# Does a portable generator need a transfer switch?



## m1lreese (Mar 29, 2018)

When I asked the question citing concerns about frying the well pump, surveillance, stereo equipment, appliances, etc. using a portable with HD of 10%, this was the response I got.

*The stereo and the surveillance should be protected by surge protection by means of a surge strip. The appliances and the well pump should be protected by GFI, and they probably are already by means of GFI breakers and/or GFI receptacles.

The correct practice of protection of these items when dealing with a generator is to let the generator start and level out before the power is actually applied to the designated location. This only takes a matter of seconds.

The portable generator would be installed with a subpanel loadcenter and an outdoor receptacle that would have to be plugged in.*

Also, what is a subpanel load center? Should I expect all portable quotes to include that?
Is it common to add a whole house surge protector? Would that compensate for the harmonic distortion?


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## aandpdan (Oct 8, 2012)

Subpanel load center means that there is another panel attached to your load center that only handles the generator loads.

I prefer an interlock. It would allow you to power ANY circuit. It's often MUCH cheaper - especially if your current load center maker supplies them. It also allows AFCI and GFCI breakers to function normally, something most transfer panels don't do - when in the generator position.

You still need an inlet - to feed power to the interlock or panel.

Don't worry about THD and your appliances. Most contain switching power supplies and can easily handle a wide range of voltages/frequencies.


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## m1lreese (Mar 29, 2018)

aandpdan said:


> Subpanel load center means that there is another panel attached to your load center that only handles the generator loads.
> 
> I prefer an interlock. It would allow you to power ANY circuit. It's often MUCH cheaper - especially if your current load center maker supplies them. It also allows AFCI and GFCI breakers to function normally, something most transfer panels don't do - when in the generator position.
> 
> ...


That makes sense. I've learned a little more. 

With the subpanel, the connection is simpler. Start gen. Plug it in. Power comes back to things not powered by gen. Unplug. You can overload it too, you just have to know to switch a couple things off. You technically can add all the circuits.

With just an interlock kit, you have to switch it at the panel manually. The you have to know when the power came back. There are things you can add to send an audible alert so that's not too a big deal. So basically, the main advantage of the subpanel is the convenience of not have to flip the interlock, which might be scary or added complexity to some, like my wife if I'm on a road trip and I'm not there to get everything going.

On the flip side, the interlock setup is going to cost me <$700 compared to $2700 with the subpanel (different electricians) compared to $7800 with an 11KW Generac standy. 
(Add $1200 for the 12KW portable generator with the first two options.)

So, ultimately I will go with the interlock setup. I may likely add a whole house surge protector as well.


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