I have read the Home made Heat Bank thread (and the faq on DIY Heat stores plus a few other threads) from start to finish with great interest.
As it wont let me post a reply to the group on the original thread, I'll reluctantly have to start a new thread.
I am in a similar situation needing more pressure for showers particularly, but for the DHW in general. I currently have a bog std vented primary feeding CH and indirect DHW tank via pump motorised 3 way valve. I'm happy enough with the CH - its the DHW that's the problem. I dislike the energy useage of a 3bar shower pump c 850watts for a Stuart Taylor pump I saw, so would like to make use of the pressure there for free in the water mains. I have a friend with a very nice but very expensive Pandora Heat Bank - there's absolutely no way I want to shell out that sort of money!!
On the whole, thanks due to a number of contributors I am reasonably clear on what is required. I have a specific queries before I take the plunge next week:
1] So, adding 2 Essex flanges gives 4 connections to the main body of the tank (coil connections now unconnected and treating the tank as a direct) Where should the flow and return to the boiler be connected and where should the flow and return to the PHE be located?2] And related... is the positioning of the Essex flanges on the tank critical/is there a good spot ie a certain distance from the top/ bottom to locate them?
Now for the heat exchange circuit...
3] Are there any concrete recommendations for the capacity of the PHE? eg is 100kW regarded as a minimum for DHW at mains pressure ad flow? I see gea-ecobraze PHEs are recommended, so will probably go for one of these. Is there any heat output (kW) stats for the gea- ecobraze PHEs? ...are they not quoted as this would depend on the rate of primary flow.... mmmm...??4] What rating does the pump need to be? I know the water needs to go round fast for the PHE to get enough throughput. But it's only shifting a tiny volume of water (if it's all juxtaposed to the tank), so presumably a "high geared" design is required - if there is such a thing - big impeller, but not hugely powerful motor?? Is a standard CH pump not overkill for this job? Basically I want to avoid using more electricity on the pumping than I have to, so want to get this "tuned" right.
5] I get a bit nervous (plumbing is fine and electrics yep thats fine too, but electronics - not especially my forte) with talk of triacs and making up the electrics for this from components. I understand why the flow switch cannot directly switch the pump. Are there any suitable relay circuits available off the shelf to operate a pump off a flow switch? If so any suggestions of make and model again would be really useful.6] On the circuit diagram on
8] Also referred to in
Cheers
Mike