Looking to buy a Generator but what size?

[jes]

I agree --- buying a natural gas generator to run a central air conditioner does seem to be over doing it. No, I don't want to spend that kind of money. You probably don't remember me, but I'm the one that posted so much during Ivan --- I have the two disabled elderly parents to care for and I have no other family to help. After Katrina the heat was truly life threatening. I am too afraid to work with a regular gas generator by myself. Also, the gas lines after Katrina made me worry even about gas for the car. My quote for a 5KW natural gas Briggs and Straten is about $5,200. The quote for a 12KW is about $2,300 more. Neither will run the central unit --- I want to be able to have two window units --- one for my parents and one for myself. I don't want to spend the extra $2000.00, but I don't know how to determine what I'll need. How do you convert amps to watts. My television just has amps. So if the back says 1.80 amps do I multiply that by 110 to get the watts? I don't want to over kill, but then again I don't want to wish I had purchased the larger unit either. Maybe I should just spend the extra money and forget it. I've decided definately not to buy the 15KW that may or may not run the central unit --- just too much money for something I may never use.

[Recurve]

Typically, multiply amps by 120 (nominal line voltage) to get watts -- or by 240 for 220/240 volt appliances. The higher volt values (120/240 instead of 110/220) give you a bit of margin.

Windows units (efficient 120v ones) are definitely the way to go for essential a/c.
If the rooms are far apart, you might want to consider two smaller generators rather than one large one and having to use long extension cords -- you lose power with longer distance from the generator.

Natural gas does seem like a good idea.

[GeneratorPower]

hey all I ended up getting a coleman 2500watt continuous 3125watt max at Walmart for $300. I couldn't find anything else that came that close even online for the price I also did some calculating and 2500watts will be pleanty to run my refrigerator, tv, several lights and several fans which is all I really need it for anyway. I just really couldn't justify spending more than about $400 for an item I may use once or twice a year. anyway it works for me it will run for 10-12 hours on 3 gallons which I don't think is bad and it starts easy and isn't any louder than other generators(except hondas of course).

I seriously doubt the word "continuous" appears anywhere on that Coleman machine. It probably says "Running Watts", which is an advertising gimmick. Typically, a generator will have three true ratings. Maximum watts, continuous watts, and surge watts. They are all different and this is what makes the difference between brands and prices.

Maximum: What the generator can put out, in watts, for up to about 30 minutes.

Continuous: What the generator can put out for days at a time, as long as you keep fuel in the tank.

Surge: What the generator can put out for up to 1 SECOND. This is the motor starting ability of the generator. That is, it measures how much kick the generator can provide to start capacitive loads like air conditioners.

A typical Coleman or Briggs/Stratton generator will have, say 5500 "running watts", which according to the definition above is actually maximum watts. What they NEVER tell you is the true continuous rating. That's because models like these can lose 30-80% of that "running watts" rating after just 30 minutes or less.

Any time a generator heats up it loses power. How much loss depends on the quality of the windings in the alternator, primarily. Bench tests in the generator industry prove that discount machines are inexpensive for a reason.

Now, that is not to say they are useless. They just aren't designed for home backup. Sure you can use them for home backup, but you've got to watch the power output constantly.

If you try to pull too much power, the breakers will NOT trip. You will get a low-voltage condition on the output. That's no problem for a light bulb. It's a big problem for compressors, microwave ovens, refrigerators, and anything else. Low-voltage causes odd things to happen in motors, and will burn them up.

Part of my job at work is to help people pick the right generator and the right size generator for their application, and sometimes it's not as straightforward as it seems.

For example, did you know a 4-ton central air conditioner could take only 5500 watts while running, but over 40,000 watts on initial start-up? Or did you know that some of today's newer refrigerators use only 200 watts while running and about 800 on startup? Older fridges use about 800 while running and 2100 on startup. So when someone asks you how much power you need for a fridge, it's not a simple answer.

Or for example, a circular saw. Sure, you could run these off a poor-quality generator for a while. But after a couple days of use, you'll probably be buying a new saw. Repeated starts and stops under low-voltage conditions cause shortened lifetimes of power tools.

I had a man come into my generator store a few weeks ago wanting service on his 2500w generator. It was about a $300 generator when new. He told me that his $200 Milwaukee power saws keep getting burned up when he uses them on the generator. I asked him how many saws he's gone through. He said 10.

Needless to say I explained to him why his generator couldn't do the job, even though the saw would work for a while. He left the store with a $1500 Honda generator, a 3000w model. Except the Honda has truckloads of surge capacity to handle his saw safely.

We also heard a lot of stories out of Katrina, when people were buying $500 generators from Home Depot. They would plug their cell phone chargers into them, and after about a day or so, the charging circuit in the cell phone was fried. That's because of the jagged power signal these generators provide. Again, fine for light bulbs, but murder on a cell phone or computer.

The one thing that really scared me during Katrina was an older lady who came in to buy a generator. She was considering plugging her life support machine to one of these $500 generators. I explained to her why this was not a good idea. Sadly, we see this a lot. But once the machine is fried, it's fried. Try getting a replacement ventilator during the aftermath of Katrina on the gulf coast.

The only thing that is easy is incandescent light bulbs. Everything else requires expertise.

I'm all for people getting what they can afford, as I totally understand that. As long as people understand what they cannot or should not do with what they purchase.

If what you can afford is a $500 generator, by all means, buy one. It's better than nothing. But don't push it beyond its limits and for heaven's sake make other arrangements for critical electronics. Don't plug your momma into a Coleman!

[DanKellFla]

GeneratorPower, great post, Thanks. But now I have some follow up questions. (Hey, you started it. ) Is there a way I can find out the continuous watts rating is for my generator? I bought the Craftsman model that is rated 5550/8600 watts. It has a 10 Hp Brigs engine. On of the reasons I bought is was because it has more power than I am going to us most of the time. The biggest reason I got it was because it can power my hot water heater as long as there is no other significant load. A Honda that can do that is way beyond my budget. How does running everything through a properly sized surge protector work? What about a UPS that is in line with the surge protector and then attached to the electronic equipment? How about something that lets me know how much power I am making? A multimeter? I have used them for some low power applications, but not something that produced a lot of power. Thanks for any information. Or, if you just do feel like answering, thanks for reading.

[MiamiensisWx]

GeneratorPower, thanks for the useful information.

[jbgreig]

Ibgreig,

What brand of natural gas generator did you buy? I also have a 5 ton central unit and some people say a 15 KW will work and others say it won't. Then I hear that Briggs and Straton will be fine, but the Guardian won't. I am so confused. We're running out of time ---- don't want to be caught in the rush. This is a tremendous expense so I don't want to make a mistake. Would you share what you've learned about the best units to buy and sizes. I haven't heard of the 16KW - everyone is quoting me on 15KWs.

Sorry, I've been AWOL. Generac has a new line of NG generators out this year. They claim that the 16KW Propane/15KW NG will start a 5 ton AC. I have talked to a company up North, and they assure me that it will start a 5 Ton in a NG configuration. I guess it has a different alternator that will handle the surge.

It's a Generac 5243 (steel enclosure) or 5244 for an aluminum enclosure. There are also "hard start kits" for compressors, which supposedly allow for running larger ACs on smaller generators. I figure one or the other will allow for the 5 ton to start.

Email me if you need any more info. I will probably order one in the next week or so, and I'll let you know.

I have an American Standard 12SEER unit, for what it's worth.

Anyone have any experience with the hard start kits?? I'm out of my element when it comes to that..

[jbgreig]

I agree --- buying a natural gas generator to run a central air conditioner does seem to be over doing it. No, I don't want to spend that kind of money. You probably don't remember me, but I'm the one that posted so much during Ivan --- I have the two disabled elderly parents to care for and I have no other family to help. After Katrina the heat was truly life threatening. I am too afraid to work with a regular gas generator by myself. Also, the gas lines after Katrina made me worry even about gas for the car. My quote for a 5KW natural gas Briggs and Straten is about $5,200. The quote for a 12KW is about $2,300 more. Neither will run the central unit --- I want to be able to have two window units --- one for my parents and one for myself. I don't want to spend the extra $2000.00, but I don't know how to determine what I'll need. How do you convert amps to watts. My television just has amps. So if the back says 1.80 amps do I multiply that by 110 to get the watts? I don't want to over kill, but then again I don't want to wish I had purchased the larger unit either. Maybe I should just spend the extra money and forget it. I've decided definately not to buy the 15KW that may or may not run the central unit --- just too much money for something I may never use.

Certainly valid points. Why am I still planning to get a generator that will run an AC? I lived through Rita last year. I was one of the few around who rode it out. Had little damage, but had some water leak in around windows and doors. I was here to wipe it up.

Neighbors and friends who were not here came home to mildew on the walls, mildew smells everywhere, etc, if not much, much worse. I was without power 16 days. About 8 days into it, my wife and my now 19 month old daughter came back. There was no way they could fill the gasoline generator every morning and night as I had. They had to leave the next day and go elsewhere until power was restored.

I had two 8000 btu ACs, dehumidifiers, manual transfer switch, everything. My house was pretty new, and I have "cracks" in the molding where the wood swelled with the heat and humidity and then shrank when our power was restored and the 5 ton AC could come back online. The joints are all exposed.

I had to leave because of my job after about 10 days, and it killed me to leave the house since parts of it had been properly maintained during the power outage. I had to pack up the refrigerators and freezers and haul everything out. I came back to an oven, and literally moments before the power came back on.

The peace of mind is worth it next time I leave. No worries about the house, humidity, or anything else. Do you know what 100% humidity does to paint, firearms, fishing reels, computer equipment, etc?

It is totally about insurance. If I knew a hurricane was coming this year, I'd get one for sure. I think the chance of one coming in the next 20 years is high enough that I will invest in a reliable method of keeping my house in order.

As a last point, I'll say the Generac 16KW with an auto transfer switch DELIVERED is about $3500 or so. It's an easy install if you are comfortable in a breaker panel. If not pay an electrician a couple hundred bucks. I wouldn't pay much more, but at that price (less than my insurance deductible) it's a no brainer. Now my wife and daughter can be comfortable and safe when my job calls me out of town.

I guess it just depends on your requirements, as I stated earlier. And don't ask local dealers. I hate to say it, but a FRIEND after Rita wanted $5800 for a 12kw, installed. I could have bought it for $3000 and it is a SIMPLE install.

Look online, order early, and enjoY!!

[GeneratorPower]

GeneratorPower, great post, Thanks. But now I have some follow up questions. (Hey, you started it. ) Is there a way I can find out the continuous watts rating is for my generator? I bought the Craftsman model that is rated 5550/8600 watts. It has a 10 Hp Brigs engine. On of the reasons I bought is was because it has more power than I am going to us most of the time. The biggest reason I got it was because it can power my hot water heater as long as there is no other significant load. A Honda that can do that is way beyond my budget. How does running everything through a properly sized surge protector work? What about a UPS that is in line with the surge protector and then attached to the electronic equipment? How about something that lets me know how much power I am making? A multimeter? I have used them for some low power applications, but not something that produced a lot of power. Thanks for any information. Or, if you just do feel like answering, thanks for reading.

Good questions! First of all, there is really no way to tell what your unit can do continuously without putting it on a load bank and doing a test. But we can do an approximation. A Honda 5000W generator would have an 11hp engine. Yours is 5550 mated to a 10hp engine, so that right there is a significant difference. A wild donkey guess would be it probably has a continuous output of around 3500W, but it could be as little as 2500 or as much as 4000. I doubt it would be higher than that.

A surge protector does absolutely nothing for the power quality problems that you'll experience. Surge protectors are designed to protect from overvoltage conditions rather than undervoltage. Plus, they can't smooth out the signal any, which is what will fry sensitive electronics.

A UPS probably will not help much either. In fact, most UPS's won't even recognize generator power as a valid power signal so they will stay on battery until exhaustion. We see that a lot with Generac whole-house systems and portable generators without inverter or AVR technology will usually cause the same problem. The deal is that the power signal is jagged and distorted, rather than the clean, smooth power of your utility. The UPS is designed to look at the input signal from the plug and see if it's acceptable. If it's not, it will switch over to battery. However, this is only a problem with certain kinds of generators and UPSs. You'd just have to try it (at your own risk).

To monitor power usage, you could get a multimeter with a clamp on it. It's called an Ammeter but it's not low-wattage one built into most multimeters. It looks like a big claw that opens up. You run a wire through it, and it tells you how many amps are being drawn through that wire. However, you can't just clamp it around say, an extension cord, because the extension cord actually has two current-carrying wires inside and they flow in opposite directions. Thus, the currents cancel out and you read zero. You'd have to slice open the extension cord and clamp the meter around just one of the internal wires. You can leave the insulation on the internal wires.

If you want to get into it, you can make an adapter like I made a while back. It's basically a very short extension cord (mine is 12" long). I split the jacket open and exposed the black wire. Without stripping the insulation off, I simply clamp my meter around it and presto, I've got a very accurate current meter that I can plug any appliance into.

The clamp meters are about $50 at Lowe's or Home Depot.

That will tell you, in amps, how much power you are using. Multiply by 120 to determine watts. This trick will work with a big generator cord too, but there are three current-carrying wires inside. You would need to measure the red and black wires separately, and add them together, to get the full draw. Ignore the white and green wires.

But really, it's voltage you would need to be concerned about. The generator has reached its limit when additional loads placed on it cause a decrease in output voltage. Voltage at the outlets should read around 120 all the time. Put a 5500 watt water heater load, lets say, on YOUR generator. It will supply power for about 20 minutes before the voltage output will start to go down. The generator can't handle the load anymore so voltage goes down. Thus, the heating elements inside the water heater don't get as hot and the effectiveness is reduced. I don't think that would damage the water heater because it's just like a light bulb -- resistive.

Anyway, if anyone reading this gets anything from it, I would hope you would see that these types of calculations aren't always easy.

Understanding that can help tremendously.

[DanKellFla]

Thanks. My water heater has a 4000 watt element. Hopefully, it will be enough. It takes a little less than an hour for the water to get warm. I don't plan on running the water heater when anything else is attached to the generator. I don't think I have a real choice anyways. I am not looking to run anything critical off this generator. I haven't had a generator in the past and I survived, so I admit, this is a luxury. Mostly to keep my wife and kids happy so I can do clean up work after the storm. Fortunetly, I live in an area that typically gets power back in about 3 days. So this isn't going to be a long term solution at all. If things look bad enough, I will just go visit some relatives out of state for awhile.

I think I can handle the math. I have some extra 12 ga romex that I should be able to use to make a short extension cord. But I have to be careful of the copper line. Once I cut the outer insulation, the copper is exposed.

Just to let you know, a friend of mine bought a little Honda generator for his mother. It is a fantastic piece of equipment. Totally different from my noisy beast. You get what you pay for. I am just looking at light bulbs, a fridge and an old TV that seems to be invulnerable. But I am not looking for something to use long term. Just something to get my by for a few days and give me a chance to set up the house for some time without power. After that, I just make a claim to the insurance company and let them deal with it.

[jbgreig]

That will tell you, in amps, how much power you are using. Multiply by 120 to determine watts. This trick will work with a big generator cord too, but there are three current-carrying wires inside. You would need to measure the red and black wires separately, and add them together, to get the full draw. Ignore the white and green wires.

Ahhh, a question I have asked. I have a Fluke Clampmeter, with the true RMS, inrush, and all the gizmos. Question: How do you read a 240V circuit? I have been told that you clamp the red wire and the black wire and add the two amps together to determine your 240v amp load.

I disagree. I say that you measure one of the hot leads and that is your amperage at 240v.

Opinion? Sounds like you are familiar with the procedure...

[wayoutfront]

just want to add because I can't stress it enough

improperly running a generator or using an improper generator and frying your capacitor start motors on your appliances is an exclusion on most all Insurance policys

so make sure you do it correctly, or you will be out of pocket for a significant amount of dollars to replace fridges, AC's etc.

so spend the extra $$$ up front

don't shoot the messenger

[ROCK]

Just bought a 5550 Briggs 10hp from Home Depot. They gave a $125 rebate so I am using that to buy a 5,000 btu window unit. I plan on connecting it through my dryer breaker (30 amp) since my dryer is gas and uses 120. Kill the main and all non-essentials breaker and back feed my panel with the gen. Only problem is that I want to put my gen in the backyard out of site while running and this requires a 45 ft run of wire from the breaker box (outside) to the gen. Anyone know what kind of voltage drop I will see since it quite aways from the panel?

[DanKellFla]

GeneratorPower, I know that you have a reasonable bias towards the Honda/Yamaha type generators. Honestly, if money was no object, I would get a permanently installed back-up generator that went through a power conditioner. But, I have limits. So, I make compromises. When I did my research on what generator to buy, I calculated that I would need about 3500 watts at any given time, except for the water heater. I wasn't very concerned about the quality of power delivered to the water heater. For some reason, I had my suspicions that 5500 Watts was for ideal conditions. That is why I bought something larger. I also took into consideration that my yearly run time would probably be around 60 hours a year. Which brings me to my question.
What do you think of the Crafsman (B&S) that I bought?

[Alladin]

GeneratorPower, I know that you have a reasonable bias towards the Honda/Yamaha type generators. Honestly, if money was no object, I would get a permanently installed back-up generator that went through a power conditioner. But, I have limits. So, I make compromises. When I did my research on what generator to buy, I calculated that I would need about 3500 watts at any given time, except for the water heater. I wasn't very concerned about the quality of power delivered to the water heater. For some reason, I had my suspicions that 5500 Watts was for ideal conditions. That is why I bought something larger. I also took into consideration that my yearly run time would probably be around 60 hours a year. Which brings me to my question.
What do you think of the Crafsman (B&S) that I bought?

Hi DanKellFla! Your Craftsman genset uses the 10 HP, Briggs & Stratton OHV Intek engine. Briggs & Stratton is the largest maker of portable gensets in the world for good reason. All things considered, they are the best. That engine sips gasoline and is very quiet.

My genset is similar. I have the Coleman Powermate 5,000 genset. It uses the same B&S engine. After hurricane Ivan we were without power for 8 days. Prior to the storm, I had stored 80 gallons of gasoline. I was able to run two 8,000 BTU window A/C units, my 26 cubic foot refrigerator/ freezer, a ceiling fan and several compact fluorescent bulbs. Total draw on the genset was 2,500 watts. I ran the genset 24/7 (except to refuel and change oil) for 8 days and still had 10 gallons of gas left over!

Ten months later, Dennis hit us and we had to repeat the whole process again! 7 days without power, but I cranked up the genset and ran the aforementioned appliances without a problem. We were comfortable even though the ambient temperature was very high. Without those A/C units, we would have been miserable!

When using a portable genset, at lot of attention is given to surge watts (the extra wattage needed to start a compressor). Some people make the mistake of thinking that they need to size their genset to account for the surge watts needed to start all their compressors at one time. Generator sales people use this idea to sell bigger gensets.

In reality, the surge watts created by a compressor only last a few milliseconds. Do you know what the odds are of three compressors all cycling on at the exact same moment? You've got a better chance of winning the lottery! The only surge load you need to account for is the largest single compressor. The other surge loads can be ignored.

Also, if you're worried about the surge created by the compressor cycling on, then just set the thermostat to its lowest setting. The compressor will stay on all the time. We set the window A/C units to 60º F and used the rooms in the house (by opening and closing doors) to control the inside temperature. It worked great.

[Alladin]

If you want to get into it, you can make an adapter like I made a while back. It's basically a very short extension cord (mine is 12" long). I split the jacket open and exposed the black wire. Without stripping the insulation off, I simply clamp my meter around it and presto, I've got a very accurate current meter that I can plug any appliance into.

The clamp meters are about $50 at Lowe's or Home Depot.

Or, you can buy an AC Line Splitter 81066 from Sears for $10.00 and then take all the amp readings you want with your clamp meter (I use a Greenlee CM-310). The AC Line Splitter has the advantage of allowing you to take two readings. One reading gives you regular amps while the other reading gives you amps X10 (this is important for low amp readings).

[sponger]

4000 watts will be plents for what you want to run. Make sure it is rated for 3500 watts or more, not surge rated to 3500. For example, pep boys had at 2000 watt generator listed as a 3500 watt. In general, you would like to run your generator at 1/2 load, 70% maximum. A typical fride side by side will use 1100 watts, a light is 175 watts and a fan will use 500 watts or less, depending on speed, size ect.


I hope this helps!

[Alladin]

A typical fride side by side will use 1100 watts, a light is 175 watts and a fan will use 500 watts or less, depending on speed, size ect.


I hope this helps!

No. A typical side by side refrigerator will not use 1100 watts (that's over 9 amps!). It would be more on the order of 800 watts for the average unit.

A light is only 175 watts if you have a 175 watt light bulb!

If you have a fan that uses 500 watts, then it will produce enough wind to blow all your pictures off your wall! The average ceiling fan or 20" high velocity floor fans draw about 100 watts or 200 watts at high speed respectively.

[bevgo]

I live in an apartment and would have to keep a generator outside. I wold also have to store fuel outside. I don't know if this is practical at tiis time. Walmart has one for around $500.00 and I could put it on layaway. I am really unsure what to do but really want to be able to return to my apartment as soon as possible or stay for a TS without having to nearly die from the heat. I have a grandchild to consider also. I am unable to wire it into the apartment but could run fans and the fridge on it so we would have some comfort measures for power outage. I am concerned that power will go easily since the infrastructure may not be as strong after last year and we still have a number of trees leaning and weakened from Katrina.

[Alladin]

I live in an apartment and would have to keep a generator outside. I wold also have to store fuel outside. I don't know if this is practical at tiis time. Walmart has one for around $500.00 and I could put it on layaway. I am really unsure what to do but really want to be able to return to my apartment as soon as possible or stay for a TS without having to nearly die from the heat. I have a grandchild to consider also. I am unable to wire it into the apartment but could run fans and the fridge on it so we would have some comfort measures for power outage. I am concerned that power will go easily since the infrastructure may not be as strong after last year and we still have a number of trees leaning and weakened from Katrina.

I think the generator you are referring to at Wal-Mart is the Coleman Powermate 6250 that sells for about $525.00. The reason why the price is so low is because the version sold by Wal-Mart has a 10 hp Tecumseh engine. That engine is an older side valve model. It is noisy and is uses a lot of fuel.

You would be better off getting the Coleman Powermate 6250 with the 10 hp Briggs & Stratton OHV engine. It's much less noisy and it is more fuel efficient. Ace Hardware sells them for $599.00. Home Depot even has a newer version of that same generator with the Briggs & Stratton OHV engine for $599.00 and it includes a free Coleman Powermate 20-Amp Convenience Cord. That's the best deal I've seen.

I can tell you from experience, that most of those generators in the stores now will just sit there for now. However, when the first storm enters the Gulf of Mexico those generators will sell like hotcakes and gas cans and gasoline will be in short supply too. If you intend to get a generator, then get it now and horde away as much gasoline as you can.

You didn't say on which floor your apartment is located. If you're on the ground floor it won't be too difficult to secure the generator outside and run heavy duty (12 gauge) extension cords to your appliances. Just try to keep the total cord length connected to each generator outlet to 100 feet or less.

[beachbum_al]

We have one but I would have to go in to the garage to see what size. I know it is pretty big because we ran the fridge, the t.v. and satellite, and a lamp on it last year during Katrina.