The fridge says, "HRRMMWMMMWMMMWMM"
June 20, 2016 12:15 PM   Subscribe

Help me make a noisy evaporator fan . . . less so.

We got a new fridge!

Specifically a True T-12-HC. Read lots of great reviews, and I've been around them in professional kitchens a number of times. It is aesthetically, practically, and size-wise exactly what we wanted. (We're getting a separate under-counter freezer for ice/frozen things).

Here's the thing: it's loud! We knew it would be a little louder that the old one, but the evaporator fan on this model runs all the time. It does seem to be working properly; there's no rattling or anything, it just seems to be a loud motor. We're not a noise-sensitive household, and can probably live with it, but it's a little annoying, especially because the fridge is great in every other respect. For various reasons we're committed at this point, at least for the next six months or so. Warranty is essentially void, although local professional service is available cheap.

On further reading, it seems like this fan's baffling/silencing/noise-cancelling is largely non-existent. The expected use is in noisy professional kitchens, so there's a lot of sheet metal screwed directly to sheet metal resonating directly through the frame, etc. This motor is probably going to be loud no matter what, but I'm thinking it could be dampened by suppressing the amount of vibration that gets to the frame.

So the question: Is it worth popping the hood on this sucker and doing some DIY noise suppression? I'm pretty handy, and have all the tools, basic knowledge of electricity, mechanics and refrigeration. I'm thinking a cutout rubber gasket between the grill and the fan, silicone washers between every screw, and maybe rubber screws (like what you'd put around a computer fan) directly around the grill.

Anyone have any experience with this sort of thing? Would replacing the metal fan blades have any effect on sound? Any other suggestions?
posted by aspersioncast to Home & Garden (7 answers total) 1 user marked this as a favorite
Is it the evaporator fan (the one inside) or the condenser fan (the one outside underneath) that is the source of the noise? I can't imagine you can do much to suppress noise from inside the fridge that is getting through the insulation.

If it is actually the condenser fan then yes if it is vibrating and causing other things to vibrate and rattle isolating those things will cut down on the noise. Getting at the source by balancing or replacing the fan blade if it is out of balance or replacing the fan motor with a higher quality unit may make a difference. If a flat sheet of metal is vibrating adding a layer of dynomat will suppress noise from that and absorb some of the noise from the fan/moving air.

That style grill is often kind of loosely held together. Some caulking between the individual components can reduce some rattle there.
posted by Mitheral at 12:49 PM on June 20, 2016

This is probably not the problem, but... just in case--- refrigerators usually are shipped with the compressor isolator bolts tightened down. Is it possible that they did not get loosened on delivery? That might cause excess noise.
posted by H21 at 1:18 PM on June 20, 2016 [1 favorite]

My old work employed a lot of these(both of the stand up and under counter variety), and we had a mechanical engineer sort of guy on staff who worked on them. Some of them were quiet, some of them were loud.

A good tech could pop in some thick rubber washers and check if the blade is balanced, or swap out the entire fan for an alternate one.

I'm willing to bet, by the way, that you're talking about the condenser fan. You can barely hear the evaporator fan on these from the outside because they're built like brick shithouses and the fan is basically closed inside.

I think you're on the right track, and H21 was above as well with having someone check the balance, isolation, maybe add some washers, and maybe a different fan. I know several of the under counter ones burned out fans and had them swapped with much quieter ones(with similar or greater CFM!)
posted by emptythought at 1:22 PM on June 20, 2016 [1 favorite]

I think this applies to your model:
"Make certain the metal strap holding the compressor during shipment is removed. Failure to cut strap could result in excessive noise and vibration (freezer)."

From page 9 (document pages, not pdf pages) of this document.
posted by gregr at 2:14 PM on June 20, 2016 [1 favorite]

You all are great. Thanks for weighing in.

For clarification:
    it's definitely the evaporator fan, inside the top of the fridge. The condenser fan is also loud, but intermittent, as expected.
    I found that metal strap thing as well! The strap is definitely gone, and isolator bolts are tight enough, but not too tight, with linchpins and nylon washers. There's no rattling from the condenser or the grill, just the general motor hum when it kicks on.
    there was a loose machine screw in the grill, but tightening it doesn't change anything.
    so I went ahead and removed the grill just to see if that was the culprit. No dice. It really seems like the motor is just loud. It always sounds like it's revving up.
    fridge was professionally uncrated and set up, but transported, leveled etc. by yours truly. Clearance is as required in the manual, I know how to use a level, voltage requirements are tested and it's on a known-good breaker.
Soooo. I guess the follow up will be checking out/changing out the fan/motor, since rubber washers on the grill seem pointless. I'll also dig into the motor specs a little and see if fan speed is adjustable. Balancing the fan blades seems like great advice; it seems like the kind of noise that might be due to a bent blade or uneven spin.
posted by aspersioncast at 7:00 PM on June 20, 2016

It's unlikely the fan is adjustable for speed (short of adding external TRIAC or frequency adjustment). Even if it is, slowing the fan down can cause icing of the coil which will at best reduce efficiency and at worse prevent your fridge from cooling.

Have you seen the fan motor? Is it a shaded pole or conventional induction motor? If it is a shaded pole motor replacement with a good quality induction motor can reduce vibration because of its increased mass and generally higher quality construction/bushings but finding one that fits the form factor of the shaded pole motor can be difficult. Also you need one that is rated for wet environments.

The mounts on these fans tend to be kind of weedy; some reinforcement might help.

Be careful when messing with this that the fan is located on the shaft in the correct position if it is adjustable. The depth in the shrouding if any is critical to good operation.

If you take a shaded pole motor apart make sure you observe the location of the shaded pole relative to the front of the motor. Flipping the coil pack over (an easy mistake to make) will reverse the direction of rotation severely impacting the efficiency of the fan.
posted by Mitheral at 8:15 AM on June 21, 2016 [1 favorite]

So for posterity's sake, just a follow up for anyone considering this: We've just learned to live with it, and it also seems much quieter after a couple weeks of operation. Totally into it now, because it's just incredibly practical to have a fridge that's just a big box without all the special nooks and shelves.
posted by aspersioncast at 9:24 AM on July 17, 2016

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