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Metering system - usual point of measurement for Heating & Cooling

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Designing a metering system
Step 1: project definition
Step 2: Design of the different components of the measurement system
  • Select the meters (no content yet)

We propose here below some guideline to define the points of measurement according to the energy use and the required breakdown of the measurement (the breakdown means how the energy use consumption will be reported, it can be reported as building global consumption or consumption per floor or area)


This energy use is the major consumer in tertiary building.

Legend for the following schemes :
Fig K41.png

Contents


Refrigerant fluid – Split and Multi-split systems

The external unit is supplied from the LV switchboard and it supplies all internal units.

Electrical diagram


Fig K42.png

Data to collect according to consumption breakdown :

  • Global consumptions: aggregations of each split system consumptions
  • Area consumptions: consumptions of the corresponding split system which includes internal units and external unit consumptions

Method of measurement

  • Direct metering : electrical meter

Usual point of measurement locations :

  • Feeders in the main electrical switchboards for small buildings or floor/tenant panelboard for large buildings

Breakdown between Heating and Cooling :

  • Some split system can be inverters. In order to break down the heating and cooling consumptions, an additional measurement should indicate the mode of operation, such as :

- Control signal

- Measurement of the supply and return fluid temperatures


Refrigerant fluid – VRF/VRV (Variable Refrigerant Flow/Volume)

The external unit is supplied from the LV switchboard and it supplies all internal units.

Principle


Fig K43.png

Electrical diagram


Fig K44.png

Data to collect according to consumption breakdown :

  • Global consumptions: aggregations of each VRF system consumptions
  • Area consumptions: consumptions of the corresponding VRF system which includes internal units and external unit consumptions

Method of measurement

  • Direct metering : electrical meter

Usual point of measurement locations :

  • Feeders in the main electrical switchboards or floor/tenant panelboard

Breakdown between Heating and Cooling : Two kinds of VRF exist:

  • 2 pipes : all terminal unit heat or cool at the same time.

In order to break down the heating and cooling consumptions, an additional measurement should indicate the mode of operation, such as :

- Control signal

- Measurement of the supply and return fluid temperatures (at the outdoor unit level)

  • 3 pipes : each terminal unit are independents. Some unit may heat while another one may cool at the same time. The breakdown is therefore very difficult to realize.


Air system – Rooftop

The rooftop is supplied directly from a LV switchboard. The air distribution in the duct system is provided by the rooftop.

Electrical diagram


Fig K45.png

Data to collect according to consumption breakdown : This system is normally used for a large open space area such as supermarket sale areas.

  • Global consumptions: aggregations of each rooftop consumptions
  • Area consumptions: possible if the rooftop is used for a dedicated area otherwise it is not possible to make an area breakdown.

Method of measurement

  • Direct metering : electrical meter

Usual point of measurement locations :

  • Feeders in the main electrical switchboards or HVAC switchboard.

Breakdown between Heating and Cooling :

The rooftop provides most of the time only cooling.


Air system – VAV (Variable Air Volume)

Principle


Fig K46.png

Electrical diagram


Fig K47.png

Data to collect according to consumption breakdown :

  • Global consumptions :

- Air Handling Unit consumption

- electrical batteries consumptions for electrical heating

- boiler consumption for hot water production and pumps consumption for distribution.

  • Area consumptions: possible if the AHU is used for a dedicated area otherwise it is not possible to make an area breakdown.

Method of measurement

  • Direct metering : electrical meter

Usual point of measurement locations :

  • Feeders in the main electrical switchboards or HVAC switchboard.

Breakdown between Heating and Cooling : We assume that cooling is provided by the AHU. Heating can be provided either by :

  • electrical battery in each VAV terminal unit – then the consumptions of heating has to be metered in each sub-panelboard (floor or area).

or

  • hot water battery from a central boiler – heating consumptions has to be metered from the central heating boiler with an heat meter.


Water system

In the case of a two pipes system only heating or cooling is possible at the same time in the building (2P inverter). In the case of a four pipes system cooling and heating can happen simultaneously (4P). This is the same for a two pipes and two wires system (2P+2W).

The picture here below describes the different elements of the system :


Fig K48.png


Combine heating and cooling – 2 P inverter

Typical systems of type combine heating and cooling are reversible heat pumps.


Fig K49.png

Data to collect according to consumption breakdown :

  • Global heating and cooling production : Heat pump consumption
  • Global heating and cooling distribution: Pumps electrical consumption
  • Area consumptions: heating and cooling consumptions of the dedicated area

Method of measurement
Heat pump consumption :

Direct metering : electrical meter

Pump distribution consumption

  • Direct metering : electrical meter

Area consumption

  • Direct metering : heat-cold meter, such meter is able to split heating and cooling consumption

Point of measurement locations :

  • Heat pump and pumps consumptions : feeders in the main electrical switchboards or HVAC switchboard
  • Area consumptions : after the area pipe derivation, but location may strongly depends on the water distribution

Breakdown between Heating and Cooling :

Global consumption: the solutions to break down heating and cooling are :

  • Use of heat-cold meter at the heat pump level – this may require a communication interface (M-Bus, RS485, …) instead of pulse communication
  • Control signal from the heat pump controller
  • Measurement of the supply and return water temperatures

Area consumption: the solutions to break down heating and cooling at this level are

  • Use of heat-cold meter at the heat pump level – this may require a communication interface (M-Bus, RS485, …) instead of pulse communication


Independent systems for heating and cooling – 4 P


Fig K50.png

Data to collect according to consumption breakdown :

  • Global heating and cooling production :
  • Boiler(s) gas consumption
  • Chiller(s) electrical consumption
  • Global heating and cooling distribution
  • Pumps electrical consumption
  • Area consumptions: heating and cooling consumptions of the dedicated area

Method of measurement
Boiler consumption

  • Direct metering : gas or fuel meter
  • Indirect metering : heat meter - boiler efficiency shall be taken into account (% or m3/kWh)


Fig K51.PNG

Gas consumption for heating = heat meter consumption (kWh) x boiler efficiency (m3/kWh)
(ratio kWh/m3 is around 11 for natural gas)

Remark: measuring both incoming gas consumption and heating production with an heat meter enables to check the boiler efficiency that can evolve with time.

Chiller consumption

  • Direct metering : electrical meter

Pump distribution consumption

  • Direct metering : electrical meter

Area consumption

  • Direct metering : heat and cold meters

Point of measurement locations :

  • Chiller and pumps consumptions : feeders in the main electrical switchboards or HVAC switchboard
  • Gas consumption for boiler: utility meter location or boiler room
  • Area consumptions : after the area pipe derivation, but location may strongly depends on the water distribution

Breakdown between Heating and Cooling : With a 4P distribution, heating and cooling are naturally independent.



Independent systems for heating and cooling – 2 P inverter


Fig K50.png

Data to collect according to consumption breakdown :

  • Global heating and cooling production :
  • Boiler(s) gas consumption
  • Chiller(s) electrical consumption
  • Global heating and cooling distribution
  • Pumps electrical consumption
  • Area consumptions: heating and cooling consumptions of the dedicated area

Method of measurement
Boiler consumption

  • Direct metering : gas or fuel meter
  • Indirect metering : heat meter - boiler efficiency shall be taken into account (% or m3/kWh)


Fig K51.PNG

Gas consumption for heating = heat meter consumption (kWh) x boiler efficiency (m3/kWh)
(ratio kWh/m3 is around 11 for natural gas)

Remark: measuring both incoming gas consumption and heating production with an heat meter enables to check the boiler efficiency that can evolve with time.

Chiller consumption

  • Direct metering : electrical meter

Pump distribution consumption

  • Direct metering : electrical meter

Area consumption

  • Direct metering : heat-cold meter, such meter is able to split heating and cooling consumption

Usual point of measurement locations :

  • Chiller and pumps consumptions : feeders in the main electrical switchboards or HVAC switchboard
  • Gas consumption for boiler: utility meter location or boiler room
  • Area consumptions : after the area pipe derivation, but location may strongly depends on the water distribution

Breakdown between Heating and Cooling :

Global consumption: heating and cooling productions are independent.

Area consumption: the solutions to break down heating and cooling at this level are

  • Use of heat-cold meter – this may require a communication interface (M-Bus, RS485, …) instead of pulse communication.
  • The cooling or heating mode can also be given by the operator himself in the data analysis system.


Independent systems for heating and cooling – 2P+2W

The location of the point of measurement for heating depends on either there are electrical independent floor HVAC panel boards or floor panel boards that mix lighting, HVAC and office equipment.

Independent HVAC floor panel


Fig K52.PNG

Non independent HVAC floor panelboard


Fig K53.PNG

Data to collect according to consumption breakdown :

  • Global cooling : chiller(s) electrical consumption
  • Global cooling distribution : Pumps electrical consumption
  • Global heating : aggregations of electrical batteries consumptions of each area
  • Area consumptions :

- Heating : electrical batteries consumptions of the dedicated area

- Cooling : cooling consumption of the dedicate area


Method of measurement
Electrical batteries consumption

  • Direct metering : electrical meter

Chiller consumption

  • Direct metering : electrical meter

Pump distribution consumption

  • Direct metering : electrical meter

Area consumption

  • Direct metering : electrical meter for heating

Usual point of measurement locations:

  • Chiller and pumps consumptions : feeders in the main electrical switchboards or HVAC switchboard
  • Electrical battery consumptions:

-Independent HVAC floor panelboard : feeders in the main electrical switchboards or HVAC switchboard

- Multi energy use floor panelboard : feeders in the main electrical switchboards or HVAC switchboard

  • Area consumptions : cold meters have to be installed at the floor level in the technical room

Breakdown between Heating and Cooling : Heating and cooling productions are independent.

Remark: Electrical batteries in FCU can sometimes be used as booster and combined with a central water heating. Point of measurement for heating shall then be added according to the type of production (combine or independent) in the corresponding paragraphs.