perspective

A BTU meter is an energy calculator for chilled water. It calculates

energy consumption by multiplying the flow volume by the difference in water temperature between the supply and the return lines of a chilled water system. And for this to happen in an effective manner, it is important that it is always installed in the return line.

There are two common types of meters available in the market – the mechanical and the ultrasonic meters. Each has its advantages. The mechanical is a low-cost option. It is powered by a battery or by electricity mains. It is AMR (Automated Meter Reading) -compatible. An ultrasonic system is also AMR-compatible. It is also powered by a battery or by electricity mains. It has a maximum battery life of 11 years. Further, the ultrasonic system has no moving parts. It can be operated constantly at double the nominal flow, with no damage. It requires minimal maintenance.

Speaking of the AMR, there are two types – the Mbus and the Modbus. The Mbus (Meter Bus) is a European standard for remote reading of water and energy. The meter data is converted into a protocol and read from a central point. The meter data can, then, be exported in various formats. The Modbus is a compact, binary representation of data for remote reading of various

electronic devices, including BTU meters.

And that brings us to the billing system. A computerised energy-billing system shall acquire all the parameters from various meters with Mbus or Modbus protocol installed at various locations, as specified by the design consultant. The system would be running for 24 hours a day and would be recording data every few minutes or over any predefined time period, using appropriate level converters and data converters. Reports, or bills, can be generated on a daily basis or a monthly basis, as per the requirement. The reports, or bills, that would be generated shall have a feature wherein the client can enter values for fields, like the unit costs. This will be decided

All options consideredSyED TAqI HUSSAIN GIvES AN OvERvIEW OF METERING OPTIONS AvAILABLE AND THE BILLING SySTEM.

IMportAnt fActorS to bE conSIDErED DUrIng DESIgnIng A bIllIng SyStEM InclUDE thE tIME of rESponSE, DAtAbASE, thE coSt for opErAtIon, SElEctIon of ApproprIAtE IntErfAcES AnD MInIMAl MAIntEnAncE.

while taking the formats of the reports from the client. It is possible to take a backup of the data the system has recorded after a specific period of time. This backup can be taken in the form of a CD or by forming a copy of the original files and compressing them. The whole system will be flexible enough to be expanded to include more number of meters at a later date, with cost implications.

Important factors to be considered during designing a billing system include the time of response, database, the cost for operation (user-friendly training), selection of appropriate interfaces and minimal maintenance.

An AMR and billing system is a one-time investment. So clients need to be very careful in selecting one, for after it is installed and commissioned successfully, it will generate a steady revenue for the investment. Also, the end-users will be completely satisfied, as the system is accurate, tamperproof and will bill only as per usage. Immediate advantages of the billing system include the obsolescence of logs books, zero tampering and the avoidance of human error while recording readings.

The writer is Key Account Manager (HvAC Controls) at Dutco Tennant. He can be contacted at taqi.hussain@dutcotennant.com.

PHOTO COURTESy GLyN HIGH-TECH DISTRIBUTION

26 clIMAtE control MIDDLE EAST August 2009