I am configuring an alternative energy system for my home. I need help in deciding on a Trace 4024 sine wave or a Trace 3624 modified sine wave inverter. My biggest concern is whether modified sine wave will adversely affect motor life in a refrigerator. Anyone have experience with these inverters?

The system will be grid-connected, hybrid (Wisper 600 + Helios 75w PV). Average wind/sun days will generate 4.2kw/d or 213.5 ah/d.

Continuous AC load will be about 3.3kw/27.4a. Appliances will include a 19cf Maytag 'fridge (360w/3a), florescent lights, overhead fans, coffee pot, microwave, dish washer.

-- J. SCOTT CURRAN (SCURRAN@UTMB.EDU), August 07, 1998

Answers

Scott,

Might I suggest that you contact Roy @ 4Winds,

email = 4windpwr@infoblvd.net

web site = http://www.infoblvd.net/4windpwr/

Roy lives off-grid, and I know he uses the DR3624 modified sine wave unit. He's a regular on the GN Home Power Generation site, is very knowledgable, (he's a dealer, sells what he uses) and does a lot of work responding to questions on that site. He's also quite happy with the 3624.

The literature I've read, including reports from an inverter manufacturer (forget who, you can find the report off the web page http://www.windsun.com) indicate that the modified sine wave is only a problem when dealing with audio equipment and where every ounce of effeciency is a probelm. [Of course you pay a good bit extra for that last little bit of efficiency.]

-- Rocky Knolls (rknolls@hotmail.com), August 07, 1998.

I would suggest dumping the fridge, regardless of which inverter you buy. Get a dc model and save the ac power. You don't mention your battery bank. I have a sunfrost 19 on order in 24V. IMHO, buy the best you can afford. This shit gets expensive in a hurry. If you can afford it, buy the true sine wave.

If money is tight, put the extra in your batteries!!!!!

What kind and how many amphours are you considering. This makes all the difference. If you are planning to run strictly of the wind/sun, what happens on a calm night?

Whatever you are figuring as your usage will be wrong.

Good Luck,

Will

-- Will Huett (willhuett@usa.net), August 12, 1998.

I am configuring an alternative energy system for my home. I need help in deciding on a Trace 4024 sine wave or a Trace 3624 modified sine wave inverter. My biggest concern is whether modified sine wave will adversely affect motor life in a refrigerator. Anyone have experience with these inverters? The system will be grid-connected, hybrid (Wisper 600 + Helios 75w PV). Average wind/sun days will generate 4.2kw/d or 213.5 ah/d. Continuous AC load will be about 3.3kw/27.4a. Appliances will include a 19cf Maytag 'fridge (360w/3a), florescent lights, overhead fans, coffee pot, microwave, dish washer. Hi J.:
 
"Modified sine wave" inverters are typically a square wave with a step or two introduced to crudely simulate a sine. This is true of the Trace "mod sine" units.
 
In reply to your question .. AC motors run hotter and about 10% slower on modified sine.
 
As one who is living with solar energy (and has for years) .. I'd like to pass along some comments and suggestions:
 
1) From your posting, I read it to mean you will have a Whisper 600 wind generator and one Helios 75 watt solar panel. Your 4.2 kilowatthours per day figure is astronomical production from such a small system. .. unless you regularly have up to 30 mph winds and many hours of sun per day, every day. As one who has been actively involved with solar energy for nearly 30 years, I'd like to know how you arrived at your figures?
 
2) The Maytag fridge will eat you alive in electric consumption. As you already surmised, you'll need 3-5 kilowatt-hours/day just to feed it. Get a unit made by SunFrost or LowKeep. They both use the Danfoss DC compressor, consume about 1/10 the electrical power of the Maytag per day .. and will still keep food just as cold as the Maytag .. if not colder.
 
3) Regarding your other planned loads:
a) florescent lights -- good move here.
Models with electronic ballasts are vastly more efficient than their transformer-based counterparts. While both *do* use transformers, the electronic versions use far less iron and wire, thus have far less loss than their overweight transformer-only cousins.  
b) overhead fans
Use them sparingly .. if at all... and only when you have an excess of power stored in the batteries. Fortunately, heat and lots of sun tend to go hand-in-hand .. so this may not be as difficult as it may seem.  
c) coffee pot
See suggestion "b" .. electrical heating is very inefficient. Propane stove with a stovetop coffee pot (with proper safety precautions) would be recommended.
 
d)microwave
This appliance alone may limit you to a sine-wave inverter. Microwave ovens use a device called a "triac" to trigger on and off cycles in the microwave. A triac is designed to sense a particular point in the curve of a sine wave (think of an escalator). Modified-sine inverters don't have a smooth rise or fall to the wave. Instead .. like stairsteps, they go straight up and straight down .. in a few steps. This leads to erratic triggering of the triac and less than predictable operation of the microwave oven. I've used a microwave on both mod-sine and true sine. No comparison... go with the true sine.
 
e) dish washer
Make dishwashing a family project if/when running on solar power. Far less power consumption; cleaner dishes; less water usage (if done properly); and less time. Nuff sed.
 
 
Suggestion: If you're not familiar with the equipment, pay a few extra $ and get some competent assistance. Wiring a utility-intertie inverter into your grid-connected home isn't a project for beginners. It often requires a licensed electrician to ensure it's done properly.  
Question: Hot water - electric or gas? If electric .. you'll need to be sure it's not accidentally a part of your electrical loads.
 
** And finally .. Trace makes some excellent inverters. So does Exeltech (Houston .. 800-886-4683). I've used both. I have an Exeltech.
 
 
Hope this helps.
 
Dan

-- Dan (DanTCC@Yahoo.com), December 05, 1998.