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help with copper to pex? best way to plumb this runtal?

fiddlermd
fiddlermd Member Posts: 59
I am currently converting a mudroom from about 10' of baseboard to a 4' runtal unit. The baseboard ran around a corner, and now one of the sides is getting a closet so I needed to get rid of it.
Anyway, here's the situation at the moment:


All the copper right now is 3/4"
I am thinking of running this into pex so that I can keep it close to the floor/corner. This way the closet should fit pretty well (I might need to notch it). Unfortunately the pipe runs into the floor so I can't really hide it ...
2 questions:

1- is pex the right way to go here? any cons? Do i need to insulate if it's gonna be behind a closet?

2 - how would you run the right side of the runtal? from the bottom or from the side? Bottom would be less visible but harder to plumb..

Any advice appreciated - thanks!

Comments

  • JakeCK
    JakeCK Member Posts: 390
    No access via basement or crawlspace?
  • fiddlermd
    fiddlermd Member Posts: 59
    unfortunately, no... the mudroom is on slab.. it seems that this space was installed after the house was built to connect the garage and the house..
  • Big Ed_4
    Big Ed_4 Member Posts: 1,775
    You want to use diverters tees's off the baseboard loop to feed a radiator .
    I have enough experience to know , that I dont know it all
  • fiddlermd
    fiddlermd Member Posts: 59
    In the photo, top left is the supply and top right is the return - why do i need a diverter tee? this system is plumbed in series with other baseboards btw.
  • fiddlermd
    fiddlermd Member Posts: 59
    I did... but don't understand the advantage of this versus a standard in-out system as it is now.. what's the main advantage? I guess from the principle, i could extract more heat from the water??
  • mattmia2
    mattmia2 Member Posts: 3,964
    Depends on the flow rate of the loop and of the Runtal. Runtal I believe says max 1.5 gpm per tube but I think it also has a 1/2" connection which is only good for about 1.5-2 gpm so I don't understand how they expect you to feed a 4 or 6 tube at up to 1.5 gpm per tube. The 3/4" baseboard loop is good for around 5 gpm. You have to figure out what flow the original system designer designed the loop for and if you can make that happen through the Runtal baseboard without a bypass or diverter Ts and with the current piping and pump. You will also likely want the diverter Ts or bypass to balance its output with the output of the rest of the loop.
  • fiddlermd
    fiddlermd Member Posts: 59
    I am fairly certain there was no "design" as such (knowing the plumber who ran the thing).. most of this was an old baseboard run.. the boiler got upgraded to an IBC G3 unit and the zones got split up so this zone has a hallway right next to this mudroom, a small bathroom and a small bedroom, all in series. I have no clue how to figure out flow rates or anything.
    Based on what that FAQ said and what i've read here, I guess the diverter makes sense to keep the flow normal cause the 1/2" would reduce it to the whole loop?
  • mattmia2
    mattmia2 Member Posts: 3,964
    Someone should have at least ballparked the resistance of the loop and boiler and looked at the pump curve to make sure it had enough flow through the boiler under the possible operating conditions of different combinations of zones open and closed. If this was designed for a conventional boiler and you now have a condensing boiler there may be options of operating it different ways. The section of 1/2" will offer more flow resistance so it will reduce the flow of the whole zone and may be noisy or even erode the pipe if the flow is too great for the pipe size. The diverter Ts or bypass will allow it to operate more or less the way it did with the baseboard. You will need to look at the temp and flow at the panel rad to figure out how much heat it will output.
  • fiddlermd
    fiddlermd Member Posts: 59
    what if it were run like this with regular tees? given that main piping is 3/4 and runtal is 1/2... would this setup have any advantage/disadvantage versus a 3/4 setup with diverter tee?


  • Larry Weingarten
    Larry Weingarten Member Posts: 2,284
    Hello, A thought is to plumb it along the lines of what you show, but make the horizontal line a full 3/4" and add a balancing valve in it, so you can force more or less water through the Runtal and still find the balance that gives the other radiators sufficient BTUs.
    Yours, Larry
    mattmia2SuperJ
  • fiddlermd
    fiddlermd Member Posts: 59
    I ended up ordering a diverter tee - seems simple enough i guess..
  • mattmia2
    mattmia2 Member Posts: 3,964
    Make the bypass full size and put a ball valve on it to balance like Larry said.
  • fiddlermd
    fiddlermd Member Posts: 59
    what do you mean ' full size?' - the one i ordered has 3/4 x 3/4 x 1/2 .. where would the ball valve go?
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,304
    You will be fine with one diverter T and one regular T. The bypass will be 3/4 and the two branches to the runtel will be 1/2. The diverter T will go on the return, with the arrow (or band) following the direction of flow through the bypass.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • bob eck
    bob eck Member Posts: 928
    I was told to use a globe valve not a ball valve or gate valve to balance systems.
  • mikeg2015
    mikeg2015 Member Posts: 1,183
    > @bob eck said:
    > I was told to use a globe valve not a ball valve or gate valve to balance systems.

    Yes globe valves generally are better for flow control given their shape. But not sure it really matter much in practice at lower velocities in a residential heating system unless the valve it mostly and again, velocity is fairly high.
  • mattmia2
    mattmia2 Member Posts: 3,964
    A globe valve has more uniform control, a ball valve has more resistance to erosion, the washer in a gate valve doesn't do so well in a partially closed position with flow over many years. You could also go with a valve that is designed for balancing but those are more expensive.
  • fiddlermd
    fiddlermd Member Posts: 59
    given the aesthetics of these valves and my setup as seen in the photo up on top, where would a valve go? I'm assuming it would have to be on one of the vertical runs? to the radiator?

    Also, I have 3" from the floor to the radiator. The pipe has to run along the floor. so I have very little room.
  • JakeCK
    JakeCK Member Posts: 390
    edited September 2019
    Edited out, for some reason it posted the link again. :s
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,284
    Hello @fiddlermd , The valve would go in the horizontal pipe that runs between"T"s . That pipe should be 3/4".

    Yours, Larry
  • fiddlermd
    fiddlermd Member Posts: 59
    Wouldn't the diverter still limit total throughput?
  • JakeCK
    JakeCK Member Posts: 390
    > @fiddlermd said:
    > Wouldn't the diverter still limit total throughput?

    Not necessarily. 3/4" pex can easily deliver over 30k btu/h at a delta t of 20 degrees depending on flow. I doubt very much you need anywhere close to 30k btus for a mudroom.