Thermal store?

[mysteryman]

It is true that the thermal conductivity of copper is better than that of stainless steel. However, it is the boundary layer on each surface of the metal where most heat resistance occurs, and this masks the effect of the different metal. A declared rate of 20 kW is still 20kW regardless of the material used in manufacture. The relative volume of the coil is not important; the heat is inside the cylinder whether or not it is also inside the coil.

 

[D_Hailsham]

However, it is the boundary layer on each surface of the metal where most heat resistance occurs, and this masks the effect of the different metal.

Can you give a link which backs up your assertion?

A declared rate of 20 kW is still 20kW regardless of the material used in manufacture.

Agreed

The relative volume of the coil is not important; the heat is inside the cylinder whether or not it is also inside the coil.

Agreed, but if a stainless steel coil has to be much longer than a copper coil to provide the same heat output to the water, then it will take up more space in the cylinder.

 

[rnirvine]

Hi all. I am a newbie self builder trying to specify a heating/ hot water system with woodburning boiler stove, solar thermal panels (Velux) to run UFH (90 sq m) and provide for 3 bed home , 2 showers and bath.
I have had conflicting advice regarding material type for the 300ltr thermal store with two reputable heating suppliers swearing that the best type is stainless steel for durability or copper for efficiency.?? HELP

jb236, did you get anywhere with your velux panel, thermal store and stove boiler system? I'm doing a similar thing and would like to know what make of pumping station and heating controls you used.

thanks