How sensors can help to achieve a clear bill of health

BMS, BEMS, Sontay, wireless sensor

Hospital and healthcare buildings comprise various environments that need to be considered carefully when installing sensor equipment. Sandy Damm of Sontay, explains what specifiers and contractors should think about when installing sensor equipment.

Hospitals and healthcare estates bring unique challenges when it comes to installing a building-management system. There are a number of different areas and services that need to be catered for. They include treatment areas, clinical laboratories, A&E areas, sterile theatres and catering and housekeeping facilities. The sensor needs of each area are complex, and each one requires unique treatment.

To help specifiers of building-management systems (BMSs), the Department of Health has developed ‘Health Technical Memorandum (HTM) 03-01’. This document offers guidance and advice for installing a BMS/HVAC system in this specialised environment.

The DoH document outlines the basic controls needed within BMS.

• Starting, set-back and stopping the plant.

• Controlling volumetric air flow.

• System or room pressure controls.

• Temperature control and indication.

• Humidity control and indication.

• Monitoring the plant’s operating state and indication of plant failure.

• Low air flow and filter state.

One of the greenest hospitals in Spain is the University Hospital Sant Joan de Reus building. This 93 000 m2 building makes extensive use of Sontay sensors. (More information on the MBS web site. Search for Reus.)

HTM 03-01 also states that the controls installed must be simple to use, robust and reliable.

The location of controls is extremely important in hospital and healthcare buildings. Whether they are placed within the rooms, plant equipment or ducts, the sensors must be easy to find, easy to read and provide accurate readings. To ensure sensors are easy to use, they should be marked with either ‘raise’ or ‘lower’ or a +/- mark so the operator can easily and quickly change the settings. An analogue or digital indication of the temperature is also needed on a local panel or at a staff base.

A key part of providing the right comfort level in hospitals is accurately and reliably measuring temperature and humidity.

Relative humidity can be between 35 and 70% depending on the area.

The temperature can vary between individual areas within the hospital. For example a cooler temperature may be required in operating theatres, but a higher temperature will be needed in wards to increase patient comfort. According to HTM 03-01, the temperature set-points can generally range from 16 to 25˚C. The industry standard for temperature is sensors that tolerate ±3 K over the entire range (-10 to 70°C) but it is also important for devices to remain accurate within the manufacturer’s specification (± 3K) for the life of the device.

Increasingly popular wireless sensor technology can also provide benefits to hospital environments and assist in measuring temperature, humidity and CO2. Hospitals are often very large and complicated buildings, so creating a controls strategy for the whole space can be problematic. Wireless sensors are a good option because they are easy to install, cost effective and reliable. By eliminating the need for structural cabling during sensor installation, wireless devices can greatly reduce engineering time and installed project cost. This enables faster and easier installation on new buildings and also opens up the opportunity for control specialists to retrofit energy efficient HVAC controls into existing hospitals and healthcare establishments.

Seamless integration of wireless technology is essential, and making sensors compatible with current building control systems aids this process. For example, Sontay has recently introduced an RF input/output module that works with sensors and routers. This device acts as a local I/O with connectivity to typical HVAC equipment such as fan-coil units or variable-air-volume boxes. The module can take any 0 to 0 V DC, 4 to 20 mA, resistive or VFC signal from wired devices in the field and transmit them to a SonNet receiver. The receiver can be read by a JACE controller through a Niagara framework. The strategy within the controller uses this information to calculate control values, which are then passed back through the I/O module to alter damper positions and other output connections in the field.

Wireless sensors are a good option for large and complicated buildings such as hospitals because they are easy to install, cost effective and reliable.

Communal areas in a hospital will require optimal ventilation, which can be achieved by monitoring air quality and CO2 levels. With the diverse mix of people and procedures, the air quality could be pretty poor so by measuring it and ventilating where required, the hospital will be a much more pleasant place to be. High CO2 levels can cause drowsiness and feeling of giddiness which could be detrimental to patients who are already poorly, so it is important to measure this and ventilate accordingly. Modern devices can measure important variables within the overall space conditions including air quality, CO2 for occupancy alongside traditional temperature and humidity measurements.

Areas such as operating theatres require regular wash downs to ensure sterilisation. Sensors in these areas must be able to withstand this procedure, so they must have protection of IP65 or above.

Energy savings can be made by using lighting controllers and light level sensors in rooms such as toilets and consulting rooms to ensure that lights are switched off when the rooms are not in use. Products such as lighting controllers and light-level sensors can be used in such areas. Occupancy detectors can also be used to control other parameters, such as heating, when rooms are not in use.

Sandy Damm is managing director of Sontay.

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