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.

DHW secondary components assembled ready to install (remotely from cylinder). A service isolation valve and in-line 'Y' strainer are visible in the mains water inlet (bottom right) which are not shown in the diagram. The electrical connections to the pump and flow switch, and the triac electronics are not shown in this photograph.

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 \        ------------          |
 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