Spotlight on Heating Ventilation and Air Conditioning Controls

AC unit remote control -Book an air conditioning service

This month, I’ve been speaking with our colleagues at BMSI (Building Management Solutions Integrators) about Heating Ventilation and Air Conditioning Systems (HVAC).

The majority of HVACs are operated by control systems known as Building Management System (BMS) or Building Energy Management System (BEMS). These management systems are mandatory for larger buildings with an energy bill of over £10,000*. However, mini-Building Management Systems are increasingly being installed to benefit smaller buildings and businesses. A mini-BMS will usually have a smaller number of control points (including the boiler and AC split units), reflecting the needs of a smaller building and helping to make sure the right level of control and efficiency. A mini-BMS is also supported by bespoke online reporting where the user can see the various points, temperatures and time schedules, removing the need to purchase dedicated BMS software.

Together, we have looked at the problems that can occur with building control systems and highlighted ways in which these problems can be prevented, and ultimately save your business money.

I asked our Technical & Energy Services Manager at BMSI, Dave Holden, what are the common problems that he finds with BMS. He tells me there are many different manufactures of BMS systems each with their own personalities. He went on to say, the BMS industry as we know it today has been around since the mid 1970s when PC based and intelligent BMS systems started to be introduced. Most of these systems have been upgraded over the years and some of you remember the fun that was had when the year 2000 came around.

Some of the building stock that the BMS systems are installed on can also be on the old side, with some Air Handling Units (AHUs) and boilers dating back to the 1960s. Some of the common problems our engineers find include on site plants being turned on and left in ‘Manual’, a lack of maintenance on the mechanical plant and easily repaired items not being replaced. Businesses can help solve some of these problems by employing a proper maintenance regime and employing a ‘Spend to Save’ approach on faulty BMS items. These are examples that can potentially waste a huge amount of energy. If a cooling valve is faulty and fails to open then the heating will have to come on to compensate for the extra cooling load. Sometimes for the case of replacing the cooling valve actuator at around £400, the extra heating load required can easily exceed the cost to replace the actuator. In some cases when the AHU has been left running in ‘Manual’ and has not been turned off at night, the extra running costs can range from £1,500 up to £30,000 a year**. Dave also said that training your site staff will help in identifying issues.

A little winter maintenance goes a long way

Here are a few additional suggestions of checks you can undertake:

1. Check frost protection temperature settings – if set too high it can result in heating systems running unnecessarily, out of business hours.

2. Make sure time settings are correct – these may not match the building occupancy hours.

3. Don’t conflict heating and cooling settings – this is when systems are running at maximum capacity whatever the weather. This is not only expensive in energy and monetary terms, but could result in additional maintenance, as systems are working harder than they need to be.

4. Minimise the time ventilation is set to run. In the winter, a building’s heating system should start before employees arrive. Therefore it’s most efficient to delay mechanical ventilation until the start of occupancy time (if possible).

5. Maintain dampers, valves and actuators – control systems rely on these devices to regulate them. If mechanical components are damaged or defective, they will operate less economically.

6. Censor the sensors – BMSs take readings from the internal and external environment to regulate the system to the chosen settings. Faulty sensors, such as temperature, humidity, actuator positions, equipment run/stop status, could result in inaccurate readings and therefore not allow the BMS to operate as it should.

7. Make sure sensors are installed in the most effective location – sensors in the wrong place could result in unnecessary energy use.

Our BMSI colleagues tell me that having a properly maintained BMS system can often save up to 20% of building energy costs and the best place to start would be a BMS audit such as that outlined above.

Sources:
* Carbon Trust http://www.carbontrust.com/media/7375/ctv032_building_controls.pdf
** BMSI http://www.bmsi.co.uk £1,500 based on 2 x 3kw fans / £30,000 based on 2 x 55kw fans

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