Thermal stores

[Balenza]

gas4you wrote

but the basic physics just doesn't add up.

I think you mean acheiving boiler condensing for a percentage of the boiler run time during the re-heat.
DPS's states their small 125 liter UV cylinder which uses a plate hex for the re-heat produces 100/L more hot water over a one hour period than a 300L UV cylinder reheated using a coil.
Its due to the efficiency of the plate during re heat and the fact that the heated water is pumped directly into the top of the cylinder where its needed unlike a coil which is at the bottom and relying on slower convection currents.
Thats how DPS describe it anyway. I ve seen a few plumbers install systems this way. Their not the usual "run of mill" type of plumber (no offence to anyone) IMO. The re-heat times are what impresses them and the ability to match the heat exchanger exactly with the boiler output.

Which is more efficient.? The super fast re-heat with less condensing (subject to store temp)taking place with the small volume of water or the slower reheat with more condensing taking place with the large volume of water. ?

 

[Doctor Drivel]

gas4you wrote

but the basic physics just doesn't add up.

I think you mean acheiving boiler condensing for a percentage of the boiler run time during the re-heat.
DPS's states their small 125 liter UV cylinder which uses a plate hex for the re-heat produces 100/L more hot water over a one hour period than a 300L UV cylinder reheated using a coil.
Its due to the efficiency of the plate during re heat and the fact that the heated water is pumped directly into the top of the cylinder where its needed unlike a coil which is at the bottom and relying on slower convection currents.

Thats how DPS describe it anyway. I've seen a few plumbers install systems this way. Their not the usual "run of mill" type of plumber (no offence to anyone) IMO. The re-heat times are what impresses them and the ability to match the heat exchanger exactly with the boiler output.

Which is more efficient.? The super fast re-heat with less condensing (subject to store temp) taking place with the small volume of water or the slower reheat with more condensing taking place with the large volume of water. ?

Plate Heat Xs are so efficient that the bottom on the cylinder would be quite cool promoting condensing. The plate takes all of the boilers output and puts the hot water at the top of the cylinder. A coil that takes all the boilers output would be quite large and takes up lots of space inside the cylinder.

I have used a cyl' stat, bronze pump and plate heat X to heat a direct cylinder. It worked out cheaper than buying a larger cylinder with a large indirect coil.

People should get to understand:

1. thermal storage,
2. CH buffering,
3. neutral points
4. what plate heat exchangers can do and give.

As a rule of thumb, to promote condensing in boilers you generally need larger rads and cylinders, which take up space.

In small UK homes smaller cylinders is far more desirable. Preferably no cylinders at all with a high quality, high flowrate combi.