TSI HM685 Hydronic Manometer Review
Last week I wrote about the TSI HM675 Hydronic Manometer 
. Today I will be discussing its older brother the TSI HM685 Hydronic Manometer. The HM685 manometer is an upgrade over the HM675 and has the same features but with a few upgrades. First the HM685 can calculate flow, heat flow, impeller diameter and brake power.