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MonoFlow system problems

Guy_6 Member Posts: 450
maybe I didn't read it correctly, but it sounds like the radiators/convectors?? are airbound. When the pump is "pulling" the air is spread across the element. When the pump stops, the air settles to one end and the hot water lays as it should. If this is happening in the uppermost part of the system, I would suspect air. I grew up with a monoflow system and was always cold in my room. After I moved out and got into this business, I installed auto vents on a few problem convectors. They aren't a problem any longer (great-now that I'm not there!). Check the system pressure as stated above, then check for air.


    STEVEN MARKS Member Posts: 154
    monoflow system problem

    Customer complaining of temperature swings thru out the house, also complaining some radiators not heating. 3 zone system with taco zone valves. All zones are 1" split returns with 1-1/2" mains. Zone 1 I found the wire for the end switch broken off the valve.
    The problem that has me stumped is this. I turned up the thermostat for the second floor and waited for the radiators to get warm. Most of the radiators are now working. The last 2 radiators are luke warm, the 3rd to last in hallway is hot, the 4th to last in bathroom is cold. I traced piping in basement and found monoflow tees on both supply and return for each radiator. I thought maybe the radiator valves were broken but when I turned down the thermostat the pump shut off and the radiators in the bedroom and bathroom soon became just as hot as all the other radiators.
    Stumped? Anyone with ideas?

    Thank you Steven
  • Mike Pfluke
    Mike Pfluke Member Posts: 9

    In many cases if you have radiators on upper floors you need to have more pressure in the boiler to promote circulation. I had a similar problem one time I jacked up the presure and all the radiators heated evenly
  • Mike
    Mike Member Posts: 94
    monoflow systems

    Has this been an on going problem? Or is this new? With a mono flow system, several things need to be addressed. Are all the tees installed in the proper direction of flow? One tee installed backwards, will kill the system. Second, does the pump have enough head,to over come the added resistance of the tees? Especially, with the tees on the supply and return of each radiator.
    STEVEN MARKS Member Posts: 154

    Thanks for the responses.
    Customer complains this started 5-6 years ago but unsure. The monoflow tees that I can see are installed properly. Monoflow tees are installed on both supply and return. Most of the mains are covered with asbestos so that I can not see all of the tees. This is an old system. The pump is an older B&G. I still have to look up the pump curve after I figure out wich pump it is. B&G doesn't always make it easy. NO numbers on pump. Boiler pressure was at 15 psi. The pump is on the return. I do know that over the years 2 zones have been added. One zone has its own pump with fin baseboard. The other zone was tapped of the main using radiators and existing B&G pump. An indirect heater was also added at some point in the past. What would be the pressure drop per monoflow tee?
  • Wayco Wayne_2
    Wayco Wayne_2 Member Posts: 2,479
    Larger circulator

    might do the trick. Air lift one in. (budump bump) WW

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  • clammy
    clammy Member Posts: 3,087
    fixing momo flow systems

    I have had excellent luck with fixing momoflow systems and it was all mainly due to luck ,What i have found out is that momo flow systems like there own pumps basically because they have there own system pressure drop designed in but when some one adds zone valves it disrupts the whole game .The newer usually base board zones work great and you geat uneven heat from all the existing raditors becuae of the lesser pressure drop on the baseboard zones get more flow and get satisfyed while the momo flow just humps along .Do your self a favor and remove the zone valve off of the momo flow system and install another pump and relay for the 2 zones that where added after you do this that momo flow system will work properly and start to heat evenly as it did ions ago .It seem that adding zones is not as easy as some switching it all to zone valves some times you have to think like water .peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • Uni R
    Uni R Member Posts: 663

    Or even just a new one - just in case the current one is correctly sized but not working properly...
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