BMS: Who is in Control?

Building Management System (BMS) is basically an electronic system that get installed in many modern type of Buildings, consisting of sensors, actuators and processor type controllers, all linked together to form a network that communicate together utilising a programmed software language known as protocol.

Sensors send signal referred to as inputs to the controller where it is processed and  output signal is sent to an actuator to perform a function (on, off, open, shut or modulate ).

The other fancy names for such system is Building Automation and Control System (BACS) and Integrated BMS (IBMS).  

The purpose of this system is to monitor and control all the electro-mechanical systems to ensure:

a-      Safe operation to protect operators, occupiers, equipment and systems from damage or causing and /or spreading of smoke and fire. By both sending early warning alarms and automatic interventions such as shut down.

b-      Optimum operation to ensure systems consume power/ fuel to match the load or need, therefore reducing waste and operating cost.

c-      Building operators can monitor and control through their computer screen at a central location (control room) and mobile phones. Like a TV remote control, if you like.

d-      Provide a historical data of system performance to aid the maintenance regime to keep equipment and system at optimum operating conditions as to elongate its life and reduce the probability and frequency of breakdowns.  

BMS also have brothers and sisters it connects to and interface with within the same building or remotely. Such as, but not limited to, Fire Alarm, CCTV, Access Control, Public Address, Traffic and Environmental Control.

In a bigger and more critical buildings BMS have a big brother called SCADA (Supervisory Control and Data Acquisition). As far as I know, SCADA’s has as an industrial origin but then brought in for two good reasons. It utilizes industrial type processors called programmable logic converter (PLC) perceived as more reliable for critical operations than the Digital Direct Controllers (DDC). The 2nd is, in a building which contain other non-Building Services systems such as Tunnel Ventilation System, Rail Systems (Signalling, Telecom and Platform Screen Doors), Medical Systems & Equipment and Aviation related systems which will require a SCADA to act as the overall communicator, integrator and controller sitting above the BMS. Therefore BMS become a sub-system although it can operate as standalone if and when SCADA fails.

In one project the wording “Supervisory Control “caused some scope clashes between SCADA supplier and BMS supplier. The situation didn’t help as the BMS system referred to in the specification as Environmental Control System (ECS). Which I believe is a common terminology used in France. The issue is that ECS was understood to be a system which controls Heating, Ventilation and Air Conditioning Systems (HVAC). So BMS supplier didn’t allow for control of electrical and plumbing systems. So when the scope was pushed to SCADA supplier said “Noh. its like zis!” we only provide Supervisory Control.

The lesson learned, especially for any control system, was, do not rely only on the headline name or some generic scope that was simply copied and pasted. The system scope must be written in details that defines it’s;

1-      Functionality: Define which systems it will control, monitor and interface.

Control means: sensors, actuators and controllers are all the scope of BMS.

Monitor means: The equipment (such as Chillers, packaged booster pumps and Generators) come already factory fitted with its own sensors, controller and actuators. BMS will only monitor to report on status and mimic any alarms or faults. If the BMS is required to do some basic direct control such as on /off, shut down or start up then such control to be listed. If there is a SCADA system then this scope can be taken away from BMS to avoid duplication (since SCADA can provide supervisory control).

Interface means: The main controller of BMS is in contact with other electronic systems controller with some specific exchange of signals for a specific action (for example Fire alarm sending a signal to BMS to shut down all the air circulation equipment within a specific fire zone). 

2-      Limitations:  This should be a clear statement as to where the BMS scope starts and ends, supported by interface diagrams with scope line clearly marked as well as geographical locations of its main head control and controllers.

So how a BMS is born?

In brief, BMS is conceived during project inception by an interface between the Client and Design Consultant.

 After the requirement are established, then it start to grow and develop into a design with drawings arms and specification legs. 

The system birth is conducted by specialist BMS supplier who will ensure the delivery of a healthy functional system.  

However BMS system being a network type therefore it can never be procured as any other standard systems.

It has a long menu of options/ shopping list in terms of type of equipment, system set up (Architecture) and interface. Therefore it has to be tailor-made and led by the BMS designer.  

BMS Design:

BMS design in the early days, when buildings and MEP systems were much simpler, were prepared by Mechanical Engineer and sometimes by Electrical Engineer. But nowadays it is prepared by a specialist Controls Engineer.

However my observation is that such Engineers tend to come from electronic back ground so their focus will be on system circuitry and interface but not necessarily know how MEP various equipment need to function and controlled. 

Therefore BMS design needs to split into 2 main activities;

One, conducted by the MEP systems designers: Produce control schematics for each equipment that require control. Together with control description including sequence of operation, set points, higher and lower limits, maintenance and critical alarms.

Two, conducted by BMS specialist to produce:

1-       Overall system architecture /schematic.

2-      Layouts to show the location of all Control Panels, Servers, Work Station and other devices together with cable containment routing (Geographical scope).

3-      Schematic diagrams to indicate the interface with all other systems including scope demarcation lines.

4-      Material and performance specification including points schedule.

5-       Cause and affect matrix in collaboration with design team.  

All the above to be reviewed by all of the design team to ensure no scope gaps before submittal for client approval.

Team effort indeed.

BMS Tender & Procurement:

Normally a number of BMS specialist companies are invited to tender, either directly by the client or by MEP contractor. The contractor may have its own BMS subsidiary or affiliated preferred company, which is ok if the scope is part of overall contract lump sum and assuming it meets the requirement.

However if it is a Provisional Sum or an addition to the original contract. Then competitive tender process needs to take place before selecting a BMS sub-contractor.

In many projects the BMS bidders are given the design document that relates only to BMS to base their price and technical proposal. That is fine assuming such documents cover all the scope. But in reality it never does. In many design documents such as Design Reports, Specifications, O&M strategy, Fire & Life report, CFD reports, etc. you will always find a hidden scope covered by few words at end of a paragraph such as: The system shall be controlled and monitored by BMS. Or shall be interfaced with BMS.

Such sentences maybe small but the impact on the project can be disruptive and breeding ground for clashes, disputes and claims.

Therefore it is wise to include all other project documents in the tender to avoid the above scenario. And allow sufficient time for bidders to raise RFIs and cover all the scopes.   

BMS Engineering & Installation:

BMS Sub-contractor starts this stage by submitting all the necessary documentations: shop drawings, material approval and technical data of the various products and performances, certifications, warrantees, etc. together with material samples.

Control Panels will be assembled and tested in a factory. Normally followed by a factory acceptance test (FAT) to ensure quality, safety and reliability operation of control panels.

Site activities includes cables containment, cables pulling and fixing the various BMS equipment (normally sub contracted back to the MEP contractor) as first fix. Wiring, Programming, T&C all done by a specialist team.

The rooms where BMS control panels reside need to be ready and clean and fitted with Power, Lighting, AC, and Gas Suppression ( if applicable) before it is handed over to the BMS installation team. Dust, heat and humidity all can impact on the performance. Also programmers spend a great deal of time on site and the work require a degree of concentration ( I have seen bunk beds installed in such rooms during T&C) . That’s why the rooms needs to be fully lit and sufficiently cooled (or heated) and dust free. Parallel work of other trades such as painting, drilling and carpentry, should be avoided at all cost. Supervision Engineers must be in control to ensure the above.

So as it can be seen BMS require attention and specialisation at all stages to ensure that the building stays under control.

Essential or nice to have:

As mentioned, BMS is not off the shelf product but have to be tailored for each project. Therefore it require good deal of thought and effort.

My theory is BMS features can be divided into essential and nice to have. Essential are the functions that control and/or monitor to control to perform the functions mentioned earlier. The nice to have are additional features that mainly, although others might argue it is essential, provide additional information for example the system operators would appreciate as to save effort in physical inspection. For me, any function that the system can still achieve its required control function if it didn’t exist, I consider it as non-essential.

For example monitoring the position of a motorised air damper, control valve or electrical switch gear. If this feature didn’t exist the BMS system can still function (open, shut or modulate) therefore such feature can be considered as nice to have or, if you like, an enhancement.

However we must agree that there is a thin line between essential and nice to have. In some critical operations related to fire and safety such features become essential and we must not ignore them.

For commercial buildings there must be a scope to Value Engineer BMS system. And in consultation with the Client O&M department any added features can be viewed against savings in the initial investment. But the VE exercise must be conducted before engaging sub-contractor not during construction.

Last thought. For clients; it is worth spending time in engaging with designers on refining the BMS system by reviewing and questioning the system functionality before going to tender for two good reasons. To avoid costly variations in scope change and to optimise the initial investment to match your exact needs.

End.