Inverter Generators

[KTurner]

I actually had that. I had not kept water in the batteries and they went bad. I went to get new ones and they were close to $200. They take a long time to charge, say 8 to 10 hours. So I have to run the generator 10 hours to charge. The inverter generator was $500. It seemed to me that it is a better solution.

A new set of batteries was only $200? What type/quantity batteries were you using? I've seen basic car batteries (non deep cycle) cost more than that, for just one.

Keith

 

[BobRip]

A new set of batteries was only $200? What type/quantity batteries were you using? I've seen basic car batteries (non deep cycle) cost more than that, for just one.

Keith

Golf cart batteries from SAMs club. Two six volt in series.

 

[SPYDERLK]

If a power outage happened frequently, I could do the following:

I have a 7000 watt pto generator, and a 3000 W invertor. Not an invertor generator, just an invertor.

I could get a lead acid battery bank, and keep it charged. I could consider a solar panel too for this. [Then I could use the invertor to run the fridge during an outage], and while my Generator is running, charge the batteries back up, while still running the fridge at the same time. I may be able to cut my generator run time in half that way, but throwing more load on the generator while it is running, but let the batteries power the fridge half the time.

It will work but not so well due to the fact that most [inexpensive] invertors output a "modified" sine wave. Since this is a euphemism for square wave you will not get full performance from an induction motor. Since compressor motors are sized to run at or close to their nominal peak they will overheat on an invertor during a long run. I dont like to use a mod sine invertor on induction motors that need to run near their peak for long.
larry

 

[EE_Bota]

It will work but not so well due to the fact that most [inexpensive] invertors output a "modified" sine wave. Since this is a euphemism for square wave you will not get full performance from an induction motor. Since compressor motors are sized to run at or close to their nominal peak they will overheat on an invertor during a long run. I dont like to use a mod sine invertor on induction motors that need to run near their peak for long.
larry

Well, you guessed correctly that my invertor is about as cheap as they come.
I am not sure what type of wave it puts out. I can always have a look with my scope, I suppose.

One hopeful aspect that should make it less important is that most refrigeration compressors and deep well pumps have good cooling relative to many other motors...compressors sit in an oil bath, and can transfer their heat directly to the oil, and also, out the condenser coil. Deepwell pumps, and some sump pumps, can transfer their heat to the water, sometimes with an oil intermediary (in the case of a submerged sump pump, I am not sure about a well pump.)

If the invertor cannot run a motor, it is close to worthless.

I need to bone up on invertor waveforms. I took a power electronics course in school, but I need to have another look that the book and my class notes sometime, since most of that leaked out of my head at some point.

Here is a discussion of the waves. If it is estimated that for a non-sine case, 20% of the power is not used, but lost, and some or all of that power loss has to be exchanged across the condensor coil, it may be a relatively worthless proposition.

Inverter Selection

I have right much beef in my freezer, but it's not mine, but belongs to a buddy instead. He has so much, we decided to diversify the storage locations in case of a freezer failure...so he would not lose it all. He knows if push comes to shove, I'll fight a heck of a fight to keep from losing his beef.

Heck, I may be better off just getting some extra propane around, and some Ball jars, and if the worst happens, try to can it.

 

[Greg H]

Hi, I usually hang out at the Hearth forum but I saw this thread that might answer a specific question I had.
I too survived hurricane Irene, and I'm looking to improve my set up for next time.
We were out of power for 6 days, not as long as some folks but more than most.
The 7550 watt Troybilt generator worked fine, powering the whole house when I needed it, but of course it sucked down the gas.
I also have the cheapest Chinese inverter generator that you could possible find.
www.giobikes.com/Generators/GIO-950w-Mini-Generator
My thinking like others here was to run a critical, low wattage appliance for extended periods of time without burning 5 gallons of gas.
My question is this: when I plugged in my Kill-o-watt meter under Hz it says dC. It does this while at idle and under load.
The big generator shows 60.1 Hz, my cheap inverter shows dC and my puresine Xantrex inverter reads 60 Hz.
So I'm assuming this is a modified sine wave inverter rather than a square wave and I know its not a pure sine wave. I'm guessing the kill-o-watt meter isn't capable of reading the modified sine wave. Until I saw that I was perfectly happy with my set up.
Do you think this is still safe for the fridge or furnace? The last thing I want to do is burn out an expensive piece of equipment while trying to save a few bucks.
I ran the fridge on it for a total of 15 hours or so with 5 hours for the longest stretch. Then I ran into a fuel feed problem which I have since fixed. Didn't notice any humming or other problems.

Thanks

Greg H
Central CT

 

[BobRip]

Ah Hahh,
{an "Ah Hahh" moment}
Keep the door shut and/or add more insulation and/or fix any door seals.

If you want to change the cycling from short and frequent to long and infrequent you can "fix" that quite easily and the fix is reversible.
Find the temperature sensor and "insulate" it, just a little bit, no need to put thick foam around it, maybe a few layers of duct tape as an experiment.
This will cause it to lag both the cooling and warming phases of the cycle, i.e. your fridge will come ON when warmer and switch OFF when colder.
It will run for longer, but then stay off for longer - is that what you want ?

The extra insulation is a good idea. The thermostat insulation will not help. The problem is not short compressor on/off times, but supplying power long enough and often enough so the food would not spoil. The thermostat insulation would just increase the temperature swings. The ideal refrigerator would have a lot of insulation so they warm up slowly and an oversize compressor that would cool the unit quickly. Compressors are sized to run about 50% of the time. This means 12 hours a day.

 

[bcp]

Fill all empty space in refrigerator and freezer with water jugs. It will stay cold longer.

Bruce

 

[EE_Bota]

The extra insulation is a good idea. The thermostat insulation will not help. The problem is not short compressor on/off times, but supplying power long enough and often enough so the food would not spoil. The thermostat insulation would just increase the temperature swings. The ideal refrigerator would have a lot of insulation so they warm up slowly and an oversize compressor that would cool the unit quickly. Compressors are sized to run about 50% of the time. This means 12 hours a day.

Also, adding more insulation has to be based on the actual design of the unit. I find that many seem to run their condensors under the side unit shell, so putting insulation there will ruin the efficiency of the unit. This, obviously varies widely.

Many have the condensor in plain view on the back of the unit. Some are under the unit. Some, unfortunately, are where I said...the unit's sides radiate the heat outward.

 

[Reg]

Fill all empty space in refrigerator and freezer with water jugs. It will stay cold longer.

Bruce

That is a good strategy for holding freezers over for long power cuts, but it takes a LOT of power to get all that water down to temperature and if/when you need the space again you have to chuck out all that energy investment.
Just FILLING the space with dead air would help toward the problem of frequent cycling, i.e. pack it with empty (air filled) gallon milk jugs.
This effectively makes the fridge smaller relative to its compressor and reduces the inrush of warm air every time you open the door.

Of course, opening the door less often may help towards solving OTHER problems as well (-:

We're straying from the topic of "Inverter Generators"

 

[ultrarunner]

Fill all empty space in refrigerator and freezer with water jugs. It will stay cold longer.

Bruce

Yes... and you will have extra water too!

I bring home cold packs that meds are shipped with... otherwise they would just be thrown out...

Anybody need styrofoam "Ice Chests" many meds must be protected from Heat so we have a steady supply.

 

[Larry Caldwell]

I have plenty of water thanks to a 2500 gallon cistern, but I freeze ice cubes and bag them up for the freezer. Not only does it stabilize the freezer temp during a power outage, but I can use the ice cubes to make ice cream, chill a cooler of beer, etc. Have you noticed the price of ice? Wow! Making your own is sure cheaper.

 

[BobRip]

This changes the subject a little. It seems we have to oversize our generators to handle motors starting. I know they sell a well pump that starts slowly and runs off of a very small power source. .Grundfos SQFlex Solar Submersible Well Pump

Most motors are induction motors connected directly to the AC power when starting. They start and reach full speed in just a few seconds. They are cheap and reliable, but do not start easily. It would be nice if all motors start slowly and reduced that startup current.
This would cost more I am sure, but it would be nice to have this option. Of course some motors may really need to reach full speed quickly. This would also give the inverter generator a chance to ramp up. Also air conditioners could be more easily run off of non dedicated circuits.

 

[BobRip]

Another thing you can do is temporarily wire your hot water heater to 120 volts instead of its normal 240. It will pull one quarter the power and one half the current. It will also take four times a long to heat water, but that may work for your particular need. I don't have a good way to do this easily and neatly without going into the panel.

 

[Larry Caldwell]

Another thing you can do is temporarily wire your hot water heater to 120 volts instead of its normal 240. It will pull one quarter the power and one half the current. It will also take four times a long to heat water, but that may work for your particular need. I don't have a good way to do this easily and neatly without going into the panel.

It would be simple to do it at the water heater. Just install a DPDT (double throw, double pole) switch on top of the water heater and hook one side of the switch to an extension cord pigtail. Then just throw the switch and hook up an extension cord from the generator. You could energize it with either 120 or 240.

I have made up a couple of 240v. extension cords that I use to power my air compressor or welder when I move them out of the shop. I also wired in 240v. power to outbuildings, so have 240 available in the pump house, the wood/garden shed, and barn. I can plug in a 240v. milk house heater and get some real heat when I need it during cold snaps.

 

[BobRip]

I was thinking of putting a single pole double throw switch next to the electrical panel. I feed the house through a mechanically interlocked breaker. I would switch one of the hot water tank leads from the breaker to the neutral. Actually that would be pretty simple.

 

[Larry Caldwell]

Nah, you don't want to be messing with the wiring during a power outage, possibly working in the dark or under time constraints. You have to switch both legs if you want to make it work, so DPDT is the only way to go. Otherwise you have to disconnect one hot leg in the panel and move it to neutral to run the WH off of 120, and there is no way to connect a 240v. generator with a single pole switch. With a DPDT switch, it doesn't matter what you feed it with, it will work both ways.

 

[whistlepig]

Its best for me to keep it simple for the generator hookup. Last time I used it was during an ice storm in February. I had to use the loader to move fallen trees just to get my generator to my back deck. By the time I got that done the tractor and me had a quarter inch layer of ice. It was forty degrees in the house before I got heat from the generator.

 

[BobRip]

Nah, you don't want to be messing with the wiring during a power outage, possibly working in the dark or under time constraints. You have to switch both legs if you want to make it work, so DPDT is the only way to go. Otherwise you have to disconnect one hot leg in the panel and move it to neutral to run the WH off of 120, and there is no way to connect a 240v. generator with a single pole switch. With a DPDT switch, it doesn't matter what you feed it with, it will work both ways.

I would feed the generator to the panel through the generator breaker just like I always do in a power outage. The breaker has a cable with connector to plug into the generator. At you stated one leg of the hot water heater wire would be connected to neutral on the panel. Single pole double throw switch would work nicely. No problem.