heat bank variation with minimal cylinder size

[mafj]

Hi,

I am considering a DIY upgrade of standard unvented heating + hot water system powered by a gas boiler.

I consider heatbank and combi boiler. Both good upgrade allowing removal of cold water tank and having pressurised direct hot water.

I like idea of heatbank over simple boiler for main reason:
* faster hot water as I have boiler far from bathrooms but could put heat exchanger at each bathroom as well as kitchen.

What concerns me about heatbank is the size of the cylinder. I am not quite sure why I'd need a cylinder. Cannot I have a closed loop system similar to combi boiler heating system?

 

[Dan Robinson]

Oh dear

 

[mafj]

Looks I am looking for information on: Hybrid tankless water heaters

As with combi boiler system, boiler needs to provide enough bang to support continous flow of hot water, e.g. for shower/bath + 3 sinks. ANd has some water tank for faster start and to avoid boiling.

Combi system looks actually way more expensive as it would require new boiler. While Hybrid tankless (with small tank that is) will reuse most components, that is my 14kw (little low but for a start should be enough) standard boiler and most of plumbing

My idea is on the boiler loop is:

boiler -> pump--->3way valve (1)->(bottom)cylinder(top)->PHE1 -> PHE2 -> PHE3 ---> boiler

3way valve(2)->radiators->boiler

pump->bypas->boiler


Advantage: changes from original sytem limited.







However, obvious it is, I have limited understanding