By popular request!
Couple of upfront disclaimers:

#1 Im an electrical engineer, so dealing with stuff like this is second nature for me. If you are ever in doubt about attempting a genset install through any method Ill mention below, HIRE AN ELECTRICIAN. Residential voltages CAN kill you, and it will hurt the whole time you're dying.

#2 Generators are great tools to have, but they also present their own hazards. Carbon Monoxide is the biggest hazard when operating a generator during an outage IMO. Why? Because just like I saw one of the neighbors do, he had it on his porch. This can allow CO to enter the house via your soffit vents. Take heed. Proper ventilation is a MUST.

#3 I cannot opine about different states electrical codes. NC is currently on the 2017 NEC. Other states are on 2014, with some still on 2011 or 2008 even. Some dont even follow NEC. When doing anything in a house you may potentially sell down the road, caveat emptor.

NOW, on to the fun stuff...

Having recently been through the generator buying process to use as a home backup, and installing a transfer switch to make that happen prior to this weeks record breaking snowstorm, Ive been asked to throw one of these together. There are plenty of others here who can also provide knowledge, and I hope they will feel free to do so.

When we purchased our current house, it came with the realization that we dont live in a metropolitan area, and when there was a breakdown in .gov services, we are essentially on our own. Power is one of those items. Because of our population density, we are literally last on the list to be considered for restoration if one of the more populated cities/towns around us is also out. Our lines are also aerial, which means any of the lovely southern pines we have that lose a branch in ice/freezing rain are likely to take a line with it. In my Homestead thread, Ive discussed plenty about options from my personal standpoint that led me to my ultimate decision. So, lets discuss some of those factors. Ill cover four main topics: fuel type, generator type, installation type, and wants vs needs/generator sizing.

Fuel type:

So, this one is fairly simple. Probably 90%+ of generators out there for personal use are gas powered. Some are "dual fuel" meaning they can run off of gas or propane. Propane generators are great for folks who have other propane appliances because adding a line usually isnt that hard. Most commercial generators tend to be of the diesel variety. Also worth mentioning that some of the "whole house" offerings are offered in natural gas as well, but being in this forum, Id wager thats something the majority of us dont have access to. So, lets stick to gas, diesel and propane. Gas is the obvious winner here IMO. You can get it anywhere. Gas can be stored when treated. Gas doesnt have some of the temperature issues that diesel does. Propane also has an element of temperature sensitivity to it, but it also doesnt have as much energy per gallon, meaning that generators that can use propane are generally rated for less wattage on propane. On the btu/gal scale, diesel is the king at 130k, e10 gas is next at 111k and propane is 91.6k. Gallon for gallon, gas outpaces propane by about 20% and its reflected in the generator ratings.

Generator type:

Thanks to Honda, the advent of inverter generators is becoming a lot more popular. I own one of the Harbor Freight Predator 3500 inverters, and its been flawless thus far. Generally speaking, youll run into three types of generators these days: "smoke and noise", aka, your constant speed generator, the newer inverters, and PTO. The latter are pretty rare because of the cost of buy in of needing to own what usually amounts to a 30 or 40+ hp tractor, and theyre usually fairly large wattage wise. I wont spend much time on those, but will on the first two. Your constant speed generator makes power very simply. It spins a magnet around inside a copper coil. Theres obviously some more physics involved which I can dive into in depth if requested, but suffice to say, every portable generator operates in the same manner. It has to operate at full speed 100% of the time to maintain the frequency of 60Hz. The more wattage its listed for, the larger the magnets and coils, and subsequently the motor. Ill explain why thats an issue in the generator sizing. Inverter generators function differently. They use a smaller motor and an output stage that is similar to a traditional generator, HOWEVER, they then convert that AC voltage to DC. Once in DC, its then inverted (hence the name) back to AC voltage. The result is a cleaner sine wave thats more akin to the utility companies power than the choppy wave a traditional generator produces. The other trade offs are, because of the inverter in the mix, these generators dont have to run at 100% to maintain the frequency. And that means less noise, and less fuel consumption for light loads.

Installation Type:

This is where things get tricky. In a pinch, its easy enough to drag extension cords into the house (protip! Depending on location, your dryer outlet makes an excellent inlet in bad weather) but that leaves you with having to swap cords around for different things you want to power. A step up from that is a hardwire transfer switch. Some of these are hardwired to the generator itself, or there is an inlet box that uses an extension cord to the generator. The important thing to note is this is where you start having to play in your electrical panel. A transfer switch allows you to select from line (the power company) or gen (your generator). Flip the switch, the circuit is powered normally. These usually come in the 6-10 circuit variety and can run 120 or 240v circuits. Lastly, theres the "whole house" option. This can be accomplished one of two ways. First is the interlock kit. These have become really popular in the past few years, but the code issues surrounding them are a little fuzzy. Basically you have to turn off your main, slide the interlock into place, and then you can turn on your backfeed breaker that powers your entire panel from your generator. The second, more commonly seen in a whole home install, is the auto transfer switch. Power drops out, the generator starts automatically, and its like the power never went out.

Wants vs needs/Generator Sizing:

If youve read my homestead thread, you know that I had three options on the table. A small inverter with the transfer switch (which was my ultimate solution) a large portable in hopes I could run the well paired with a backfeed interlock, or the whole home. In order, those are also in least to most cost items, because once you get outside the 7500w area or so on a portable, the cost really goes up quickly. So, this is not a once size fits all. If I lived further north where winter weather was more prevalent and/or we had more of a history of power outages, I would have strongly considered a whole house. But as we dont have those issues, I picked option 1. Heres why: I fired mine up yesterday at 11am EST and cut it off at bedtime. During that time, it used about 70% of its 2.1 gallon tank of fuel. Now, lets compare that to a much larger portable, something in the 9kw range. The Harbor Freight Predator 9000w will run 13 hours at 50% load on an 8 gallon tank. Guessing at some of the math, I would say I averaged between 25-50% load yesterday. So, 1.5 gallons versus 8 gallons of gas. Give or take. Yes, its not 9000 starting watts, but its not nearly as loud, and it sips fuel. Dont misunderstand me, for people who need the wattage, thats about your only option, but when picking what you absolutely need vs want, ask yourself this. Can you start it, and run it for a 3-4 day extended outage and be able to store enough fuel to do so? My answer was no. 15 gallons of gas which I bought before the storm would last me approximately a week in an extended outage, even more if I managed how often I ran the generator. Whole home generators suffer a similar fate in that they are able to produce enough wattage to handle your entire house, however, they also run at constant (full) speed 100% of the time. With more wattage comes more motor and more fuel consumption that (IMO) is ultimately wasted. With my reliance on well water about to end, the smaller inverter was the clear winner. Picking the right generator for you is about balancing wants vs needs and including some convenience factor in there as well.

This post brought to you by a Harbor Freight Predator 3500 inverter and a transfer switch.

Definitely can't argue that. Our local propane provider wont install a whole house with less than a 500gal. So if you're not using 750gal a year, your tank fee is something like $149 a year. Kind of a catch 22, but worth it when you need it.

My genset has a bowl drain thankfully.

I'm not overly experienced but I've been trying to solve my own power problem for the last three or so years to better prepare myself for storms that knock down power for multiple days at a time around here

When I upsized my tractor one of the primary things I was looking for was PTO HP to power a whole house genset.  Not because I really wanted to run the whole house 24/7 but I wanted the option if things got bad and me or the neighbors needed to cool down/clean up.  I had looked pretty hard at PTO generators before the tractor purchase but when it came time to actually fork out the cash for a unit I had a tough time getting a clear understanding of where what part was made and the expected useful life, output exactly, etc.  Also minding the tractor running the load started to become an issue in my mind, when the AC kicks or shuts down in who want's to have to stand there and watch RPMs?  There are solutions to all of this but it added the complexity of use which is something I wanted to avoid since my family might have to run it without me.

I looked at a lot of the Honda's in the 5-7,500 range (no not even close to my whole house goal but can handily cover every one of the essentials) and was going to pull the trigger on those but I'm gone a lot so electric start was sort of a big deal so 6 could run it without me so that got me pretty solid in the $2.5k range.  Randomly about this time I started getting into welding but no 220 outlet and a desire to be able to weld away from the house made me reconsider my generator choices and shop a little more...then disaster happened, I found engine drive welders  Long story short I've got an engine drive welder with a 40 amp and 4x 110 (2x 15 amp) outlets that will surge load to run peak 11k watts and steady 9.5k watts at only slightly more than the Honda was going to be (think it was $4,100 all said and done).  It's not the perfect setup but it covers a lot of ground and gives me a lot of flexibility for welding or constructions projects out and about.

So long story short, for me it's not as simple as figure out the household items you want to run and go from there.  Homesteadish living can leverage the system many other ways so an open mind is good when considering what you'll eventually end up with.

As mentioned earlier, codes vary. In our case, here in NC, I was told I could not have a transfer switch for our main panel feed unless we could accommodate all the panel loads either via generator capacity or automatic  load management.  Switching off excess loads, manually, prior to connecting was a no go.

We ended up going the whole house, autoswitch route for the NC retirement house. We already had a self owned 500 gallon LP tank for the furnace, but eventually added a second one. The big advantage to self owned tanks is the freedom to use whichever supplier you want at refill time.

For roughly 20 years we had made do with a gas fueled, portable brushless 3600 rpm unit with
< 5% THD. No problems with any electronics (including UPS units) or appliances.  Aside from extension cord hassles, the biggest management issue was keeping up with rotating a dozen containers of fuel so nothing got too old before getting used (+ storing far enough from the house to be safe, but close enough for availability & security)

On the first point, 200A incoming service is 48kw. Short of a commercial diesel, you wont even get close to that. It would be worse on 400A service.

Tell me more about the propane tank thing. Ours is a lease tank, and I despise the provider and the tank fees.

Our whole house is a 22kw on a 200A autoswitch with one load management module on the 5 ton heat pump.  The electrician & code enforcement guy were content with that.  The folks I had talked to earlier were adamant about not putting in a manual transfer switch with a generator connection point without seeing the generator first.

We bought a new 500 gallon above ground tank last fall.  We went through Southern States Coop. for the purchase & install. None of the other local propane suppliers were interested in giving me a quote - just wanted me to take their "free" tank.   The tank through Southern States was $1590 (purged but empty), delivery to the house & install was another $116.  It would have been more if I hadn't already done the site prep & provided leveled concrete blocks for the feet.  It was installed parallel to our existing (self owned) tank so there was no additional cost for a regulator, just connecting pipe & fittings.   The existing 500 gallon had a new regulator from when we did the generator install.

Any recommendations for a 16-22kW whole house generator?  Propane fuel.

No complaints about the Honeywell/Generac system we bought via Costco. We've had it a few years now and had zero issues.  It exercises weekly and has functioned as designed during all outages so far. It supports all our appliances including a 5 ton heat pump. We do spend a couple hundred a year for a maintenance contract to protect the 10 year parts & labor warranty that came with the system as part of a promotion. There is also a monthly fee for the cellular monitor system (optional) that sends text messages on system status changes.

This interests me, do you need an inverter setup or is it a 'nice to have'? Does it matter to my fridge and furnace or just to my smartphone and laptop?

Obviously a transfer switch is the way to go but what about shutting off the main and backfeeding across each leg?

So voltage regulation is a solid alternative to an inverter? I want dual fuel and the Champion unit is on my list but its almost a grand. I found a Firman unit but its not an inverter. This would be primarily for backup power at home or possibly at the RV. If I grab the Predator and a fuel conversion kit I'm almost to the cost of the Champion unit.....

The 3600 RPM generators with low Total Harmonic Distortion (THD) numbers + AVR should be fine for household use. Look for ones with a THD < 5%.  That is the degree of variation they may exhibit from a perfect 60 cycle sine wave.  If they meet this standard it will be clearly listed on their documentation (it's a selling point).  If you don't see a reference to it, they probably don't meet that standard.

All our house backup generators over the years have had an advertised THD < 5% - a Porter-Cable BSI-5500, Costco champion dual fuel (7K/9K)  & the Honeywell/Generac  whole house. No problems with freezers, refrigerators, pumps, etc.  Also no issues with UPS units & electronics.

As much as you have contributed to all the forums in the past I'm inclined to believe you, but how hard did you have to twist the guys elbow for him to admit this? Seems like the are opening themselves up for issues admitting that they "hand pick" generator components for Costco, but keep the same model number. Or is that a custom model # for Costco?

As memory serves, the Costco versions  were the only Champions with  < 5% THD  on their packaging  & listings.   The model # is slightly different (at least on the 7K version) when I looked them up a while back.

Have a 10kw DuroMax on order. House already has a transfer switch. Should be enough for well pump, refrigerator, freezer, gas furnace, etc. Eventually will run a line from the main propane tank for it. Until then it will be gas or propane bottles. Looking forward to trying it out.

Great thread! Recently bought a new place that was wired for generator back up, there is this box with a switch and a cord coming out next to the main panel. Attached File

I was told I would just need to throw the switch and plug a generator in. Do I need to just figure out how big of generator to buy?

What's the cord look like?

This is the cord coming out and the switch on it.
Attached File

There is also an extension cord with the same ends. Thanks

That's what it looks like to me. Buy a generator with an L14-30 locking plug, size of your choice based on what you want to run, and you're set.

VERY informative read on if you should be grounding your generator...

http://www.arrl.org/files/file/Technology/pdf/Portable%20Generators%20and%20OSHA%20Construction%20Standards%203-05%20

Brought to us by this tangential and equally interesting thread... especially this linked video:

How I did mine.

Wonky Coleman 6250 genset power makes my 6 year old gas range computer not work well enough to use the oven so my wife can bake bread.  Unplugging the extension cord to the range and plugging in the rest of the house puts enough load on the generator to stabilize everything and will allow the oven to function.  Grundfos Alpha pumps, multiple computers, boiler controller, cable modem, old refrigerator, old well pump, new microwave dont care.  The LED 150 watt garage lights flicker a little on gen power.

Lost power during the recent storm, about midnight.  I woke up at 6, house temp had dropped 15 degrees.  It was zero outside with gusts to 50 mph, and we had gotten a foot of snow overnight.  Once the sun came up I ised the snownlower to cut a path from the barn to the house, pulled the old gen to the house, and fired it up.  I keep it full of stabilized gas, and fire it every couple months.  It does need a small burp of ether to start, but will start without further problems.  I wired a power inlet box inside the garage on its own breaker shortly after moving in.  Shut off the main and water heater, start the generator, plug in to the power inlet, turn on the power inlet breaker on the house panel.  Verify boiler startup.  Power was back on in the afternoon, shut off inlet breaker, unplug and shutdown generator, blow path to barn clear agin, put generator away, walk back in and turn on main.  Wife was kind enough to turn on the water heater when she noticed it off later.

We had a 22 hour outage a week or so back, so I thought I'd get a decent handle on consumption by the 22kw whole house unit. We have 2 inter-connected 500 gallon tanks & I have been logging fill levels periodically so I had good numbers for pre & post.

Unfortunately, the number I came up with looks too low to be real. Prior to the outage, we had approximately 65.5% available (average of both tank values, ambient temp at notation was 58° F). After the event, averaged value was 64% w/ambient temp around 85° F. With 1000 gallons between the 2 tanks, each % point represents about 10 gallons, so only a difference of about 15 gallons. I would think my readings should be within a +/- 1% (+/- 10 gallons)

I had the tanks topped off a couple of days later & they added 164 gallons to fill both tanks to the 80% point, suggesting there was about 636 gallons already present, which is pretty close to the 640 gallon guesstimate I was making based on the 64% average on the last read. It still seems unlikely that consumption is <= 1 gallon/hr, but that is what the numbers suggest. Temperature variations may have played some part, but I don't think it could have been enough to throw my estimates off too much.

During the outage, we conducted ourselves normally, doing the normal things. Cooking, laundry (& clothes drying), running the 5 ton heat pump (ambient temps were in the 90's during the day w/high humidity) & ceiling fans, etc. No special conservation was done.

I bet that's actually about right. I'd wager that anytime you were doing anything in the house that you were over 25% load. 5 ton heat pump is probably only 30 amps of actual draw to run. That's 30ish percent of capacity. I'd wager if you did the actual load balanced math, you were at or below 25% on a per hour basis over the 22 hours. Backing that out is pretty tough unless you know exactly what your appliances draw.

That’s close but probably a little low.
Probably closer to 1.5 gallons an hour.
I would just look up minimum consumption on your particular generator.
My 21kw with a liquid cooled Ford lr425 in-line 1800 rpm engine is 140k btu if I remember correctly.
I’m normally pulling 5-8kw depending on how many AC units are running.

Yeah, our problem with trying to  figure the low power use consumption from published data is that the literature typically only lists 1/2 & full load consumption rates.  Based on our typical electric bills, our averaged hourly rate is something like 1/8 to 1/10 the full load rating on the generator if our use was steady state.   The selection of the 22kw model was based on the largest single load the machine would have to start, the 5 ton heat pump.

We were in Dinosaur Nat. Monument in Utah the past two days and boondocking with the HF 3500 and it will not run the 13K BTU AC for more than a hour when it is over 101 degrees .  No real worries as we rarely camp when it is a 100.  I just realized it has it's own hour meter after I installed a aftermarket one .

Do you know the altitude of your camping spot?
Power decreases 3.5 percent for each 1,000 feet above an altitude of 500 feet. For example, to operate at 4,500 feet (4,000 feet above rated generator altitude) multiply 3.5% x 4 (4,000 ft) = 14% power loss. Then multiply .14 x your generator’s power rating. Example, 4,000 watts x .14 = a loss of 560 watts at that altitude.

The big three are absolutely horrid about proprietary parts. They bend you over a stump for controllers, AVRs and such.

The trend has been to split functions so off the shelf parts can't be swapped in without a bunch of rewiring.

Been seeing a high percentage of failures with the Kohler Decision Maker panel.

Generac wiring sucks...on a good day.

I highly recommend installing a good surge arrestor. It might save your controller.

If I were going to buy once-cry once, the Blue Star units would be my choice. http://bluestarps.com/

They are using good engines, Marathon heads, Basler controllers, standard AVRs, etc.

You are going to pay more up front, but the first time you have to buy parts it will start coming back to you.

Transfer switches are similar. ASCO is the only ones I'll use, for the same reasons.

That makes sense now, closest town to us was 4750 ft.

Timely bump. I'm putting this here because a genset is one of his major uses, but...

A friend of mine has all propane appliances. I mean propane everything, including backup genset for his house. He has two owned 1000 gallon tanks, underground. He just had his filled last week at the price of $1.19 a gallon. Now, for those keeping track at home, I just paid $2.39 a gallon to fill my 330 gallon and I pay a yearly tank fee. Because he owns the tanks, he shopped four different companies against each other and saved himself a bundle. Granted, it's hard for people to float that kind of bill but he averages a fill every 2ish years, so...

OUCH. I got filled this spring and another 300g on contract this winter for $1.09. Would have never thought the price would be that different depending on location.

Attached File


Works fine, runs everything, almost 15 years -  not the most efficient but it's natural gas so it's pretty transparent except a bit of noise

hopefully this helps someone, i have been hacking on it for years and it will probably never be finished...

http://losdos.dyndns.org/wiki/reference:generator_oracle

LP is usually rail car or truck from the pipline distribution.

I too dont understand the regional variability of things like propane/heating oil. I have friends who live up north who pay less for propane than I do and they heat their entire house with it. I do know there is some seasonal variability (i.e. dont get filled in the dead of winter), but still, we have a TON of it within the borders, its hard to export, and its relatively easy to deliver from cradle to grave so to speak. The only thing I can think of is that theres enough demand to float that price. Otherwise I dont have a clue.

damn that thing is big.

I have a 21kw that usually pulls about 6kw when all 3 ac's are running plus general household stuff.

If we have an extended outage running the dishwasher & electric dryer easily doubles that.

60kw is a ton of power

Tagged.

Anyone have a good electrical load calculator?  One that gives any answer in actual watts needed vs.  "buy this generator"?

Thanks,

http://losdos.dyndns.org/wiki/reference:generator_oracle#output_capacity