Big benefits from ACH550 drives in retail HVAC applications

ABB UK AC variable speed drives offer retail users many opportunities for energy saving and improved environmental control compared to using valves and dampers.  Like many specialist applications however, building controls have a number of unique requirements, and the ACH550 is specifically engineered to meet these demands.

ACH550 drives can be used for the simplest to the most demanding HVAC applications up to 355kW. The drive is programmed with several HVAC applications, including supply and return fans, cooling tower fans, booster pumps and condensers. The intelligence within the HVAC control panel means that the user is given direct and understandable instructions in clear text at all times.

The ACH550 is also equipped with an extensive library of pre-programmed HVAC application macros that, at the touch of a button, allow rapid configuration of inputs, outputs, and parameters for specific HVAC applications to maximize convenience and minimize start-up time.

HVAC

The Chartered Institution of Building Services Engineers (CIBSE), recommends that retailers should regulate temperatures: 19 to 21°C for small shops and department stores, while supermarkets should maintain a temperature of 19 to 21°C in winter and 21 to 23°C in summer to keep customers comfortable. Maintaining these levels is particularly challenging primarily due to the constant footfall of customers entering and leaving a building and the variations in temperature and humidity that this induces.

According to the Carbon Trust, a large number of stores in the UK operate with open doors during winter. As such, HVAC systems have to work extra hard to compensate for the difference in temperature and the extra energy needed costs the retail sector £1 billion per year. The addition of revolving doors or a draft lobby can help reduce losses, however retailers need to look carefully at some of their policies and understand how they are wasting energy. Until then, many of their motor-driven applications will be working unnecessarily hard to compensate for heat losses.

HVAC Application areas

VSDs are suitable for new and existing applications. Retrofitting drives is easy and cost effective and as such should seriously be considered within a company’s energy efficiency strategy. Typical applications include:

– Air conditioning

– Air handling units

– Supply/extract fans

– Cooling towers

– Chilled water pumps

– Refrigeration

Air conditioning

An air conditioning system removes heat from indoor air for thermal comfort. Traditional air conditioning systems regulate temperature by using a compressor that is periodically working at maximum capacity or switched off entirely. The compressor pumps refrigerant gas up to a high pressure. It then enters a heat exchanger where it loses heat to the outside. In the process the refrigerant condenses into a liquid. The liquid is then returned to another heat exchanger, this time at low pressure. As the liquid refrigerant evaporates it absorbs heat from the inside air, returns to the compressor and repeats the cycle.

A VSD installed into an air conditioning system is used to control the speed of the compressor motor which regulates temperature. By installing a drive, retailers can eliminate the stop/start cycles because the temperature is controlled more accurately.

The offers a number of advantages, including:

– Improve system efficiency

– Extend component lifetime

– System less prone to breakdowns

– Lower running costs

– Quieter than a standard air conditioning unit’s compressor.

Air handling units

A significant proportion of all energy consumed in stores is accounted for by the air handling units (AHU) and associated plant. The AHU is used to condition and circulate air within a HVAC system. It works by supplying conditioned air through duct work to occupied spaces within the building, helping to regulate the temperature.

The AHU includes a blower or fan driven by an electric motor, heating and cooling coils, a filter and controls, all housed in a sealed metal enclosure located in a mechanical room, on the roof, or to the side of the building.

The air handler fan or blower changes speed, helping to maintain a constant pressure in the duct work as the volume of air through the blower is regulated. The temperature of the water within the heating and cooling coils is used to control the temperature of the air supplied by the air handler. The air from the occupied space is returned to the air handler through the return air duct by a return fan or blower. Building air volume can be controlled mechanically using dampers or guide vanes; or electrically by controlling blower speed.

Solution

Air handling systems are sized to cope with maximum volume requirements, meaning that it is necessary to reduce blower or fan volume most of the time. Using a VSD to control motor speed reduces the electrical energy consumed by the motor.

The offers a number of advantages, including:

– Reduced energy costs due to lower motor speeds

– Less noise from the air handling units

– Reduced shock and vibrations by avoiding resonant frequency

– Eliminate stress on motor belts, pulleys and keys

– Lower torque starts

See also ABB guide to VSDs in retail environments.

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