Is my pump too big?

Le John

I have a tenant that is complaining about velocity noise in the baseboard loop. I hear it slightly but I didn’t think it was out of the ordinary. It’s a Lochinvar Noble with a Grundfoss 15-58 on speed 1. There are two zones at 25 feet 1/2 inch pipe per loop. Do you think I could be over pumping the zones? There are no issues with heat. I was wondering would a smaller circulator help? 

Happy New Year to all here on heating help! 

Ironman

What size boiler? Is it piped p/s? How much BB element on each loop?

The 1/2" pipe is probably what's causing the velocity noise. There are some smaller circs available, but you may under-pump the boiler and cause it to short cycle, in fact, it probably already is with two micro zones like that.

hot_rod

3, maybe 3-1/2 gpm in 1/2" copper to keep it quiet. Generally over 4 fps velocity you start to hear noise. Unreamed tube can add to velocity noise, hard to correct that condition
Adding a balance valve like a Quicksetter would allow you to see and adjust flow a bit.

It would be good to know the heat load of the space, then build the emitter, piping, pump around that.

As Bob mentioned, we need to see how it is piped at the boiler.

Le John

Happy New year @Ironman . 

The boiler is a Lochinvar Noble NKC 199 piped primary secondary with 25 feet of baseboard on each loop. I set one of the zones in the manual open position so the boiler hovers around 12- 14% with both zones open. I also limited the boiler firing rate to 20% to help with short cycling.

do you recommend going to a smaller circulator like a Taco 007e or leave the Grundfoss 15-58 as is on speed 1 or Speed 2? 

Ironman

Low speed on the 15-58 cross references to a Taco 005, 006; medium cross references to a 005, 007, or 008. So changing out the circ to a 007 won't help, it may make it worse.

Robert_25

Speed 1 on the 15-58 is still a pretty steep pump curve.  If nothing else looks out of sorts I would try an Alpha circulator.  I have some micro zones in my system paired with an Alpha and it is dead quiet.  

Ironman

The Alpha or a pressure differential bypas valve would also be my recommendations. The Alpha would probably be easier and less expensive overall.

EBEBRATT-Ed

Slowing the pump to get rid of the velocity noise will reduce the heat output from the baseboard slightly.

You could try reducing the flow but the boiler may short cycle, I am surprised it isn't short cycling now.

The real fix is 3/4" loop, more baseboard and run lower water temp save$$. But may not be cost effective

Le John

Ironman said:

The Alpha or a pressure differential bypas valve would also be my recommendations. The Alpha would probably be easier and less expensive overall.

Thank you @Ironman @Robert_25  When you reference the Alpha is this the Grundfoss Alpha2 15-55?

Ironman

Yes.

Le John

Great thank you @Ironman @Robert_25  @hot_rod @EBEBRATT-Ed . I will try this and report back.