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Max ft of baseboard per loop

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Is there a way for calculating the maximum ft of Baseboard finned tube heaters you can put on one 3/4" loop before the temperature drop renders further elements ineffective. The baseboard in question in 600 BTU ft 180 Degree water temp.

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  • kpc_14
    kpc_14 Member Posts: 38
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    usually

    around 67'....kpc
  • Steve Sisti_2
    Steve Sisti_2 Member Posts: 4
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    Now I'm puzzled. I have a new installation using a Pennco furnace 15B series model 15120 AGA input 120,000 BTU/hr. There are four zones in the house. On a 20 Degree day, 3 zones do fine at maintaining a 70 degree temp. The fourth zone which is 37 ft x 22 ft open space with no interior walls and two walls of windows, has 36 ft of 600 btu/ft finned radiator in a single loop. First two heaters are very hot to the touch and give off plenty of heat, third heater I can hold my hand on the fins and it's not very hot, last heater in the loop is barely warm but the copper tube is relatively hot. On a 20 degree day, I can't get the room to 70 degrees...max is 67 degrees. Is there an obvious reason why the baseboard temps drop off so radically from the first two heaters to the second two. In a quick conversation with Pennco, he thought I was at the maximum btu's a 3/4" line could handle using 600 BTUft heaters (37 ft). I did shut off the other three zones and still no rise in temperature. I would estimate the total line length in the lop at 135 ft from the boiler through the heaters and return to the boiler.

    Any help would be appreciated.

    Steve
  • kpc_14
    kpc_14 Member Posts: 38
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    tell us...

    about the boiler...how are the zones controlled? valves or circ. pumps? what size is the near boiler piping? any pictures? kpc
  • Steve Sisti_2
    Steve Sisti_2 Member Posts: 4
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    There is one circulator pump on the side of the boiler. The zones are controlled by the opening and closing of a solenoid valve, one for each zone. My understanding is that a call for heat from any zone triggers the appropriate solenoid valve to open and allow water flow to that zone.
  • kpc_14
    kpc_14 Member Posts: 38
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    what zone valve.....

    and what pump? sounds like you could be starved for flow on that zone what all others are calling. Waht size pies are feeding the zones?
  • Rich L.
    Rich L. Member Posts: 414
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    pumps

    Is there only one pump Steve? Could you post a few pictures?
  • Steve Sisti_2
    Steve Sisti_2 Member Posts: 4
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    There is only one circulator pump providing water flow to all four zones. But remember,in my test I shut off the requirement for heat to the other three zones...those zones remain cold to the touch, thus they are getting no flow and the circulator pump is pumping only to the one zone in question. I will find out the size, and rating for the single circulator pump and come back to you.The "piping" appears to be 3/4" copper in and around the boiler...at some point I can not see, the copper pipe transitions to 3/4" Pex( I believe)it's "plastic" tubing running to all the baseboard. I will also see if I can get some pics of the boiler piping.

    I really do appreciate your interest in helping. Thanx much.
  • Rich L.
    Rich L. Member Posts: 414
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    3/4\" near boiler pipe

    Steve if your near boiler piping is only 3/4", it's undersized for a 120,000 btu boiler. At a 20 degree Delta T (temp differential) you need to move 12 gpm. To accomplish this your near boiler piping needs to be 1-1/4". Also the reason I asked about the number of pumps is that depending on your how your boiler is piped you may need 1 pump to circulate water through it (boiler) and another pump to service your zones. If you get a chance post a few pictures, it'll help.

    Good luck, Rich L
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