Hi,
I just bought a central vac, and although it's supposed to be 67 db I found it to be quite loud for my taste. It's a good little unit, made in Canada (I should say assembled in Canada, because most components are actually made in Mexico). The motor is rated at 537 airwatts (whatever that is), but it's a 10 amps motor.
It is badly designed as far as soundproofing goes. The motor is located in the top of the canister with the exhaust port, but there's also the controller there with slots in the canister so air can exits directly that way. There is also a double pane top lid with a 4 inches hole in the bottom pane so air can also exit that way. The exhaust port has a muffler mated to it, but with all the other openings, running with or without the muffler didn't make a difference on the noise level.
You can see what I'm talking about on the following pic.
Anyway, I wanted to make it quieter, so the first step is usually to seal the thing. So I sealed the top lid slot and the numerous small slots near the controller and it was noticeably quieter. Before the tape it was quite annoying, now it is acceptable. And there is now a difference in sound level when I put on or take off the muffler.
But then I was wondering what happened with the inside temps. So I measured the temps on the side of the canister, in the top hole inserting the probe in the top lid slot, and inside the exhaust stream in the muffler. I first left the unit running for half an hour before taking the measurements.
Stock casing: 49 C / 120 F
Stock top lid: 59 C / 138 F
Stock exhaust: 60 C / 140 F
Taped casing: 49 C / 120 F
Taped top lid: 61 C / 142 F
Taped exhaust: 62 C / 144 F
So, am I right to assume it is safe to have the unit running with all slots sealed but the exhaust port?