Help with humming, very long run / high head

dwright1542

We have an unusual setup that was put in in the 50's/60's. It's a third floor baseboard, one continuous loop all the way around, about 250 feet, with LOTS of turns, and about 1750sq feet, in Delaware, so 61000BTU's give or take. It's also 30ft of rise, plus another 80 feet of pipe (40 each way) from the boiler, so total loop is 375ish feet, 3/4in copper. The pump is a Taco 009-F5.

The problem is: The rooms above the boiler and pumps, which is in a wing of the house, hums something awful. I mean AWFUL. House is from 1855, so no insulation. System bleeds fine, no apparent air in any of the 3 circulators on that boiler.

I've had multiple people look at it and noone has had any GOOD suggestions. Anyone have a recommendation of someone REALLY good at hydronic systems in Philly / Delaware?

Jamie Hall

Can you identify, exactly, which piece of equipment -- pumps, fans, what have you -- is generating the hum? It may not be just one item, sadly.

Usually that sort of telegraphing hum comes from the metal pipe being in solid contact with a beam or the floor or walls, and taking the hum from a piece of equipment and driving it into the structure. Often the only solution is to make sure that all the pipes are isolated from the structure with resilient pads.

EBEBRATT-Ed

What @Jamie Hall said is the first thing to check. Shut the pump off and see if the humming stops. You need to find out what device is causing the noise. Pipe could be rubbing on something and check things out like Jamie said.

It could be high velocity. If you have a valve on the discharge side of the pump try throtteling the valve temporally and see if the noise changes

Ironman

It's probably the Taco 009. Some of the older ones would do it worse than others.

That's a high head pump and as Ed mentioned, if the velocity is too high, that could be the issue.

A 375' loop of 3/4" is rediculous and the high head pump was probably added to compensate for it.

I'd try using a Grundfos ups26-99 starting on low speed and see how it does. It's a high capacity pump with less noise.

dwright1542

It's definitely when the Taco is on. We're fully hydronic, and the pipes don't run in the wall in that portion of the house. they're suspended from the basement ceiling with plastic pipe strap. There are 2 other loops on that same boiler that don't hum.

Yeah I'm handy but no heating guy and I knew that loop was probably not the best idea. I'm not sure how else they would have added it though. I'll lookup the other pump, thanks!

EBEBRATT-Ed

@dwright1542
The real fix is probably to split the loop. Run a 1" supply to the halfway point and tie into the baseboard. Then take the one that is the supply now and connect it to the return on the boiler

dwright1542

EBEBRATT-Ed said:

@dwright1542
The real fix is probably to split the loop. Run a 1" supply to the halfway point and tie into the baseboard. Then take the one that is the supply now and connect it to the return on the boiler

I wish that were possible. The current loop is on the 3rd floor, inside small kneewalls. It's physically impossible without massive surgery. I'd probably consider putting some kind of mini boiler on the 3rd floor, getting rid of the extra length, and just running a gas line up the chase.

Solid_Fuel_Man

How many feet of baseboard is on the loop? Total run of 375' if 3/4 copper isnt out of and ordinary 0015e range or Alpha 1. Is it all heating well, just a noise issue?

Solid_Fuel_Man

Plus its absolutely best practice to have a high head pump on the supply pumping toward the loop, and away from the expansion tank. 

dwright1542

Solid_Fuel_Man said:

How many feet of baseboard is on the loop? Total run of 375' if 3/4 copper isnt out of and ordinary 0015e range or Alpha 1. Is it all heating well, just a noise issue?

There's 125ft of baseboard. It is heating fine...it's just a noise issue. And it's only a noise issue because I sleep above the boiler that fires that loop. In fact, they extract every last little bit of heat. The last 8ft of baseboard is in an otherwise unheated stairwell before the loop drops back down to the basement.

dwright1542

Solid_Fuel_Man said:

Plus its absolutely best practice to have a high head pump on the supply pumping toward the loop, and away from the expansion tank. 

I checked, it is on the supply line. Actually all the loops on both boilers have the pumps on the supply line.

motoguy128

What the total temp drop on that loop? Supply Temperature? Might be able to use that to estimate flow rate. Maybe you can use a pump like an Grundfos Alpha as mentioned and be OK.

hot_rod

I'd try what @Ironman suggested. Wet rotor circulators should be almost noise free.

A hissing type noise is usually a symptom of over-pumping, excessive velocity in the piping. Usually over 5 fps you start to get velocity noise. Copper or any metallic piping will transfer that throughout the building unless all the piping is isolated from the building. Even then you will hear the noise in the fin tube.

Excessively long circuits that require high speed, or high head circulators are most prone to velocity noise.
Stay under 8 gpm in 3/4 M. Any flow restriction devices like balance valves can also add to the flow noises.

dwright1542

motoguy128 said:

What the total temp drop on that loop? Supply Temperature? Might be able to use that to estimate flow rate. Maybe you can use a pump like an Grundfos Alpha as mentioned and be OK.

Do you want to know from the point leaving the boiler to the point re-entering, or just from the start of the loop on the 3rd floor to where it drops back down? (Sorry if that's a stupid question)

dwright1542

hot_rod said:

I'd try what @Ironman suggested. Wet rotor circulators should be almost noise free.

A hissing type noise is usually a symptom of over-pumping, excessive velocity in the piping. Usually over 5 fps you start to get velocity noise. Copper or any metallic piping will transfer that throughout the building unless all the piping is isolated from the building. Even then you will hear the noise in the fin tube.

Excessively long circuits that require high speed, or high head circulators are most prone to velocity noise.
Stay under 8 gpm in 3/4 M. Any flow restriction devices like balance valves can also add to the flow noises.

It's not hissing. It's a humming like a tuning fork humming. I can hear it everywhere, but I can't pinpoint it. Let me also clarify that the noise is NOT on the 3rd floor loop. It's in the rooms above the boiler, which are heated thru radiators on a separate loop on the same boiler. The noise only happens though, when the 3rd floor pump is on.

Jamie Hall

Which simply means that the vibration is from the pump for the 3rd floor. Where you hear it depends on what pipe or pipes and beams it's "telegraphing" through.

There are many many reasons why a pump might hum -- vibrate. Some of them include the piping layout leading to the pump, operating the pump at the ends (high head, low flow, or high flow, low head) of its characteristic curve, imbalanced impeller, the list goes on. How is the pump mounted?