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[Crossir]

Well I have a question on my circulator pump. I have a Taco 0011 stainless steel pump. It seems that at lower water temps 150-160 it runs quiet and smooth. As the water temps climb to the upper limit the pump sounds rough, like it I has air in it or not getting enough water flow to it. Basically I have s 600' loop and the pump is at the mid way point in my basement. The one way breakdown is; 10'-1 1/2 black iron, 240'-40mm  logstor, 45'- 1 1/2" pex, 10'-1 1/4" copper, 1-5"X10"X50 plate exchanger. I appreciate any information.

[mlappin]

Mine used to do the same when in the basement, mounting it at the boiler ended the noise.

May be something different with yours though.

[slimjim]

How old is it? How long has it been doing this?

[Crossir]

The system is new, up and running for 10 days.

[slimjim]

That's weird, it runs fine at lower temps and ALWAYS makes noise at higher temps? Perhaps a bad bearing?

[fireboss]

maybe cavatation?

[Smokeless]

Partially close a ball valve on the out going flow when it is making noise to see if it goes away. This will  rule out cavitation.

[Crossir]

Ok, so I have a ball valve about 50' away on the return, I need to close it about half way before the noise goes away. Also I noticed if I turn the circulator off for a few seconds then back on, it runs smooth for about 20 seconds before the rumbling starts to build again. And yes, every time the water temps swing I get the same noises. I am guessing it is cavatiton but don't you need some air for that to happen? Anyway, other than moving the pump closer to the boiler, is there any other options? Will cavatation damage the pump, if yes,how much time do I have?

[dukethebeagle]

sounds like the pump can pump more then the amount of water thats coming to it
just a guess

[Chas]

I have the same issue with my pump. It's a Bell & Gossett NRF-36 in my basement 180' from the boiler. It gets noisy if I set it on the highest speed. I've always figured it was trying to pump faster than the water was flowing to it.

[shepherd boy]

If you put your pump down stream like in the house on a nonpressurized boiler like an outdoor furnace you create a vacuum in the suction line. Water will boil at a much lower temp in that vacuum and can be putting steam in the circulator at 180 degrees. Putting the pump on the stove where you push the water could solve your issue. The longer the line and the bigger the pump the greater the chance of this issue.

[mlappin]

If you put your pump down stream like in the house on a nonpressurized boiler like an outdoor furnace you create a vacuum in the suction line. Water will boil at a much lower temp in that vacuum and can be putting steam in the circulator at 180 degrees. Putting the pump on the stove where you push the water could solve your issue. The longer the line and the bigger the pump the greater the chance of this issue.

 

Exactly what mine was doing, didn’t figure in boiling at a potential vacuum.

[slimjim]

Good point Shepard boy but looking at his line sizing I wouldn't think he would be pulling a vacuum. However, perhaps there is enough somewhere in the near boiler plumbing to create the vacuum.

[Crossir]

Thanks for all great info. Slim, the only thing that may restrict the flow in my lines are the fittings that go on the 40mm logstor. I went with the Watts mechanical (single bolt) fittings. They have a much smaller ID than I realized when I ordered them.

[shepherd boy]

All piping will have some friction and needs pressure or suction to move the water. Smaller pipe requires more to move the same gpm. Did some calculation on an 011 pump (30 GPM max flow).. If friction is great enough on input side to drop gpm to 17 gpm water will vaporize at 176 degrees. So if you figure half pulling and half pushing if gpm drops to 8.5gpm you could vaporize in the feed line at 176 degrees. In a pressurized boiler situation, however,  at 10 psi you can stall it dead on a return, and never vaporize because the boiler pressure overcomes the negative pressure of the pump.