Delicate situation

CanadianPlumber

Moved the meat and potatoes to another professional only site.  So, secondary circuit pumping into the low loss header instead of away.  Aside from air entrapment and noise issues how would the system be affected if purged?

hot_rod

where is the PONPC?

both the primary (boiler) pump and the secondary pump should pump away from that point.



The PONPC is where the expansion tank connects to the system piping, and if establish that at the low loss, or hudro-separator, both pumps will add their head to the circuits.



Pumping into the boiler HX assures the boiler "sees" the head added by the primary pump and keeps the pressure switch closed.



Pumping into the distribution from the PONC at the low loss header sees the same head pressure increase.



"Pumping Away" an industry must read classic, printed long before low loss headers or hydro-separators were popular, still all the same concepts in this book apply. Even more so when mod con boilers are protected with pressure switches.