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ESBE valve + converted gravity question

I am adding a bypass to my gravity converted system that came with my house. It's already 25 years old but I'm trying to keep the boiler and my 4-year-old chimney liner as happy as possible.

Was going to do a simple bypass but I got a great deal on an ESBE valve body. The piping diagram, though, looks like I need to have 2 circulators and pump it P/S in order to use on converted gravity. Am I reading this right? The ESBE instructions are hardly comprehensive.

I do worry that if I added the ESBE without P/S that the flow could be so slow through the old gravity pipes that the 3rd floor never gets warm before the thermostat on the 1st floor stops calling.

Am I overthinking this?


  • Zman
    Zman Member Posts: 7,572
    You need a circ on the boiler side and a circ on the system side. The drawing has a 3rd one which is unnecessary. The primary/secondary should be tied together with closely spaced tee's or a hydraulic separator.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Bill_17
    Bill_17 Member Posts: 68
    Zman is correct. The ESBE diagram's 3rd circulator is shown with a dotted line around it. The full document indicates that is an alternate, but less desirable, location as compared to being installed on the outlet of the boiler.
  • Bill_17
    Bill_17 Member Posts: 68
    See attached ESBE diagram
  • hot_rod
    hot_rod Member Posts: 22,244
    you would need to analyze the circuit. It’s possible a dongle circulator could be adequate for the boiler glue and distribution, on a direct, non primary secondary piping. There are loading units that are a pump and valve in one assembly. Commonly used on wood fired boilers
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream