Gravity HW conundrum....

kevin coppinger_4

said a by-pass was a waste of pipe if using the 2107 and the BFU room sensor...the second floor rads have trv's now... a 15-58 seems to do the job...I measured the edr and compared it to the Hot tech topic article written by Steamhead...on sizing circs...I did kick it up to spd. 3 to see if that would make a difference...
The mains were cut down to 1 pipe size less than 1/2 of the total diameter..1.25"....I am piping away.

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kevin coppinger_4

About a month ago....

I converted a older gravity hw system. The boiler was 16 yrs. old Weil- Mclain 73 series that was still running as gravity...yes it was very inefficient, but all rads were hot, some too hot!
I replaced it w/ a Buderus 215-6 w/logamatic & BFU rm. sensor.... All runs well except for 1 Radiator.... on the first floor fairly close to the boiler...
Me thinks air, bleed out rad..no air...ain't an air problem...
Do some detective work including pulling away a bunch of insulation and discover that about 20 + years ago they piped two rads a bit diferent...supply runs to the second floor rad 1st then goes to the basement, then does a 180 turn back to this 1st floor problem rad and the back to the boiler...Second floor heats fine but not this 1st floor rad... all piped in 1.25" copper...Grundfos 15-58 is the circ. on spd. 2 as per spec from the chart on Hot Tech topics...any ideas? ty,kpc

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Paul Pollets

It Dependz

Kevin, did you revalve the radiators with TRV's? I'd also be using a 26-64 pump if there are 3" mains, presuming you're 'pumping away'. Make sure there's a full 11/4" bypass on the boiler or you can expect condensation.

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Mike T., Swampeast MO

Is there a TRV on the 2nd floor rad on the offending circuit (the one downfeeding a rad on the first floor)?

Not sure where you are, but is the system just being used occasionally or perhaps just for testing?

If so, has the system run long enough for the TRV on the upper rad to be satisfied?

Did you happen to notice if the hand valve on that rad was throttled down--like WAY down?

If what I suspect is happening is indeed happening turn the TRV on the 2nd floor rad to minimum, run the system in moderate weather and see if the downstairs rad now heats. If it does, I suspect that the TRV is hogging the flow and not reaching setpoint in moderate weather.

In that case your only real solution will be to cut that goofy supply chain right after its connection to the 2nd floor rad and then pipe in a new supply to the 1st floor rad.

kevin coppinger_4

I did not...

realize it was piped that way until today...good thought...bummer for me. kpc

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Mike T., Swampeast MO

Aren't after-the-fact discoveries fun? Kudos for looking!