DIY Heat Bank

This article is about making a DHW Heat Bank using readily-available separate components.

There are also a mains feed via ball-float fill valve and an overflow on the F&E tank which are not shown in the diagram.

Components

Normal Y-plan (or S-plan, W-plan etc) vented CH+DHW system with

• Direct HW 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

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 but is an inductive load so to be on the safe side the circuit shown is used to drive it:

                     ----------+--- LIVE 240V AC
                    |          |
                    |         100R 
                    |          |
                 -------      === 0.1uF
                | PUMP  |      |  600VDC
                 -------       |
                    +----------
         100R       |
       --/\/\-------+---------------
      |       ------------          |
FLOW \       |     MT2    |         |
 SW   o      |            |       -----
      |      |    TRIAC   |      | MOV |
       ------| G          |       -----
             |     MT1    |         |
              ------------          |
                    |---------------
                    |
                     -------------- NEUTRAL
 
 Triac: BTA16 600B (Maplin)
 MOV 250V AC (Maplin)
 Resistors 1W
 Components wired up on strip of chock-block