Yep.... It hums...

[suprz]

Just got done installing the Progressive industries hardwired 30amp unit... luckily I installed it in the electrical bay. When I first plugged it in, it was silent. I went into the rv and turned on a DVD and went back outside to read the display and that's when I heard the hum. Darn! I shut off the DVD player but the him continued. I'm very glad I didn't put it under the bed! Oh well... It's not "too" loud and it's on my side Of The bed so the wife probably won't even notice but it is disappointing. On a good note, it already saved me cause the first extension cord I plugged in, the EMS gave me a error of reverse polarity. That cord had a aftermarket female end on it. I unplugged it swapped the white and black on the cord and all was well

[myredracer]

I mounted our 30 amp PI EMS under a dinette seat next to the converter/panel. It never ever makes an audible hum and it's screwed directly to wood. Some simple rubber grommets from the hardware store may be all that's needed to provide enough noise reduction. Or just turn on the furnace or AC to mask the hum. :R

[SoundGuy]

bob213 wrote:
I think it was "Soundguy" who posted that that he remounted his into a plastic tool box or the like and got rid of the hum. Hopefully he will post here.

Progressive bolted the contactor directly to the box in which it's mounted so when it vibrates that vibration is transmitted into the plastic box and is amplified. The solution is to isolate the contactor from the box but with the parts jammed tightly into the box there's really insufficient room so I ditched the Progressive box and mounted the parts in a plastic tool box. My EMS sat under the sofa so it was clearly audible but isolating the contactor solved this issue entirely. A series of pics starts here.

[bob213]

I think it was "Soundguy" who posted that that he remounted his into a plastic tool box or the like and got rid of the hum. Hopefully he will post here.

[MrWizard]

unscrew from the steel
place on foam or rubber
then test it

you will learn more and quicker than playing with the sound deadening material lining

[Boomerweps]

Noticed my hard wired 30 amp unit humming the other day when I was checking the voltage after plugging the TT back in. The extension cable got disconnected after it was covered for winter, don't know when, just saw it before I removed the winter cover. Mine is installed on the carpeted wheel well under the aft dinette bench. With bench installed, it muffles the humming to the point I can't hear it 😉

[suprz]

If the unit itself is vibrating, I can't feel it. It is screwed onto a steel box though. So it may be giving off some vibratory resonance that is being amplified by the steel box. I'm going to do some experimenting with some sound deadening material that I will place over the unit to see if that helps. I can also put eternabond on the sides and floor and top Of The metal bay To Help deaden any amplification the box may be doing

[MEXICOWANDERER]

Resonant Frequency

60 Hz.

It comes from the transformer laminated winding. Silicon steel wafers in which copper windings are wrapped around. 400 Hz military transformers produce a different hum -- higher in pitch and softer in intensity. For many years GM Delco produced an automotive alternator with a 7-pole rotor that created a unique hum when it was charging hard.

Spun fiberglass as used for an enclosure wall (air needs to circulate within) will help block the noise. Harmonic resonance actually creates it's own (minor) heat in small transformers and a good deal of heat in alternators.

Make absolutely sure the noise is not being transmitted from the device to a soundboard floor.

Gum rubber mounts seem to work well for mechanical noise isolation.

[rk911]

we have the 50-amp hardwired PI unit and I've never heard it hum. I heard it sing once but never hum. it obviously knows all the words. :B

[suprz]

Someone on these forums said it is the "contactor" inside the unit that makes the humming sound. I will see if it bothers me on our next trip. I can usually sleep thru a war but I may do something like insulate the bay etc.. To cut down on the hum noise

[Johndanielscpa]

I installed a 50 amp hard-wired in my fifth wheel, and it hums as well. I took it to a local service shop; they were unable to do anything about it. The hum comes from within the unit, not due to vibration on the outside. It drives me crazy at night, because I can hear it sitting at my dining table. Following - in case someone mentions a fix.