New installation. Unfortunately I was bullied into an oversized wall mount combi boiler. It is a 151,000 BTU gas hot water boiler, and I have a 1,600 sf home in zone 1. Thanks to this forum I learned (albeit too late) that I only need 60 BTU/sf on the high end. The reason for the oversize was my "DHW needs". So instead of heating needs being the priority, he said I had to be able to handle the once in a blue moon event where I have just: a) started the dishwasher, b) started a load of white laundry in hot water, c) was doing dished in the sink, and d) was also taking a shower, I now have a boiler that can do that. Convenience over function. How American. I wish I had stuck to my request for the 100,000 or 131,000 BTU furnace to be put in. Not only is the 151 too big, it is also significantly louder (dB) than the 131 or 100.
Being this is the way it is, I am searching for advice on how to make what I have as quiet as possible. The boiler is mounted to a 4x8 sheet of plywood, The plywood is attached to six 2x4 studs. The studs are screwed into six individual floor joists. The studs do not touch the floor, so the whole caboodle is hung from the joists (including pumps and piping). I feel the vibrations from the boiler are being amplified by the plywood, and transmitted into the house structure, like a subwoofer. The noise is not steady but cycles and speeds up like a bad thrash-band base-line wuuub wuub wub bub bub bub thrummm. Because the boiler is oversized it starts up and shuts down more frequently, and goes through this harmonic pattern repeatedly. I may have been able to cope with the noise if it were steady. I did finally get ODR installed, so the boiler is doing less short cycling, and running at low-fire mode more often.
What can I do to quiet the thing down?
Attach some sound deadening insulation to the plywood? What is that and where do I get it?
Ideally (aside from a miracle: getting the correct sized and quieter boiler) I may bite the bullet and have the boiler moved. Right now the plywood board is in the cellar directly under my living room couch, where I like to sit and relax. The plywood is mounted such that it attaches to half a dozen joists, so it puts that vibration energy into many locations of the floor and walls. I want to have the boiler moved from the side wall to the back wall of the house (so it will be turned 90 degrees), and attached parallel to the joists (actually one single joist). This one joist is the last one before the foundation wall, and only 9' long. Combined with the single short joist span, and the further away location, and some sound deadening material, I can again nap on my couch (if the opportunity arises), which is much more likely in winter than turning on all the hot DHW taps simultaneously. Thank you for your attention, it feels better talking about it, but I want to do something(s) about it.Hindsight really is 20/20