Recently I heard someone say (not on the Net) that with hot air systems, you need a higher VOLUME of heated water. I shall not purport to understand that, but I am curious about your experiances. What made me think to ask is the post from a GreenWood operator who is having some trouble with his hot air system. These Refractory Mass Natural Draft unit have a very low water volume. The GW100 claims to have only 8 gals. I know nothing about pump size/speed nor W2A HX so I am hoping some will chime in with their findings and some ideas for the member in duress.