Why We Don't Use Glycol

[@BrianSmith-nw2jo]

How do you know if the anti-freeze valves have operated especially if you are away on holiday etc.

[@pt6423]

I disagree with the reasons for not using glycol. I agree it lowers the efficiency of the heat transfer. Glycol is slightly slippery so it will lubricate the pipes and water immersed bearings inside the pump. I would add glycol in a SMALL amount for lubrication purposes only AND add anti freeze valves. Best of heat transfer VS longevity of the system. Anti freeze in an internal combustion engine does two things. It stops the engine furring up and lubricates the pump. If you run the engine without antifreeze the pump will seize eventually never mind damage from freezing. Heat pump engineers are obsessed with efficiency figures over safety of the system. Changing glycol/inhibitor is a schedule service item and should not be avoided.