Standby Generators

[Matt Meiser]

Its looking pretty likely that we're getting natural gas this summer--just waiting on their board to approve the project. One of the things that would let us do is get a standby generator and I'm thinking it might be worth considering doing that while we are having the conversion work done since I understand they might need to deliver the gas at a higher pressure, install a bigger meter, and we might need to install a regulator before the house. I really don't know much about them though. I'm thinking we could go with a smaller one if we didn't put the AC or stove (which will eventually be gas anyway) on it. If the heat is really bad we can always use our camper and its AC which will run off a standard 110V circuit. But I'd want to run the well, sump pumps, fridge, freezer, basic lights, etc.

Some questions:
- Is the power clean enough to run electronics?
- How expensive are they to run?
- Anyone install their own?
- Brands and dealers to look at or stay away from?

Right now we have a basic 5500W generator that meets our needs other than I've had electronics fail within a couple weeks of using it on more than one occasion so we don't use them on it anymore. It doesn't do any good though if I'm not home to hook it up. If I could solve those two problems it might be worthwhile.

[Dave Johnson29]

Matt,

Get an auto start generator and you can get a manual or auto change over switch panel. Depends on how much you want to spend.

To size the generator, turn on everything that is likely to be turned on then go time the meter (in seconds) for 10 full revolutions. Look on the meter and it will have a rating per revolution. From that you can work out how many KWHours you need for the generator.

As far as I am aware the Natural gas powered ones use the gas at the normal pressure that will be in the house. They are not cheap to run on Natural gas as they develop less power than a propane or gasoline powered motor.

[Matt Meiser]

The gas utility gave me the information today on pressure. I need to look into it but the utility can deliver the gas at something like 7" of pressure or 2 lbs (going from memory here). She said many, but not all need more than the 7" which is what appliances take.

[Charlie Reals]

The gas utility gave me the information today on pressure. I need to look into it but the utility can deliver the gas at something like 7" of pressure or 2 lbs (going from memory here). She said many, but not all need more than the 7" which is what appliances take.

Matt,
The gas company will deliver your fuel at 7" water column which is approx. 1/4 # some of your appliances will work down to 3.25"wc but no lower. I have 30 years as a gas serviceman for the utility company.
Charlie

[David Kreuzberg]

I have a Guardian (Generac) 15Kw which we installed ourselves. We did the grunt work of placement and roughing in, then got a local retired electrician to wire in the transfer switch for $100. It's worth its weight in gold- saved our butts several times during ice, lightning and wind storms. We got it after we replaced the basement carpet for the second time. Ours runs on propane, and the manual says it uses about a pound an hour at 50% load. If you're on natural gas, your run time would be unlimited. Cost $3,000 with transfer switch, delivered, no tax, as I recall. Buy it- you won't regret it.

[Tom Godley]

When they ran my gas line I was asked upfront what I was planning to operate - the utility sized the supply line and meter. I have a 450k pool heater and my outdoor grill is at least another 150k - plus all the other normal stuff inside -- it adds up. I believe I have a 2" or 2.5" line to the house -- it is all plastic.


Once you have a conventional electric panel installed - the only options are to replace that panel with one designed for a generator or to add a sub panel that will only supply the circuits that will be powered by the generator. I went with the third option - A transfer switch before the existing panel that switches the whole panel over to the generator. Today you can purchase generators that will provide enough power for 5 or 6 tons of cooling for a reasonable price - years ago this was not the case. I installed relays on the low voltage circuits to keep the A/C units off when the generators were running - this kept the load in line.

Today I would just make sure I had a unit large enough to power everything.

[Charlie Reals]

[QUOTE]When they ran my gas line I was asked upfront what I was planning to operate - the utility sized the supply line and meter. I have a 450k pool heater and my outdoor grill is at least another 150k - plus all the other normal stuff inside -- it adds up. I believe I have a 2" or 2.5" line to the house -- it is all plastic.

The large pipe size is for volume, With the load you stated I doubt if you have a pressure set as that is a common load. Now, You do bring up a very good point that the service line is plastic. I was in on the early days of plastic use and helped work the safety problems. Be very careful where you dig as a common post hole digger will cut the line. Also be very aware of static electricity if you cut the line. We had several people blown out of holes before we learned that. That was back in the seventies and the company I worked for never did the homework until an accident happened.
Charlie

[Scott T Smith]

Its looking pretty likely that we're getting natural gas this summer--just waiting on their board to approve the project. One of the things that would let us do is get a standby generator and I'm thinking it might be worth considering doing that while we are having the conversion work done since I understand they might need to deliver the gas at a higher pressure, install a bigger meter, and we might need to install a regulator before the house. I really don't know much about them though. I'm thinking we could go with a smaller one if we didn't put the AC or stove (which will eventually be gas anyway) on it. If the heat is really bad we can always use our camper and its AC which will run off a standard 110V circuit. But I'd want to run the well, sump pumps, fridge, freezer, basic lights, etc.

Some questions:
- Is the power clean enough to run electronics?
- How expensive are they to run?
- Anyone install their own?
- Brands and dealers to look at or stay away from?

Right now we have a basic 5500W generator that meets our needs other than I've had electronics fail within a couple weeks of using it on more than one occasion so we don't use them on it anymore. It doesn't do any good though if I'm not home to hook it up. If I could solve those two problems it might be worthwhile.


If you run on NG, as other have indicated the line is sized by volume, not pressure. You will definitely need to take into account the generator's consumption volume when sizing not only the line, but also the regulator.

NG is a great option - how often do we have a NG outage at the same time as a power outage? The fuel never goes bad, and you don't have to worry about refilling your tanks during an outage.

Re the electronics, higher quality generators should not have a problem. Kohler and Cummins Onan both make very good small generators, and they have a nationwide dealer network. Additionally, they can provide you with models that will be suitable for electronics. They are used in a lot of RV's, which is an application (and size) similar to yours.

OR - you can purchase some separate UPS's and run your electronics off of them, and use the generator to keep the UPS fed. That will eliminate the potential problems, and this is a common method used in mission critical applications (such as telecom, etc).

Start off by determining how much generator that you need. HVAC is probably your biggest draw (if you're all electric). Electric water heaters, electric dryers also pull a lot of load.

5500 watts will usually take care of the bare necessities (fridge, microwave, toaster oven, some ceiling fans and lights, computers, etc, and a well pump if you have one). 5500 Watts is probably insufficient for electric dryers and whole house air conditioners though.

Depending upon your HVAC system you may want to come up with a strategy. IE if you have a zoned, split system with multiple units, then perhaps you would only power the ones most important during an outage, and thus save on your generator sizing/gas consumption.

Fuel consumption depends upon two things - size of the generator and the amount of loading. Usually, you will consume about the same amount of fuel per actual KW demand, but spend more during low demand if your generator is oversized. Generators seem to run best if they always have around 40% - 60% loading on them, (and go up to 80% or so based upon appliances that kick in and out such as well pumps, HVAC, etc).

My 5500W propane generator will run for 3.5 days on 120 gallons of propane. It works out to around a hundred bucks a day, give or take, depending upon the price of propane.

My 5500W diesel generator goes through about a gallon of fuel per hour, with average loading.

The 10KW diesels also burn 1 - 1.5 gallons per hour, depending on loading, as does the 12KW. We won't discuss the fuel consumption for my bigger generator... :(

I'm going to guess that you'll be in the 10KW - 15KW range, depending upon how many other gas appliances that you have. You will typically end up with a much better engine longevity if you have a water cooled, as opposed to an air cooled engine on your generator.

One tip to use when comparing the motors - look at the oil change intervals recommended by the manufacturers. Light duty gas engines usually have 50 hour oil change intervals. Heavy duty stuff is 200 hours. The higher the oil change interval, usually the tougher the engine.

Although Generac is a major brand, they have a reputation for building an "inexpensive" product. You will not see them used as often in mission critical applications by knowledgeable users, as compared with Kohler, Caterpillar or Cummins Onan. They are probably not a bad option for lighter duty applications.

Automatic Transfer Switches are the best way to go, as most of them will also start and exercise the generator on a weekly basis (a good thing). As I recall ASCO is the largest manufacturer of ATS's, but the major manufacturers also offer their own. If you size your generator more towards "bare minimum" instead of "powering everythign", then a sub-panel fed by the transfer switch is usually a better option (and it keeps you from overloading the generator).

[Dan Friedrichs]

OR - you can purchase some separate UPS's and run your electronics off of them, and use the generator to keep the UPS fed.

Actually, many cheaper UPS's have what's called a "modified sine wave" output, which is a marketing term meaning "not a sine wave", and are probably much dirtier than even a cheap generator. The pricey ones are better, of course.

You actually probably don't need to worry about the quality of the output power from the generator. Really, nothing runs on 120VAC. Any piece of electronics has a power supply inside that converts it to DC before converting it to whatever voltage it wants. They're filled with big filters to take care of any junk on the input.

[Matt Meiser]

Actually, I've had 2 UPS's fail after I used them on the generator. Not right away but within a week or two. I've never had another UPS fail other than bad batteries. We also had a microwave fail about a week after. Reading later I learned that most people say not to run electronics on an inexpensive generator. Could be coincidence though.

[Dan Friedrichs]

I've heard that cheaper generators do a poorer job of regulating the voltage, which causes surges and sags which could easily damage electronics. I'd be curious to put an AC voltmeter on the output, and make sure it's within ~10% of 120V.

In terms of power quality, though, I wouldn't worry (assuming the voltage is reasonable). Even most UPS's just put out a square wave, giving the correct RMS voltage, but it's certainly not a sine wave, and it makes a mess of the spectrum.

[Scott T Smith]

Actually, I've had 2 UPS's fail after I used them on the generator. Not right away but within a week or two. I've never had another UPS fail other than bad batteries. We also had a microwave fail about a week after. Reading later I learned that most people say not to run electronics on an inexpensive generator. Could be coincidence though.


Matt, I'd be inclinded to suspect your generator...

[Scott Gibbons]

I have a 15k Generac (Nat Gas) I have installed two of them in two different homes. I have done the Gas portion and the Electrical all myself, if you have any questions let me know! Scott.Gibbons AT Live.com

[Matt Meiser]

I'm looking pretty hard at this 14kw (13kw on NG) Generac (http://www.amazon.com/Generac-5503-Air-Cooled-Automatic-Generator/dp/B001DZLKHI/ref=sr_1_1?ie=UTF8&s=hi&qid=1270692808&sr=8-1) unit. I was thinking we'd go with a 10kw/9kw unit but the price difference is only about 10% for 40% more capacity.

[Scott Gibbons]

I would for the cost difference. As the saying goes, you only need it when you dont have it :)

[Mike Cruz]

You'll eat up 14kW pretty fast if you try to run any of the big items (AC/Heat, ovens, dryer, etc). Otherwise 14kW will pretty much run the house fine. I put in a 15kW (gasoline version) this winter. That comes supplies 50 amps. It "could" run any of the big items listed above, but then I would have to be very careful with whatever else is running at that time...meaning I would have to make sure the well pump didn't try to come on. If you move to a 20kW or above, you will likely not have as much trouble. From what I remember, a 25kW or above lets the average home run normally. The challenge I found was in the jump from 15kW to 20kW in price. My Generac was (with 15% off at HD) $1900 plus tax. I could have gotten a 17kW for $300 more, but it still only had a 50 amp receptical, so I would have gained nothing. Increasing to the 20kW+ size immediately jumped the price to the $7000+ range. So, for me, it didn't make sense to go larger...

[Matt Meiser]

Well, after researching more and looking at the amount of electrical work that would need to be done to accommodate keeping the big loads off the generator, we are now looking at a 20KW unit from Generac that comes with a 200A service entrance rated transfer switch. Wiring becomes a snap--remove the wiring from the meter to the panel and insert the transfer switch in the path. Of course we still haven't heard for sure if we are actually getting gas so...

[Mike Cruz]

Technically, 20kW will only supply about, what, 100 amps? So, putting in a 200 amp panel just lets you put in more circuits, but your 20kW generator will only supply 1/2 of that.

Also, make sure that that generator has ONE receptical that supplies the full 100 amps. When I was looking at generators, I was looking at the Generac's as well. The 15kW version had a 50 amp receptical. While the 17kW version could produce 70 amps, it still only came with a maximum of one 50 amp receptical. I suppose you could have something plugged into the 17kW 50 amp receptical AND something in a 20 amp as well, but since I was using this for my house and not multiple tools/equipment, the 17kW version would have been a waste. Had the 17kW version had a 70 amp receptical, I would have gone for it. I called Generac and asked if I could either get a 70 amp receptical installed at the factory or have one put on after market through an autherized service center and was told that any modification would void the warranty.

So, just make sure that the 20kW comes with a 100 amp receptical, or you will be wasting money...

[Brian Elfert]

I paid a whole lot more than $1900 for my 8KW standby generator. My Kohler cost $4,000 with 100 amp transfer switch. (Just the generator and switch with no labor.)

I bought my standby generator shortly before they started to be available everywhere. The generator was installed when the house was being built so I was able to wire selected ciruits to the generator. My goal is to keep the house from being damaged with either frozen pipes in winter or flooded from the sump pump in the summer. I don't figure on living a normal life when on generator.

I live in an urban area and I have lost power twice in 8 years. Neither time would it have caused issues to not have a generator, but $4,000 is better than a flood basement due to sump water or frozen pipes.

[Matt Meiser]

Technically, 20kW will only supply about, what, 100 amps? So, putting in a 200 amp panel just lets you put in more circuits, but your 20kW generator will only supply 1/2 of that.

We're looking at hard-wired fixed generators so no receptacles. Generac rates it at 75A continuous and its got a 100A breaker. The transfer switch would switch the entire house from utility to generator. Yeah, we'll have to be conservative--can't sit in the hot tub while the ac in the house runs and a cake is baking in the electric oven.

But since the house has 200A service, we'd have to have a 200A service entrance rated transfer switch.

[Scott T Smith]

Matt, you probably already know this but be sure that the gas line and all of the regulators feeding your place is sized correctly for the 20 KW engine needs, PLUS the needs of your home (furnace, water heater, stove, etc). The generator needs.will pull much more volume than your standard home NG needs.

[Mike Cruz]

If you are not being selective with your panel (ie only powering certain breakers) and are powing the whole thing, I would bypass the transfer switch and put in an Interlock Switch. It fits directly into your existing box, and is a simple piece of metal that will not allow both the main and the generator breaker to both be on at the same time. A LOT less money, and a LOT less intallation.

Of course, if yours is going to have an automatic start upon power loss, never mind....;)

[Matt Meiser]

Scott, we are hopefully getting gas this summer which is why I'm looking into it. Originally my plan was to be generator-ready with the gas plumbing but LOML wants it now since she's the one that has to worry if I'm not around and the power goes out. Auto-start is one of the requirements.

[Scott T Smith]

Scott, we are hopefully getting gas this summer which is why I'm looking into it. Originally my plan was to be generator-ready with the gas plumbing but LOML wants it now since she's the one that has to worry if I'm not around and the power goes out. Auto-start is one of the requirements.


Matt, I think that you're on the right path with the 200A ATS. Be sure to get an ATS that contains some type of pulse-charger for the generator battery, as well as a clock mechanism for exercising the generator. Optionally, you can use a fifty-dollar Battery Minder pulse charger to keep the battery charged, but the exercise clock system is a must in the ATS. It is not necessary to test the auto-switching function of the ATS weekly, but it's a good idea to test it yourself manually twice a year or so.

There are a lot of different recommendations regarding frequency as well as duration of exercising the generator. Personally I like either 15 minutes a week or every other week. That will allow it time to come up to operating temp w/o wasting fuel.

Presuming that your generator is water cooled, a very, very, very good option to get is the water heater/circulator. This keeps about 95 degree water circulating inside the motor and significantly reduces wear on the generator during cold starts. It's mandatory for larger diesel installations, but still a very good idea for gas installations (especially in cold country).

Sometimes it's the simple things... don't install the genset near your bedroom (noise and exhaust), and if there is a prevailing wind at your home try to install it downwind (not always possible, but good to try).

The sound enclosures have come a long way, and are a worthwhile investment.

As part of the installation, either do a load bank test at max output for an hour or two or simulate it yourself with your home loading. At a minimum, this will verify that the gas supply is adequate.

[Brian Elfert]

Running a new generator at maximum load for one to two hours is a necessary on some models to break in the engine. The engine on my standby generator ran like crap until I ran it at maximum loaad for two hours. Compression on one cylinder was low before that.

I used a whole bunch of electric heaters and some custom wiring to load my generator.

[Art Mulder]

We have these Generac units all over the University here (where I work).

But I'm curious. What sort of annual/regular maintenance do you have to do with one of these things in a home environment. Do you basically need to commit to buying some sort of an annual service agreement/contract when you get this thing? That's got to add up! At my previous work we'd see notices 2-3 times a year about them testing the generator and how it affects our emergency power.

[Matt Meiser]

From my reading, basically change the oil and filters regularly. The generator exercises itself weekly.

Unfortunately I think this is going to be on hold due to my shop roof. :(

[Matt Meiser]

Back to looking at these since we think we can swing doing it this year. Since I started looking, Generac has introduced a new model of 20KW generator with an intelligent 200A transfer switch that will shed up to 2 AC units via the thermostat wiring and 4 other loads via contactors so we can easily wire in our AC and if needed add a contactor for the hot tub, though it probably won't call for heat when the AC is on. However later when we go to a heat pump, that would change.

They did the survey for the gas main down our road on Monday and are supposed to start construction around the corner from us a week from today. They are going to run down the other road about 1.25mi, then come back and pick up at the corner and run down our road, so he said 2-3 weeks before the main is pressurized in front of us. At that point they can run our service line at any time and we can get the whole process going.