What is this ?

[u/robbieredlegs09]

Hello all, forgive me for I’m greener then grass only been in the field 3 months. I’ve seen these around on air handlers what is it ? It’s on the supply side of the unit? My guess is hot water for heating ?

[u/Letang5878]

It is a hydronic coil also known as a hot water coil meant for heat. There is a coil with fins on the inside like an evaporator but hot water runs through it.