Generator Advice
beedigs
| Posted in General Questions on
hi! new build (one story, 2300 sf, all-brick) and trying to figure out the details… priority of build is durability, good indoor air quality, energy efficient, airtight, good moisture management. That being said, looking at installing an ERV + VRF system, using induction stove, heat pump dryer, all electric. Is it a must for us to have a generator in place since we can’t do too much everytime electricity is out? If yes, any reco on generator brands and type? Where would be the best place to put the generator? Thanks much
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Generac is who I prefer since parts and service is local to me.
Any of the big brands are good. I would base the brand name on who you would like have service it and repair if needed.
Location needs to be at least 5ft from a door or windows. 10 ft from a gas meter/regulator. Height maybe something to think about due to climate ( water, snow).
Size depends on your needs/wants.
The bigger the unit the more fuel it consumes.
May just the necessaries for heat, lights, some receptacle, etc ?
Whether you want a generator depends on many factors:
• How frequent are power outages in your area, and how long do they last?
• How mild or severe is your climate, now, and as the climate changes?
• How good is your envelope? Would it stay warm/cool inside for the duration of a power outage?
• Are you willing and able to live primitively for some time, perhaps cooking on an outdoor camp stove, or eating foods that don't need cooking and sleeping bundled up in a cold-weather sleeping bag?
• How much food do you keep in your refrigerator/freezer(s) and how much would it cost to replace it all compared to the cost of a generator?
• Are you preparing for storms and such, or for the complete collapse of modern civilization?
You can size a generator for the minimum necessities or the whole load. And you can consider a battery backup as another option. A generator can be a permanently installed automatic system, or a portable unit you roll out of the shed when needed. Lots of options.
Note that the need for a generator isn't particularly more on an all-electric house compared to a house with a traditional natural gas furnace, as you still need electricity for the furnace blower motor for it to run. But you do need a bigger generator to run a heat pump, if you decide you need to cover that.
This is a cost/benefit decision for the most part. If you live in an area where no one can remember the last time the power was out, then the cost is high for limited benefit. If you live in an area with frequent outages (I'm in a rural area and we have frequent multi-hour outages and usually at least a few multi-day outages every year), then a generator is a BIG benefit and the cost is worth it.
I install large commerical generator plants as part of my work. In general, after the cost of the unit and installation is factored in, it doesn't cost much more to size a unit to run everything than it does to run only critical loads. I recommend an automatic transfer switch (ATS) ahead of your main panel (this means you need a "service rated" ATS with a main breaker in it), and a suitably sized generator for your entire home. With an all-electric home, you'll need a bigger genset than most, but you'd probably still be OK with something less than 20-25kw. you might even be OK with 12kw if you do load management (and code requires some of that now).
I don't like the Generac units. They are not particularly reliable. The Kohler units are much better, and not much of a cost premium. For my commerical projects, we specifically disallow the use of Generac in our bid specs (we typically get bids from Caterpillar, Onan, and Kohler, sometimes a Katolight too). The issue is reliability. It doesn't matter how easy it is to get service if it breaks all the time, you want a unit that doesn't break. One of my smaller residential Kohler units has been going for almost 20 years now, and aside from oil changes, all I've had to do was replace the alternator (the 12v one) once at around 5,000 hours of operation. This was a liquid cooled unit, 1800RPM, which costs more, and is more reliable, than the typical 3,600RPM air cooled residential units.
The air-cooled units are fine if you are only expecting ocassional outages. Liquid cooled units are better if you expect frequeny, long-term (days) outages or have very large sustained loads.
Pick a fuel source you have already if you can. This means if you have natural gas available, use that for your generator. Next is propane, last is Diesel. Don't use gasoliine since it's difficult to safely store over long periods. Gasoline should only be considered for portable generators.
Bill
I'm not familiar with the code requirement for load management and would be interested to learn more. A pointer to a good resource on that would be appreciated.
This is a good starting point:
https://www.mikeholt.com/download.php?file=PDF/11_Generators_and_Standby_Power_Systems.pdf
The usual way to deal with this is to lock out large non-critical loads (electric water heaters, central air conditioners). Kohler's system can automatically stage several loads with optional relay modules that the generator and ATS system can intelligently control (they make sure that not too much is running at any one time by cycling through the loads automatically). There are probably other systems out there too, but I'm most familiar with the Kohler system.
BTW, regarding the noise comment, it does make sense to plan where your generator would be installed to allow for this. I did some extra work extending gas and electrical lines at my house so that I could install the generator near the garage, on the opposite side of the house from the bedrooms. Place the generator so that its noise while operating won't annoy you or your neighbors. The permanently installed systems are much better about noise than the portable generators are, but they're not silent.
Bill
Thanks! That's a very nice summary.
tnx for ur input and including brands that i am not even aware of that are better quality (only know yamaha, generac and honda at the moment)...so it sounds like kohler system can help with planning the whole setup, am I right? (ATS vs no ATS based on which non-critical loads we lock up, where to put generator and doing necessary plan for piping/lines, etc)...if not, then who does the planning, the electrician? the appeal of convenience and cost makes a natural gas line hookup be the best choice for fuel..but do they hav units that have dual fuel? this is just for storm prep/other emergency use.
Sounds like you're most familiar with the portable generator brands. The permanently installed are a little different, and have some other players in the market. Generac markets most heavily, and I'll give them credit for "discovering" the residential standby market, but I don't consider them to be the best quality product in that market segment.
For smaller systems, an electrician can generally plan the project for you. For more complex things, you hire a consulting engineer (like me, hehehe :-), but that's very rarely needed on a residential project. To give you some perspective, "engineered" projects like I normally work with tend to be large. My current project is a 150kw installation, and that's "small" by my standards. Most of my projects are 500+kw, and often over a megawatt. Residential systems are much simpler, and usually an electrician can handle the entire job.
Load management depends on what you have that needs power. It's most common to cycle large loads with these systems, such as electric water heaters, central air conditioners, things like that. Whomever you have plan your project should be able to identify what needs to be controlled. Each device being "managed" will get a relay (contactor), so that the ATS/generator system can drop those loads when capacity is short.
A typical natural gas unit can be switched over to run on propane with minimal effort ("minimal effort" ranges from flipping a switch to swapping out a metal disc "oriface" and/or a spring in a gas regulator). There are units that can run on both gas AND liquid fuel, but those are much less commony in permanently installed sytems.
If you have natural gas available, I'd select a genset that can run on that. If you want to maintain an ability to also run on propane, keep whatever parts you need to do the switch on hand, and keep in mind that small tanks like used for BBQ grills often can't power a generator. Propane has to "boil off" (change from the liquid in the tank to a gas), and with excessive draw rates, a tank will "freeze up" and not provide a sufficient amount of gas to run a large load. This is why you sometimes need minimum size tanks that are larger than you'd expect, and how large that "minimum size" is depends on both the size of your load AND the lowest expected outdoor air temperature you expect the system to operate in. If you call a propane supplier and tell them the BTU consumption of your generator, they will be able to recommend a minimun size tank to handle that load.
I caution you against liquid feed propane systems. They carry a lot more risk, and I don't recommend their use with most residential systems. All typical residential propane systems are gas systems.
Bill
There is some very good advice above, but one thing that has not been mentioned is noise. Generators can make quite a racket so be careful where you locate them (this means also from your neighbors) and get the specs before purchasing.
Conrad
My personal, anecdotal experience with Generac has been terrible. We installed two in 2008 in coastal SC and one in Atlanta, GA. All were maintained professionally twice per year. Both in SC were replaced within 4 years because repairs were too expensive and they were very unreliable. They consistently had problems starting. Both ran on propane. The one in Atlanta require a new, expensive, stator after only 6 years of very minimal use and was replaced. By contrast, a Kohler at my business (not sure the age as it was there when I bought the building in 2008) has been going strong with only minor repairs and irregular maintenance since I do it myself.
Identify necessary electrical loads. View main service loss as constituting an emergency- act miserly.
I take some offense to the notion to stay away from diesel generators. Every decision ought to be based on a full assessment of the conditions/requirements. I don't have an NG line attached to my place. I do have propane, but no way would I want to rely on being connected to it: you cannot have your tanks filled unless they're below 25%(?); can't assume a propane truck can make it to my place if things are bad. I have a tank of diesel (I have tractors and other diesel equipment). I ensure that my tank is filled going into winter, the season of power outages: I don't run my tractors very often in the winter in which case the fuel is pretty much all available for my generator. Is my vintage generator loud, a bit. BUT, for crying out loud, it's an emergency! My neighbors aren't close enough for that to matter. One's neighbors are likely more focused on their own power issue than the noise of your generator (unless you're running a 45kw unit!).
I spec'd my generator years ago: vintage- early 90s, 7.5kw (Onan with Kubota diesel). Cut-over is all manual: I've got computers and such on UPSes, so no interruptions there. The generator will start no matter what, and it'll run until the end of time (we'll all be dead before it dies). NEVER have had an issue where it couldn't handle the loads I was asking of it. Sigh, and I'm thinking of building a near all-electric house... (mitigation will be a wood stove- I have ample firewood)
Be mindful of how to hook the generator into your home! (I had to educate my electrician!)
I hope you didn't think I had meant to discourage diesel gensets in my earlier post, I did not. Almost all commerical generator installs I do are diesel units, including my current 150kw project.
The reasons I specific fuels in the order I did is as follows, for clarification:
1- Natural gas. If you have natural gas available, it's a no-brainer to use it for your generator UNLESS you have good reason to suspect it won't be reliable in an emergency. In hurricane and earthquake zones, natural gas is sometimes intentionally shut off to limit fire risk in a disaster. If you're in one of those areas, that might be something to consider. In most areas though, natural gas eliminates the need to store fuel on-site, which means a smaller installation and no risk associated with a bit fuel tank. For a typical residential installation with natural gas service available, natural gas is the best choice for a generator fuel supply in almost all cases.
2- Propane. Chances are if you have propane available, you already have a big tank, so you don't need any additional fuel storage. Propane doesn't degrade, ever, so it doesn't matter how much your run your generator -- your fuel supply will always be ready to go and will require no maintenance at all. Most residential generators are intended to run on gaseous fuel, and can be switched between natural gas and propane, so using one of those two fuels allows you to choose from any of the commonly available standby generator systems targeted at the residential market.
3- Diesel. Diesel is a good option if you don't have natural gas service, and if you don't have propane already or are concerned a generator will exhaust your propane supply too soon (generators are a BIG fuel consumer when running). Diesel engines tend to last the longest, but the fuel requires maintenance (known as "polishing") periodically if you store it for a long time, even with stabilizer. Stuff can GROW in diesel fuel, and then you have issues with clogged fuel filters. You can also get water accumulation in the fuel tank, and while diesel engines typically have a water seperator to deal with this, it is another maintenance item. If you're prepared to do a little extra maintenance, I would have no problem recommending a diesel generator if you don't have natural gas available and don't have enough available propane capacity.
I'm actually keeping an eye out for a used 7ish kw diesel generator as a backup for my natural gas unit.
It really comes down to what fuel you have available at your site.
Bill
Bill, not at all. I enjoy well-rounded discussions! I'm here (in life) to learn and to spill all that I know :-)
Here's what I have (though it's not mine):
https://www.youtube.com/watch?v=GL-N_G9cGi4
Anyone who gets one that needs help getting it in tip-top condition can contact me. Once you upgrade the voltage regulator (and clean up a bunch of the wire connections) they're dead-reliable: original voltage regulators used big, fat capacitors, and capacitors have a shelf-life (I discovered shortly after a long awaited commissioning to production- had the unit for a couple of years before being able to get it set up to function as I wanted- had to have my garage built); a modern, cheap, voltage regulator board is easily retrofitted- voltage output is super rock steady. People claim that these engines have been known to run some 20k hours: lots of them used for light towers. And failures of the generator head are almost unheard of, even after all these years.
A 7.5kw unit is a nice size for many homes (a good balance of fuel economy to kilowatt capacity). You need to be a bit of a tinkerer to run on the older gensets though. I use an older Kohler 20RZ myself, which I got used and refurbished myself. You're right about the older gensets tending to be very reliable.
You can get new capacitors from places like Digikey and Mouser Electronics. They're cheap, and usually easy to replace. It's the electrolytic (usually larger round cylinders) capacitors that wear out over time and need replacing. Use higher temperature rated capacitors for longest life, since they last longer as the operating temperature goes down from their max rated temperature (and it's not linear, running at half the rated temperature might get you 8+ times longer life).
Flight Systems is a good source of replacement regulator boards for these older generators.
Bill
I wish to make one point about propane, and that's that one just can't top off a tank whenever one wants. You have to be under 25%, I believe, before it can be filled: I'm talking about via truck; this is the only delivery that I am familiar with. This makes it kind of hard to be prepared heading into any known periods of unstable power. I think that my tank is somewhere around 30% now (plus or minus), and that's how it was at the start of the winter season. Heading into the heating/unstable power season I fill my diesel tank and I know that if need be I could run for a good month solid: not likely ever going to face a situation this bad; if so then it's likely that the electric power ain't ever going to come back on, in which case there's a lot more trouble at hand than just running out of fuel!
But, to be sure, one should analyze their own needs, and attempt to do so thoroughly because we're talking about EMERGENCY situations.
Mark, I don't think I've heard that rule about having to be under 25% in order to fill a propane tank. Maybe it's a regional thing or just something I somehow missed, but I've had propane tanks in the past and have often had them on jobs and it's not something I recall hearing.
The rules I know are that you should refill the tank before it gets to 20% because below that it won't have enough pressure, and a "full" tank is really 80% to leave room for expansion.
It's possible that I have it backwards, but I'm pretty sure that that's how it was for one delivery company in my neck of the woods: they wouldn't fill unless under a certain level (for sure under 30%). No idea if this had to do with physics or with expense (as they want to deliver more). Our propane is only used for cooking and laundry (dryer), so it only gets refilled every few years or so (not enough to really be familiar with the process). Note that all this talk motivated me to check my tank (32%) :-)
As you note, it does appear there are concerns with running low (kind of like if you were to run low with most fuels):
https://www.kauffmangas.com/blog/gas-gauge-guidelines-what-to-do-if-your-propane-gauge-is-below-20/
It's possible that my supplier figured that they'd prefer to fill lower and that they figured I wasn't going to drop into the unsafe zone. They're running in my area every week, so perhaps they figure one week isn't going to drop me into that danger zone.
I probably won't hit below 30% for several months, that's how limited my use is.
Bottom line is that one should be very sure of how their system is going to operate when you really need it. It is, after all, your emergency system.
Do you have a good reason not to install solar? It seems like a no-brainer for a mostly electric house --- if only just to cut down your bills!
Personally a generator does not make sense compared to solar -- but obviously there are a lot of variables.
Solar isn't a backup power source. Many solar systems will shut down if they lose grid connectivity. An off-grid solar system with batteries is FAR more expensive to install and maintain than a typical generator, and will have less runtime too if you have crummy weather. Solar and generators serve completely different needs. Many off-grid solar installations actually have backup generators to backup the solar system in case of prolonged periods of crummy weather.
Bill
This isn't a straight-up comparison. Unless your solar can go off-grid (batteries) then it's not a backup source. When the grid drops so does your grid-tied solar.
I once was going to build an off-grid home. My aim, however, was for micro-hydro: it runs when the sun ain't out! (slow and steady)