Circulator Pump Noise

[Jac04]

My Taco 007 circulator pump makes a faint gurgling noise when running. Like there is a tiny bit of air in it. There is no detectable gurgling in any of the baseboards or other piping - it's just at the circulator pump.

Background:
I just recently had a Navien NCB-180E installed to replace a failed Navien CH. All plumbing as well as the circ pump remained the same, as the NCB was essentially a direct replacement for the CH. I can't remember if I had this same noise about 4 years ago when the CH unit was first installed or not. The system pressure is set the same now as it was previously, which is 11.4 to 11.6psi at rest, and nothing else has changed.

Is this something to worry about, or is this just a little air left in it from the new unit installation? Will any air eventually find its way out?

Wondering if I need to get the installer back out or if I need to try to purge the air out myself somehow. The NCB unit is self-filling and self-venting, so I'm not quite sure what to do.

 

[Jac04]

Oh, one more thing...

The pump was completely silent on an initial call for heat this morning. The very faint gurgling noise didn't start until the supply temp got up to about 110F.

 

[Sponsor]

 

[Dana]

It's possible that the noise is cavitation rather than air(though that would be more likely when the system is cooler, at a lower pressure.) What is your system pressure, and where it the expansion tank & vent in relation to the pump?

 

[Jac04]

System pressure is 11.4 to 11.6 psi at rest and it usually gets up to about 19.4 psi on a call for heat. The vent & expansion tank are just upstream of the pump. See attached picture.

 

[Dana]

Bumping up the pressure to 14-15psi cold won't hurt anything, and would help if the symptom is cavitation rather than air.

The length of straight pipe into the air scoop/vent is a bit short from the nearest tee of the hydaulic separator manifold but not short enough to be a problem. (The rule of thumb is 10 pipe diameters minimum to the nearest tee or ell, but in your case there's a reduction in diameter between the manifold and the air scoop.)

The pump being on the other side of the ell from the expansion tank means it's not getting quite as much protection against cavitation as it might if it were in a straight line, but the length of pipe between the ell and the pump looks long enough to quell most of the turbulence induced by the turn.

Bottom line- it's probably not cavitation. If it's air the air scoop will eventually catch it all, and the noise will go away. Any time you open up the system some amount of air gets in, and it sometimes hangs around in pockets for weeks, with the flow pulling in random amounts of air as it moves by. But as long as it isn't vapor locked and you have flow it'll eventually go away. On my system right after I clean the filter I'll hear a bit of sizzle coming and going on the primary loop for a couple of weeks.

 

[Jac04]

Thanks again Dana. I may give it a little time and see what happens, since I don't seem to have any flow problem. Too bad it's not cold enough yet around here for this new unit to stretch its legs a little. Heck, it's supposed to be 70F outside here today & tomorrow.