Design Considerations - A Manufacturers Perspective 1 Introduction - PowerPoint PPT Presentation

Design Considerations - A Manufacturers Perspective 1

Introduction  Ormandy Group, established in 2000, are a leading UK manufacturer of water heating & cooling systems covering:  Commercial  Industrial  Food / Pharmaceutical  Marine / Off-shore  Nuclear  Residential / Domestic  Background in bespoke design for specific applications or installations. 2

Objectives  Provide a basic definition of an HIU.  Outline the design considerations for the specification and manufacture of an appliance.  Illustrate the effect that changes to the specification can have on component selections. 3

Definition of an HIU  So what is an HIU / Heat Interface Unit?  a.k.a. consumer unit, heat station or hydraulic board.  A means of providing heating or cooling energy to an end user from a central energy centre or distribution network.  A pressure break between the energy centre/distribution network and the end user.  Typically a wall mounted appliance of similar size & appearance as a domestic combination boiler. 4

Benefits of using an HIU  For the energy provider / landlord:  Protect the primary energy plant/distribution network from pressure loss or leakage at point of use.  Reduce risk of supply disruption.  Reduces labour/maintenance costs.  No gas supply - no gas safe registered engineers required.  No requirement for annual gas safety checks.  Basic service items and operational checks.  Simple, robust mechanical or electro-mechanical components. 5

Benefits of using an HIU  For the energy provider / landlord:  Enables fuel/energy flexibility which brings the possibility to increase the overall fuel/energy efficiency for a site.  CHP  Air to water heat pumps  Solar  Wood chip/pellet  Traditional gas fired boilers  Bio-fuels  Flexibility during the mechanical installation & commissioning phases  Staged installation, primary system installed up to point of use ready for fit out of individual residences. 6

Benefits of using an HIU  For the end user / tenants:  Simplicity  Is the unit switched on  Does it have pressure in the secondary circuit  Is the rooms thermostat or programmer working - enable signal to HIU.  Reliability  No complex gas / burner controls  Safety  No combustion  No risk of gas leakage  No risk from Carbon Monoxide 7

Design Considerations  Temperature profiles  Energy Rating – kW duty  Operating Pressures  Differential Pressure / Pressure Drop  Control Method – temperature & operation  Demarcation  Package size / working envelope  Approvals  Energy Metering  Price . . . 8

Design Considerations  Temperature Profiles – Typical Examples  LTHW Central Heating – Radiators  80 / 60°C Primary (Flow / Return) – 70 / 50°C Secondary  LTHW Central Heating – Under Floor Heating Systems  80 / 60°C Primary – 50 / 40°C Secondary  CHW Cooling – Fan Coils / Chilled Beams  6 / 13°C Primary – 8 / 15°C Secondary (2°C approach temperatures)  DHW (Domestic Hot Water  80 / 20°C Primary – 10 / 60°C Secondary  55°C Secondary flow at specific request of the client. 9

Design Considerations  Temperature Profiles  Summer / Winter / Weather Compensated ?  Plate heat exchangers are designed to provide a rated performance around one set of parameters, i.e. typically designed for full load duty.  If the supply from the central energy centre / distribution network changes the performance of the plate heat exchanger may alter as a consequence of the change in supply primary conditions. It does not become less efficient. 10

Design Considerations  Temperature Profiles – cont’d.  Effect of close approach temperatures, e.g. In CHW appliances. 10 kW Duty 10 kW Duty 10 kW Duty 0.34 l/s Flow 0.34 l/s Flow 0.34 l/s Flow 6/13 °C Primary 6/13 °C Primary 6/13 °C Primary 7/14 °C Secondary 7.5/14.5 °C Secondary 8/15 °C Secondary 3.97 m² H.T. Area 2.10 m² H.T. Area 1.46 m² H.T. Area 11

Design Considerations  Temperature Profiles – cont’d.  Effect of close approach temperatures, e.g. In CHW appliances. 20 kW Duty 20 kW Duty 20 kW Duty 0.68 l/s Flow 0.68 l/s Flow 0.68 l/s Flow 6/13 °C Primary 6/13 °C Primary 6/13 °C Primary 7/14 °C Secondary 7.5/14.5 °C Secondary 8/15 °C Secondary 7.5 m² H.T. Area 4.5 m² H.T. Area 2.7 m² H.T. Area 12

Design Considerations  Energy Rating – kW Duty  The following illustrate what would typically be expected for residences for up to 3 beds / 1 – 2 bathrooms.  LTHW Central Heating  5 – 10 kW  CHW Chilled Water  6 – 12 kW  DHW Domestic Hot Water  40 – 60 kW (approximately 12 – 21 l/min DHW flow) 13

Design Considerations  Operating Pressures  Primary Circuit (central energy plant / network)  PN10 – typically operating up to 6 barg.  PN16 – or greater is possible dependent on control valve selection.  Qn. – do you want to pipe a supply into a private residence which operates at pressures up to PN16?  Secondary Circuit (end user / tenant)  PN10 – typically operating up to 3 barg.  DHW Circuit (end user / tenant)  PN10 – typical operating pressure dependent on mains supply. 14

Design Considerations  Differential Pressure / Pressure Drop  Differential pressure allowance in the primary system of 50kPa for each appliance. Achieved across a range of duties by using appropriate BPHE and control valve selections and increasing pipe sizes as duty / flow rates increase.  Depending on type of control valve used – requirement for differential pressure between primary flow / return circuit to operate effectively.  Pressure drop in the secondary heating / cooling circuit external to the appliance – effect on recirculation pump selection. 15

Design Considerations  Control Method – temperature & operation  Primary flow rate modulated by a control valve based on secondary set-point temperature. Internal control system within the HIU.  Primary flow rate modulated by a control valve based on secondary set-point temperatures. External control system, i.e. BMS.  Primary flow ON/OFF, possible either via BMS or programmer / time clock and wiring centre.  How do you protect the diversity of the system? Differential pressure control valves / PICV’s on the primary circuit or flow limited valves? 16

Design Considerations  Control Method – DHW controls  Direct acting temperature control valve  Fast response (3 seconds) for instantaneous DHW  Adjustable temperature range from 45 – 65 °C.  Typically set for 55 – 60 °C  Lower supply temperatures met by blending at point of use. 17

Design Considerations  Demarcation: At what point do you draw the line between what is or should be included in the scope of the HIU from a particular supplier? 18

Design Considerations  Package Size / Working Envelope  Largely influenced by the temperature profiles & flow rates which effects the size & type of BPHE, i.e. single or multi-pass, and pipe sizes.  Required pump size to generate suitable secondary circulation head.  Consideration of the ideal orientation of BPHE’s so as to avoid entrapment of dirt or air locks.  Always aim to have good accessibility for routine maintenance or future servicing activities.  What size or envelope does the HIU have to fit into. 19

Design Considerations  Approvals  Which water supplier or water undertaker is responsible for supply to a development or building?  Do they insist on any approvals for installed equipment?  Is this for a complete appliance or only the wetted parts providing potable water.  Does the specified / installed equipment carry the relevant approvals? 20

Design Considerations  Energy Metering  Meter type – mechanical vs ultrasonic.  Method of extracting usage data – Mbus, Wireless, Radio, GSM, etc, . . .  Power Supply – internal battery vs mains powered.  Long term accuracy of the metering solution? 21

Design Considerations  Price . . . 22

Thank you Ormandy Group Duncombe Road Bradford BD8 9TB Tel: 01274 490 911 Fax: 01274 498 580 e-mail: sales@ormandyltd.com Web: www.ormandyltd.com 23