Welcome! Here are the website rules, as well as some tips for using this forum.
aux boiler piping with storage question about Caleffi Diagram
I am putting in a gassification boiler with storage to supply infloor hydronic heat. I plan to include a mod/con aux boiler for backup and when away. I found this figure in Caleffi 17 and am wondering why the aux boiler return isn't plumbed to the bottom (cold) part of the storage tank. I thought mod/con boilers liked a cold return??? The text says that it is plumbed this way so it only heats the top of the tank but that should be taken care of by the sensor placement...What don't I understand???