Heat Banks

[gordonspants]

A Google finds this - http://www.bes.co.uk/products/117.asp
£££ Ouch. Clever. But £££ Ouch. It'd be £200+ for the 3 port
And it'd be interesting to know it's response time as it's spec'd for ufh which seems to work with the changing of the seasons rather than tenths of seconds.
Could use a modulating pump assembly (as on next page of link) designed for ufh as a shunt pump, setting flow temp to 'cold', all swiched on by a flow switch - so pump pumps, and ensures cold water down to bottom of store, mod pump speed would depend on amount of energy taken from the plate by the hot tap. Still £233 tho'!

 

[BigBurner]

The DPS link showing a RAVK valve looks like it's just 2 port - which would be simplest plumbing-wise as opposed to 3 port - just control the RAVK valve opening dependant on hot water temp, then throttle back a smart shunt pump as req'd to keep hot water temp reasonable - still need a tmv though for safety.

The RAVK is the TMV. It senses the DHW outlet temperature. The head is fast reacting, most UFH valves are.

You're right, hunting could really screw it up, so maybe a standard circ pump would be better - and cheaper, which is A Good Thing As long as it never fully shuts off, that'd work.

A 15mm by-pass around the pump (from outlet to inlet of pump) with a set flow regulator in-line to maintain a set by-pass flow - valve will not hunt then. BES Part number: 17527. Flow cartridges less than £1. 4 litres/min 17529. A Grundfos 15-50 can pump up to 60 litres/min. Keeping it at 4 litres/min, or less, will ensure the pump will not be stressed when occasionally the RAVK closes 100%, which will be a very rare in real operation.
http://www.bes.co.uk
This regulates a "constant" by-pass flow, and then the valve passes a progressive flow.

When the RAVK totally closes the by-pass ensures the pump is pumping with water running through it. It would be interesting to see if a Smart pump would work well using a by-pass flow regulator. If using a Smart pump on the CH it would be worth fixing it on the DHW to monitor.

But before any of that, antistratification within the tank would be better and cheaper

• Anti-stratification spreaders
• A DHW plate pump that only sends back to the store very cool water at a flow rate only necessary to maintain DHW outlet setpoint temperature, not upsetting stratification.
• A large plate heat exchanger. The largest you can get. This ensures that the maximum amount of heat is extracted from the store water and transfered to the cold incoming DHW. It also ensures only very cool water enters the bottom of the store, enhancing condensing operation, promoting high economy.