Plumbing Radiant & Manifold?

[kwright]

Two questions, both out of curiosity more than anything else:

1. I've noticed in some photos and schematics of plumbing for radiant heat that use water heaters, the cold water return is plumbed into the fitting on the lower side of the unit, where the drain valve typically is installed. This is versus the more typical for home hot water supply whereby the cold water input is tied into the top "IN" fitting. Is there a particular reason for this?

2. In a typical manifold setup, where one set of manifolds is placed above the other on the wall, does it make a difference which manifold is tied into the hot (output) or cold (input) coming/going to the heat source? I'd think it really doesn't make any real difference, as I believe I've seen it done both ways in different photos. However, it might be the most logical for the HOT (output from heat source) to go into the top manifold, and the cold return from the floor connect into the bottom manifold.

Interested in thoughts or opinions...

 

[Franz©]

1, the water returns to the bottom of the heater either way, but flow efficiency may be improved by not returning thru the top & dip tube. Since a water heater isn't a boiler, when operated at low pressure the water will often stratify in thermal layers in the AH.

2, Ideally the return manifold shold be higher for purposes of bleeding air from the loops. The temperature differential between out and return is very minimal.

 

[kwright]

Thank you for the quick and helpful reply.

 

[badgerboiler]

Pump the return to cold and the supply from the hot. A micro bubble air eliminator will make your life better.

MA