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Need help planning/designing moving and resizing of baseboard radiators

loop
loop Member Posts: 5
in Radiant Heating
Hi guys,

I'm looking to move and resize a number of cast iron baseray baseboard radiators in a large room to make space for some future renovations. The house currently has 3 zones, where one of these zones is dedicated to this room, is on a taco-007 pump, and piped with black pipe in a two-pipe configuration with monoflow tees on the supply side. The room has 35 linear feet of baseboard (15' + 10' + 10', 17850 btus I think), is 16.5' x 27' with 8' ceilings, 11 windows, located in IL, and we're open to ramping up the insulation.

I've attached the current radiator + pipe layout, and the proposed radiator layout with what I think the easiest retrofit (for me) would be, if I was to keep with black pipe, and had all the fittings readily available.

My main issues/worries/questions are:
* Is downsizing the room to 30 linear feet of baseboard OK?
* I'm having a hard time finding threaded monoflow tees that match the existing pipe diameters. Anyone know where I can source these, or how to work around them? E.g. I was thinking of taking out the monoflow from the 15ft radiator, but am worried I would have to unscrew all other pipes to get to it.
* How would you layout the retrofit compared to my proposed layout?
* Do I need to up the pipes I've mentioned from 3/4" to 1 1/4" or would sticking to 3/4" be fine?
* Would you replace the black pipe with PEX, and if so, what diameter of pipe would you use and would you stick with a monoflow loop or home runs to a manifold?

Thanks a lot in advance!

Comments

  • NoelAnderson
    NoelAnderson Member Posts: 49
    A couple of things:

    1. Never cap off a monoflow tee, it causes too much restrictions.
    2. You can use one supply line and monoflow tee off it, instead of having a supply and return line.
    3. Instead of a supply and return lines, you could go into manifolds and then run a home run system to each baseboard using 1/2" pex.
    4. Even cheaper in price, since this is one room and so the individual baseboards do not need to be balance separately. You can just pipe them in series with pex (More than likely 3/4" diameter.) and save money.
    loop
  • loop
    loop Member Posts: 5
    1. Good to know!
    2. Would this approach use a 3/4" loop with monoflows that come off at 1/2"?
    3. I like the idea of a homerun but am not sure if I want to go through the extra effort of removing the black pipe all the way to the utility room.
    4. This would definitely be the easiest approach and probably less restrictive in flow (less fittings, no monoflows).

    Is there a specific type of PEX that is preferred? From what I've read PEX A, HePex or PEX-AL-PEX seem to be used with radiators. And should i be going for expansion or crimp style fittings?
  • TerrS
    TerrS Member Posts: 172
    So I am no expert here, but I can tell you in my house I installed 2 buderus radiators and they put off 3 times the heat of my old base board fins. I am not saying this is your solution but they are only 2.5" thick and come in different lengths. There is a proportion valve and I have 60% water thru the radiator and 40% bypass down stream.
    loop
  • loop
    loop Member Posts: 5
    Those would be great for our bedrooms. Unfortunately, this room is mostly knee high walls due to the large windows :neutral:.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,828
    edited September 2022
    The pipe layout that you have pictured is known as a reverse return system and does not require a monoflo tee anywhere. If there are existing monoflo tees in the system they are from a previous design to the one you currently have and should have been removed when the redesign/zoning project was completed. Are you sure those tees are of the monoflo type? A photo would help.

    In this text, that I used for teaching a one day seminar on the subject, there is a section that explains the monoflo piping design and illustrates a one pipe design. http://media.blueridgecompany.com/documents/ZoningMadeEasy.pdf You have indicated in your diagram that you have two pipes, a supply and a return. The discussion of Monoflo starts on page 22.

    Your proposed repipe will work but this might work just as well.

    In the beginning (and on the last page is a quick reference guide) of the text there is an explanation of how many BTUh can travel through a certain size pipe. Since your total radiation in this zone is less than 40,000 BTUh, a 3/4" pipe can do the job. and if you do have real diverter tees that are 1-1/4" thru with a 3/4" branch, I would not worry about any restriction in those Tees. The reduction orifice inside is no more restrictive than 3/4". But with the existing design, they were not needed and if they are there, they were used in error, and since that section of piping requires less than 40,000 BTUh, the mistake was of no consequence

    The proposed repipe will save you in material. Just keep in mind; using a 1-1/4" pipe where you only need 3/4" pipe is not a problem. (however, the reverse is not true)

    Hope this helps

    Mr.Ed

    EDIT:
    When you break apart the old Cast Iron Baseboard radiators, the 15' radiator will only have one left end and one right end that has threads for connecting pipe. The intermediate sections are put together with push nipples in most cases and will not accept threaded pipe or fittings. You may need to purchase at least one left and one right end with the threaded connection. If they are still available. Can you tell if they are Weil McLain or Burnham or some other manufacturer?
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    loop
  • loop
    loop Member Posts: 5
    Hi Ed, if you were to repipe all of the above with PEX, would you also suggest doing it in series as per NoelAnderson's post, a single pipe loop with monoflows, or a two-pipe loop like it is now but with no monoflows?

    I've attached a pic of one of the monoflows, some have the red ring on them, others look like this B&G.

    The existing radiators are Burnham Baserays, and I think the same style as the current 9As. I'm ok with buying new 6/4ft baseboards and scrapping the 15ft so I don't have to deal with separating/pushing back together + the cost of the tool.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,828
    To keep the cost and labor to a minimum, I would use as much existing as I could like in the diagram I provided. If there is a problem with headroom in the basement, and I wanted to remove all that old pipe (that basement space will get colder now) then I would 3/4" PEX with O2 barrier a series loop. the last radiator on the loop would be as much as 20° cooler than the first radiator on the loop, but I would correct that with a higher water temperature if needed. You probably won't need to do that. By deducting 5 ft of baseboard and no other changes (like ceiling/wall insulation, or Full ceiling to floor insulate draperies) that room will be just fine on its own thermostat. If there is a problem, it will only happen on very cold nights. If that happens then raising the water temperature will resolve that.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • hot_rod
    hot_rod Member Posts: 22,120
    A home run system with 1/2" pex is a fairly easy DIY project, get rid of all that steel pipe :)
    TRV are an option for individual zoning or add actuators on the manifold for zoning.
    3/4 pex is also possible on the manifold if you want to group radiators to lessen short cycling of the boiler.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,828
    You can select which radiator gets the hottest water based on where you want the most heat. but dont over think this, it is not a 20,000 sq ft airplane hanger
    It is only going to be 10 to 12 degrees different 20 at the most.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • NoelAnderson
    NoelAnderson Member Posts: 49
    If this is one room as you have said, and it has its own pump and thermostat, you will not need valves to balance out radiators since all of them will be putting heat into the same room. Also since it only needs 17,850 BTUs, it will require around 1.8 GPM using a 20 degree temperature drop. At 1.8 GPM. a 1/2" diameter pex flows 3.1 ft./sec. At 1.8 GPM. a 5/8" diameter pex flows 2.2 ft./sec. I would use Ed's piping diagram that is a series circuit with 5/8" diameter pex going to the radiators and cut out all of the iron piping. Staying over 2 ft./sec. will keep from having air problems, and under 4 ft./sec. will keep noise levels down. You will probably need to put in a smaller pump because a Taco 007 will probably be too large. I would try a Grundfos Alpha 2 on slow speed.
  • loop
    loop Member Posts: 5
    Ed, the 2nd layout you've drawn is exactly what I was thinking and is the correct positioning of windows. It'll be what I'll be aiming for once I start working on this.

    Noel, would sticking with a taco 007 and 3/4" result in sufficient ft/sec flow, just a higher GPM? What's the risk of having higher GPM, more heat -> short cycling? The taco has a flow rate of 0-23GPM, although I'm not sure what it means by 'head feet' in order to figure out what the actual GPM would be. Is it the height of pipe from the motor to the highest point in the system?

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