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Old 02-22-2015, 01:55 PM   #1
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More Questions on Inverters

There is another thread regarding inverters and I didn't want to steal the thread, but I'm trying to wrap my head around inverters and their use and design. A few questions for those of you with experience dealing with inverters.

1. I see "Modified Sine Wave" and "Pure Sine Wave" inverters listed. Whats the difference. The Pure Sine Wave units seem to be a good bit more expensive for a comparable output. Does it matter which we use in an RV for powering TVs, DVDs, radios, etc? Not looking to power any heavy loads, just some entertainment system items.

2. I see a number of "portable" units listed in the 600 - 1000 w range. They advertise you can plug into a 12v power outlet. I was thinking maybe the easy way to get power for the front TV would be to just hit a 12v hot wire in the fuse panel or elsewhere under the dash, hardwire and mount a 600 w unit in the area with the DVD player. It has 2 outlets. I could use one for the TV and one for the DVD. (I'm assuming my TV and DVD don't draw more than 600 w, I'll be verifying that before doing anything).

3. Am I correct in my thinking that as long as the TV and the DVD are powered by the inverter, there is no need to switch them over to gen power or shore power? If gen is running or plugged into shore power, then the batteries would be receiving a charge. It really wouldn't make any difference whether they are powered 100% of the time by the inverter, except I guess for wear and tear on the inverter itself.

4. Are the larger units that are hardwired into the basement area usually automatically switched off and power rerouted to the outlets from the gen or shorepower when either of those power sources is available? Or is the inverter always furnishing the power for the connected outlets and just relying on the shore power or generator to keep the batteries charged as I mentioned above?

Thanks your your responses. I have no experience with inverters, but would like to power my TVs and DVD players without having to run the generator or hook up to shore power.

jt
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Old 02-22-2015, 02:11 PM   #2
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Hi harleyjt,
1. The attached file explains modified vs pure sine wave inverters better than I can explain it.

2. If you coach does not have an inverter, what you describe is a method of providing the 120 VAC power. You will need to be really careful on where you tap into the 12 VDC (should be coach powered not chassis powered battery powered) and the size wire you use. These inverters are made for autos where one wants to run 120 VAC accessories.

3. You are correct.

4. The hard wired inverters have a transfer switch built into the inverter. They have a pass through feature that when external 120 VAC is available the inverter goes into pass through hmode and is not supplying the AC power.
Attached Files
File Type: pdf Modified And Pure Sine Wave Explained.pdf (110.0 KB, 17 views)
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Old 02-22-2015, 02:14 PM   #3
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You need to watch the current draw. 600 watts will pull about 50 amps @ 12vdc.
This means you would need 10 gage wireing to the inverter. If you plan on hard wireing the AC side be very careful because with MSW (Modified Sine Wave) inverters have voltage present on the neutral line do their design. It is much more efficient to use an inverter that has an internal transfer switch. It is much more efficient to run 120 VAC over longer distances 600 watts at 120 VAC is only 5 amps.
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Old 02-22-2015, 02:18 PM   #4
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Hi Harleyjt.

My first blog post will be about inverters/chargers, batteries and power sources. But as that is a large topic I will help answer these questions right now for ya.

1) Modified Sine Wave (MSW) or Pure Sine Wave (PSW) Inverter differences.
Okay so to the basics of Alternating Current power. 120 volt AC power (VAC) is a sine wave going both directions (positive and negative) 60 times per second. (60 Hertz) These waveforms are created by AC generators and the magnets and coils pass one another and alternate the magnetic fields. DC power is all on one side and is flat. AC powered electronics rely on this fluctuation. A MSW inverter recreates this wave form digitally. If you were to look closely at the wave form on a Oscilloscope you would see stair cases walking up and down the waves. For most everything these wave forms work fine. But occasionally you will see an appliance that does not like them. For example, Newmar is using the PSW inverters in all their diesel pushes now because the residential refrigerator ice machines do NOT like the modified sine waves. Pure sine waves are nicer but not required. Just be aware that occasionally you will find something that doesn't play nice with them.

2) When choosing the inverter you would like to purchase consider the "duty cycle" that you will be using the inverter at. Inverters can and will exceed their rating but can only do so for short periods of time. This allows extra power for high current draw startup. Consider how much power you will need and for how long. Also consider how many 12 volt amps you will need to feed the inverter or you will likely be changing the fuse frequently.

3) As long as your 12 volt system is charging you will be fine to run the tv and dvd from the inverter. Though if you go with a more robust system (IE: the Magnum MM612) there is an A/C passthrough if you are on AC power. This will eliminate the need to run the inverter at all times.

4) This is answered in line 3. The hardwired systems are much better and will last for years to come whereas the portable units tend to be a bit flakey in my opinion.

I hope this helps.
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Old 02-22-2015, 02:19 PM   #5
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Quote:
Originally Posted by harleyjt View Post
There is another thread regarding inverters and I didn't want to steal the thread, but I'm trying to wrap my head around inverters and their use and design. A few questions for those of you with experience dealing with inverters.

1. I see "Modified Sine Wave" and "Pure Sine Wave" inverters listed. Whats the difference. The Pure Sine Wave units seem to be a good bit more expensive for a comparable output. Does it matter which we use in an RV for powering TVs, DVDs, radios, etc? Not looking to power any heavy loads, just some entertainment system items.

2. I see a number of "portable" units listed in the 600 - 1000 w range. They advertise you can plug into a 12v power outlet. I was thinking maybe the easy way to get power for the front TV would be to just hit a 12v hot wire in the fuse panel or elsewhere under the dash, hardwire and mount a 600 w unit in the area with the DVD player. It has 2 outlets. I could use one for the TV and one for the DVD. (I'm assuming my TV and DVD don't draw more than 600 w, I'll be verifying that before doing anything).

3. Am I correct in my thinking that as long as the TV and the DVD are powered by the inverter, there is no need to switch them over to gen power or shore power? If gen is running or plugged into shore power, then the batteries would be receiving a charge. It really wouldn't make any difference whether they are powered 100% of the time by the inverter, except I guess for wear and tear on the inverter itself.

4. Are the larger units that are hardwired into the basement area usually automatically switched off and power rerouted to the outlets from the gen or shorepower when either of those power sources is available? Or is the inverter always furnishing the power for the connected outlets and just relying on the shore power or generator to keep the batteries charged as I mentioned above?

Thanks your your responses. I have no experience with inverters, but would like to power my TVs and DVD players without having to run the generator or hook up to shore power.

jt
harleyjt
My coach, (as built by Safari Motor Coach in '96), has a 2000 watt MSW inverter/charger, however I seldom use the inverter function.

In '02 I added a 400 watt MSW inverter up in my entertainment center with which I can, (and do), power my 24" LED TV AND my DirecTV receiver AND my DVD player.... ALL at the same time..... when I have no generator or shore power.

Mel
'96 Safari, 137k miles
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