120V Reefer off Inverter?

[newhaul]

Dont know the specific numbers but a pure sine wave inverter is more efficient than a modified sine wave inverter
http://www.xantrex.com/documents/tec...-universal.pdf

[sailorchic34]

Originally Posted by kish

You state:
It would be interesting if you could provide links to this assertion.

Below are two links to the users manuals or spec sheets. Specifications are in the back

The cheap wagan 700 MSW inverter as I have is 90% efficient and uses 0.3a on standby. I did find a listing that listed the standby loss at 0.95A
http://wagan.com/media/pdf/manuals/w...ser-manual.pdf
BTW I checked the wagan 1000 watt inverter and the specs were the same.

The xantrex prosine 1000 has a peak efficiency of 89-90% and a standby loss of 22 watts or about 1.76a on standby.

http://www.xantrex.com/documents/Pow...e1000-1800.pdf

So the prosine will use up to either 2 or 5 times the load on standby idle then the far less expensive wagan. I also checked other manufacturers and while all list roughly 90% efficient, standby loss has been twice the amp load for pure sine compared to modified sine wave. As a 120v fridge is generally off for 5/6ths of an hour, standby loss becomes important.

The reason of course for the higher draw for pure sine inverters, is that pure sine wave units have far more complicated circuits with more power transistors, etc.

For a simple 120V fridge compressor you just don't need the expense of the more complex pure sine inverters. I mayself have yet to find anything that does not run on a modified sine inverter.

BTW the Xertrex inverter/chargers normally installed on boats have a 85-90 percent efficiency based on. Generally the lower the load the higher the efficiency.

[Viking Sailor]

Originally Posted by newhaul

Dont know the specific numbers but a pure sine wave inverter is more efficient than a modified sine wave inverter
http://www.xantrex.com/documents/tec...-universal.pdf

TECH DOCTOR:
Modified sine wave products are
initially more economical than true sine wave
products. In addition, MSW inverters have the
advantage when the load is a simple induction
load like a motor, or a resistive load like a light
bulb. MSW inverters easily fill this role and
typically use DC more efficiently than their TSW
counterparts. However, with today’s technological
advancements and the rapid proliferation of
sensitive electronics that require true sine wave
power to operate correctly, operators often now
prefer the TSW inverter in lieu of the more limited
MSW inverter, particularly when it can now be
purchased for roughly the same price

From your own reference.

[StuM]

LOTS of conflicting information on the intertubes about the relative efficiencies of TSW and MSW.

A lot depends on what you are using it for. If you are running any sort of motor, they are a lot less efficient running on a MSW, they will run hotter and use a lot more energy (I've seen figures up to 30% more). For some other loads, the MSW can be more efficient.

Note also that efficiency of an inverter varies with load. Peak efficiency will normally be at about 2/3 rated load and efficiency curves vary considerably. If you have two inverters, one rated at 93% Peak efficiency and one at 90% Peak efficiency, the relative figures may well be something like 80% and 85% when running at 30-50% load, so the one with lower Peak efficiency would be more efficient if that is your typical load. :-(

Taking the above into account, I really don't think anyone can realistically claim that one is more efficient that the other.

[SV THIRD DAY]

That's it....where is that unflow button.....

[StuM]

Originally Posted by sailorchic34

So the prosine will use up to either 2 or 5 times the load on standby idle then the far less expensive wagan. I also checked other manufacturers and while all list roughly 90% efficient, standby loss has been twice the amp load for pure sine compared to modified sine wave. As a 120v fridge is generally off for 5/6ths of an hour, standby loss becomes important.

The reason of course for the higher draw for pure sine inverters, is that pure sine wave units have far more complicated circuits with more power transistors, etc.

For a simple 120V fridge compressor you just don't need the expense of the more complex pure sine inverters. I mayself have yet to find anything that does not run on a modified sine inverter.

It would be interesting to compare the power draw when your compressor is running off both types of inverters. As stated in my other post, motors running on MSW run hotter and use more energy than when running on TSW. It may well be that the additional power requirement of the motor when running on MSW more than offsets the lower standby draw. YMMV

[sailorchic34]

Originally Posted by StuM

It would be interesting to compare the power draw when your compressor is running off both types of inverters. As stated in my other post, motors running on MSW run hotter and use more energy than when running on TSW. It may well be that the additional power requirement of the motor when running on MSW more than offsets the lower standby draw. YMMV

The compressor runs slightly hotter on MSW then on shore power. But that may be due to the square wave causing the windings to run hotter as they have a near zero ms rise time from minus peak to plus peak. I suspect that the AC fridge amp load for MSW and TSW would both be close to each other.

While I don't have a TSW inverter, I do have shore power, So will test that when back at the dock.

EDIT: If someone wants to send me a TSW inverter to test, I would be more then happy to run a comparison.

My thinking is that as the circuit complexity is far more complex with a TSW inverter that the TSW inverter would have an overall higher energy use on the DC side. So what we really need is both AC and DC amps and voltage to determine the overall efficiency of an inverter.

That the TSW inverter has a standby loss generally twice that of a MSW inverter, means at low loads it would have a lower overall efficiency.

[StuM]

Originally Posted by sailorchic34

The compressor runs slightly hotter on MSW then on shore power. But that may be due to the square wave causing the windings to run hotter as they have a near zero ms rise time from minus peak to plus peak. I suspect that the AC fridge amp load for MSW and TSW would both be close to each other.

If you compressor is hotter, that extra heat is a symptom of extra energy consumed, so you confirm the hypothesis. You are correct in your reasoning, it's the "shoulders" of the squares in the MSW that cause the extra consumption and I frequently see figures quoted of up to 20-30% extra power used. But I've never measured it myself.

The AC fridge load should be the same for direct mains power and TSW since they are both "true sine wave".

So a comparison of energy between direct shore power and the MSW power should give the relevant numbers (as long as the "Watt hr meter" is on the AC side of the inverter for the MSW test) without needing a TSW inverter.

Comparing those hourly consumption figures to the standby load of the inverters would tell whether TSW or MSW is overall more efficient in this specific case of primarily driving a dorm fridge.

[twinboat]

Originally Posted by sailorchic34

Below are two links to the users manuals or spec sheets. Specifications are in the back

The cheap wagan 700 MSW inverter as I have is 90% efficient and uses 0.3a on standby. I did find a listing that listed the standby loss at 0.95A
http://wagan.com/media/pdf/manuals/w...ser-manual.pdf
BTW I checked the wagan 1000 watt inverter and the specs were the same.

The xantrex prosine 1000 has a peak efficiency of 89-90% and a standby loss of 22 watts or about 1.76a on standby.

http://www.xantrex.com/documents/Pow...e1000-1800.pdf

So the prosine will use up to either 2 or 5 times the load on standby idle then the far less expensive wagan. I also checked other manufacturers and while all list roughly 90% efficient, standby loss has been twice the amp load for pure sine compared to modified sine wave. As a 120v fridge is generally off for 5/6ths of an hour, standby loss becomes important.

The reason of course for the higher draw for pure sine inverters, is that pure sine wave units have far more complicated circuits with more power transistors, etc.

For a simple 120V fridge compressor you just don't need the expense of the more complex pure sine inverters. I mayself have yet to find anything that does not run on a modified sine inverter.

BTW the Xertrex inverter/chargers normally installed on boats have a 85-90 percent efficiency based on. Generally the lower the load the higher the efficiency.

Just as a point of information,

The Xantrex, ProWatt line of PSW inverters, 600, 1000, 2000, idle at <.6 amps with 90% efficency. They don't have a charger or transfer switch.