Honeywell - Community Heating Design Principles & Schematics

Community Heating - Design Principles - Schematics

Simple Schematic - Community Heating Scheme

The key elements of a community heating scheme comprises five parts:

• The Energy Centre - generation of heat energy takes place at the energy centre using solar energy, ground source heat pumps, combined heat and power engines, biomass boilers or any other suitable methods to generate heat.
• The Distribution Network - it is a network of highly insulated pipes that use water as a medium for conveying heat energy to the users.
• The Energy Substation or Pressure Breakers - they are used for heat transfer from High Temperature Hot Water (HTHW) to Low Temperature Hot Water (LTHW), providing a pressure break for hydraulic balancing of the network.
• Hydraulic Interface Unit - provides the separation of the primary and the secondary network, billing mechanism and comfort controls for the users.
• Domestic Dwelling or Commercial Unit - consists of programmers for time and temperature control of various zones, thermostatic radiator valves and room thermostats. Thermostatic mixing valves are used at the hot water outlets to prevent scalding and pressure reducing valves are used for saving water and protection of pipes and fittings.

Energy Centre

An energy centre is the heart of a community heating scheme. Various routes to generate heat are adopted to reduce cost and gain maximum benefit for the users and the energy provider. The most common heat sources are combined heat and power engines, biomass boilers, ground source heat pumps and solar energy. Heat storage may be used to store the heat during low demand times of the day and use it during peak hours, and absorption units may be used to provide cooling during summer.

Variable frequency drives (VFD), commonly known as inverters are recommended for use with the pumping set to save energy, improve equipment life and maintain the required pressures with varying demand.

Honeywell Series 300 pump protection valve, safety valve and surge anticipation valve is also recommended for pipework protection from water hammers and pump protection from surges.

A Honeywell BA295 Reduced Pressure Zone (RPZ) valve is recommended for use at the distribution system and boiler filling system for protection up to fluid category 4. Backflow preventers are ideally suited for industrial, commercial and residential applications to prevent any contamination of the water supply line.

Open protocol building management controllers like the Honeywell Hawk and Lynx are used for managing demand for optimum use of energy by sequential and preferential operation of various heat generation sources and reduce cost significantly by reducing the overall scheme size including the plant size, distribution network and fuel consumption through intelligent and interactive control.

Typical Distribution Network

A distribution network delivers the heat energy to the users using water as a medium via a network of highly insulated pipe, and provides hydraulic controls for protection and balancing. It is recommended to have leak detection on the network with the use of a suitable open protocol building management system for pin-pointing a leakage during an event.

The water controls on the distribution network comprise of the Honeywell Series 300 valves and their types and roles are described as below:

Honeywell Series 300 - Types

The pilot operated control valves are available between sizes DN40 to DN450 and up to DN900 on special request for control of water distribution networks. The key features are:

• Basic valve - Mainly used as a shut-off valve, a manual, electro- magnetic solenoid or float valve can be used as a control valve.
• Filling valve - Used in water supplies and for industrial and commercial applications for the filling of reservoirs, tanks and cisterns. It is controlled by the main storage medium via a float valve and impulse link pipework.
• Altitude control valve - Controls the water level in water reservoirs without the need for using a float valve or other ancillary controls.
• Magnetic solenoid valve - Mainly used as a shut-off valve.
• Flow rate regulator - Also called flow rate limiting valve, it controls to a fixed flow rate, independent of fluctuating operating pressures and take-off flow rates.
• Safety valve - Controlled by the medium flowing through it via a pilot valve. It is preferably installed in branches of supply pipework and protects downstream parts of a system which are at risk from unacceptable excess pressure.
• Pressure sustaining valve - Controls the pressure on the inlet side.
• Pump control valve - Protection valve in pressure boosting systems to provide a water hammer free shutdown and start-up of pumps.
• Surge anticipating valve - Prevents negative pressure and water pressure shocks in long pumped pipework systems caused by sudden pump shutoff.
• Protection valve for deep well pumping - Permits pressure shock free starting and stopping of deep well pumps.
• Priority valve - Combination between pressure regulating and pressure limiting valves. It is used to ensure priority drinking water supply to important systems. In addition downstream installations are protected against excess supply pressures.