Programable TRV statagy with cast iron rads?

[Orionaut]

As above.

I have old cast iron rads (400Lbs each)

I have programmable TRV's

The problem is massive overshoot when the heating first comes on!

(Anybody who has a similar set-up will know what I mean but I will explain for anybody who doesn't if necessary)

I am trying to figure out a strategy for reducing the impact of this, but was just wondering if anybody else had already worked one out?

 

[Orionaut]

Overshoot?

Rads fill up with hot water fairly quickly and then become massive storage heaters. By the time the TRV's have an opportunity to respond the amount of heat stored in the rads will make the rooms get up to 25C or more!

They have been "off" for two hours now but the rads are still hot and the room is still at 23C which is wayyyy to hot for me despite the TRV's being set at 17C.

 

[Orionaut]

What I am tempted to try (The terrier valves are quite versatile) is to aim for a burst heat at switch on (Say 19C at 18:00) but with a shut down to 5C shortly after (say after 30 Min) , then a lower switch on value, say at around 17C at 19:30/20:00 Hrs.

As I said to begin, I am just wondering what others have done. I am sure I am not the only person with CI rads.