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Old 05-02-2015, 06:55 AM   #197
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If anyone bothers to look it up the difference between a modified sine and "pure sine" inverter is one or more extra Square wave pulses per cycle. Modern solid state devices can turn on and off during a cycle allowing more steps thus a better wave shape without a prohibitively huge filter. It is still not as clean as a generator under constant load. The fast rise steps cause heat in things like transformers and motors. If the system is designed for it there is no problem with a modified sine.
The same devices that made a "pure sine" or multi step output possible also made DC motor control much more attractive by chopping the DC and controlling the on time of each pulse. The power supplies for those systems are much more immune to input power shapes as the first thing they do is convert to DC to charge a big capacitor and go from there.
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Old 05-02-2015, 07:15 AM   #198
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Quote:
Originally Posted by nothermark View Post

If anyone bothers to look it up the difference between a modified sine and "pure sine" inverter is one or more extra Square wave pulses per cycle.
I spent the time to research the differences and here's what I had found on the first page of a Google Search.

http://www.xantrex.com/documents/tec...-universal.pdf

DonRowe.com: Frequently Asked Questions About Power Inverters

Best Inverter for an RV – Pure vs Modified and Watts

COTEK

Power inverter - Wikipedia, the free encyclopedia

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Old 05-02-2015, 04:03 PM   #199
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There are 145 coaches all made by CT Coachworks and all of them have a 3000 watt MSW inverters with 8D AGM batteries. residential refrigerators, washer/dryers, garbage disposale, 32" led televisions and microwaves.
I too am very happy with my appliances.
Good for you. I'm glad that you are a happy camper.
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Old 05-02-2015, 04:24 PM   #200
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Thanks Richard. You have made my point for me. I have been around this topic several times on this forum and in pre-RV life. A MSW inverter is FULL of noise and does not deliver the usable power many devices need. Without having been trained in electrical power, as I was many, many moons ago, and working with it in industrial applications, the common RVer has no concept. Just because the MSW inverter is running RV devices it does not mean that they are running efficiently. What most folks don't understand is that with most devices if you lower the available voltage to a device the device will demand more current. The higher current may be greater than the wires and components that pass it can handle. Thus, many devices running on MSW inverter end up having a shorter than normal service life.

It is so long ago since I used the formulas to prove my point. But I do recall working them and a square or saw tooth wave form can not produce clean, usable power unless it is filtered and fiddled with significantly. And that is the major difference between the MSW and the PSW inverters: the way the wave form is produced and filtered. The cleaner and truer the sine wave the more expensive the inverter because of what it takes to accomplish the end results.
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Old 05-03-2015, 07:06 AM   #201
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Rick
Here is a copy of Samsung's reply to my email concerning the use of MSW inverter power for their product:
Thank you for contacting Samsung.

I understand the concern with wanting to replace your Samsung refrigerator in your RV. I will be happy to assist you with your inquiry.

As long as the modified sine wave inverter emits the proper power to the refrigerator then the RF197ACBP should work in your RV.

The refrigerator needs 120v on 15amps in order to operate at specifications.

If you have any other questions or concerns please feel free to respond to this message. If for any reason the information we provided did not resolve your issue, we have various contact channels that are available to assist in resolving your concern.

For Immediate assistance with a live agent, you can chat with us here
Samsung’s Social Media Team is available to assist with providing up-to-date information or answering
questions 9AM to 10PM EST (Mon – Fri).
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Yes, I would have loved a pure sine wave, since we already knew some appliances like those with built in clocks can burn up using the MSW, but having a perfectly good MSW inverter already in the coach, I decided against replacing the MSW upon receipt of the above email. That along with several members of the Monacoers blog attesting to having no problems. Yes, I could stay up nights worrying about shortening the life of our Samsung, but I am not that anal retentive (yet). The majority of our inverter use is the two or three nights a year when we dry camp in a parking lot awaiting a reservation at campgrounds nearby. We usually have the generator running while traveling so the amount of time the Samsung actually runs on MSW power is pretty limited. Our Norcold 1200 was a very poor refrigerator that required a half dozen stops at repair shops and delayed/terminated camping vacations awaiting a fix. Coupled with its propensity to burst into flames and Norcold's cavalier attitude in hiding the number of lawsuits and the number of revised 'fixes' in those little wired boxes that did not appear to stop the fires and at times were the source of shutting down a Norcold that was not 'at risk', sure wore on me as the main safety 'officer' of our family. I am cheap, cheap, cheap, but a Samsung that works great with wonderful size that maybe doesn't last as long as it might with a $2,000 PSW inverter versus a Norcold that might kill my family seems like a pretty easy choice to make. After a year we only wonder why we didn't make the change earlier. But then, did I mention I was cheap?
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Old 05-03-2015, 08:06 AM   #202
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Well, after over 200 posts on this thread and looking at the voting statistics, it is CLERALY overwhelming in favor of having a residential in an RV versus the "normal" absorption type refrigerator used in years past.

Times are changing and peoples needs are changing so obviously the industry is changing with what they marketplace is demanding.

Companies and businesses that refused to change with the ever-changing marketplace have gone by the wayside.

Look at what happen to a well known worldwide trademark such as Kodak, refused to change and stuck with their core technology Then some years later filed for bankruptcy. It is now a completely different company.

Dr4Film ----- Richard
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Old 05-03-2015, 09:13 AM   #203
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Quote:
Originally Posted by flynnwalter View Post
Rick
Here is a copy of Samsung's reply to my email concerning the use of MSW inverter power for their product:
Thank you for contacting Samsung.

I understand the concern with wanting to replace your Samsung refrigerator in your RV. I will be happy to assist you with your inquiry.

As long as the modified sine wave inverter emits the proper power to the refrigerator then the RF197ACBP should work in your RV.

The refrigerator needs 120v on 15amps in order to operate at specifications.

If you have any other questions or concerns please feel free to respond to this message. If for any reason the information we provided did not resolve your issue, we have various contact channels that are available to assist in resolving your concern.

For Immediate assistance with a live agent, you can chat with us here
Samsung’s Social Media Team is available to assist with providing up-to-date information or answering
questions 9AM to 10PM EST (Mon – Fri).
Visit us on Facebook
Visit us on Twitter
For support by phone, you can reach us at 1-800-SAMSUNG

Thank you for being a Samsung Customer!
Samsung Online Support

Yes, I would have loved a pure sine wave, since we already knew some appliances like those with built in clocks can burn up using the MSW, but having a perfectly good MSW inverter already in the coach, I decided against replacing the MSW upon receipt of the above email. That along with several members of the Monacoers blog attesting to having no problems. Yes, I could stay up nights worrying about shortening the life of our Samsung, but I am not that anal retentive (yet). The majority of our inverter use is the two or three nights a year when we dry camp in a parking lot awaiting a reservation at campgrounds nearby. We usually have the generator running while traveling so the amount of time the Samsung actually runs on MSW power is pretty limited. Our Norcold 1200 was a very poor refrigerator that required a half dozen stops at repair shops and delayed/terminated camping vacations awaiting a fix. Coupled with its propensity to burst into flames and Norcold's cavalier attitude in hiding the number of lawsuits and the number of revised 'fixes' in those little wired boxes that did not appear to stop the fires and at times were the source of shutting down a Norcold that was not 'at risk', sure wore on me as the main safety 'officer' of our family. I am cheap, cheap, cheap, but a Samsung that works great with wonderful size that maybe doesn't last as long as it might with a $2,000 PSW inverter versus a Norcold that might kill my family seems like a pretty easy choice to make. After a year we only wonder why we didn't make the change earlier. But then, did I mention I was cheap?
Surely Samsung is talking about the fridge's supply circuit in general and not trying to say, that the unit draws 15amps @ 120vac.
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Old 05-03-2015, 09:26 AM   #204
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The topic is RESIDENTIAL REFRIGERATOR UPGRADEand inverters is a side topic. If a rr "has enough power" from a MSW inverter than the conversion is simple. Only the manufacture can define "enough power" correctly for their product. Often inverter manufactures advertize PEAK power and not sustained power output. So, when upgrading to the rr the major question is: Is my inverter putting out enough usable power for this wanted refrigerator and the other things we now have to operate simultaneously?
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Old 05-03-2015, 09:30 AM   #205
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They are referring to the amps required for compressor start up. Once it is started it draws 2-3 amps depending on the model.
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Old 05-03-2015, 07:07 PM   #206
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Residential refer compressors are designed for AC power supply. An inverter either PSW or MSW will provide adequate AC supply as long as it can provide the required amperes for the appliance ( capacitors smooth out the sign wave). I would be more concerned with sensitive electronics for type of inverter you have.
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Old 05-03-2015, 08:27 PM   #207
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Just for grins since I'm sitting in camp I thought I would read these references.

Quote:
Originally Posted by Dr4Film View Post
I spent the time to research the differences and here's what I had found on the first page of a Google Search.

http://www.xantrex.com/documents/tec...-universal.pdf

Brings up the zero crossing issue. That is kind of interesting in that the problem has always been turning off the switching device in the circuit. Crossing zero volts is a way to do it. OTOH detecting zero crossing is a problem for microprocessors as he pointed out. Good designs do not have the problem. I do wonder what kind of devices he is talking about.

I would also wonder about his graphic.

DonRowe.com: Frequently Asked Questions About Power Inverters

Other than his recommendations not much there.

FWIW his comments about laser printers are probably related to the fuser in them. They use circuitry similar to inverters to control the temperature.



Best Inverter for an RV – Pure vs Modified and Watts

Brings out the stepped sine wave inverter. That is what Wikipedia says is going on. I would concur because it is quite reasonable to Pulse width modulate the supplied DC at a high clock rate relative to 60 cycles. That is what is done to get the stepped sine wave. The output is filtered to smooth out the pulses. That will also result in the conversion losses common in todays inverters.

COTEK

Written by marketing. No technical value.

Power inverter - Wikipedia, the free encyclopedia

Spells it out:

"A power inverter device which produces a multiple step sinusoidal AC waveform is referred to as a sine wave inverter. To more clearly distinguish the inverters with outputs of much less distortion than the "modified sine wave" (three step) inverter designs, the manufacturers often use the phrase pure sine wave inverter. Almost all consumer grade inverters that are sold as a "pure sine wave inverter" do not produce a smooth sine wave output at all, just a less choppy output than the square wave (one step) and modified sine wave (three step) inverters. In this sense, the phrases "Pure sine wave" or "sine wave inverter" are misleading to the consumer. However, this is not critical for most electronics as they deal with the output quite well."

Dr4Film ----- Richard
My real point is that when folks start tossing around technical terms they should look at definitions and sources from the technical folks not the marketing department. I find it interesting that we would not believe a salesman about a motor home but we will use them as a source for technical bits. ;-)

Here is another bit of information. Anyone who learned all about this stuff before the mid 1980's has a very different picture. I fall into that category. The difference is I was back into hands on controls in the 1980's where I was building things like this. The advent of power FET transistors, pulse width modulating IC's and micro processors radically changed power conversion technology. The technology has matured with several twists since then. That is why we can even buy a "true sine inverter" that runs at better than 30% or so conversion efficiency.
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Old 05-03-2015, 08:28 PM   #208
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If you only use your MH at non hookup places like we do then it seems like the dumbest idea ever. If you only go to places that have hookups would seem to be the best idea ever. So it all comes down to what you want to use your MH for. For me if I wanted to be in a place with hookups I'd stay in my driveway
We stayed 6 nights w/o hookups (3+3). The only reson we stayed at a park with hookups in between is because we wanted to catch up with washing the clothes. If we had solar, even better. Less generator use. Love the residential fridge compared to the Nevercold.
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Old 05-03-2015, 09:16 PM   #209
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Virtually every single stick home in the desert has a 120V AC power line installed directly to it from the local utility substation. And those stick homes that have made a dedicated effort to be "off grid" have an alternative power system of wind/solar power genreationwith a very large battery bank to provide power to their A/C, swamp cooler, and refrigerator.

A motorhome with a residential refrigerator is designed to be plugged into 120v AC shore power most of it's life. Yes, they do have a generator. And yes, with a substantial investment of technology and hardware they can be outfitted with a solar power system.

If placed in the middle of the desert with no external 120v AC power to connect to, in the OEM configuration, most motorhomes equipped with a residential refrigerator will need to run the generator. That requires fuel, and wear and tear of the generator.

A motorhome with an absorption refrigerator, (setup in the same desert right next to the coach with the residential refrigerator), with a full propane tank can run for at least a few weeks, with frozen-hard ice cream in the freezer!

When that coach, (with the absorption refrigerator), drives away because it still has fuel in it's tanks, it's driver can arrange for help to have fuel delivered back to the coach who had to run the generator to keep the beer cold.
Nope. Solar is cheap and it doesn't take that much of it. There seems to be a lot of misunderstanding on what modern fridges draw for power. Mine draws less than my Visio TV. Right around .95 amps at 117 volts. We dry camp often and for the most part have noticed no difference in genny run time. Always about 45 minutes per day when we are cooking, microwave, toaster, coffee maker etc.
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Old 05-04-2015, 12:30 AM   #210
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I think this is where we see some of the confusion.

If you're in the desert, an absorption fridge will run a very long time on a good supply of propane. The generator will not be needed.

If you're in the desert, a residential fridge will run a very long time on a good solar power supply to maintain the batteries. The generator will not be needed.

We are entering a new age of technology. I think that solar will eventually replace propane. It is cleaner, more efficient and less costly to operate.

Now, if you're thinking of using a residential fridge in a system that's really set up to run a propane fridge, then of course it's reasonable to surmise that there may be some limitations.

It may also be true that we will never completely totally eliminate having propane on board. You can't beat the taste of rib eye steaks prepared to perfection on the good old propane barbeque.

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