MAKING CHILLED WATER SYSTEMS RELIABLE WITH THE NEW 4120.30 ANALOG FLOW/TEMPERATURE SENSOR

03 Mar 16 Chilled water is commonly used in industrial processes such as aluminum anodizing, mold cooling and plating applications as well as the vast majority of large commercial buildings. Any good energy conservation strategy should include monitoring the system efficiency but there are additional benefits in doing so. When one of these machines goes down it’s like giving your budget the ole one two.  Not only is production down… the cost of the repair itself can be a wallet buster.

Many might believe that a great many catastrophic failures occur without warning, but this is simply not true. The fact is that the vast majority of breakdowns provide ample warning if you know what to look for. The simple fact is that long before almost every significant breakdown, there will be a glaring change in system efficiency. So not only is it a good idea to know how efficient your chilled water systems are for energy saving reasons, experience shows that by acting on efficiency change, breakdowns will almost never happen.

So how does one measure efficiency of a chilled water system?
Speaking in terms of Imperial units the efficiency of a chilled water system is normally measured in KW/Ton. Basically, this is a measure of how much electrical power is needed to produce a certain amount of cooling.

To calculate tonnage:
  Tons = 12,000 / 500 * GPM * TD

Where:
  TD is the temperature of the water entering and leaving the chiller evaporator

  GPM is the gallons per minute flow rate going through the chiller 12,000 and 500 are constants in the equation.

Divide the result of this calculation into the kilowatts the chiller is consuming and you get KW/Ton efficiency.

Most chilled water systems will automatically unload as needed, which means that the KW/Ton will change when the load on the chilled water system changes. Therefore, it is important to benchmark how many KW/Ton the chilled water produces at varying loads under normal operation. This will not only help you understand how much your chiller costs to operate it will also give you the tools for an early warning sign of impending failure.

What your machine probably has and does not have to track efficiency

Based on the calculations, the first thing needed to determine efficiency is the amount of power (in this case KW the chilled water system is using at any given time). Most modern chillers come with this reading available from the factory and it can be clearly viewed on the systems control panel. The other item that comes with your chilled water system is either a supply or return water sensor. This is needed in order to control the system’s capacity. Typically, smaller chilled water systems have a return temperature sensor while larger ones have a supply water sensor. Getting that information out of the systems control panel and into a data log is something we know a great deal about and can help you with.
This leaves two sensors that are not typically supplied by the chilled water system manufacturer which are either the return temperature sensor (on larger systems) or the supply water temperature sensor (on smaller systems) and the GPM flow rate.

The ideal solution is the 4120.30 analog flow sensor

It combines both flow and temperature into a very economical compact easy to install unit. If your chiller has a supply water temperature install the 4120.30 in the return or vice versa.

Each sensor offers operators two choices of communication, both (2) 4-20mA outputs (one for flow the other for temperature) and Modbus RTU protocol. The accuracy on the flow side is +-2% over range while temperature accuracy is less than +-0.5°. What is also really unique about the 4120.30 analog sensor is that it can be field calibrated in circumstances where large lengths of straight pipe do not exist.