DIY Heat Bank
This article is about making a DHW Heat Bank using readily-available separate components.
Components
Normal Y-plan (or S-plan, W-plan etc) vented CH+DHW system with
- Direct HW cylinder (a standard Indirect cylinder could be used, either with extra tappings via e.g. Essex flanges, or Tee-ing the connections from the boiler into the top and (existing) bottom connections of the cylinder.)
- Pump (standard 15/50 CH circulator type)
- Plate Heat Exchanger (PHE)
- Thermostatic Mixing Valve (TMV) 22mm
- Flow switch wired to switch on pump when flow is detected
PHE
From:
GEA-Ecoflex Unit 8, Waterside Business Park Redwall Close Dinnington-Sheffield S25 3QA Tel.: +44-(0)1909 551 107 Fax: +44-(0)1909 550 885 e-mail: info.uk@gea-ecoflex.com
Copper brazed plate heat exchanger model:- BP12M-20-G1G1
Spec
Compact gasket-free Brazed Plate Heat Exchanger consisting of corrugated pressed stainles steel plates (1.4401), which are brazed together with copper in a special vacuum process. Designed, produced and tested in sites with quality systems in accordance with DIN ISO 9002 requirements. Pressure-Vessel Approval according TÜV and EC Pressure-Equipment-Directive (CE).
Specification for 1 x M12-20-GG | ||||
---|---|---|---|---|
Operational data: | Side A | Side B | ||
Media: | Water | Water | ||
Condition: | liquid | liquid | ||
Heat exchanged: | 50 | kW | ||
Mass flow: | ||||
Volume flow: | 0.64 | 0.24 | l/s | |
Temperature inlet: | 82 | 10 | °C | |
Temperature outlet: | 63 | 60 | °C | |
Pressure drop: | 29.65 | 3.91 | kPa | |
Surface margin: | 1.49 | % | ||
Content: | 0.5 | l | ||
Heat transfer area: | 0.22 | m² | ||
Design pressure: | 30 | bar | ||
Design temperature: | 200 | °C |
Note this is probably under-sized for this application: 100kW would be preferable.
Flow Switch
Farnell order code 730890 Manufacturer Part Number FS22 FLOW SWITCH, 22MM 3.75 L/MIN; Switch Poi £11.60 + VAT & p&p
This is a reed-switch whose contacts are rated 15VA, max 1A AC, into resistive loads.
The pump is rated 82W, 0.36A @ 230V AC and is an inductive load so the circuit shown is used to drive it.
----------+--- LIVE 240V AC | | | 100R | | ------- === 0.1uF | PUMP | | 600VDC ------- | +---------- | --100R-------+--------------- | | | FLOW \ ------------ | SW o | MT2 | | | | | ----- ------| G TRIAC | | MOV | | | ----- | MT1 | | ------------ | | | +--------------- | -------------- NEUTRAL Triac: BTA16 600B (Maplin) MOV 250V AC (Maplin) Resistors 1W Components wired up on strip of chock-block
- Discussion of design of circuit from sci.electronics.design
An alternative requiring no electronics would be to use a flow switch capable of switching the pump directly. These ara available from DPS.
TMV
This is a standard 22mm Thermostatic Mixing valve used for limiting the temperature of water to washbasins in hospitals, schools etc to prevent scalding. Available from Screwfix, Toolstation etc.
See Also
- Discussion: Home Made Heat Bank on uk.d-i-y
- Discussion: DIY Heatbank - fine tuning of system (incl CH) on uk.d-i-y
- Domestic Hot Water
- Domestic Hot Water Systems
- Thermal Stores and Heat Banks
- Central Heating