Building Management Systems (BMS) Mock Exam

Sample questions

1. 01Which of these sits at the automation level of a BMS?

   • AA web interface that staff use to change the schedules
   • BA plant controller running the boiler house strategy
   • CA pressure switch fitted across an AHU filter bank
   • DA current relay fitted inside a fan motor starter

   Why: The automation level is where decisions are made: the outstations and plant controllers that read inputs, run the strategy and drive outputs. The current relay and the filter pressure switch touch the plant, so they are field devices. The web interface is tempting because it is where settings change, but it is the management level: it sends settings down, it does not do the controlling.

2. 02The BMS sends a varying speed reference to the drive on a supply fan. What type of point is that?

   • AAn analogue input from the drive
   • BAn analogue output to the drive
   • CA digital output to the drive
   • DA digital input from the drive

   Why: A varying command sent out from the BMS is an analogue output, in the same family as a valve or damper position. A digital output is tempting because it also goes out to the plant, but it is only an on/off command such as start or enable. Inputs come into the BMS from the plant, not the other way.

3. 03A packaged chiller has its own controller that is not on the BMS network. The BMS enables it from a digital output and reads a fault contact. The facilities manager wants its refrigerant pressures on the graphics. What is the position?

   • AThe fault contact can be rescaled in the outstation to show each pressure
   • BThe BMS only sees what is wired to it, so those values are not available
   • CThe values already sit in the outstation and just need adding to the graphic
   • DThe head end can poll the chiller controller for them over the BMS network

   Why: A stand-alone controller is not on the BMS network, so the BMS only gets the enable it sends and the status or fault signals wired back; it does not see inside the plant. Polling over the network is tempting, but the chiller is not on that network. A fault contact is an on/off digital input and cannot carry a varying value.