Respironics M-series: requires pure sine power?

[DigiSage]

If I were to use an inverter with my Respironics M-series A-flex w/ humidifier, does the inverter need to output pure sine? Or not?

[OldLincoln]

I'm not an electrical engineer and I haven't slept in a motel in a long time, but I would not think so. The unit itself is DC (no wave) and the adapter uses house current which isn't pure. Also people run them directly off camping generators.

However, there are pure sine converters available if you don't have one yet. You might check out this site:
http://www.dcacpowerinverters.com/pure_ ... rters.html

[ww]

I looked up the link to the inverters. The first problem I saw is they carefully ignore the efficiency issue which is probably the most important specification. They are cigarette lighter units which is limited to 10A@12 volts or 120 watt input. With an efficiency of 80% (highly unlikely) they could only put out 100 watts (not 300 watts). I can't imagine any engineer stupid enough to design a humidifier that would require a sine wave output from an inverter. The humidifier will in turn take this beautiful (and expensive to create) sine wave, full wave rectify it to make dc and then try to filter it to heat water. How dumb! The square wave output inverters are much more efficient and much lower cost and should work on all but the poorest designs out there! In general humidifiers pull too much current and should not be used under portable conditions. A pass through humidifier pulls no power and should be used where a humidifier must be used for portable or emergency operation. It also costs less than the inverters.

[DigiSage]

Thank you both very much!

[Bearded_One]

You would be better off powering the CPAP machine directly from 12 VDC rather than using an inverter. Not only do you not need an inverter, you also don't need to use the power brick.

[DigiSage]

I do, however, need the heated humidifier. Even with the humidifier in non-heating mode, I wake up in pain from such a dry nose. The humidifier is hard wired to an a/c adapter.

[rested gal]

LINKS to Battery operation, camping, power outage
viewtopic.php?t=9682

[JeffH]

[quote="DigiSage"]I do, however, need the heated humidifier. Even with the humidifier in non-heating mode, I wake up in pain from such a dry nose. The humidifier is hard wired to an a/c adapter.

[Bearded_One]

Batteries are expensive and heavy.

If you use the heated humidifier you dramatically increase the power that you will need. A CPAP machine draws about 12 to 15 watts and a heated humidifier draws about 50 to 100 watts average.

A battery that would power your CPAP for a few nights may not power your humidifier and CPAP for even one night.

[DigiSage]

The power supply that came with my CPAP machine / humidifier combo puts out 50 watts, it is true. However, that is max usage, I use a heating setting of 1 out of 5. Even assuming it actually uses 50 watts total the entire time, the BG-C444 batterygeek setup would work for more than 8 hours:

http://www.batterygeek.net/v/vspfiles/S ... _444Wh.asp

However, as I said in a prior post, passover mode is not an option for me, I basically wake up bleeding otherwise. Not every time, but it's HORRIBLE. I'm really moisture sensitive. So it is a necessity for me.

Thanks for the help everyone!

[Collin]

I often use my RemStar M-Series powered by a Zantex inverter which supplies power through a modified sine wave.
I have used this system for several months at a time on at least four occasions.
I use the humidifier without problems.
The electrical system in use supplies power to our second home through a series of solar panels that provide 24 volt power to the inverter.

[Pineapple]

Respironics has released a humidifier that will run on DC (see akcpapguy's post viewtopic.php?f=1&t=30711&st pictures on page 2)

It used to be listed separately on cpap.com, but now I only find the one listing which states it can run on DC (perhaps they sold all the old ones) You could always email cpap.com to verify this. https://www.cpap.com/productpage/respir ... ifier.html

[feeling_better]

I do, however, need the heated humidifier. Even with the humidifier in non-heating mode, I wake up in pain from such a dry nose. The humidifier is hard wired to an a/c adapter.

The HH of M-series is run off of 110V AC. The cable is coming from the power supply box, but it is the 110v coming from the box. [There is also another internal connection between the HH and the machine, for reading the setting for the HH level.]

I have read somewhere that the HH does not work reliably if supplied from the output of many types of inverters. Here is my guess as to why: The heater may be simply controlled with a light dimmer type control. These dimmer type controls (triacs) gets messed up if the input waveform is not close to a sine wave. The output waveform shapes of different inverters vary in its closeness to sinewave. One of the posters ealier here who said the HH works for him/her may have a 'better' waveform output for his/her inverter.

[ClayL]

I spoke with Respironics technical customer service and was told that a 300 watt modified sine wave inverter would work fine.

I have operated my RemStar M Series Pro on one and it did operate properly.

I also got the following info regarding the current required from the battery

The blower and associated circuitry requires 3 amps at 12.6 volts.
For eight hours of use that would be 3 X 8 = 24 amp hours.

The humidifier requires 170 watts. Amps = watts/volts. 170/12.6 = 13.5 amps. Eight hours of use would = 13.5 x 8 = 108 amp hours. You might want to increase that by ten percent or so to allow for the inverter efficiency. 1.1 x 108 = 119 amp hours.
Total amp hours for eight hours use would be 119 + 24 = 143 amp hours.

You should be able to calculate the time it will operate if you know the amp hour capacity of your battery.
You don't want to use more than about half of the capacity if you want the maximum number of recharge cycles from the battery.

[feeling_better]

I also got the following info regarding the current required from the battery

The blower and associated circuitry requires 3 amps at 12.6 volts.
For eight hours of use that would be 3 X 8 = 24 amp hours.

The above and other power consumption you mentioned are all absolute max values, almost never needed in practice. Here is an actual measurement of the dc power for cpap portion of m-series (not including the humidifier), which I had posted a while back.
viewtopic.php?f=1&t=34881&p=298836#p298836