Differential pressure switches detect quickly flow in the heat exchanger. They are extremely reliable since they are not affected by dirt and have no flow restriction. It can be installed on any pipe size.
Compressor protection Detect water, glycol, or methanol flow easily.
Include 1x Compressor protection switch 2x Stainless Tee 3/4" 2x Stainless shorth Nipple 3/4" 2x Stainless flexible braided Teflon lines 14" each
If using reversible water to water heat pump then 2 flow switches in series should be installed for complete protection on each side.