Surge Guard 35530 HUMMING...
Surge Guard humming...
So here's the story so far.
Just before Christmas, the good people at 'TechnoRV' sold me a Surge Guard 35530 hard wired surge protection unit for my travel trailer.
Out of the box I noticed it looked like the plastic casing was slightly deformed, nothing serious but not as perfect as I expect from a nearly $200 dollar piece of electrical hardware.
I called Eric the owner of TechnoRV and he assured me it was quite normal and that he foresaw no issues with it's operation, but that if I was at all unsatisfied he'd replace it immediately.
I wired the unit into my trailer and at once noticed a significant electronic humming coming from the unit.
I was about to undertake a short trip and had no time to remove the unit so I called Eric at TechnoRV to find out if it was likely to fail and cause a catastrophic incident, he said not and referred me to TRC in Clearwater FL. who distribute the thing.
TRC confirmed it was not common but also not unheard of to hear a hum, and most importantly, that it was not at all dangerous.
Eric very graciously insisted he send out a replacement unit. I finally had time to install it yesterday only to have it exhibit the exact same noise as it's predecessor.
I again called TRC and spoke to Steve in their technical service department who is intimately familiar with these units.
Being a good company man he said he had heard of a few units humming, but to have been supplied two, and have both make a similar noise was very uncommon. Perhaps it is my power supply he suggested.
I described my dedicated 30amp supply that I'm plugged into while parked at my home, and since I'd recently been on a trip and plugged into pedestals at two campsites, both of which triggered the same humming, I seriously doubted that supply voltage or amperage to the trailer in this case was the issue. He acquiesced.
In desperation I researched all I could find about the Surge Guard and similar units on the market. All have their fair share of detractors and all it seems at some time or other hum.
I found, and was intrigued by an entry in one of the many forums I visited, the essence of which follows.
Apparently, during manufacture, the mechanical contacts may get a light coating of oil on the 'blades' to prevent corrosion etc. This coating can cause a less than perfect connection and may cause a low frequency hum.
The engagement and disengagement of these blades during a normal power up sequence does not, it seems, remove this coating.
However, if one leaves a load on the protected A/C circuit when the blades close, the arcing that occurs is enough to burn off the coating on the mating surfaces sufficient to improve the electrical connection.
To say this sounded unlikely is an understatement, but I figured it worth the ten minutes it would take to test the theory.
I plugged a small ceramic heater with a fan into an A/C outlet in the trailer and set the fan and temperature on high.
I then went outside and disconnected the shore power cord, waited a second or two then reconnected it. A little over two minutes later I heard the unit reconnect with the usual 'thunk!' I repeated this cycling two more times over the next few minutes before venturing
back inside to listen for the result.
I am pleased to report that the unit is now almost completely silent. Problem solved ! Go figure!
I embarked on this course of action with total skepticism, but am pleased to report it cured it for me. I wish I'd researched a bit more before I contacted TechnoRV, and put them to the expense of sending out a replacement.
I have contacted Eric at TechnoRV to let them know the outcome of my experimentation and experiences.
They and TRC have been most gracious and attentive throughout, having stood 100% behind the product they distribute. I can assure anyone that they are still top of my list to call whenever my RV needs anything they can provide.
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