I wonder if I can get some advice on a radiant heating project. I have a high efficiency boiler running 4 short zones in a small house. On one circuit that currently has two small radiators I would like to be able to use the return line from the radiator, through a mixing valve to get the temperature down to underfloor range. This is for the same room using the radiators. The return line would come back to the mixing valve and also to the main return to the boiler and the under floor circuit would have its own pump. I have attached a primitive diagram.

My questions is,should this be attempted? Is there a 'proper way'?  I realize that both pumps must come on when heat is called for.

Thanks for advice.

DavidAB

You might find that an inefficient radiator like underfloor tubes with no plates is close enough without mixing down the temperature.

It's a shame to run a high efficiency condensing boiler at high temperatures and then mix it down.

This could certainly be accomplished. Whether you should proceed largely depends on how much you are willing to spend to accomplish this. To determine what would is required, you would be well advised to hire someone who is experienced with this sort of heating system remodel. A schematic of the existing system and the associated system flow rates and temperatures would be the starting point. Then you would want to accomplish a proper room-by-room heat loss analysis and proper hydronic radiant floor heating system design before proceeding with this remodel.

This could certainly be accomplished. Whether you should proceed largely depends on how much you are willing to spend to accomplish this. To determine what would is required, you would be well advised to hire someone who is experienced with this sort of heating system remodel. A schematic of the existing system and the associated system flow rates and temperatures would be the starting point. Then you would want to accomplish a proper room-by-room heat loss analysis and proper hydronic radiant floor heating system design before proceeding with this remodel.

On thing to keep in mind for this project: If you are just adding radiant floor heat to the same zone that you are stealing the return water from, is that that room's heating demand remains the same. You are simply changing how you provide the heat. If your radiators are doing an adequate job of maintaining temperature, then adding more emitters in the form of floor heat, will overheat the room, or cause short cycling when that zone calls for heat. If the radiators are inadequate, then adding floor emitters will help keep the room warmer, if done properly with adequate heat released into the room. YOu don't say whether you want more heat in that zone, or what your floor type is. Both of those matter a lot!

Scott