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
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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.
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Provide a basic definition of an HIU. Outline the design considerations for the specification
Illustrate the effect that changes to the specification
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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.
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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.
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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.
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
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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 . . .
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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.
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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
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Temperature Profiles – cont’d.
Effect of close approach temperatures, e.g. In CHW
appliances.
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10 kW Duty 0.34 l/s Flow 6/13 °C Primary 7/14 °C Secondary 3.97 m² H.T. Area 10 kW Duty 0.34 l/s Flow 6/13 °C Primary 7.5/14.5 °C Secondary 2.10 m² H.T. Area 10 kW Duty 0.34 l/s Flow 6/13 °C Primary 8/15 °C Secondary 1.46 m² H.T. Area
Temperature Profiles – cont’d.
Effect of close approach temperatures, e.g. In CHW
appliances.
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20 kW Duty 0.68 l/s Flow 6/13 °C Primary 7/14 °C Secondary 7.5 m² H.T. Area 20 kW Duty 0.68 l/s Flow 6/13 °C Primary 7.5/14.5 °C Secondary 4.5 m² H.T. Area 20 kW Duty 0.68 l/s Flow 6/13 °C Primary 8/15 °C Secondary 2.7 m² H.T. Area
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
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
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.
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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
Pressure drop in the secondary heating / cooling circuit
external to the appliance – effect on recirculation pump selection.
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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?
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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.
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Demarcation: At what point do you draw the line
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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.
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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?
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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?
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Price . . .
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Ormandy Group Duncombe Road Bradford BD8 9TB Tel: 01274 490 911 Fax: 01274 498 580 e-mail: sales@ormandyltd.com Web: www.ormandyltd.com
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