On Wed, 25 Dec 2019 00:27:50 -0800 (PST), wrote:

Hi All,

Happy Christmas / Bah Humbug (delete as appropriate).

In the olden times, it was recommended to plumb the towel rail into the hot water circuit rather than the heating circuit.

What was the thinking behind this?

And is it necessary today?

TIA

Chris
Have seen it done that way, on old CH systems, so that it acts as a
bypass loop, if both HW and CH zone valves are shut. These days regs
call for a bypass loop with an auto bypass valve in it where the pump
might be running when all zone valves are closed eg. on pump over run.