CPAPtalk.com

Lyn wrote:

Ergin wrote:Stay away from S8 because its DC circuit is flawed and you'll have to buy
and carry around the mysterious RESMED DC-DC converter.
Despite the small size it is twice as heavy as 420 too.

I may be wrong, but I believe that there is less than 1 pound difference in the weight of the 2 machines & their h/h.

Running from DC 12V

420G: 1.54lbs
S8 elite: 2.96lbs + the weight of the mysterious DC-DC converter

All,

Seems clear to me. Don't try to use an S8 with other than the ResMed converter.

When it comes to $500+ equipment stick to the manufacturers warnings.


Cheers DSM

Not sure I'd call the design flawed though ?

[quote="Anonymous"]From cpap.com:

[quote]Weight

ResMed S8---Machine: 2.9 lbs.
Humidifier Docking Station and Unfilled Water Chamber 1.5 lbs.
Total: 4.4 lbs.

PB420e----Machine: 1.54 lbs.
Humidifier Weight (when empty): 1.76 lbs.
Total: 3.3 lbs.


Actually, you forgot the .21 lbs for the power module required by the PB420E. But, all I'm really trying to say is that the S8 isn't "twice as heavy as the 420." Then again, I'm biased. I have an S8 Vantage & love it. I have hauled it & it's not a problem.

I need clarification. If I buy the S8 Elite, do I also need to buy some convertor? Does the PB 420G have the exhalation assist?

chicagocard, PB 420G, 420S, and 420E machines do not have relief or "assist" for exhaling.

If you buy a ResMed machine, you just plug it into the wall in the U.S. You don't need a converter to make an S8 work in your house. Dunno about in other situations, like when using a battery during camping trips.

chicagocard wrote:I need clarification. If I buy the S8 Elite, do I also need to buy some convertor? Does the PB 420G have the exhalation assist?

The answer is NO if you intend to run only from regular power outlet.

If you want to run your S8 from a DC source, such as car battery, you have
to buy some kind of converter.

IAFAIK you only require the 'invertor' if you want to run the S8 range with a Heated/Humidifier.

My S8 has a 12v socket. I believe that if I plug 12v in it will run.

With an inverter you plug in the standard 115v cable.

Cheers

DSM

Just did some checking.

http://www.thecpapshop.com/product_page ... ctCatID=26

This device is called a ResMed 'converter' and is used to provide 12 v suppy from either 12 or 24v source.

Other posts talk about smoothing circuits & elsewhere there is talk of need for a pure sine wave. But 12vdc is dc not ac - a battery provides the most smoothed 12vdc of any source. There is no sine wave in a dc voltage. Onle a/c delivers either a sine wave or modified sine wave.

It appears to me (but I may be wrong) that people are confusing the role of an 'invertor' with that of a 'convertor'. The convertor appears to deliver a gauranteed 12v *dc* from either 12 or 24 and that the reason to use it is to avoid pluging the S8 into a 24v dc supply & frying the power supply.

It may also ensure that people don't plug in reverse polatrity of the DC in which case it may fry the power supply.

But I would imagine all these issues apply to all other 12v dc xPAPs?

Cheers

DSM



What is still unclear to me is that if I have a 12v battery and

http://www.internetage.com/cpapinfo/s8-12vdc-1/

I hope the above factual pictures help put the fictions to rest.

Notes

- This was a jerry rig to prove a point
- The h/h was added but *did* not run whilst the 12vdc cable was plugged in
- The S8 was running off a 12volt car battery - the 12v cable plug centre pin is negative (thus outside is +ve)


FACTS:

So the 'Converter' is an aid to lay people to get the connections & voltages right. It accepts 12 or 24 VDC in and delivers 12VDC to the CPAP. H/H won't operate while using 12VDC cable.

The 'Inverter' is used when running off 12vdc to deliver 115vac to run the CPAP and H/H.

The S8 requires a clean inverter with a pure sine wave output & won't accept a shaped or modified square wave current.

Cheers

DSM

#Update - I checked a PB420S 12v powerpack & it has the center pin of its power adapter set to positive so if anyone were to buy a powerpack (the S8 requires 2.5 amp current according to its specs) and it has the wrong polarity on the 12v plug, then the power pack or the S8 power supply will get damaged.

This applies to if the same was done to a PB420 or a Remstar running on 12v.

As a further test I got a 1.5 amp powerpack that does have a negative center pin on its plug & the S8 worked off that. But, I was only doing this as a test I would not recommend anyone else try this other than with approved parts to run their machines unless they are very confident they know what they are doing.

The Remstar AUTO I have requires 3amp at 12v and it too appears (like the PB420S ) to use a positive center pin on the 12v plug.



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CPAPopedia Keywords Contained In This Post (Click For Definition): CPAP, clean

Pulled the trigger on a 420G - arrived yesterday.

Works just fine, and I'm amazed at the small size and low weight. Can't wait to pack it in my carry on bag.

Thanks to all who posted messages.

You made a good choice.

Sometimes though it can be hard to know what to buy when so many 'experts' post totally inaccurate data about machines.

This thread was a good example of some people making statements about aspects of machines for which they hadn't any facts nor real world knowledge.

Cheers

DSM