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Which T&P Valve?

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Javelin
Javelin Member Posts: 158
in THE MAIN WALL
Heating Gurus,



I have a Triangle Tube Prestige 250 boiler hooked up to a Smart 40 Indirect Hot water heater. Which T&P relief valve am I supposed to use? The manual seems to have two suggestions - one based on tank size, the other on BTU - but they differ:



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Determine T&P relief valve size by the follow- ing specifications, unless they conflict with local codes:

- TR 20/30/36/45 - SMART 20/30/40/50: 3/4”NPT with an AGA Rating of 100,000 BTU/hr. (Watts 100XL-8 or equivalent).

- TR 60/80/100/120 - SMART 60/80/100: 3/4”NPT with an AGA Rating of 200,000 BTU/hr. (Watts 40XL-8 or equivalent).



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Also, the Watts 100XL-8 is about $14 from PEX supply while the Watts 40XL-8 is about $130.. Why is there such a difference in price? Something I'm missing?



THANK YOU IN ADVANCE!

Comments

  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,637
    Neither one

    Here in California, you have to use a relief valves rated higher than the input rating of the boiler.



    Look at this chart (over 200,000 BTU) for correct sizing:



    http://media.wattswater.com/F-SF.pdf



    As far as the higher price, it's probably related to their insurance costs and not the manufacturing costs.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
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