What is BTU Meter and how to calculate energy consumption for billing tenants

What is BTU?

Before we proceed to learn what is BTU meter, let us see what is exactly BTU or British thermal unit.BTU is the amount of energy required to heat a single pound(lb) of water by one degree Fahrenheit.

 
What is BTU with example
Let us assume the flame will burn for exactly one hour and will give out exactly one BTU.
Before starting the process, water temperature is at 50 degrees Fahrenheit, after one hour of one BTU(thermal heat energy) process will increase water temperature by 51-degree Fahrenheit.
the mathematical expression of the process is
 
BTU/Hr=lbs x Delta T
 
Delta T is the amount of temperature difference before and after the process, So here
 
BTU/Hr is 1 (which is considered as a flame)
 
Mass of water in lbs is 1
 
and delta T is 51-50=1 degree-Fahrenheit
 
 
let us see the second example to find the delta T for the given BTU
 
What is BTU with example
 
Let us assume that mass of water is 4 lbs and given BTU (flame or heat energy) is 2 and  find the delta T ie, Temperature increased of water after one hour
 
BTU/Hr=lbs x Delta T
 
now Delta T = BTU/lbs
 
Here the temperature increased is 0.5 degree-Fahrenheit.
Have a look at this video
 
How to calculate the energy consumption by BTU Meters
 
BTU Measurement System is used to measure individual energy consumption in any liquid heating/cooling systems. This system is also used to measure the performance of the energy saving system or the loss of efficiency which is directly tied to the loss of revenue.

BTU Meter is supplied complete with flowmeter and temperature probes.

The system real-time detect the temperature of supply and return pipe. It also monitors the instantaneous flow rate according to Heat Exchange of Thermodynamics principle. The BTU meter automatically integrates energy consumption and transfers it to the computer. The consumption volume can be checked by a tenant or operator with no worries. It provides real-time information such as instantaneous temperature, flow rate, energy consumption, and others.

How to Install BTU Meter  

Careful attention to the site selection for the system components will help the installers with the initial installation, reduce start-up problems, and make future maintenance easier. For example, do not install the flow meter where it will be difficult for personnel to perform periodic maintenance.

• The Main Unit

Find an easily accessible location where wire connections can be made and meter readings can be taken from floor level. Mount the System enclosure on a vibration free surface.
Avoid locations such as the plenum of a fan coil, heat exchanger or any housing that may contain electric motors or other strong sources of electrical interference.

• The Flow Meter

When properly installed, the flow meter will only measure flow associated with that portion of the piping system for which the energy measurement is being made. The flow meter may be
installed in either the supply or return line. Choose the location with the longest straight run of unobstructed pipe. Please refer to the flow meter installation manual for specific information
regarding the straight run requirements for the flow meter used with this SYSTEM BTU Meter.

• The Temperature Sensors

The two temperature sensors must be located in such a manner as to accurately measure only the temperature of the supply line entering and the return line leaving the portion of the piping system for which the energy measurement is being made.

If possible, find an easily accessible location where wire connections can be made from floor level. This will facilitate any future service. Place the temperature sensors away from strong sources of electrical noise that might affect the performance of the sensors.

One temperature sensor thermowell will need to be placed in the same pipe with the flow meter. It should be located on the downstream side of the flow meter. The downstream distance between the thermowell and flow meter should be at least five pipe diameters, leaving enough clearance to remove either sensor from the pipe without interference from the other sensor.

What is BTU with example

Click here to download onicon flowmeter installation and operation guide for the detailed study

Operation of BTU Meter

When the water or other liquid passes through the pipeline, the flow meter measures the instantaneous flow rate and sends it to the BTU meter then the temperature sensor measures the return pipe temperature and supply pipe temperature and also sends it to BTU meter.

According to the above formula, BTU meter integrates the cooling or heat consumption. If T1>T2, integrates cooling consumption, otherwise integrates heat consumption. Finally, BTU meter stores the data and displays on LCD and can connect to existing BMS system.

Measuring principles

Prerequisites knowledge to understand below calculation

BTU meter calculates energy consumption by flow rate and temperature difference, the formula is:

btu-measurement-system

No need to worry about this complex calculation, from the above parameters of supply, return temperature and flow rate, BTU meter calculates the heating/cooling energy consumption and send it through any building networking protocols like BACnet, Modbus etc to the existing BMS system or HMI display to the owner and this data can be used to bill the tenants.

Source from https://www.flotech.com.sg/products/energy/btu-measurement-system/

Now let us see

How to calculate electrical costs for cooling and power consumption

A BTU is approximately a third of a watt-hour. 1000 BTU/h is approximately 293W.  Kilowatt-hour (kWh) is most commonly known as a billing unit for energy delivered to consumers by electric utilities.

Cooling or heating cost calculation

For calculating the heating/cooling cost to the tenants,  use the formula where we translate the BTU/h to Watts needed so we get the correct costs associated with cooling or heating of the tenants.

Note: Normally in the building, they will add extra cost like operating Cost (electricity, maintenance, meter reading, invoicing tenants) with energy consumption.
 
Please leave a comment if you don’t understand and share your words if you know much better than this post .so that I can add with this post to make understand the reader in a better way.
 
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