Winner announced for Hydronics CSI

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We are excited to announce that Nolan Stanley, Ferguson Enterprises, is the winner of the most recent Hydronics CSI contest — Full flow boiler piping

Full Flow Piping Hydronic CSI Answer


This was to be a Full Flow/Variable Primary System. Problem with current boiler piping: New install with six boilers, three boilers on one housekeeping pad, three boilers on another housekeeping pad that is across from it. Find all flow related and other potential issues.


• Air separator is now located where the hottest system fluid is and where the entrained air is least soluble.
• Expansion tank is now located on supply header common to both banks of boilers.   This ensures true pumping away from point-of-no-pressure-change. (PONPC)
• Motorized isolation valves are now used to isolate flow thru a boiler that isn’t firing.
• Pressure actuated bypass loop needed to be installed so that if no boiler is firing and isolation valves are closed, system flow is still maintained.  (Crest boilers feature the option to leave isolation valves opened if no bypass loop is used)
• This system was to be full flow.  While Primary/Secondary would have been a good choice, to achieve full flow and balance, the supply and return headers needed to be first in, last out.
• (*System fill, backflow, gas piping, venting left off intentionally to focus only on system piping)

Nolan Stanley’s Response

• These boilers are not set up as a Primary/Secondary system OR as a reverse return flow through system.

• Judging by the title of the article, we are using the system pumps to Flow through the boilers.
This system should be piped as a big reverse return header through the boilers.
One supply Starting at B4-B5-B6, then swinging down to B3-B2-B1.
And one Return Staring at B1-B2-B3 and swinging up to B6-B5-B4.

• The air separator should be moved to the supply side of the system were the water is hottest, air is less soluble at high temperatures and will therefore be removed more easily.

• The expansion tank needs to be moved to the supply side as well so we are pumping away from the point of no pressure change.

• There needs to be check valves on the outlet of the pumps so they can not backtrack through each other.

• There is no system fill.

• Nothing has isolation valves.

Mechanical Hub and Lochinvar thank all of those who participated and keep an eye out for the next installment of Hydronics CSI!

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