Boiler short cycling on a mixed radiant/baseboard system

cgailey

I recently added a single radiant loop in my kitchen floor and tied it into the loop that runs through the garage heater (which comes off the top of the manifold past all of the other zones), and I am worried that because this is not thermostatically controlled (no zone valve, etc) that there is avoidable short cycling of the boiler.  So my question would be, what is the best way to deal with this issue.  My thoughts are to install a temp sensor in the floor which would be linked to a zone valve at the boiler.  I have also seen where a separate circulator is used on a loop that gets mixed down to a lower temp and calls for hot water from the boiler at a set threshold. 



Ideas, suggestions?



Thanks

Alan (California Radiant) Forbes

Kitchen Loop

So, the kitchen heating is controlled by a garage thermostat?  And you have a high temperature loop in the kitchen floor?  What kind of tubing is it and is it attached, embedded or suspended in the floor?



"I have also seen where a separate circulator is used on a loop that

gets mixed down to a lower temp and calls for hot water from the boiler

at a set threshold."



This is the correct way to heat your kitchen if you have tubing embedded in the floor.  If you have tubing suspended in the joist bays, high temperatures may work fine, but I would separate it from the garage loop and have it respond to a kitchen thermostat for better control.

cgailey

suspended

It is suspended in the joist bays, and it is rehau-pex oxygen barrier 3/4".  So far it is working great as far as keeping the floor warm but not too warm.  It wouldn't be hard to separate the loop from the garage heater loop, so I may do that.  The thermostat for the garage heater only controls the fan on the radiator.  The water is on a constant cycle through that radiator, as it is a direct loop off the top of the manifold from the boiler with no valve control (save for an isolation gate valve.  I went with this loop because I wanted the floor heat to be separate from the rest of the zone on that floor of the house.  We heat with a woodstove 24/7, and the main floor zone only calls for heat in the mornings before we restoke the fire.  When we bought the house, there was a loop off of the garage heater that went to a short (3 foot or less) baseboard just inside the door from the garage, which I removed when I remodeled that floor of the house.  It was also not thermostatically controlled.  I realize this is an antiquated way to operate a heating system, and I'm hoping to increase efficiency through reduction in short cycling of the boiler.



Would it be easier to control an individual loop with a zone valve, or with a separate circulator from a temp sensor? Also, any recommendations as to how I would incorporate the temp sensor.  My thought is to embed it in the thinset under the tile, similar to how electric heat mats operate. 



Thanks for the input!