Interlock vs Transfer Switch


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Old 05-15-18, 10:03 AM
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Question Interlock vs Transfer Switch

Hello! Thanks for taking the time to read this and possibly offer some advice in my situation. I have purchased a Duromax XP12000EH 9,500-watt 18 hp dual fuel powered portable hybrid gas propane generator since the home we just purchased last year lost power for about a week during the hurricane. My dad is disabled so we'd like to make sure we have power for his care and it'd be nice for us too We researched having a standby generator but for the price portable is what we can do for now.

A side note, we are also adding an apartment in the garage for me so along with the generator install we asked for quotes to add an extra sub panel or replace the current panel to make extra switch space.

I've had two electricians come out and here is what they recommended. Both make good arguments for their choice but I can't figure out what would really be best for our situation.

#1: Transfer switch with 12 spaces. The one he priced me automatically switches he said. He would be moving the switches of items in the main house we would want powered and that would open up those switches for items in the apartment. With permitting this would be just under $1500. This option the generator would be parked somewhere near the back of the property near the garage and I would be installing the above ground 250 propane tank near there.

#2: Interlock with new bigger panel. He recommended this so we could choose anything and not be limited to what could be powered in the home. I had originally liked this idea before the first electrician came in and recommended the other option. My concern with this option is the first electrician said my box was a good one so I don't really want to downgrade to a worse one just to make it bigger, if that makes sense or matters. He just came today so I don't have the pricing on this yet. With this option the generator and propane tank is going to be parked by the front corner of the house near dads bedroom. He snores loud and used to be a truck driver so the noise may not be too bad of an issue for him.

We live on 2.5 acres in the woods so locations not really an issue. I've included photos of the panels they asked to see when giving quotes incase that helps you understand what I got, the one with all the inside switches is a siemens

Thanks for any suggestions on what you would do for yourself in this home/situation or what you think I should do.
 
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Old 05-15-18, 02:34 PM
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I assume that you are not going to worry about heat or a/c when on generator? As they are on your outside panel and 60 amp breaker is too big a load.

The interlock solution works but here seems to be someone that has their own idea of their standard solution. It is normally marketed as a cheap solution for existing panel. Instead of a new panel you could install interlock (basically a 3-way switch) on the feed to the panel. Some places don't like this for portable generators though.
 
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Old 05-15-18, 04:13 PM
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No a/c. Figure we'll do fans/portable ac to save on wattage.
 
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Old 05-15-18, 06:07 PM
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No electric furnace, no water heater, no dryer..... iffy on the well pump.
I see a 2P40A breaker marked in red..... gen. What is that for ?
Please don't say that goes to a generator receptacle.

Some inconsistencies.... If you have a 12 circuit transfer panel installed..... it needs to be near the main panel as the circuits are removed from the main panel and connected to the transfer panel. So I'm not sure how this moves the generator location to the back.

You have a lot of circuits there. If you opt for the interlock system.... you'd have to turn off the 240v circuits. I use and would opt for the interlock system.

Does your main panel have a main breaker in it ?
 
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Old 05-15-18, 06:34 PM
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We bought the house last year, everything is marked as the previous owners had it. I think they may have back fed into the house I think y'all call it?

The panel with all the house switches is located in the garage while the main house breaker with the a/c switches is located on the side near the front of the house (opposite ends of each other, L shaped.)

Maybe I've misunderstood the electrician on the transfer panel but I thought it would be located next to the main panel in the garage, and the plug for the generator would be put near there too.
 
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Old 05-15-18, 06:52 PM
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I might have misunderstood..... the transfer panel connects to the panel with all the small breakers in it. So yes... it will be in the garage.

Make sure 12 circuits will be enough to supply your standby needs.
 
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Old 05-15-18, 07:05 PM
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Do they make bigger ones?
 
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Old 05-15-18, 08:34 PM
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Side note, it looks like you have a mixed bag of breakers in that panel. They should match the panel brand.
 
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Old 05-16-18, 10:28 AM
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The only thing I don't like about interlock is that it requires some knowledge of what to do. My parents had one, and it was a multi-step process to get everything set up and running. (turn off all breakers except 2, 5, 7...) Startup generator. If you want hot water, turn off 18 and turn on 27, etc etc. Easy for you or me to do, but it was sort of overwhelming for them.

The transfer panel is really only one switch (line/gen). There aren't any other decisions or things to do or worry about.

If it were my decision, I'd go with the 12 (or whatever size) transfer panel. It gives you the power you need where you need it, and it is easy to use. It should also be less expensive since you don't have the labor to replace the whole panel. But honestly, either solution seems good.
 
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