Current options for permanent backup generators

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MAC702

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Clark County, NV
These are not my normal area, but I have established clients that want the ability to have significant electrical service if the grid goes out for days or more. We briefly discussed the convenience of natural gas (which they have) versus the completely independent ability of diesel with a significant fuel tank. They are wanting to go diesel, and have the ability to survive-in-place for a while, even if all services are cut off. They have a good-sized home in a gated and "guarded" community.

I do NOT want to become some sort of "dealer" of a particular brand of generator, nor do I want to do more than a couple of these installations in my entire career. But, I've done all the various types of work necessary and am confident I can do a proper installation.

They have a 400A service with 200A panel in the service and a 200A panel in the room on the other side of the wall. So finding the circuits they want and running them into a transfer switched panel in that room shouldn't be too daunting.

They are currently thinking about which circuits they'd want to power, including possibly the two downstairs air conditioners, sacrificing upstairs. I don't know how well that would work in their high-ceiling main living space. At the moment, I'm just guessing at about a 20 kW unit. I see no reason for any kind of automatic transfer switch. This would be something they'd just go into the utility room and start the generator and turn the switch, perhaps even with a set of instructions for turning loads on separately. They are pretty competent people.

Am I okay in thinking this is doable for an experienced electrician without hiring a contractor that does nothing but generators? Subcontract out the pouring of the mounting pad, and I'd bet a fuel delivery company would set the tank and arrange filling, just like with propane.

Generac is the big name, but perhaps not for the right reasons. What brands should I be looking at? I assume remote starting should be an easy option for these larger units, even though it would be from an inside room just inside from where the unit would sit outside.
 
Whether automatic or manual, you MUST include a transfer switch that makes it impossible to connect the two sources at the same time, which means they can never be connected to each other, even if you try.

The easiest thing to do would be to put all of the loads you want on the generator in one panel, requiring only one transfer switch, but your physical arrangement may make that difficult. Two will work together.

Even though you say you don't require automatic switching, it may cost only a little more than a manual transfer switch of the same rating. That's half the reason for having a stationary generator anyway.


I'm not a dealer, and will install systems I buy or the customer buys. I usually install Generac because that's what the customer asks for or recognizes. Any competent electrician should be able to wire a unit

Again, you MUST use a transfer switch. I'm happy to talk with you if you want my number.


Added: The first switch is a service disconnect, so, unless it follows a main disconnect, your transfer switch becomes the disconnect for whatever follows it, and it must be service-rated

Grounding moves there, and every downstream becomes a sub-panel, and must be re-wired with a four-wire feeder, with neutrals isolated from grounds, including 120/240v circuits.
 
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I've never seen a large generator without an ATS. Manual switching is only used for small generators. It's possible to do, but I wouldn't. Large generators are normally automatically exercised for a few minutes on a weekly basis. If they do everything manually, this might not be done and the generator reliability will lessen. Some brands keep their control electronics in the ATS.

I agree with Larry that moving all the emergency circuits to one panel will make this easier and cheaper. Then only one ATS is required. I recently did an install of two ATS's on a two panel 400 amp service because that's what the client wanted. It would have gone much faster if we had reorganized the panels and used one ATS.

As far as what circuits to power is concerned, you should advise them to select the minimum they can live with. Running a generator 24 hours a day is expensive (in both fuel and maintenance). Getting a smaller generator will save money. I believe an 80% load is the sweet spot. You should also see what the manufacturer says about how long it can run between maintenances. For some brands, it's just 24 hours.
 
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Yes, I was already planning on moving the switched circuits into one panel and using a transfer switch. I guess I didn't make that clear, but thank you for making sure, as I do understand why it's necessary.

I guess what I was thinking was an "automatic transfer switch" was one that automatically turned on the generator and switched the panel over. By manual, I was meaning you'd go start the generator yourself, and then flip the transfer switch, which would break the line feed and then engage the generator feed to the critical-circuits panel. Sorry for the confusion.

Learning that an ATS isn't a big deal, and has benefits, is exactly the kind of stuff I need to know at this point.

They are getting serious about this. I'm also their firearms instructor and they are adding to their sporting collection with some more defense-oriented stuff. I just helped them get a couple pallets worth of ammo, too.
 
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MAC702 said:
They are wanting to go diesel, and have the ability to survive-in-place for a while, even if all services are cut off.

Am I okay in thinking this is doable for an experienced electrician without hiring a contractor that does nothing but generators?
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As an electrician you can do all the electrical work but I'm guessing that you are not a diesel mechanic.

You really need the people that are certified and will be performing any maintenance to do a start up and check out of the mechanical.
 
MAC702 said:
the completely independent ability of diesel with a significant fuel tank.
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"Significant fuel tank" normally means "bulk storage" to the authorities so you may wish to check with the fire marshal's office to see what hoops they will make you jump through.
 
growler said:
"Significant fuel tank" normally means "bulk storage" to the authorities so you may wish to check with the fire marshal's office to see what hoops they will make you jump through.
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VERY good point. Hopefully diesel is fewer hoops. I'd hope the fuel delivery outfits should be able to know the drills.
 
growler said:
"Significant fuel tank" normally means "bulk storage"
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MAC702 said:
Hopefully diesel is fewer hoops.
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I don't drive my diesel F350 very often. I started have problems with it and the mechanic told me the fuel was old. He told me to top it off with fresh fuel, drive it until the tank was empty, refuel, and then don't let it sit for months at a time unused.

I suspect a huge tank of diesel fuel for the generator will have the same issue.
 
Coppersmith said:


I don't drive my diesel F350 very often. I started have problems with it and the mechanic told me the fuel was old. He told me to top it off with fresh fuel, drive it until the tank was empty, refuel, and then don't let it sit for months at a time unused.

I suspect a huge tank of diesel fuel for the generator will have the same issue.
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There are stabilizers that can mitigate these effects for at least a few months.
When I farmed, I always put an additive in my bulk tank going into winter when I wasn’t going to be using much fuel.

But I’d guess once you start talking about 6 months or more, you’ll have problems.
 
I am in the process of installing a Kohler 20 KW generator at a location that has no natural gas available. I would not use diesel because it can go bad fairly quickly, and if they want to be able to run for a significant period, it will take a pretty large tank.
I would in their case, install it w/ natural gas, and if they are that worried about gas failure, set it up to use propane as a backup. The Kohler can run on either, and there are separate pipe fittings. And the addition of a switch.
Another reason for an ATS is, how do you know the power is back on if you are running on generator? The ATS knows.
 
Diesel or gasoline has a shelf life, even with stabilizers added.

Diesel may still be a better option after a certain capacity size though.

LP and NG don't go bad. NG service may not be too likely to go down very often unless in an area where seismic activity would be what is likely to take it down.

Around 20 kW is where you start to not have option of air cooled engines and must go with a liquid cooled unit - price usually goes up.

Something not yet mentioned is load shedding controls - this can allow you to back up even more loads, but automatically disable less critical ones if other load is too high, is more common to be associated with automatic transfer systems than with manual transfer systems.
 
Very good info, guys. I will be meeting them tomorrow for a shotgun class and lunch, and we'll be discussing the generator options. I'm starting to like the NG/propane idea more. Unfortunately, the NG meter is on the other side of the driveway. I could probably do a pipe into the garage and across the three doors by the ceiling, then back outside.
 
MAC702 said:
I could probably do a pipe into the garage and across the three doors by the ceiling, then back outside.
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What you should do (imo) is call a few gas/plumbing contractors and get pricing.

I found a small plumbing contractor that works with small electrical contractors.
 
If they’re willing to do a bulk tank of diesel, why not a bulk tank of propane?

like others have said, nat gas with propane backup. I know my generac changes over with basically a flip of a switch and then a quick programming change in the controller. Also like mentioned before, the odds of them ever needing fuel source other than nat gas will probably be slim to none in their lifetime.
 
MAC702 said:
I can see that. Good point.
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Your customer may want to consider where they'll be storing their diesel fuel-- the stuff tends to freeze in the winter!

If the heat the house with fuel oil, they might be able to use that to run the generator.

They could install a 2nd storage tank next to the one for the furnace.
 
It never occurred to me that a generator was available that could switch from NG to propane. I knew the metering devices in grills and water heaters and furnaces were different, so I just assumed that the carburetion of the two for an internal combustion engine was also different enough that they couldn't just easily swap from one to another. Knowing that I didn't know enough about the subject is why I created the thread, though. I talked with them at brunch after our shooting lesson today, and everyone now likes the NG/Propane idea. I always preferred the propane tank to the diesel tank anyway just for cleanliness of the fueling process.

That said, we might get below the freezing (gelling) temp of diesel once every twenty years here.
 
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