Adding circuits to a radiant floor

According to the chart in this http://www.radiantsite.com/files/inf...esidential.pdf Btu output is dependent on the size of tubing used and the spacing of it. For a 1/2 tube spaced 12" apart the Btu output is 10-20h, 9" a part it's 20-30btuh, and 6" it's 30-40btuh. Would adding one length of tubing in each bay increase the Btu output in higher heat loss areas providing that the circuit is the same length as the existing circuits in that zone? Like adding another section of baseboard in series to an existing system.

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Originally Posted by nevea2be

Would adding one length of tubing in each bay increase the Btu output in higher heat loss areas providing that the circuit is the same length as the existing circuits in that zone?

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A heating system is going to transfer the same number of BTU/h regardless of the heat loss it is working against. The limitations of heat transferred includes the capacity of the heat source, the circuit surface area, thermal conductivity of all heating system components and and insulative properties of the flooring.

Adding an additional length of tubing in any or all circuits increases the radiant surface area of a circuit, giving the liquid more surface area and more time to transfer heat, regardless of the length of other circuits in that zone or the heat loss in that zone.

There is certainly a point of diminishing returns, for example, at some point a lengthened circuit will return the liquid at room temperature, and all extensions of length beyond that do not add any BTU/h to the room. When that point is reached is driven by the heat loss.

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Originally Posted by nevea2be

Like adding another section of baseboard in series to an existing system.

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Electrical resistance is additive in series and reduces the amount of radiated heat by reducing the current, and therefore the wattage. Less watts, less heat.

Increasing a single circuit from the manifold gives the opportunity for more heat transfer up to the point where the liquid comes back at room temperature.

Each circuit from a given manifold is operating in parallel to the next. Increasing the length of every circuit increases the efficiency of heat transfer up to the ability of the heat source to keep up. Once the circuits are all lengthened to the point that all liquid is returning at room temperature, a larger heat source is required to increase the number of BTU's transferred per hour.

-HF

Noel

Great job Hangfire. Thank you so much for your answer.

Dang hang, your good.

Thats almost like saying it doesn't matter how much heat your radiant tubing can put out.
Your radiant mass can only emit so much.