What is a Chiller / Heat Pump?
Chillers and heat pumps come in a huge variety of shapes and sizes, using different technology to achieve the same outcome for the exchange of energy.
The efficiency of this process is measured by the ratio of usable energy (media water, water/glycol or air) to the energy used (typically electricity). Both measures have units of BTU/(h·W) (1 BTU/(h·W) = 0.293 W/W).
Monitoring water supply temperature, flow rate and water return temperature is an important part of the process. The first step in improving chiller operating efficiency is to calculate current conditions (produced energy/consumed electricity), known as COP.
COP = COOLING POWER / INPUT POWER
There is not one generic schematic valid for all kinds of chiller or heat pump piping. The schematic shows an Energy Valve fitted to monitor flow and delta T through a chiller.
However, they all have one thing in common; their maximum achievable power depends on the volume flow x delta T. Too small delta T limits the output of the plant. Often in low delta T situations, more machines are running than are actually required, as there capacity is limited.
The Belimo Energy Valve™ is a great product to create transparency and ensure correct long-time operation. Belimo do not recommend the correction of delta T issues at the plant. Implementation of any type of control here may starve some units and not deal with others, which are creating the issue.
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Total Cost of Ownership (TCO)
Often, the symptoms of low delta T is presented as a lack of capacity from the plant during peak periods. This naturally leads to the instinct to increase the capacity. Using the Energy Valve to diagnose and actively correct low delta T at the heat exchangers, can prevent the need to upgrade entirely.
Common Issues with Chillers and Heat Pumps and Why You Should Choose the Belimo Energy Valve™
Problem: Ongoing monitoring of chiller performance
In older chillers, it is difficult to monitor thermal output. Ideally, we want this to compare against the power consumed for a true COP. Historical benchmarking has become increasingly important in recent time. The capability to measure performance against this time last year or against a time with similar conditions, enhances informed decisions on maintenance and replacement.
Solution: Use the Energy Valve built-in energy meter
By monitoring the flow rate, along with entering and leaving water temperatures, you can build a good picture of how well your chiller is performing thermally, and with the addition of an electrical consumption meter, you can obtain the whole picture or coeffi cient of performance (COP). Even if your chiller already offers real time output data, the Energy Valve is able to monitor and log this data for 13 months and provides a useful backup if the on-board feature fails.
Problem: Unknown glycol levels
Glycol is heavier than water, so too much reduces your pump effi ciency, and with too little, there is a risk of freezing. Getting this level right requires testing of the water. This is often a manual process reliant on facility management staff remembering to conduct the tests, but this manual process leads to a fear of a lack of glycol, which often leads to overdosing.
Solution: Continuous glycol monitoring
The primary chilled water circuit is the best place to monitor the levels of this important part of your water. Energy Valves monitor glycol concentrations in the hydronic circuit and the BMS can alarm, or even auto-dose the system, if the level should fall below a predetermined limit. By monitoring and logging the glycol content, you can manage the balance between too excessive and insuffi cient concentrations in the system. Energy Valves automatically adjust the thermal energy calculation based on the level and type of glycol in the system which could otherwise affect the readings by 30%.
Success Story - University of Miami
University of Miami The Belimo Energy Valve™ Cures Medical University's Low-Delta-T
The University of Miami medical campus saves thousands of dollars and increased plant capacity with the Belimo Energy Valve retrofit.