fintube noise, near boiler piping

Bob B_2

I have a W-M cast-iron boiler, about 12 yrs old. 3 zones of hw-baseboard fintube. I inherited it with the purchase of this house about 1.5 years ago.

I'm following up on my problem from last year of the baseboard being very noisy. Last year we lived with the noise and called it an annoyance. This year it is waking up my 2.5 yr old, so it has been elevated beyond annoyance!

Short story is that the zone upstairs runs in series along 3 outside walls. The baseboard is recessed into the wall. There is very little insulation behind it (maybe 1/2 inch of rock wool). It groans and moans and tings and pings quite a bit. Actually I've been able to get rid of some of the tinging and pinging by strategic placement of cardboard where metal might hit metal (on the brackets that hold it up, where some fins might have been hitting the back of the baseboard). But enough noise still remains.

I've had a few people come look at things. Both have suggested removing the recessed baseboard, closing up the wall (either plaster or a wood baseboard/skirt board) and then putting new slant-fin in. One thought a good deal of the noise comes from the back of the hw baseboard and the fact it is against cold studs/cold air cavity. So this is one part of it.

One of the people suggested I start with some "issues" in the near boiler piping before replacing the baseboard. For instance, I have zone valves, not circulators on my zones. He said that circulators would be better and perhaps (since the water is moving faster? not sure of his point here) it might help with the noise. And he would use Grundfos 3 speed pumps so that there is some adjustments that might help. And that my one taco 007 on there now doesn't do a particularly good job if many zones call for heat. And that it (the taco) is too close to the boiler output (it's a few inches above it) and is getting too hot. There were other issues he brought up but minor ones, ones that maybe should be fixed, I'm not sure (flow check too close to pump for instance, and other small things).

Also, he said that with a cast iron boiler like mine, that he would put circulators for each zone on the return side, not "pumping away". Is that right?


I know a picture would be helpful here but I'm at work right now. I'm looking for reality checks on:

1. will near-boiler changes (mainly circs vs zone valves) help the noise in the upstairs zone to any degree?

2. are circulators better than zone valves really?

3. is it okay to put a circulator on the return side (where the zone valves are now)?

4. should I skip the near-boiler stuff since it seems to work and go right for the baseboard replacement?

Lastly, I realize that outdoor reset and/or constant circulation might be an option, but I'm not convinced that OR will give me significant savings with my boiler after reading some recent threads.

Thanks for any thoughts.

Tom S

Jim Erhardt_3

Tom, in answer to your questions:

1. No. The noise you hear is from thermal expansion and contraction of the baseboard and connecting piping.

2. It's a matter of opinion, but in most residential systems, I think not.

3. It is ALWAYS better to pump away from the expansion tank. The preferred arrangment is the expansion tank/air separator on the supply header with the circulator downstream "pumping away." The ZVs on the returns is just fine.

4. Yes. Slant/Fin basebaord is IMO a great choice and if installed properly, will be nearly silent. Make sure the contractor takes the time to screw (not nail) the cabinet to the wall studs, and pipes the element in such a way that the piping does not bind or place torque on the element and cause it to bind in the cabinet. Basically, you want the element and connecting piping to be able to expand and contract without binding on anything. In regards to the piping that connects the baseboard, be aware that Pex tubing expands about 7 times more than copper, which can make noise-free installs a bit more difficult.

Another point ot keep in mind is to do a room-by-room heat loss calculation to determine the correct amount of baseboard to place in each room. Proportionally increasing the amount of baseboard in each room will alllow the use of lower supply temeprature, which will cause less expansion of the piping and baseboard - and less potential for noise.

Good luck in your quest for restful nights!