# COP Monitoring for Chillers, Boilers and Cooling Towers

COP (Coefficient of Performance) is an efficiency ratio of output input power in an equipment or a system. It is often used as a performance indicator of chiller cooling plant. We provide simple COP metering method by linking up all power and energy meters via a 2-wire RS485 cable. DGBox is product neutral to any brand or model of power and energy meters with either a Modbus or M-bus interface.

COP Monitoring Network

Single Chiller Plant

For many chiller procurement contract, COP measurement is not a default option but a feature needing specification request. If you missed to order that feature and thus failed some energy management compliance, our DGBox is a low cost solution not dragging you on project delivery. APAC Green keeps stocks in Hong Kong and China making a lead time as short as 1-2 weeks.

Chiller COP Dashboard

LEED Dashboard – Electrical Consumption. We can create similar page for your COP monitoring.

Chiller Plant System

Now you have smartly ordered COP meansurement in each chiller, but don’t have a BMS to workout a total plant efficiency. Make DGBox your good friend as each box can connect up to 100+ Modbus devices (exact number depends on data polling frequency and total number of monitoring parameters).

All these devices are linked up with a simple RS485 twisted pair cable in daisy chain topology, up to a 1000 meter long. It means you can now connect to the main electricity board some 500 meters away to include the power consumption on chiller pumps too.

Chiller Plant Systems

Now you have chiller systems in different plant floors serving high-mid-low zones of a high rise building. The floors may be 30-storey apart and it is too expensive to install a cable riser for this litter function. DGBox covers that scenairo already and gives you 2 options to consolidate your chiller plant data into one place for convenient dashboard access.

• Wired – If the building has a BMS in place, DGBox can talk to any near by network gate unit via a BACnet interface
• Wireless – If contractually or practically you don’t have a BMS network to interface with, DGBox can relay data via Wifi access points installed in any vertical void like staircases or lift shifts.

Geo Map with Benchmarking Charts

Chiller Plant Systems in Multiple Sites

You are facility management and responsible to monitor dozens of properties across town , or even overseas. DGBox will be your good friend again as each box can relay data to a cloud server (hosted by APAC Green, or your own server on-premise). You can access data feeding from all sites on a single login.

Get real time alerts and review historical data any time in a few clicks. Data integration with weather and occupancy data for your internal data analysis. Value generated from this kind of data consolidation is unlimited. This is made possible because DGBox can easily send data back with public Internet or GPRS at very low cost.

Portable COP Meter

We have designed a portable COP meter available for your ordering and renting. Contact us for a quotation.

The carrier box houses mainly components for a COP metering system:

• SiteLab clamp-on type ultrasonic water flow meter, with sensors on 9m long cables
• DGBox data appliance
• GSM Modem (optional) so you can view the COP dashboard from remote site via public GSM/GPRS network

Power supply can be optionally made for 220VAC or 110VAC. Electric power meter and current transformers are not housed inside the box, but to connect to the box via a 2-wire Modbus cable. Gross weight of the carrier box is about 4kg. Box size about 700 x 350 x 100 mm.

Portable COP Meter

How do we do COP monitoring?

BTU Meter with clamp-on sensors

COP is a simple ratio yielding from two parameters:

• Cooling or heating capacity of a plant
• Energy input, often electrical, to a plant to facilitate the above thermal change

In practical terms, it means we need two meters to get the nubmers

• Thermal Energy Meter: usually a fluid flow meter with two temperature sensors; also known as BTU Meter simply called Energy Meter.
• Power Meter: can be as simple as an electrical kWh meter, but nowadays it often comes with other quality measurements such as power factors and harmonics, along side with the basic power voltage and current measures; it is also known as Power Analyser

What is COP?

Coefficient of Performance (COP) is a ratio of work or useful output to the amount of work or energy input, used generally as a measure of the energy-efficiency of air conditioners, space heaters and other cooling and heating devices.

$COP=\frac{Cooling Power or Heating Power}{Input Power}$

COP is generally used as a key performance index of heat pump. It means chiller or cooling tower or boiler in plain English. For the sake of easy discussion we often shorten the formula to become:

$COP=\frac{BTU Power}{Input Power}$

or

$COP=\frac{Output}{Input}$

Higher COPs equate to lower operating costs. The COP usually exceed 1, because it is a ratio of output:loss. Measurement of COP is straight forward in engineering point of view, but becomes tricky when doing it contractually. It is because power output is generally contracted to HVAC contractor, while power input is a matter of Electrical contractor. As a result COP figure is available only in buildings/plant with a BMS or SCADA system install to consolidate measurements from the two different trades.

COP for Cooling Towers

Evaporative cooling towers are often running on open-loop water circuit, in which portion of the water is lost to ambient.  The make-up water supply may not catch up accurately for a constant mass flow rate. Still the principle of COP applies the same on them, with the following elaborated equation:

$COP = \frac{BTU Power}{Input Power} = \frac{BTU Power}{P_F + P_{liq1} + P_{liq2} + P_{spray}}$

where

$BTU Power$ = Cooling Capacity = Heat Rejection Capacity

$P_F$ = Fan Electrical Power

$P_{liq1}$ = Electrical power for the pump in Circuit 1 – often refers to chilled water circuit pumps

$P_{liq2}$ = Electrical power for the pump in Circuit 2 – often refers to condenser water circuit pumps

$P_{spray}$ = Electrical power for the spray water pump

Cooling tower heat exchange efficiency is at times qualified by other methods. You may like to review this paper by Bengt Bergsten. The paper has sections discussing features of the Cooling Tower Model, CTM, the Merkel model, the CTI Toolkit, and the effectiveness – NTU method. A coefficient of performance, COP, is defined for a cooling tower or air-cooled heat exchanger.The paper has sections discussing features of the Cooling Tower Model, CTM, the Merkel model, the CTI Toolkit, and the effectiveness – NTU method. A coefficient of performance, COP, is defined for a cooling tower or air-cooled heat exchanger.

We have packaged solutions with the following meters:

• Thermal Energy Meter: Sitelab or Zenner (both are transit-time ultrasonic flow meters; both in-line or clamp-on type sensors are available)
• Power Meter: Janitza UMG 96RM or Schneider PM6200 or Schneider PM1200