Constant Noise From Boiler - What is it? See Video.

[mdsnj]

Hi,
I was wondering if someone could advise me on what this noise might be. It's constant when the heat is on and it's driving me crazy. The boiler is old, maybe almost 100 years old, but it doesn't seem to be coming from there. It's hard to pinpoint exactly where it's coming from. We had the expansion tank changed about 2 years ago.

Please see video:

Thank you

 

[BadgerBoilerMN]

Back up so we can see the boiler and all near-piping.

 

[Sponsor]

 

[Tom Sawyer]

It's the spring coupling on that big red B&G circulator. It's on its way out so ya best get it fixed ASAP or you're not going to have heat.

 

[mdsnj]

It's the spring coupling on that big red B&G circulator. It's on its way out so ya best get it fixed ASAP or you're not going to have heat.

Sorry, I should have mentioned that the big red pump is disconnected. It was for a floor that now has it's own separate boiler.

 

[Dana]

It definitely sounds like some circulator or another getting ready to lose it though. You should be able to figure out which one it is using a length of tube as a stethoscope. There's an outside chance that it is cavitation on a pump impeller due to low system pressure, but I doubt it.

When it gets to where it's making that grinding noise 100% of the time you'll have effectively zero flow. (At least that was the case for an aging green Taco on my own system the other day. Fortunately I had a spare to swap in immediately, since it turned out to be one of the coldest days of the season, with a daily average temp of +5F, which just happens to be the 99th percentile temperature bin in my area. The overnight low was -7F, which occurred about 6 hours after the spare pump was installed.)

I the boiler is as antique as you say it is, think about updating it. The surface features of the heat exchanger plates that give it the surface area & turbulence for efficient heat exchange will have eroded to nearly-smooth on both the fire side and water side. It may have been able to hit 75-80% steady-state efficiency when it was brand new, but after 75+ years of service you'd be lucky if it's still as high as 60%. If history is any guide it's probably 5x oversized for your heat load too, now that you've taken the second-floor zone off it. By being way oversized it can still heat the place even if it was only getting 30-40% efficiency. Newer right-sized equipment would cut the fuel use by a significant double-digit percentage (possibly even by half, depending on oversizing factor and condition.)