Let's talk about Emergency Power Generators

Thread Starter


Joined Mar 1, 2017
Hi everyone,
I live in South Florida and as most people know, we just got hit bu hurricane Irma last week.
Unbelievably, our power was back on the very next morning!!!!! (Last time we were without power for right at 1 MONTH)

Anyway, I have several generators, including an inverter generator, but the one in question here is my Coleman PowerMate (dirty power) 6700 peak, 5500 watts running generator,...and it's that "dirty" part that I wanna talk about.

I know that "dirty power", more technically, power which does not have a pure 60Hz sine wave (correct?)...can damage sensitive electronics.
I do happen to have an Oscilloscope and I intend to connect it and actually see what just how "dirty" the output is. I will post the results when I do.
IIRC, I did several years ago and I seem to remember it was VERY squared and blocky. Not very smooth. I'll have to connect it again.

Meanwhile, what (if anything) can I do to get more use out of this generator (other than use it as little as possible)....such as line conditioners etc?

My Honda eu2000i inverter generator is so nice, but it's output is a bit limited. Phenomenal for running a fridge or single window AC however. Naturally, running the small Honda for the bare essentials saves a TON of fuel.

For example, my little Honda eu2000i can run my fridge (27cu ft) for 3 days on a single tank fill using eco mode. It's so quiet while doing this I can sleep with it right outside the window and hardly hear it. The Coleman on the other hand is a gas hog beast and will run about 8 hours on 5 gallons. So I try ti minimize it's use since fuel can be in very short supply after a major hurricane depending on the damage done. All 3 cars topped up allows me to safely store about 55 gallons of fuel that I can then withdraw as needed. With that, I can go more than a month on the Honda.

So I use the 5500 watt genny connected to my home via a "tap-box / transfer switch" and with that running, I have everything almost back to normal as long as I am conservative with power demands. But, running the fridge and two window AC units and some lights etc STILL uses about 6 gallons a day so I get approximately 55 gallons/6 gallons per day = or about 9 days of run time. Usually after a week to 10 days fuel stations start getting fuel again. Usually.

I do plan to buy a 3500 watt Inverter generator soon. But for now, I have what I have.

So back to the Dirty Power generator.....what can I do to condition the power output so that IF I use it it doesn't ruin electronics....or should I just sell it off and get another generator?


Joined Jan 15, 2015
Before going to whole house automatic transfer natural gas fueled 18 KW unit I used one of those Coleman Power Mates which worked just fine. Smaller than yours it is a 5 KW peak and 4 KW constant power. That 4 KW supported the house just fine less running the electric clothes drier or the whole house air conditioning. That included the TV and a few home computers. I never looked at the output wave forms but had no reason to worry about it.

While we don't get hurricanes we do get some severe summer storms, tornadoes and winter ice storms in sub zero weather. My wife's mother had brain surgery which did not go well so we did the home care thing for eight years. As her vegetative state progressed more and more medical support equipment came into the house and I began getting more and more concerned about an extended power outage. The Coleman Power Mate was the first addition and like you I rigged a pony station outside. Problem was in my absence my wife would have to drag the generator out of the shed and connect it following my written directions and pull start the thing. While nothing fancy it got the job done but when we did some major home renovations I went with a large natural gas powered unit. The power mate did fine though but did give the UPS units on the computers the fits until once on generator power they were shut down. The voltage fluctuations were more than the UPS units liked. :)

The power mate while not quite a work of art did get the job done on a few occasions, I will give it that and I never had an issue with dirty power and the home computers and medical electronics ran just fine on it. Been a few years and this thread reminds me I should drag the old power mate out of the shed and get it gone over. The carburetor will need cleaned and a new plug. This way if a neighbor needs it this winter they can use it.

As to your unit? I would see what you actually have and if in fact the power is dirty. Then if you want to get rid of it go ahead and get rid of it. Before replacing it I would evaluate your power needs so you can get what you need to support your power needs.


Thread Starter


Joined Mar 1, 2017
Yes Ron,
I saw SO MANY people try to get their generators out at the last minute before Irma hit only to find the darn thing flat out was not going to work.

If stored outdoors, there are a number of steps that simply must be taken if there is to be any expectation of it working when needed. More so in humid climates. Dry desert climates are less prone to outdoor storage failures.

I did run my fridge off the Coleman Powermate before I had the Honda and it survived. The Powermate is designed so that it generates 60Hz when running at a specific RPM....I think 3600rpm. So it's especially important to have it running just right at the correct speed.

There are line conditioners that can be plugged into a generator powered wall outlet that appliances can then be plugged into and they should help. Mainly reducing spikes I believe.

I powered up my oscilloscope this afternoon intending to get an actual output graph....but I couldn't find the darn test leads (argh).

I also had problems running (charging) my battery backups from the Coleman Powermate. As you say, they seem to need cleaner power.

My general advice to people concerning generators is to .......
1). Store them in a climate controlled location if at all possible (such as indoors, under AC)
2). Run them at least 4 times a year, once every 3 months.
3). Keep a small amount of SeaFoam mixed in the fuel to prevent gumming up.
4). Never leave fuel sitting in a generator for more than a month with out SeaFoam and no more than 4 months with it.
5). If stored outdoors in a humid climate, remove the spark plug and add 40cc's of 20-50 motor oil then turn the motor over a few times without starting it to coat the cylinder and rings, then gently pull the starter a few inches once every other month to reposition the piston in the cylinder.
6). Change the oil even if it has not been run if the oil has been sitting in the crankcase more than 6 months.
7). Do not cover the generator. That keeps moisture trapped around the generator full time. But do protect it from rain. Sheds are generally VERY humid.
8). Put a bit of non conductive dielectric grease in the electrical outlets before storage to prevent corrosion and keep bugs out. It has insulating properties but never seems to affect output.


Joined Apr 10, 2015
Looks like sound advice there Lumenosity, Sea-Foam is crucial. I'd say you've got experience with both ends of the quality spectrum there.

I'm not a fan of the inverter units though, because I've only ever experienced ones like you describe, with lousy waveform, as well as the needless added complexity. Power is power, so while some advantage can be had from lower speed throttling at low loads, it's not the fuel saver that some expect.


Joined Mar 14, 2008
I'm not a fan of the inverter units though, because I've only ever experienced ones like you describe, with lousy waveform,
You have it backwards.
It's normally the non-inverter units that have lousy waveforms.
The inverter units are designed to have a nice, stable sinewave with low distortion.
They can also reduce engine speed at lower loading to reduce noise and fuel consumption without any change in the output frequency or voltage.
That was what the TS was describing.


Joined Jan 15, 2015
That would be it for the US 60 Hz using a 2 Pole generator. The smaller diesel fueled units generally are 4 pole running at 1800 RPM.
Generator Frequency (f) = Number of revolutions per minute of the engine (N) * Number of magnetic poles (P) / 120
Conversely, P = 120*f/N

Mistakes I made when buying the first unit.
The fuel tank was a major screw up on my part. I wanted gasoline but failed to consider run times under various loads. I think it has a 1.0 or 1.5 US Gallon tank which under heavy loads only gets about 1.5 hours or less of run time so I was constantly having to add fuel. I should have considered one of the units with the 7.5 US Gallon tanks above the unit.
Wheels were another mistake on my part. I should have gotten a unit on wheels rather than 4 pads as when moving the thing it is heavy and as get older seems to be getting heavier.
Power Out. Rather than the 4.0 KW and 5.0 KW Peak I should have went with a 7.5 KW unit as at the time that was about where the electric start units were and electric start is real nice to have.

If I were to get another small unit those are mistakes I would avoid. I would have a large fuel tank, wheels for portability and electric start.

My wife has a UPS on her home electronics which has a generator setting allowing for changes in frequency and voltage without freaking out and my read was many new UPS units allow for generator power. NIce feature to have.

The battery on the whole house unit is maintained by a battery maintainer which is similar to what I use on my motorcycle during winter months. Seems a 5 year battery gets you exactly 5 years. :) I replaced the original battery about 3 years ago. The generator runs every Sunday morning at 10;30 for about 15 to 20 min as an "exercise" routine. I can also at anytime just shut off our mains and the thing will auto start and transfer. When mains power returns it waits about 5 min to make sure power remains does a transfer and then runs awhile longer under no load as a cool down.

I originally was looking at a 12 KW unit when I bought the one we have. I figured 12 KW was more than adequate. The unit on the floor at Lowes was an 18 / 20 KW unit (18 KW Natural Gas and 20 KW Propane). Talking to the store manager the model I was looking at on the floor was being discontinued. They had changed the case design so they offered me the unit brand new, on the store floor for about $1,000 off. All I had to do was haul it away. Cool with me. The main difference was here is a today's model, note the rounded corners on the framing housing. Here is the unit we added as we were renovating the whole house and added the central air.

Gen and AC.png

The yard was also totally fenced during renovations making the dogs very happy.

Anyway, going back there were things I would have done much differently which I mentioned. I would absolutely get a large fuel tank and I like the newer inverter type units, they have quite a bit of merit, especially as Crutschow mentioned and the stable frequency is really nice.



Joined Oct 29, 2013
I'm in SFL with you, and being a native I've seen my share of storms and spent many weeks running on generator power, so I know right where you're coming from. We also use a generator to power our trailer (roof top AC/heat, interior lights, etc..). The inverter generators put out really nice power and are very efficient, but for home use the small ones have one big draw back. They only give you a single phase @ 110v, and in FL the building code allows multi wire branch circuits where only 3 wires are used to carry both phases from the utility (2 hots and a neutral). So if you use a generator with a single phase output, and shunt both sides together at the breaker box to power the whole house, there is a risk that the 3rd (neutral) wire could be overloaded and cause a fire inside your walls. You would need to either use a transformer to get 2 phases, or get an inverter that gives you 220v output with 2 phases just like your utility power.

When on dirty generator power and using a computer with a UPS, turn the UPS sensitivity down and it will stop complaining. With the APC branded units you can do this in their Power Chute software that comes free with it.