Radiant Floor Loop?

Danscrew

My friend has asked me to tie in his radiant floor loop to his boiler. The loop was installed in the kitchen floor last year and not hooked up to the boiler. Not sure of the length of the loop and is only one loop what is the best way to do this. Can I just do a mixing valve off the existing circ ?  I know there is a lot more to it.   I have not seen the system or how many zones or circs there are.I am guessing the Boiler is a regular gas fired 180 Temp set up    What is a good mixing valve header i can use, or a Zone valve with stat? to control it.  thanks Dan    

Harvey Ramer

I have done this

numerous times and there are a lot of things to be taken into consideration. First and foremost, you must determine what type of boiler it is, high mass, low mass, high mass condensing or low mass condensing. Each one may require a different design strategy. Also we need to know how the radiant tubing is installed. Another thing, what kind of heat is in the kitchen now? We don't want to create a situation I refer to as "dueling banjos". That's when 2 heat sources try to outdo each other and one of them ends up doing nothing.



If it is a regular sized kitchen, it will end up being what we call a micro-zone. One of the ways I prefer handling these is with a TRV. I set it up so the radiant zone can operate anytime that anyone of the other zones is operating but is unable to turn on the boiler by itself. This is a suitable method for a low mass boiler.



A high mass boiler is a little easier. You can take a zone right off the boiler-header and mix it down for your radiant loop. This will normally not induce short cycling.



One thing I like to do in a kitchen is floor warming. I use a TRV with a remote slab sensor and just set it to maintain about a 70° floor temp. Then I take the heat emitter that already exists in the kitchen and provide a way for it to be throttled according to occupant comfort. The reason I do this is because kitchens are a room of activity and excess heat from cooking and the like. If the room were solely heated by radiant (which doesn't cool quickly) and someone came in and started bustling around, cooking and baking and the like, the room could easily overheat. Nothing left to do but crack a window. 



So best thing to do is gather information on all the particulars of the existing equipment and layout. Once you have all of that, we can help you further.



Harvey