extending radiant heat?


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Old 01-22-19, 03:15 PM
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extending radiant heat?

hi folks -- have a question about extending my radiant heat system. here's the situation: about four years ago I built an addition that opens off the kitchen. the addition is all tile-floored, and includes a laundry room, mudroom and bathroom. all the exposed tile floor in the new addition was set up for radiant heat. it tied in to the existing hot water system which uses cast iron radiators (the house is over 150 years old), and has it's own circulation pump, along with a "manifold" (I guess you would call it!) running off to three circuits (photo attached). the system works really well and the whole house runs harmoniously. the radiant is one of the nicest features of the house frankly. Now I'm finally getting around to doing the kitchen, which is immediately off the new addition. My hope is that I can just add to the new system, with new manifolds and new circuits (I'm sure there's a better name for them). I can tell you the existing system heats 180 sq. ft. and the new kitchen is 135 sq. ft. so about 75% of the existing system. or in other words, the current system will be increased +75%. Does this make sense, and sound right? I'll of course be talking to my tile guy and the radiant guy, but I want to go in with a point of view, and I need to develop the overall plan as I'm the GC (as well as carpenter among many hats!). And one last thing: the kitchen was previously heated by a hideous large cast iron radiator. I've taken that out, and the kitchen is still comfortable, with no heat of it's own! it's surrounded by heated rooms on three sides so I guess it just draws from them. But I'd still like the comfort of radiant in the kitchen, consistent with the adjacent tile floors in the addition. I'm sure it will contribute to the overall comfort of the house as well? Can you have too much heat?
 
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Old 01-25-19, 02:52 AM
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hi -- no thoughts or takers on this? let me know if you need more info thx!
 
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Old 01-25-19, 09:06 AM
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Certainly sounds do-able. Is the existing system zoned or does the radiant run at the same time as the cast iron in the rest of the house? Is there a balancing valve between the radiant supply and return to reduce the water temperature or does the radiant run at the boiler temp? What temp do you run the boiler up to?

Adding radiant to a room that is already warm enough with no radiation will not be a problem as it will contribute slightly to the overall heating of the house. When the house is warm the thermostat will be satisfied no matter how the heat is emitted.

The noticeable result will be a warm floor.

I have added radiant floor heating in the master bath and kitchen/dining area of my 106 year old house that has CI radiators. I run my boiler at 150 degrees with a 30 degree differential (so basically average 135 degree water to all emitters) so I do need a balancing valve for the radiant.
 
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Old 01-28-19, 07:02 AM
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thank you -- very helpful! the radiant is not zoned, and runs with the rest of the system. there is a balancing valve and seperate circulating pump for the system (as well as a pump for the rest of the house). It's run really well for years now and we love it and I think we'd mss the warm floor with it in the roon right next door so I think we'll go for it. good to hear I can't "overheat" the house/room as the thermostat will be satisfied. Am I correct that we just change the manifold to allow for new lines for the new room? thanks agin!
 
 

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