In smaller offices, transmitted air diffusers of the normal type work very well. For conference rooms or where larger air flows are required, sound insulated transmitted air is an alternative, i.e. a large grating on each side of the wall with a sound insulated spiral duct between


All products that are connected to the communication line communicate their supply air flow and zone membership on alterations. The FBC extract air regulator listens to all of these messages and adds up the flows that affect the current zone. The regulator can also add/subtract a nominal offset in order to compensate for any WC groups or similar.

Energy saving design of duct system

By placing flow measurement equipment so that all extract air flows are measured but only the varying flow is controlled (see image below), better measurement accuracy and lower minimum flows are achieved, saving energy.

Extract air with DCV-FB damper control with flow balance regulation through the flow that is communicated by digital bus. Adjustable offset can compensate for fast flow. The flow zones with the supply air diffuser (and with other regulators) that are to be balanced against specific extract air control are defined and allocated the same value in the "Flow zone" parameter.

The cable used throughout is a PVC-free shielded combined supply and communication cable. It is pre-terminated in the diffuser's diffuser section with ready-made contacts in the other end for rapid installation. For other products, it is connected in the same way throughout.

Cable lengths

The bus cable can be pulled for long distances in respect of communication, but the voltage drop must be taken into account for voltage supply. See electricity design guide

The limiting factor for cable length is that each CMA ("communication hub") can only have 100 nodes/products installed on it.

Power supply and transformers

In a normal situation, one transformer is installed per 12-15 diffusers/products but this is a rule of thumb that applies with short distances between products. See electricity design guide.

In some cases, you may wish to place a larger transformer in cable recesses instead of many smaller ones deployed throughout the installation. This can be done, but you must take note of the voltage drop in cables, and you will need separate thick 24 VAC cables on cable ladders.