I have an oil fired boiler (brandnew burner) that circulates water through 3/4 inch copper pipes to baseboard radiators- one big loop for each zone. I have added a bath in the basement and run high temp pex tubing in the concrete floor. The bath will be on its own zone. I have been informed that the current water temp of 190 is too high for the slab and that I should mix it down. Another says its fine, And yet another says to lower the boiler temp to 160, which I’m told will prolong the life of the boiler too. Will this create other problems? Which is the best route to go?
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go to http://tekmarcontrols.com/ and look in the essays for temp control. All you need to know to get started.
I run my nat gas boiler at 160. The only thing full bore at that temp is the Dom Hot Water tank. The basebd is tempered down with a mixing valve to about 140, the floor heat in concrete to 110.
Remodeling Contractor just outside the Glass City.
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You are asking 2 questions:
1) What is the optimal supply temperature to operate the boiler at?
2) What is the optimal temperature for the supply water to each of my zones?
The answer to question #1 depends upon your boiler design, your venting situation, max temp needed for any zone, and several other factors. If you run a conventional boiler too cold, it may condense, or take too long to get up to operating temperature. Too hot, and it may cycle too frequently, and may not attain a good steady-state efficiency. Too many factors to guess.
The answer to question #2 depends upon the emmitter output and heatloss characteristics of the spaces served by each zone. Generally, radiant floor heat is designed with enough tubing to create a large enough exchange area so that cooler supply temps are required. Cooler supply temps spread over a large area makes for the most comfort. Typical 160-190 degree water to support baseboards would be mixed down to 100-120 degrees. Floor surface temps above 87 degrees are generally considered uncomfortable. For optimal comfort however, consider mixing down all of your zones based upon outside temperatures with an 'outdoor reset' scheme.
See:
http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,62497,00.html