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Thread: Can Monoflow tees lie flat to floor joist or hang below

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    DIY Junior Member jasonnewyork's Avatar
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    Default Can Monoflow tees lie flat to floor joist or hang below

    This is a followup post to an old thread of mine. Special thanks to hj and johnjh2o1 for steering me in the right direction. To make a long story short, I'm restoring a Monoflow system in my house. I contacted B&G and one of their engineering reps helped me calculate pipe size, pumps, etc. I purchased all the materials and would like to start the project soon as the weather is no longer cold in New York.

    Link to old post: http://www.terrylove.com/forums/show...ema&highlight=

    I have one remaining issue that bothers me and I wanted to run by you guys.

    Since I'm finishing this basement, I would like to run all the pipes flush against the floor joists above. In order to do this, I would have to run the main along the bottom of the beams and the Monoflow tees would be horizontal (0 degrees) with riser pipes flush as well.

    In all the homes I've been in with Monoflow, the main always hangs down maybe 6-9" and the tees are angled at 45 degrees. I was told this is done to purge air from the risers as gravity forces the water down and the air up. Is this true? Would it be OK for me to plum with tees at 0 degrees? The engineering rep for B&G said this doesn't matter but I value your opinion.

    Thanks again.
    Last edited by jasonnewyork; 04-27-2010 at 09:35 AM.

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    Moderator & Master Plumber hj's Avatar
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    The function of a MonoFlo tee is in its construction. It can lie in any orientation. In fact, they point downwards for basement radiators. As far as air is concerned, it should be evacuated at the boiler, and NOT get to the radiation, but if it should it will still rise to the highest point in the system. I assume they gave you the parameters for the distance between the MonoFlo tee and the "return" tee from the radiator, and if you have any basement radiators, you need TWO MonoFlo tees.

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    DIY Junior Member jasonnewyork's Avatar
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    OK, thanks hj. I'm only using the monoflow loop above the main. The basement will be on a separate pumped zone with baseboards.

    They did give me parameters for the distance of the tees - 6x pipe diameter min between the tees and corners. In my case, I'm using 1" pipe, so tees spaced 6" apart min or 6" from a corner.

    I was planning on spacing the tees the width of the radiator when possilbe. They said this would be more ideal than the 6" minimum. Do you agree?

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    In the Trades Wally Hays's Avatar
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    We always tried to space them at least 18" from each other. Was there any particular reason why you are resurecting the monoflow system? Not that it's a bad thing, but there is a tremendous resistance to flow within the system and that's why you need to run a fairly large main which, naturally the bigger the pipe, the more expensive it is. If it were me, I would pipe 5/8 heat pex to all of the radiators and bring them back individually to manifolds at the boiler. From there you can either use separate thermostatic radiator valves to control heat or put several radiators on thier own circulators or zone valves.
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    DIY Junior Member jasonnewyork's Avatar
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    Wally - please read my original post, link at top of page. The manifold setup was something I considered. I ruled it out because too complicated with pipes everywhere and difficult to equalize the flow to radaitors far and near the manifold. I think that setup works best with radaint. The only other viable option was a 2 pipe reverse return but that uses twice the pipe. Since I'm doing myself, the cost of materials is 2-3x less than what a professional would charge so I'm OK with added cost of a copper monoflow setup.

    I received lots of good advice from this forum as well as my local B&G rep. I will highly recommend calling the manufacturers, either a homeowner or pro, they provide a tremendous resource for free. In return for their support, I purchased all B&G products.
    Thanks Wally

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    In the Trades Wally Hays's Avatar
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    [QUOTE=jasonnewyork;256531]Wally - please read my original post, link at top of page. The manifold setup was something I considered. I ruled it out because too complicated with pipes everywhere and difficult to equalize the flow to radaitors far and near the manifold. I think that setup works best with radaint. The only other viable option was a 2 pipe reverse return but that uses twice the pipe. Since I'm doing myself, the cost of materials is 2-3x less than what a professional would charge so I'm OK with added cost of a copper monoflow setup.

    There are more pipes but they are smaller and flexible and can be run up inside the floor joists instead of hanging down below them. Balancing is not a problem and for that matter you don't need to balance anything, they will all heat up at about the same rate. You can use thermostatic radiator valves at the radiators if you want to. My own house has 18 cast iron radiators , all piped with 5/8 heat pex to manifolds at the boiler. No balancing valves and no radiator valves. The whole system heats evenly. Nobody has done a mono flow system in 30 years except for repair work. I can't believe your B&G rep would even consider recommending that you go mono flow unless he needs the commission. Head on over to www.heatinghelp.com and post your idea on the wall over there. I doubt anybody will give you a thumbs up.
    Last edited by Wally Hays; 04-29-2010 at 07:02 PM.
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    DIY Junior Member jasonnewyork's Avatar
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    I've read heatinghlep.com backwards and forwards several times in the past year - that site is awesome. I have to check out the forum, never been in there.

    I hear you on the manifold setup but I wasn't happy about running 22 pipes to my boiler room. I'm finishing my basement and room was very tight. I broke it down to 2 choices, either use a 2 pipe reverse return or monoflow. I ended up choosing monoflow cause it's only one main pipe and seemed the most simple to me. I also plan to do everything in copper, when I ran the numbers, using PEX was more expensive due to cost of the tools. Remember I'm a homeower, so I would'nt use the PEX tools ever again.

    I have been warned by a few people about issues surrounding monoflow setups. I've spent plenty of time researching how to install as well as talked to the pros. I'm aware of the potential problems... but any system will have them.

    I will keep you posted on my progress. I plan to tear out the old system and build the supply side of the boiler this weekend.

    Jason
    Last edited by jasonnewyork; 04-30-2010 at 09:35 AM.

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    DIY Junior Member jasonnewyork's Avatar
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    Wally took your advice and searched the heatinghelp.com forums on monoflow. I found a great link to B&G site that was basically a refresher course or crash course on how to install. I'll post link in case others need it.

    http://www.bellgossett.com/Press/BG-monoflo.asp

    They answered my question about angle of upfeeding tees:
    "Pitch the main and the radiators up in the direction of flow.
    This advice goes back to the original installation books of the 1930s. The pitch makes it easier to get rid of air on start-up. Check those pipes. They may have sagged as the years went by, and that can give an installer fits. If you're having problems, always check the pitch."

    Would you interpret this as you HAVE to tilt tees or would be ideal?

    Jason
    Last edited by jasonnewyork; 04-30-2010 at 11:22 AM.

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    In the Trades Wally Hays's Avatar
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    Well, since you are doing a repipe anyway, If you install your main circulator on the feed and pump away from the boiler ( the air eliminator, expansion tank and water feed should all be piped before the circulator also) you will not have any problems purging air because the circulator will be building head pressure instead of trying to suck the water back. You can find proper diagrams at www.taco-hvac.com
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    DIY Junior Member jasonnewyork's Avatar
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    Thanks... I'm installing the pump on the feed side and the air eliminator, expansion tank, and water feed will be before the pump - just as you described.

    I think the pumps from the 30's had lower head plus air elimination was almost non-existant so installing the tees on an angle was important. I noticed too that most older monoflows were done in iron. It would be next to impossible to screw together an iron setup thats flush against the floor joists.

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    In the Trades Wally Hays's Avatar
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    Not sure what your budget is but look into Wilo circulator pumps.
    Perception is 3/4 of reality

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    Moderator & Master Plumber hj's Avatar
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    Monoflow tees depend on balancing the head pressure through the radiator against what is developed by the tee and the distance between the feed and return tees. IF the tees are too close together and the radiator is remote from the main, there could be such an imbalance that the flow to the radiator would be compromised. Therefore, the greater the distance between the tees, and even an elbow turn, improves the operation. In the "original" days when MonoFlow was first developed there were feed AND return tees which were used at every radiator. Eventually the two types were combined into a single design tee, and finally they decided only one tee was necessary as long as the radiation was above the main.

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    DIY Junior Member jasonnewyork's Avatar
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    HJ - thanks for explaining the mechanics of a monoflow tee... I'm learning something new everyday. During the system design, I forwarded all this info to my B&G rep. He assured me everything will work as intended. Since I have cast iron radiators, the tees will be spaced the width of the convectors. The pipes will come down from the floor above so makes sense to plumb this way. I have two rads on the second floor that the pipes terminate into the basement about 9 inches apart. For these convectors, the tees will be spaced 9 inches instead of the width of the unit. I don't see this being a problem since the radiators are only 30 inches wide. All piping will be done in copper. The risers will be formed using soft copper to reduce the use of multiple elbows. Each radiator has one cast iron 90 degree union elbow and one cast iron 90 degree union shutoff valve. I suppose these will provide the resistance to balance out the single monoflow tee.

    Back to my original question. So the consensus here is that it is OK to install the main flush with the floor joists as well as the risers the to convectors? The B&G rep said this would be OK but I wanted to hear some other opinions. In all the homes I've been in with monoflow, the main always hung down low and the risers either went straight up or up at a 45 degree angle.

    I will be running a B&G NRF-22 pump along with a EAS-Jr air separator. I know air was big a problem in the old days and the pump and air separation technology was not as good as today. So wondering if what I see in old homes is no longer necessary.

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    In the Trades Wally Hays's Avatar
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    I will be running a B&G NRF-22 pump along with a EAS-Jr air separator. I know air was big a problem in the old days and the pump and air separation technology was not as good as today. So wondering if what I see in old homes is no longer necessary.

    Yes, spot on
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    Moderator & Master Plumber hj's Avatar
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    The longer the distance to the radiator AND the number of fittings the GREATER the head pressure resistance is. The CLOSER the tees are together the LESS resistance they create. Theoretically, if the branch piping has enough resistance, and the tees do NOT create enough, NO WATER would be diverted to the radiator. IF you are putting the two tees that close together, I would use TWO MonoFlo tees oriented so that one was a supply and the other a return to ensure the maximum flow to the radiatory. Separating the tees by the length of the radiator DOES NOT insure the proper flows. You would have to calculate the resistance between the two tees, and a straight section of pipe creates VERY LITTLE resistance, AND compare that with the piping to and from the radiator along with any fittings. Water is VERY lazy, and if can find a "short cut" it will take it, regardles of which direction WE want it to go. I hope you do NOT have castiron valves and radiator ells, since the only good ones are brass.

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