System Design for efficiency using electronic, intelligent HIU s. Neil Parry CIBSE Accredited Heat Network Consultant

Transcription

1 System Design for efficiency using electronic, intelligent HIU s Neil Parry CIBSE Accredited Heat Network Consultant

2 Family owned Caleffi Four Italian manufacturing sites Total 233,000 square metres Branches in 12 countries: Great Britain, Germany, Portugal, Holland, Slovenia, United States, France, Uruguay, China, Japan, Australia & Brazil 300M Turnover With the amount of brass machined in one year Caleffi could build two Eiffel Towers!

3 Altecnic Purpose built Head office located in Stafford, England 40M turnover 6000 sq./m warehouse and 1200 sq./m office space Over 3200 UK distribution points stocking products and spares Key distributors: BSS, PTS, Pipe Centre, Plumb Centre, Jewsons, Grahams Key partners: Kingspan, Ideal, Worcester Bosch, Baxi, Mitsubishi, Crane, Synetica

4 Kyoto agreement 1998 Climate change act 2008 Carbon reduction targets 34% % Clean Growth Strategy UK Heat Strategy The future of heating 2013 London climate change and Mitigation strategy BEIS Heat Network Delivery Unit London Environment Strategy Heat Networks Investment Project (HNIP) Improve Energy efficiency/carbon reduction Building Regulations 2000, part L April 2013 CIBSE TM39 CIBSE KS7 CIBSE AM12 Carbon Trust CIBSE Heat Networks Code CP1 BSRIA HIU/Heat Networks Guide BG62/2015 BESA UK HIU Test Regime BEIS (Department for Business, Energy and Industrial Strategy (Formerly DECC)) Regulations, recommendations, renewables targets, Reduction commitments, advisory bodies, reduction targets, Government incentives etc.

5 What is district heating? Large scale LTHW flow and return system Connecting multiple dwellings, building, apartments etc. Providing heating and hot water to dwellings HIU s are the facilitator Central plant/apartments District heating vertically

6 Design benefits Independent of the energy source ideal for use with central gas, oil-fired boilers, CHP units, solar energy etc. Low return temperatures, low return temperatures, low return temperatures! No hot water storage tank required Minimises the risks of dangerous bacteria including Legionella Pneumophila No need to overheat the water Installation benefits Only three rising pipes required Simple commissioning No flues No gas pipe-work Operating Benefits Energy efficient heating control Ample hot water on tap Enables single apartment billing Maintenance free Efficient, robust design with intelligent control ensures high operational performance and reliability

7 Design Considerations Return temperatures System Design for low return Bypass s and preheat Pump control Variable Speed Pumping Flushing and Commissioning Diversity Factors Boiler, thermal store, pipe sizing

8 Low Return Temperature Lessons from Scandinavia Part L Domestic Heating Compliance Guide Radiators <50 Degrees C (MRT) Plate heat exchangers <40 degrees C (MRT) Cylinders <40 degrees C (MRT) GLA CIBSE Heat Networks code CP1 BSRIA HIU Std/Heat Network BG62/2015 Fairheat Ltd/BESA VWART It s not just about DHW!

9 LS = kw 4.2 x Delta T

10 Return temperatures Condensing boilers (OPEX) Renewables (OPEX) CHP Solar Heat pumps Buffer vessel size (CAPEX/OPEX) Pump size (CAPEX/OPEX) Primary pipework (CAPEX/OPEX) Larger delta T = Smaller flow rates. Smaller flow rates = smaller pipe diameters Smaller pipe diameters = Lower network losses Cooler return pipes = Lower network losses Cooler return pipes = Cooler corridors

11 Return temperatures System design Minimise system bypasses Valve control bypasses Separate flow header and a return header, not combined! VS Pump control Maximise radiator surface area Utilise UFH Be careful when lowering the primary flow temperature! It s all about the delta T! Lowering flow temperature increases required flow rate Lowering flow temperature increases return temperature Heat loss is a function of pipe diameter 80/45 is better than 70/40, 85/45 is better still A 22mm pipe loses significantly more heat than a 15 mm pipe. Lowering flow temperature reduces the HIU s DHW output Correct diversity in sizing Ensure the energy centre hydraulic connections favour the renewable sources and ensure they see the lowest return temperature

12 Return Temperatures How can the HIU assist? Power versus delta T Plate dimensions DHW production, return temperatures < 25C Heating temperature flow compensation RTL Intelligent DHW bypass HE heating pump Electronic control and fast acting, motor driven control valves

13 What return temperatures can be achieved?

14 What return temperatures can be achieved?

15 System bypasses 1: Flushing 2: System (dead head) 3: Pre-heat

16 DHW pre-heat functionality

17 Test data from Sweden and UK Preheat has a significant detrimental effect on the efficiency of the system. Depending on the selection of the HIU preheat can increase system losses up to 45% What have we learned? It s generally accepted that any HIU should have the capability for the preheat to be turned off Pump bypasses should be at the top of the riser Be careful with long lateral pipe run lengths Minimise the lateral pipe diameters Delays in response times at the taps can be exaggerated by mechanical HIU s Proportional mechanical control can cause delays over 90 seconds Non proportional Boost functions of electronic HIU s minimise the delay and can be less than 20 seconds

18 Pre-heat turned off

19 Improving the LTHW Pipe Layout Achieving 15% network losses or less (a) Reduced response time Reduced heat network losses Reduced reliance on preheat Less likelihood of corridor overheating

20 Improving the LTHW Pipe Layout Achieving 15% network losses or less Poor Single riser Very long laterals HIU s located far into the apartment Long response times Corridor overheating Reliance on preheat Better Single riser Shorter laterals Reduced response times Corridor overheating May require preheat Best Multiple risers Shortest laterals Fastest response times Lowest heat loss Least reliance on preheat

21 Variable Volume System Design

22 System Concepts 1. Energy source 2. Energy store buffer tank 3. Primary circulating pump 4. Variable speed pump 5. Remote sensor for variable pump control 6. One exchange module per apartment 7. (Flow bypass top of riser)

23 CIBSE Guide KS7 Variable Flow Pipe work Systems

24

25 Pump Control At Index

26 System Balancing

27 Heat Interface Units

28 Instantaneous DHW Direct and indirect units Direct HIU Indirect HIU

29 Indirect Units SATK30/32 BESA Tested Capacity DHW: Up to 75Kw Heating: Up to 15kW Electronic control Return Temperature Limitation (RTL) Flow rate limitation Modbus output Remote commissioning Modulating or fixed heating flow temperatures Pump safety bypass Stainless steel pipe-work Clamshell insulation DHW Effective kw DHW: Capacity examples, 10C/48C (50kW unit) Flow DHW Pressure Primary Tap Load Loss Primary Deg C l/h kpa Flow rate Primary l/h

30 Direct units SATK20/22 Capacity DHW: Up to 75kW Electronic control Return Temperature Limitation (RTL) Flow rate limitation Modbus output Remote commissioning Modulating or fixed heating flow temperatures Pump safety bypass Stainless steel pipe-work Clamshell insulation Intelligent primary bypass DHW: Capacity examples, 10C/48C DHW Flow DHW Pressure Flow rate Effective kw Primary Tap Load Loss Primary Primary Deg C l/hr kpa l/h

31 No UK Standard for HIU s

32 Control on the secondary Scaling, brought on by poor control Very low primary system delta T s Network failure do to lack of diversity C - Primary return D Primary flow E DHW flow

33 Low DP capable 2 port control valve Reverse return system required balancing using pipe-work a third more pipe-work required Or DPCV s across the network Extra cost, not shown on the HIU quote!

34 Performance Slow control valves

35 Performance Fast control valves

36 Reliability - Scaling Where and when does it occur? Almost always on the secondary side of the domestic plate Too high DHW temperatures (above 60 degrees C) Slow reaction times of mechanical control valves Relying on conduction of heat How have Altecnic solved the problem? The Altecnic HIU limits DHW temperature set points to 60 degrees C and below. The Altecnic HIU utilises fast acting electronic control and motor driven control valves The Altecnic HIU has a domestic circuit flow switch

37 System Performance

38 Reproduced courtesy of Guru Ltd Poor HIU/System

39 Reproduced courtesy of Guru Ltd Good HIU/System

40 Energy Centre Components and System Sizing

41 HIU Performance Calculations..\PHE Calculator.exe

42 UK standards Scandinavian standards DS439 BS6700

43 Boiler Sizing Quick Guide Two calculations Total heating load: (No. of apartments x heating load (kw)) Total DHW load: (No. of apartments x DHW load (kw) x Diversity) Boiler should be sized on the largest resultant figure, not both!

44 Primary Pipework Flow Rate Sizing Two calculations Heating flow rate: (no of apartments x heating load (kw)) /4.2x Delta T = ls DHW flow rate: (no of apartments x DHW load (kw) x diversity factor) /4.2 x Delta T = ls Both values are added together

45 Primary pipe-work sizing Apartment Heat Load (kw) DHW Load (kw) Heating Delta T DHW (Primary) Delta T Heating flow rate DHW flow rate Apartment primary flow rate Total Primary heating flow rate Total Primary Diversified Primary DHW flow rate DHW flow rate Total Primary flow rate

46 Buffer vessel sizing Volume of store should be equivalent to 10 minutes of primary water peak demand as a minimum. Volume of primary pipework can be included

47 Buffer vessel sizing Deg C - Litres 70 Deg C - Litres Buffer Vessel 40kW 80 Deg C - Litres

48 System calculations..\sizing spreadsheets\sizing - Presentation.xlsm

49 Sizing comparison 200 apartments A National consultant 2 bed apartment 115kW DHW Boiler size 2500kW Buffer Vessel litres Primary 80/60 DHW temp 60 C Result: Grossly inefficient, overheating in corridors, low delta T s, high pump speed/electricity use, noise, high energy cost, little to zero renewable energy source utilisation. DS439 2 bed apartment (1 bathroom) 45kW (2 bathroom 60kW) Boiler size 798kW Buffer Vessel 4889 litres Primary 80/25 & 80/35 (DHW) DHW temp 50 C Result: Efficient network, high pump turn-down ratios, large delta T s, low energy cost, cool return pipes, high renewable energy source utilisation.

50 Typical demands by apartment type Ref: CP1 (draft) Typical maximum Notes Property Type/Suitability Number of bathrooms power at 10C BCW Studio/ 1 Bed kW Suitable for servicing a shower and potentially a small bath, where the risk of a second draw off (e.g. wash basin) is low 1 bed/ 2bed kW Suitable for servicing a single bathroom with larger fittings (e.g. higher flow rate shower, larger bath) with potential to serve second simultaneous draw off from a washbasin type fitting (e.g. an en-suite toilet without a shower) 2 bed / 3 bed kW Suitable for servicing potentially 2 carefully specified and flow balanced bathrooms e.g. to service 2 simultaneous showers, or draw offs, dependent on cold water flow availability Greater than 3 bed, including luxury fittings (baths, monsoon showers etc.) >2 > or = to 45kW Likely to be practically limited to and therefore sized upon the cold water feed supply rate to the property..

51 Single bathroom and bathroom/en suite

52 Thank You Neil Parry CIBSE Accredited Heat Network Consultant