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TRV Valve install

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by leeeallen, Oct 18, 2012.

  1. leeeallen

    leeeallen Member

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    Can anyone give me some guidance on installing a TRV valve on a cast iron rad. I have 3 in a zone loop off my boiler. Presently, I just have a feed from the boiler to the first rad and an outlet from the same rad - then off to the other two rads - then back to the boiler. Do I need to plumb in a by pass T on the rad with the TRV so when the rad meets the desired temp, the hotter water flows down line???

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  2. heaterman

    heaterman Minister of Fire

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    A TRV anywhere in the line will stop flow in all the rads if piped in series.

    If you pipe in a bypass around the TRV the other rads will not be controlled at all. What are you trying to accomplish?
  3. leeeallen

    leeeallen Member

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    I want to be able to control the temps in the individual rooms.
  4. Morgan

    Morgan Member

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    Is the loop plumbed with 3/4 copper? If so install the TRV at the rad and put in a 1/2 bypass around the rad(or just go one size smaller than whatever is there now). The smaller pipe will add a little restriction but you should be fine. Remember you can only heat the individual rooms if the t-stat is calling for heat
  5. leeeallen

    leeeallen Member

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    Thanks, Morgan. There is 3/4 inch pex there now. Can you please explain to me how to plumb in the bypass?? Thanks!!
  6. heaterman

    heaterman Minister of Fire

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    The way I'm reading your post, the three rads are in different rooms, all on one loop and you want to control the temp in each room individually. If that's correct, your best and simplest option would be to run a main line (your 3/4" pex) and tee off to each rad with another 3/4" line for supply & return. The tee used in the supply line has to be a specific type called a venturi tee. These have a "neck" or restriction just after the leg of the tee that creates resistance forcing some of the flow into whatever is attached to the side or bull of the tee. About 50-60% of the flow will go straight through and on to the next tee/rad down the line. The TRV for each rad should be installed on the return side of the piping.

    Here is a good pdf showing what they are and how to use them. www.taco-hvac.com/uploads/FAQ_attachments/venturi_fittings.pdf
  7. wardk

    wardk Member

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    Do any of the trv valves have a built in bleeder? If the plugs on my rads are as stuck as the fittings were i think its almost impossible to get them out.
  8. heaterman

    heaterman Minister of Fire

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    Not that I am aware of. Each rad should have a vent on it.
  9. leeeallen

    leeeallen Member

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    Thank you guys!!! Got it. Lee
  10. Morgan

    Morgan Member

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    Venturi tees are great but its going to be more work, you will need access to the main. I would just pipe a 1/2 bypass around the element all work is in the cabinet which is easy to access. I would just sweat on a 3/4x1/2 tee and use copper to go around the element and tie back in on the far side. TRVs allow for each room to have its own temperature providing the t-stat on that particular zone is calling for heat. I would make sure my t-stat is in the room which requires the most heat.
  11. Bob Rohr

    Bob Rohr Minister of Fire

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    There are valves built to convert cast iron type rads to single or two pipe systems. This is what they look like. Basically there is an adjustable bypass to allow flow to the downstream rads on the circuit.

    Currently Caleffi does not inport this valve, possibly Oventrop or Heimeir have some in the US.

    hr

    Attached Files:

  12. heaterman

    heaterman Minister of Fire

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  13. leeeallen

    leeeallen Member

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    thanks for the info!!

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