Sub-Metering Aesthetic Energy metering is required to comply with the requirements of the Building Regulations. All energy usage for water, heat, chilled water, steam, compressed air, electricity and gas in excess of 10kW output must be accounted for with metering in accordance with building regulations and European Directives. Meters to all have digital read-outs, RS485 cable outputs and no-volt pulsed outputs for each and every meter, all connected back to the University s automatic Monitoring and Targeting system. All plant with a total energy consumption output rating of greater than 10kW (single or three phase) shall be metered using networked meters for all HVAC services, all connected back to the University s Elcomponent AMR system. TBC A10/RS485 multi-function meters with pulsed and analogue outputs complete with all associated CT s for smaller circuits. Where Metering exceeds 4 No meters, a TBC interface (with connectivity of up to 18 TBC meters) to TBC A20 multi-function meters c/w individual TBC RS485 interface modules may be used. A RS485 network line driver is necessary to ensure the communication function correctly. Use of DIN-rail mounted TBC A10 meters with integral RS485 connections may be used on smaller subcircuit metering which will integrate on the same RS485 comm s interface, provided displays are accessible to read manually. The requirements of the regulations will be met by:- a) Assigning at least 90% of the estimated energy use to be attributable to an 'end use category'. b) Providing individual fuel meters to tenanted areas greater than 500m2. c) Providing systems that enable automatic meter reading and data collection facilities in buildings with total usable floor area (TUFA) greater than 1000m2. d) Reasonable provision would be to install energy meters in accordance with CIBSE TM39. e) CHP systems must have, at minimum, 'metering to measure hours run, electricity generated and fuel supplied to the CHP unit.
Associated Documentation University of Bath Generic Metering Specification WI002-5 Landlord s Requirements Specification (Services) Outline of Requirements The overall metering strategy. End use categories are defined as: Heating Hot water Ventilation Pumps Cooling Humidification Laboratory (with energy use equipment) Lighting Office equipment Lifts and vertical transports Local kitchens and vending Dedicated computer room or suite Sports and leisure facilities Covered car parks Catering equipment LZC plants The minimum size of load (input power) at which it is appropriate to install a permanent energy meter is defined in the table below: Plant item Rated input power (kw) Boiler plant 50 Chiller / cooling plant 20 Motor control centres to fans and pumps 10 Final electric distribution boards 50 Where a primary (utility) meter measures the energy consumption of a single end use category (i.e. a gas meter connected to a heating boiler plant) no further sub-metering of the gas service is required. Only where a primary meter measures the consumption of more than one end use category (i.e. a gas meter serving a boiler plant that provides heating and hot water) and either of those services use more than 10% of the total annual energy consumption, should a sub meter be installed. Effects on electrical distribution systems Dividing a building's energy consumption by end use category can, at its simplest, be achieved by providing individual distribution systems for each end use category. However, this can lead to an
excessive number of distribution boards and will result in increased capital costs. The minimum individual end use category electrical load at which sub metering would be expected is 50Kw for lighting and small power and 20Kw for mechanical services plant. It is therefore likely that this will only affect premises, or tenanted demises, with a floor area greater than 1000m2. Functional requirements Meters should be connected together via Modbus network and onto the Elcomponent AMR via a gateway. Modbus cabling must have a 120 Ohm termination resistor installed on BOTH ends of the RS-485 loop. For pulse meters such as water, gas, heat meters use a Modbus data logger. The successful conclusion of any metering project is the receipt of data on Systemslink and the TBC GUI. An example of a gateway would be the Synapsys SIP Interface or a Modbus (RS485) / Ethernet Interface suitably addressed. Requirements for meter connections to TBC GUI Pre-Requisites for connecting Modbus meters to the GUI are detailed below: Local RJ-45 socket local to meters required for connection. (Electrical Contractor). RJ-45 sockets are patched in local Comms room and are live. (University of Bath ITS department). OPC server configured on local TBC Network. (University of Bath ITS department) Iconics UA OPC server for Building Automation Software installed on OPC server. Modbus Wiring between meters back to IME Gateway (if meters are on direct connection). Note: that it is critical that this wiring is connected correctly at time of installation and that correct Modbus wiring standards / materials are used including end of line resistors. (Electrical Contractor). Pulse output wiring back to IME pulse totalizer which is then connected to Gateway. (If meters are pulse output type). (Electrical Contractor). Meters / Pulse Totalizers need to be addressed with unique communication address. Meters can feedback their data via one of two methods: Direct Modbus connection - allows for a feedback of all parameters in meter. Pulse Output - supplies a pulse when a specific amount of energy is consumed (this is defined in the meter). The preferred method of connection is the direct Modbus link as this allows for realtime data to be read from each meter device and there is much less chance of data being missed by the data collector unlike the pulse output meters. The meter communicates with the GUI via a local Modbus IP Gateway (IME Part No. IF2E001) and this then communicates the data across the local TBC network to the local OPC server. From here the Iconics UA OPC software is configured to look at each meter and read all available registers. These registers can then be read from the main GUI server. Daisy-chaining devices to the power meter
The RS485 slave port allows the power meter to be connected in a daisy chain with up to 31, 2-wire devices. In this document, communications link refers to a chain in devices that are connected by a communications cable. If the power meter is the first device on the daisy chain, connect it to the host device using a RS232 to RS422/RS485 converter. If the power meter is the last device on the daisy chain, terminate it with the terminator provided. See Table 5 for the maximum daisy chain communications distances for 2-wire devices. The terminal's voltage and current ratings are compliant with the requirements of the EIA RS485 communications standard. The Modbus communications for each meter and IME gateway should be as follows: Baud Rate - 19200K Stop Bit - 1 Parity - None Please refer to the individual manufacturer's instructions for the configuring and register listing of each device. If Pulse Output meters are being connected, it is very important that the scaling of each pulse is documented. This will be required by TBC to ensure the reported data is correct (e.g. 1 Pulse = 1KwH) as the data from these meters are collated in the GUI to prove 30 minute usage reports to the Systems link program in the Sustainability department. Use full function multi-meters using a gateway to connect to the TBC network. The TBC has been programmed to recognise a number of meters which are listed in the approved manufacturers section. Meters not listed may be used but the vendor TBC will need to compile the registers and programme the page to display data. Water meter All main water meter or sub meter shall be pulse emitter and compliant with Water company's specification and compatible with University TBC. Water sub metering shall be installed for high water usage areas such as Laundry area, water chillers, public toilets etc at project manager's discretion. Lifecycle To be designed to a minimum 20 year life. Produce selection should be made taking into account the full lifecycle costs. All factors that influence total system cost should be identified and quantified.
Approved manufacturers Electricity meter: Elcomponent Spares To be agreed.