noise in grundfos circulator pumps

Garfield

https://www.youtube.com/watch?v=cI35uh6vjzg&feature=youtu.be

I don't know what this noise is. It sounds almost like debris in there but it seems more likely to be air. The boiler does a floor heat loop where it runs at 80 degrees and the noise is very faint or not there but on a dhw call the hotter it gets the more noise it makes. I have a valve to open near the pump and I opened it and put a bucket to catch a full flow for about a second and the water is surprisingly clean. We do lose enough water that if I turn off the feed valve in 3-4 weeks time the boiler will go off on low pressure. There's water in the boiler and 2 separate heat exchangers, one for glycol floor loop and one for hot water heater. Boiler is a triangle tube prestige 250. circulators are 26-99 grundfos I believe.

nevele

The bearings are lubricated by the water . If you've been losing pressure the bearings may have run dry and were damaged. It can happen pretty quick.

hot_rod

you could be cavitating, especially if your system keeps losing pressure.

You can also loosen that large screw to confirm there is fluid at that bearing. Carefully loosen it as fluid will drip, or spray out when the screw is removed.

If the circ runs without adequate fluid, the bearings fail quickly.

Any flow restricting devices on the suction side of that circ pump? Those can coax it into cavitation also.

icesailor

When you start and have added water, how much pressure do you have in the system?

Garfield

Hot Rod, icesailor, nevele, there's 12-14 pounds generally and about 9 it shuts off the boiler and the pumps so i don't think they would have run dry. Both pumps are in the boiler water and both are 3-4 feet below the boiler. No flow restrictions. There is calcium buildup on the threaded connections to the boiler....i'm assuming this is a small leak that never really drips but could it let in air and that be the noise?

icesailor

Is this a wall hung beer cooler boiler with a low pressure switch?

What is the pressure marked on the switch? Raise the system pressure to 18-20#. Never trust a old pressure gauge unless you have a new one of a known quality to compare it with.

I've seen far too many second floor zones not pump until the pressure was raised to not look at the pressure first. And I didn't have to bleed radiators. Just the increase in pressure squishing the air in the pipes was enough to get it flowing. The rest of the air was absorbed by the heated water.

hot_rod

you need to be careful when you add pressure, firstbthe expansion tank needs to be pressurized to the new pressure, second you really diminish the expansion tank acceptance volume when you boost the pre-charge pressure setting. keep an eye on the pressure and relief valve.

You could simply have some debris in the impeller, easy enough to remove the 4- 6mm allen bolts, with the pump isolated of course. that would quickly eliminate that variable.

But the bigger concern is why you keep losing pressure, it has to be going somewhere??

Garfield

http://www.triangletube.com/TriangleTubeProduct.aspx?CatID=1&PID=1
This is the boiler. It's an actual gauge and the circs are below the boiler several feet. One is the boiler loop circ and the other is the circ for the hot water hx.

Garfield

This is one side of the bottom of the boiler loop where it attaches to the boiler. I have since seen a kit I suppose is necessary to keep it from leaking ...or maybe a more skilled plumber.