the control damper in the exhaust duct is controlled based on the information from the position sensor to the position that corresponded to the desired air volume during the previous control. Fine adjustment is performed with the air flow speed sensor and the new point of the adjustment curve is stored in the controller’s memory. The position of the control damper stored in the memory can change if the pressure conditions of the exhaust duct change, e.g. due to the use of other fume cupboard.

What are the recommended sizing channel velocities for control dampers and measuring devices?

AVR/ACU: choose the largest possible duct size without undermining the lowest airflow
AVM: choose the smallest possible duct size
AVD/ECV: choose a device that is the size of the duct

Attention! Choose the device at most one duct size smaller / larger than the associated air duct!

What must be taken into account if the room uses general exhaust and the AVR/ACU control damper that controls it?

In general, the AVR/ACU control damper is adjusted so that at least a certain minimum amount of air leaves the room, regardless of the position of the fume cupboard sashes. If there is not enough exhaust air flow of the fume cupboards, the AVR/ACU control damper of the general exhaust opens the required amount.

If you want the air volume of the general exhaust to be the same as the air volume of the fume cupboard, measure the general exhaust duct “tighter” than the exhaust duct of the fume cupboard or equip it with a one-time control damper, so that with a larger opening of the sash, the necessary amount of air leaves the fume cupboard and the control damper of the general exhaust does not open unnecessarily before that.

Also make sure that the possible muffler of the universal exhaust duct does not interfere with the operation of the AVR/ACU control damper, i.e. the muffler does not have an inner cartridge or is placed far enough from the AVR/ACU control damper.

Do the rooms have to be airtight for isolation room pressure control systems?

Creating a pressure difference requires a large enough air volume difference between the inlet and outlet (a pressure difference of 5 Pa is usually obtained with an air volume of approx. 25 – 50 l/s). Typically, a pressure difference of 5 to 10 Pa is desired compared to the adjacent rooms. In practice, board, brick or concrete structures have to be sealed as well as possible, deviating from the “normal” construction method.

The prefab walls and ceilings used in clean rooms are usually tight enough in terms of pressure regulation.