Discoloured rocks, sticking to heater cage
Been running my sauna for about 3 months now, pretty much daily. Yesterday I entered and was greeted by a sharp smell. Not something you want in your sauna. It smelled a little like hitting a rock with a hammer, if you've ever smelled that smell.
Today I started unloading all the stones (harvia black vulcanite) from the heater (harvia legend pillar heater). I discovered that some of them have become discoloured, see the pictures. Specifically the ones that sit in the centre of the heater. They've browned a little, taking on a bit of a toasted look. Additionally the stones around the sides of the heater, the ones that touch the cage, have started to degrade the cage, see the pictures.
There's also a fair bit of shrapnel at the bottom of the heater, so looks like stones have been cracking.
Theories? Is the heater running too hot? Are the stones packed too tightly and not enough airflow? I definitely didn't jam the stones in there but they have fit together quite snugly like a puzzle.
Thanks for any thoughts