Heat Sources for PEX in Floor Radiant Floor Heating Systems

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There are few restrictions to the heat source you choose to use in conjunction with a radiant floor heating system.

Some conditions, however, must be kept in mind for any heat source:


  1. The heat source output must be sufficient to supply the heat required, including auxiliary requirements such as domestic hot water. Typical heat sources are low and high temperature boilers, designated hot water tanks, tanklesss water heaters, heat pumps, solar and, in certain regions, geothermal.


  2. The maximum temperature of the water flowing in the PEX radiant heat tubing must be regulated to assure optimum comfort and to avoid damage to the PEX tubing, and to prevent excessive floor temperatures - such as wood flooring and sub-floors.


  3. The pex tubing must have an oxygen barrier if there is any ferrous metals used in the heat source or controls. Controls such as - Cast Iron Pumps, Most Zone Valves, Hydronic Steel Radiators, Cast Iron Boilers and even some non-cast iron boilers.


  4. The heat load of the area being heated should be known. (BTU heat loss in square feet)


  5. The maximum BTU output of the radiant floor should not be more than 25 BTU's per. foot. If the load is greater than the radiant floor can provide at 25 BTU's per foot then supplemental heat must be used. (Supplemental heat is used to match the heat load when the heat loss of the area is greater than 25 BTU's per. square foot.) Each Installed system is different - thus, it is advised that you do a heat loss calculation on your space and/or building.


  6. The maximum floor temperature for radiant floor heating should not reach above 85 deg Fahrenheit. If temperature goes above this - then pex radiant heat systems may damage wood flooring or carpet padding. Thus, use mixing valves to reduce radiant heat pex tubing temperature to desired level.

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