Have I been destroying my CPAPs?

[SleeplessInVirginia]

My last two machines (ResMed), have had the humidifier heater fail.  I found a YouTube video on repairing this.  I don't know if this was the culprit in mine, but there is a temperature fuse under the hotplate that is spec'ed to fail at 120°F (apparently for safety).  So the water only ever gets warm, not hot.

The humidifier hotplate is very low-powered, and takes a long time to heat a full tank of water.  I've been running the hot water faucet until the water comes out hot, and filling the tank with that, figuring it would start off hot and the hotplate just wouldn't cycle on until the tank needs a little more heat.  The instructions say to use distilled water, which would be at room temperature rather than cold tap water.  I assumed it was just to avoid mineral build up, so I empty the tank each day and clean off any minerals.  It never occurred to me that the temperature of cold tap water would significantly increase the time for the tank to heat.

Any chance my hot tap water has been melting the fuse?

[cathyf]

Maybe somebody else has a better answer than me, but I will say that as a bread baker when I heat water up it stays at temperature for a relatively long time. (I use a thermometer so as to optimize the water temp for my yeasty-beasties ). Now the humidifier tank is wide and flat, and doesn't hold much, so it probably loses heat more quickly than in a 4-cup measuring cup.

The other question is what temp you keep your water heater at? I mean if your water heater is set to 120, then it's probably down at least a degree or two by the time you pop it into the machine. 130? Yeah, that's probably Not Good™

[SarcasticDave94]

Try it without hot water and see how it goes. I'm thinking it doesn't need to get really hot to create humidity to be pulled into the moving air going through the tub.

[Sleeprider]

I have used warm water, but not hot in the humidifier with no problem. The CPAP should be monitoring the temperature of the heat exchange plate, and like you said, it is not designed for delivering hot water. The limit is about 90 degrees F which is lower than body temperature. If you were thinking the humidifier was a hot water vaporizer, you will be very disappointed. I don't think what you have done reduces the life of the machine or humidifier, but it certainly results in lower heat input. I assume you have not had a failure in the fuse. If so, that is a machine malfunction, but a very uncommon problem. The fuse is intended to disconnect as a result of electrical input or short, not the temperature in the tank.

[SleeplessInVirginia]

Sleeprider, I never considered that either cold or hot tap water could have ramifications.  I'll have to open it up to check the fuse and see if that is the cause.  I'm sure its purpose is to protect against a machine malfunction, not stupid user damage, but it does that by temperature.  It's a thermal fuse that opens when the temperature exceeds 120°F rather than when the current exceeds some level.  Our water heater is set at 130°F, so it's possible that heat from the water I put in the tank caused the problem.

[Big Guy]

I just use cold tap water in my humidifier. Never a problem or issue.

[mrmagloo]

I always use distilled water from a room temp jug, so I've never used hot nor cold water. But I've never in all these years ran into an issue either. In addition to using room temp, you might want top consider distilled as well.

[SarcasticDave94]

I went by recommended distilled only for the first few months on my ASV in 2017. But even though I was living at a house with hard water, I decided to just use tap water instead. The only thing it makes a difference in is that you'll sometimes need to clean the humidifier tub with white vinegar and scrub it a bit. It'll not harm it though.

[Ockrocket]

Excessively hot water wouldn't blow a fuse.. but it may "cook" the thermostat sensor in the unit.

I don't like breathing warm humid air, so only ran mine cold.. in the end I found I was comfortable without any humidifier running at all.

[mrmagloo]

@Dave - I would imagine that if we didn't have well water it would be less of an issue. Even with a water softener it still often has an odor, so distilled is the only option here.