We Get Green Building Visitors and Boiler Set Points

Believe it or not someone read this entire blog. I am amazed because it obviously takes a certain kind of interest to slog through over 630 posts with 9 years of projects. I received a letter from this gentleman and he lives in Parker, CO. About 30 miles away from us. He asked to visit the house and I called him back right away. I love the interest and talking about our renovation. We scheduled a visit for Saturday and he and his wife drove north to our house to see the Tesla Roof and the energy saving features.
Unfortunately my house is rather messy right now. As it is most of the time because I seldom expend energy cleaning up after myself. And I didn’t give myself enough time to straighten up. I know it gives a poor impression. But these visitors seemed to be more interested in a tour and questions about the renovations. We talked most about floor heave and the Wafflemat solution. Then there were questions about the concrete floor and radiant heat.
Some answers I did not know as the decisions were made years ago. For instance what is the set point for the radiant system? I know the Delta T is supposed to be about 20 degrees. The water returning from the system should be 20 degrees lower than the water that is heated to circulate. The design circulating temperature is calculated for zero degrees here in Colorado and that is modulated or changed up and down depending on the outdoor sensor temperature. That number is set in the boiler and I guessed it was about 110 degrees. But I was incorrect. It was set at the factory minimum of 86°. That is the maximum the boiler would operate at when the temperature was zero but I reset that to 100° when the outside temperature is -9 which is a more likely lowest point.

Minimum outdoor temperature
Minimum outdoor temperature
Maximum boiler temperature
Maximum boiler temperature

The lowest outside temperature sensor at which the minimum boiler heat will fire is the factory low of 60°. The low set point is 80°. That means when heat is called for the lowest temperature the boiler sends is 80°. I believe both high and low settings should return the 20° Delta T that is recommended.

Minimum outdoor temperature to provide heat.
Minimum outdoor temperature to provide heat.
Minimum boiler temperature
Minimum boiler temperature

I remember the floors require 86° at zero outdoor temperature so for warmer days that are not heated by the sun the boiler will send slightly lower temperature warm water. I’m not sure how efficient that is but return water temp in a condensing boiler should ideally be 80° or below and these settings should ensure that and maximum boiler efficiency.

Our visitors had very impressive backgrounds with multiple engineering degrees both civil and electrical and seemed more than capable of designing and building an energy efficient home.
The entire blog took two weeks to read and he had a fresher background in our house history than I do.
I hope they send updates as they make progress in their design and build.

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