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[Equipment] ResMed H5i humidifier heating query
Advice, please, about my ResMed H5i humidifier.

With the humidity level set at 2.5, the unit takes 20 minutes to warm up, then the display illuminates with the message Warming Ready, and then there's ten minutes before it displays Cooling Down.

So, I fit my mask during the Warming Ready stage... but when I wake up after five or six hours, the heating element is cold.

Shouldn't it remain warm throughout the operating period, or would it need a higher humidity level setting for that?
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I expect the element to maintain warmth throughout the night to prevent heat losses from evaporation and radiant cooling from the chamber. The humidifier usually enters the cool-down mode at the end of the session after the machine shuts down, but enters a low-power and volume cool down mode. Your problem sounds like a malfunction.
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In part, I am going to disagree with part of what my friend Sleeprider said.  The H5i, at most, uses around 20 Watts.  The heater is regulated by pulse width modulation of the current to the heater.  Switching is the most efficient way of controlling the heater.  A setting of 2.5 is a bit on the low side.  Of course the setting is an individual choice; and depends on the individual and where one lives.  Southern California has a mild climate; however, I run my H5i at 5.0.  It uses most of the water in the tank in one night.  The primary source of heat dissipation from the heater is the water acting as a heat sink -- coupled with evaporation of the water.  The only time my heater plate has gotten warm to the touch was the night I forgot to fill the tank.  (We have named that mistake after one of the Monitors; but it has not been adopted into the Wiki as of this time.)

The confusing part of the OP is "...and then there's ten minutes before it displays Cooling Down."  When is this happening?
Normal operation is for one to shut down the machine in the morning; and the machine will indicate cool-down.  It that state, the heater is not powered; and the blower impeller blows air gently through he humidifier.

Abnormal would be to start warm-up, reach ready, start therapy, and have the cool-down message appear 10 minutes into therapy.  That would indeed indicate a malfunction.  

I do not use the warm-up feature, so I have not tried letting it warm up; reach ready; then not start therapy.  It may be programmed to switch to cool-down if therapy is not started withing X minutes of reaching ready status.  If that's what's being observed, then it may be a feature of the machines firmware.

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JustMongo passed away in August 2017
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I actually think we agree. The warmth of the heating plate can be barely perceptible, but the cool down cycle being indicated when the humidifier is on, seems like a malfunction. I never had a S9, so you're a better judge of normal operation...thanks JM.
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Actually, now that I read all these comments, I see that a clarification is in order. As one who starts the warm-up cycle and then picks up a book... the warm-up takes about 20 minutes, then it says Ready for about 10 minutes. If I am engrossed in my book, it will then display Cooling as I continue reading... all quite normal, presumably to save power. It starts warming again as soon as I stop reading and put on the mask. Or I can start the Warm-up for another 20 minutes...
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The Cooling Down is displayed if one hasn't started to use the CPAP within 10 minutes of it warming up. Switching the heater back on, it will then take a further 20 minutes for it to display that it has warmed up, even if it had only been cooling down for a few seconds.

So, I start using the CPAP within 10 minutes of it having warmed up, and the heating element is definitely warm at that point (can be felt underneath the unit), but cold when checked straight after waking and switching off.

I'll try a higher humidity setting tonight. The room temperature is about 19C/66F.
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The H5i, as Mongo says, is regulated and so may not feel warm all night long and specifically, depending on conditions may not feel warm in the morning. That is why the test method to find out if the heater is working is to put it in warm up mode for 10 minutes and then carefully check for heat.

Best Regards,


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PaytonA passed away in September 2017
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~ Rest in Peace ~
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Hi Ceedy,
WELCOME! to the forum.!
I wish you good luck with your CPAP therapy.
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Thank you, trish6hundred. I've been a user for nearly two years now, following CSA triggered or worsened by a beta blocker. I still see a few CSA events recorded, but it's mainly OSA. I don't snore but my nostrils seem to be a problem.

I increased the humidity setting from 2.5 to 4.0 last night, and the heating element was at about body temperature when I woke. The ResMed video at YouTube, titled "Is your H5i working?" explains that the unit has temperature and humidity sensors, so the room conditions may mean that it appears not to be working correctly.  I had my annual Sleep Clinic appointment recently, which is a meeting with a technician, and my concerns weren't fully addressed, just that the heating occurred at the start of a session.  The year before, when the humidifier was issued, I'd been told to keep the humidity setting at 2.5.

Thanks, all.
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