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2nd floor balmy with baseboard heat

solarclub Member Posts: 2
I have 3 zones, new mod-con installed to replace 40+ year old oil furnace, primary/secondary new circulators, etc. with SuperStor indirect attached.

Works great. But I experience something which began happening well before the mod-con arrived.

My second floor ambient reads 70-72 degrees on most days this winter, even with the thermostat off (not down, off). The return pipes (apparently we truly have two return pipes for a single zone upstairs...) are typically hot - well, one is warm and one is hot - when I began checking on them. My new supply circulators must have check values built in (Taco 0015) because the supply pipe from manifold to circ flange is hot but after the circ the exit flange pipe is cold.

I discovered after reading various forums this thing about 'ghost heating' or thermosiphoning' or something like that. To test the theory I twisted the ball valve nearly closed on the hot return line for that 2nd floor zone (thermo is off!) to see if I could block some of this siphoning. Sure enough the upstairs starting cooling off and the return pipe became cold to touch (over several hours).

So, each morning I visit the basement, swing that ball valve nearly closed, making sure the thermostat is OFF, and in the evening the temps upstairs are ~67 which is where we want it. At night I open the valve fully and turn the thermo ON to ~67, in case it falls overnight (the 2nd floor circ has called briefly overnight given that this month we've seen temps in the low teen's).

To the general audience - would it be correct to guess that I need a flow check valve on the return line, to stop the heat siphoning?

Thanks all!


  • Zman
    Zman Member Posts: 7,569

    Pictures of the piping would really help.

    0015 is a huge circ for a baseboard zone circ. Depending on how it is piped that may be part of the problem.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • solarclub
    solarclub Member Posts: 2
    edited January 2014

    I have one 0015 for each of the three zones as well as the primary zone (4 0015's total). I have the speed setting down to 'lo' on each of them.

    The return lines for zones are tie into a manifold, all about 5" apart, so they exceed closely spaced tee's (not by much). I'll work on the pipe pics tonight.
  • Paul48
    Paul48 Member Posts: 4,469
    Closely Spaced Tees

    For that configuration, the spacing of the tees means nothing, as far as pri/secondary piping.