Help me understand this floor heat system

[spgirard30]

I am copying this setup for my floor heat/domestic hot water system and I don’t understand why the cold water coming in is tee’ed and going to the mixing valve and to the hot water side. To me it seems like it would cool off the water before going to the heat exchanger.

To me it seems like it would go to the mixing valve and the cold water side.

Thanks for any input.

 

[spgirard30]

I just figured it out. I had my cold water supply mixed up with the line supplying domestic hot water.

 

[75gmck25]

Another consideration is that for a combo system, domestic hot water runs at about 120-125 degrees F, while in-floor heat systems run at about 90-100 degrees F. There has to be a mixing valve that allows you to get two different temps while the system is running. If the heating system was radiant fin and tube you would have the opposite problem, since it often runs more like 180 degrees F.

Bruce