Hot water zone flashing to steam

Sparkybruno

I ran a hot water zone off my steam boiler before the start of the heating season last year. Followed the advice listed on the B&G website and ran a bypass loop to temper the water (180 deg), with flow control valves and controled the circulator via Taco controller.  The system worked great until the end of the season when the circulator started to make a squeeling sound when it would shut off. I had the  B&G guy check the pump and he said the seals were too tight. So he replaced that section of the pump. This season the pump is fine but now it seems that I am somehow getting air in the system because when the zone does call for heat, I get a gurgling popping sound from the pipes, usually near the first baseboard radiator, that sounds as if the water is flashing to steam. I did drain the zone and refill it, making sure to purge the air out of the system. Before I attempt to drain and refill again, I would like advise on what to check first, maybe I am overlooking something obvious...... Thanks for the help.

crash2009

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Gordan

How high above the boiler's water line is the radiator?

If too high, the pressure at the top could be less than the vapor pressure at that temperature...

Charlie from wmass

Does you boiler have an opening for a tankless heater?

If it does I would install one and the related controls and make the loop pressurized. Did you use a bronze pump?

Sparkybruno

Checked the system this weekend and....

it was something obvious. I readjusted the bypass loop to get a slightly lower water temp at the inlet of the pump (~ 180 deg) and this seems to have eliminated the water flashing to steam. My temp gauge must be a little off. Only question I have now is, how can the water in the system flash to steam if its under pressure?  Thanks for all the replys.

Happy Holidays everyone.