whistle noise when boiler stops calling for heat

SAK

when I had the boiler reworked to have separate thermostats upstairs there began a banging sound. the Honeywell valves were closing too quickly causing a water hammer. Unhooking one spring causing the valve to close slower fixed the problem. Forward 6 years. Now I am hearing a very loud whistle type noise when the boiler stops calling for heat. reattaching the springs on 2 of the valves has only made the noise worse and it lasts longer. Approx half a minute compared to 15 seconds previously. I read it can be air in the lines (Baseboard not radiator) but there is an air scoop on top of the boiler (rather large one} Do burners whistle when shutting down? I hate to have to call the repair as its quite expensive when its not clear what is wrong.

Intplm.

@SAK Noises such as explained are very hard to diagnose from here. If possible, please post a video or at least some pictures of what you have. That said, a venting noise that lasts from fifteen seconds to thirty seconds can be normal depending on your system .

hot_rod

Try and narrow down the location. Does it make the noise if the gas valve is off? That would help determine if it is from the burners or percolation in a hot boiler block.

Alan (California Radiant) Forbes

What is the make and model of your boiler? Some pictures of it might help.

SAK

it's a Lochinvar mini fin

SAK

the thing about this noise is it has only recently started doing that. I do have an old stethoscope and I will try to go out there and try to listen where it might be coming from. I am thinking if I turn the Gas valve off to check for noise, the boiler won't light and it only makes the noise after burning.

clammy

Loss mass boiler should have been piped w a full sized by pass or primary secondary i believe its in the installation instruction that are included w the boiler , I would check if you have been taking in make up water these low mass boiler do not like taking on water and will lime up and cause whistling or kettling sounds .They generally work quite well when piped correctly and water quality is taken into account. but usually the issue does not appear directly after install unless theres some serious piping sizing issue and flow issues from the get go not to forget some massive short cycling which does not help anything . This is just from what i ve seen and its been some time since i ve had to deal w one . Its a place to start . Greatest thing about them is one guy and carry it down and the old one out . I had a teledyne lars combi for bout 18 years until i did a munchkin which is still going made it past the lars life span .

peace and good luck clammy

Alan (California Radiant) Forbes

I'd try to install a device that keeps the pump running after the call for heat is satisfied, like a delay-on-break relay. That would help to remove the build-up of heat in the heat exchanger which is possibly causing the harmonics.

hot_rod

lowering the operating temperature of the boiler may help also. Run it as low as possible as long as the home stays warm