3 November 2011

Masterclass: VRF Systems Part 67

An interface is generally regarded as the electronic hardware, which completes the information exchange between two protocols. In most instances this can be a simple, single box but it can become more complicated, depending on the compatibility of the two protocols and the extent of functions required.

Mike Creamer.

In layman's terms, an interface can be likened to a post office sorting office. On one side is postman A putting letters in postcode pigeonholes that have been collected from the local post boxes. On the other side is postman B who is gathering letters by postcode to be despatched from the relevant delivery office. In order for postman B to identify where the letters need to be sent, he must know which postcode postman A is putting to which pigeonhole. The successful interface ensures both sides of the information exchange know where each piece of information needs to go.

The analogy of the sorting office and pigeonholes works well when explaining the limitation of the amount of data an interface can accommodate. Imagine the rows of pigeonholes represent the number of units being monitored. Each column represents a function associated with each unit. Each interface has a limit to the maximum amount of information it can transmit.

Either the pigeonhole grid will be short and wide (a few units with many functions).

 


The product of the numbers of rows and columns dictates the maximum amount of information capable of being transmitted. In the early stages Mitsubishi Heavy Industries developed a simple, solid-state interface into the SuperLynk control scheme, which enabled inputs and outputs to and from the MHI system. This six-wire adaptor enabled an external source to turn the unit on and off as well as providing an output for system run, cooling, heating and systems error. This system still exists on all indoor units. There in an added benefit of having the same functions available on the central controller with a group on/off and group fault indication.

BMS - Building Monitoring System

Through the late 80s and early 90s the demand increased for a fully automated control system to monitor and control complete buildings' services.

The terminology BMS was introduced as the latest state-of-the-art method of managing energy efficiency. Ensuring the building services were operating only when the building was occupied, and maintaining the correct mode of operation (either heating or cooling), were the predominant demands of such systems.

In the early days of BMS, most people in our industry tended to view these types of systems as Building Management Systems. The true functionality of these early systems merely ensured the services were timed on and off with some form of control and provided an indication of a system's status or fault condition. In a majority of cases, this simple building monitoring system was more than adequate.

Energy bills were reduced as the systems within the building operated within pre-defined times.

Service and maintenance of equipment on these systems was also improved. Error indication was made more commonplace and has promoted a reaction to rectify the fault.

In these circumstances, the six-wire adaptor proved thoroughly acceptable as a method of monitoring both individual units and groups of air conditioning units within a building. The simple functions of turning the system on and off and providing a fault indication were both easily and competitively achieved.

 


The six-wire adaptor is still being used as an option for interfacing onto a BMS or indeed onto a bespoke control panel where on/off times and system fault monitoring are required.

Energy management

The 1990s provided our industry with a stark warning with regard to both environmental protection and energy conservation. The terms 'global warming' and 'climate change' influenced a sea change in the way air conditioning systems were designed and applied.

In December 1997 the UK Government signed up to the Kyoto Protocol, agreeing to reduce the emissions of greenhouse gases. CFC refrigerants were phased out or banned and replaced by the more environmentally friendly HCFCs.

The introduction of the Climate Change Levy in April 2001 saw commercial energy costs rise some 10% overnight. In October of the same year Part L of the Building Regulations - the conservation of fuel and power - were revised.

While these matters appear to be more to do with ecology, they are in fact a pioneering move to ensure the UK becomes more energy efficient.

These latest developments are designed not only to reduce CO2 emissions, but also reduce power consumption.

The late 1990s saw the emergence of a new job function within facilities management - that of an energy manager. In many large companies, both commercial and retail, strategies have been drawn up in order to reduce the company's total power consumption. The desire to be 'green' as well as reduce running costs has seen the rapid development of energy management systems.

BEMS - building energy management system

The development of the building energy management system (BEMS) proved to be the natural next step from BMS. Sophisticated frontend graphics promoted the information required from within the air conditioning control system.

Continuous monitoring of the return air temperature, considering how the ambient air temperature would affect the required room temperature - these were all factors which became more relevant to consulting engineers, landlords and large end users in the design and efficient running of buildings.

There are a wide variety of building energy management systems available with both open and closed protocols. The fundamental requirement for any interface is to allow individual sites to be monitored and controlled from a central, often remote, location. The latest development from this initiative has seen the production of the SuperLynk Control LonWorks InterFacE (SCLIFE).

SCLIFE

SCLIFE has the capability of controlling a network of both split systems and VRF systems with the following functions:

Inputs:
· Unit on/off command
· Operation mode command
· Set point temperature command
· Remote control inhibit command
· Fan speed setting command

Outputs:
· On/off status
· Operation mode status (heating, cooling, auto, fan only)
· Set point temperature status
· Fan speed setting status
· Failure status with individual error code
· Room temperature status
· Communication status

The simple two-wire SuperLynk control network is routed from the installed units to the LonWorks interface. The addition of a local
interface board converts the simplified SuperLynk control of split systems back into the network capability of the MHI VRF network. The LonWorks protocol has been selected, as it is currently one of the most flexible open protocols. Simple network integration from the SCLIFE ensures compatibility between all the leading BEMS control systems (Trend, Johnson, Staefa, Satchwell, etc). There is also a BACNET interface currently in development.

This product was developed with an open protocol to ensure all aspects of the building services are capable of interacting with each other and being controlled from the same source.

Hence the lighting, air conditioning, refrigeration equipment, fire alarm systems and intruder systems can be co-ordinated, monitored and controlled from one point. As part of the open protocol, they also have the advantage of being able to interact directly with each other.

There is an additional cost associated with these very sophisticated systems but the benefits far outweigh the capital outlay.

Not only are running costs reduced with these systems, but the feature of having individual fault identification benefits the end user client. In most instances, the fault is identified, and an engineer attends site before the building occupier is even aware of the problem.

Remote site monitoring

Recently the SCLIFE system has been introduced for remote site monitoring purposes. All too often, large multiple outlet retailers have decided to tackle energy efficiency with the appointment of an energy manager. Energy managers are now being appointed to ensure running costs are reduced, and branch staff are not unnecessarily tampering with controls, wasting valuable energy.

These managers generally co-ordinate the monitoring of all regional stores from a central location.

Large retailers, banks, etc, are moving towards systems which allow remote site control and monitoring from a central office. As well as controlling operation and set temperatures, there is a demand for monitoring of equipment malfunction and providing coded fault diagnosis.

 

With thanks to Mike Creamer of Business Edge who revisits his Masterclass series of articles, updating and adding to the information which proved so useful to readers when the series was first published over ten years ago. In this reincarnation, the series will cover both air conditioning and refrigeration and serve as an on-going source of technical reference for experienced personnel as well as providing a solid educational grounding for newcomers to our industry.

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