Backup Generator transfer switch


In the past two issues of Stereophile, Michael Fremer has been discussing the disastrous results to the sound of his system after having a backup generator installed at his home. The system is not running on the generator, but he believes it has to do with the transfer switch that gets installed on the AC signal path.  He describes a pre-generator experience as "intense and emotionally elevating" afterwards "everything good was gone, two large ill-focused boomboxes had replaced absolute magic".  I recently moved and had been listening to my system prior to and after the installation of a Generac whole house generator, I did not notice any change in the sound, I can still sit and enjoy the music for hours with no sense of fatigue.  Perhaps my ears are shot or my equipment is not expensive enough.  Anyone here have any experiences with generator transfer switches?

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Showing 2 responses by spatialking

I have been following M. Fremer's problem in Stereophile closely as well.   As I mentioned before in other posts, I am Director of Engineering at a green energy company and we bought that exact same transfer switch to reverse engineer.   As you might guess, his problem certainly hit close to home.

One possible problem is the ATS isn't "just a switch".  The problem with any ATS is UL108 which applies to all ATS units.   There is no relay company on the planet that can make a relay meet the requirements of UL108, rather it is left up to the manufacturer of the ATS to build enough logic and microprocessor power around a solid relay to handle the requirements.   That stuff is running full time, so expect it to bleed EMI into the lines and into your gear.   

A solid EMI brick wall filter or power regeneration system like the PS Audio one that M. Fremer installed would do the job.   The fact is, the power lines and house wiring make excellent EMI antennas, so expect some EMI to bleed into your system, and cause some havoc at some level.   

There are only two ways to eliminate the ATS and still be code compliant.   One is a manual switch, which you have to operate yourself.   The other is an ATS that has a five+ minute lag between grid failure and switch over to generator power.   That is a long time to be in the dark!  

M. Fremer also mentioned in the latest issue of Stereophile that he had a "flat topped" waveform, I assume he meant he has a clipped sine wave, for AC power.   If that is the case, he really has some serious problems there that go beyond the ATS.   
We have a customer that has the top level of his 60 Hz power waveform clipped at the transformer at the street.  His power company won't replace the transformer, since he is the only one who complained about the noise in his high end audio system.   For him, running off the solar, batteries, and inverter was the best solution.  
It is possible the main transformer down his street shorted a winding about the time of the installation and that is the reason he is having sound quality problems.   There isn't anything in the ATS that can clip a 120VAC sine wave but if he really has a clipped sine wave, it would have to be the transformer at fault.   He wasn't running from the generator at the time, so that is not the problem.

Or, as I said before, it could just be all the EMI in the ATS is flowing into his system.....