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About thermostatic radiator valves
(lemmy.ml)
I'm not an expert, but I believe it's more to do with them being in one position for very long, so it wouldn't matter in what position that would be. As long as you turn them open and then close them again once every few months, any calcium buildup would break loose. Maybe someone who is an expert can back me up :)
Depending on how much calcium is in your water, they can calcify if not being moved for a long time. Some electric ones periodically go all the way in both directions to make sure that doesn't happen. It is however very rare this happens. Usually you can leave them off for summer without problems.
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