System One heater turns off after 2 hours

New here... having an issue with my Respironics - REMstar Auto A-Flex with System One humidifier. I have it set to #5 but after about 2 hours the heater is no longer working. The heating plate is cold, but the heat light is on. Needless to say my throat and lips do not like this malfunction.
Any thoughts as to what may be causing the heater to stop working?
Don

It may think it no longer needs to stay on because there is plenty of humidity in the room.

Thanks LSAT, but I would think that the humidity light would turn off when the machine stops the heater. My mouth/lips are so dry when it does this. I was thinking that there may be a malfunction in the sensors for humidity/temperature?

Which model humidifier? 50 series or 60 series?
To find out look on the bottom of the blower unit for a 3 digit model number which likely begins with DS or REF.

The PR System One Auto with AFlex...will be either 550 or 560.

Unless you have the heated hose with model 560 the default humidification system is the "new S1 humidification system" which is a "smart" system in that it uses sensors in the machine to evaluate room humidity and will periodically turn the heater plate on or off to add humidity as it perceives the need. So it turning itself off could be that it simply doesn't sense the need to add more humidity...even though your mouth/throat/lips aren't happy. This "smart" mode uses less water.

What mask are you using? Are you mouth breathing? If so (even with a full face mask) the humidifier can't often supply enough added moisture to keep the mouth hydrated. It's a common problem even with full face mask users.
If you are using a nose only mask..you might even be losing precious therapy pressure if you are doing a lot of mouth breathing.

There is another mode of operation available that uses more water so there may be a chance of increasing the moisture in the air to your mask. In the clinical setup menu you can turn off the "new system one humidification system" and revert to Classic mode which doesn't use those room sensors and uses strictly heat...more water will be added to the air...so humidity delivered is higher.
It also increases the chance of rain out but that can be dealt with.

If you have a 60 series machine...there is an optional heated hose that would enable an even higher level of humidity (up to 90%) to be delivered to the mask and the heated hose itself minimizes the chance of rain out.

So you have several options but what they are depends on what type of system you have.
So that model number on the blower unit is important.

In case you have the 560...the heated hose is an option and if you are unsure if you have it already...the heated hose has a black coupling on the end that plugs into the humidifier...so one black end means a heated hose...2 white or gray ends means no heated hose.

Edit...the machine knows nothing about the moisture level that your lips or mouth needs...it only does the room humidity unless you have the heated hose.
I doubt that there is a malfunction in the machine humidifier sensors or heater...I think that you just need more moisture than your machine can deliver...either from mouth breathing or you just need more moisture.

As Pugsy said the room humidity makes a lot of difference if you have and are using the new sensor system.
Our summer home in CO has an evaporative cooler air conditioner instead of refrigerated air conditioning. (Also called swamp coolers)
For those unfamiliar with that type of AC, there are pads on four sides of the roof mounted unit. Water is pumped to trays along the tops of the pads. There are holes in the bottom of the trays that allows water to trickle down through the pads. A large squirrel cage type fan sucks air through the pads and into the house via ducts.
In low humidity areas like the CO high desert valley where our house is located they work quite well and are much cheaper to operate than refrigerated AC.

The point of all this is that I thought I had a humidifier problem last summer until I realized that we had started running the AC all day and it was pumping a lot of humidity into the air.
My System One was sensing that and not heating the humidifier very much. After it started cooling down in October the humidifier started using the normal half tank or so of water again.

Ok,
I updated my signature to show my breathing system parts.
It is a 50 Series.
A few items before I go any further: The humidity in the house is never above 50-55%, most always it is at 48%, so I do not believe that the system is sensing to much humidity. The system starts up ok with heat, but somewhere along the line it stops heating the water. The biggest issues are a dried out nose, throat and lips. The reason for the lips being dry, is because every now and then (each night) my nose stuffs up for awhile and I start breathing through my mouth. I can count on one finger how many nights I have been able to sleep all the way through, without any breathing machine / dry nose/lips issues. I would say that in the past when I used the system it lasted about 2 - 3 hours max at night. Then I would wake up and have to remove it. I am a very light sleeper so anything awakens me, I can thank the army for that part.

I am now determined to get this thing up and running, so that I can use it ALL NIGHT/EVERY NIGHT!

Any assistance will be GREATLY appreciated.

Thanks
Don

The biggest issues are a dried out nose, throat and lips. The reason for the lips being dry, is because every now and then (each night) my nose stuffs up for awhile and I start breathing through my mouth.

The answer is right here. It has nothing to do with the humidifier (well, in a way it does). If you mouth breathe with nasal pillows, all the air from your machine goes right OUT of your mouth, taking all the humidity with it. You a drying out because of this and no amount of humidification would help.

However, it may be that the humidification you start with is responsible for the congestion. Try turning your humidity DOWN to see if that's better for your sinuses. You may have to experiment with settings to find the "sweet spot" where you are getting adequate humidification but not so much that you are getting nasal congestion.

Never make more than ONE change each night, and it's better if you can give each change a few nights to see if it's helping.

People will come along and tell you to get a full face mask. That will help your therapy because you won't be losing the benefit of positive pressure when you open your mouth. But you WILL still have the dry mouth issue until you can sleep all night with your mouth closed.

Maybe somebody at the factory put in one of those wretched timers they insist on installing in coffee makers.
Nice hot coffee for the first couple hours, then . . . "Oh, we thought you were through; so we shut it off."

I think Janknitz hit the nail on the head.

I remember years ago when testing the Respironics humidifiers, we had to totally block the outflow of air from the machine. If we didn't do that, no current would flow to the heater plate. Sounds like the air coming out of your mouth may be causing enough leak to prevent the plate from heating up.

Maybe practise a few minutes concentrating on keeping your tongue on the roof of your mouth. You also may need to adjust the fit of the mask and consider using the lanolin product called Lansinoh to help the mask seal better.