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I've been following this thread since I upgraded my machine and humidifier and rain-out became an issue, particularly with my HeadRest mask which I had been using since last spring. Also, with the coming of colder weather, my nose started running again due to the air temperature. (I keep the house at 60F at night.) The running nose is a stubborn issue rarely mentioned by other users.

My objective was to increase the air temperature in the hose just enough to prevent rain-out, the condensation of exhaled air in the mask and to stop the running nose. I knew beforehand that I could not tolerate breathing overly warm air, and I certainly didn't want to take any avoidable safety risks.

So, I devised a solution based on the the recorded experiences of several forum members, and I can report astonishing success with the Repti-Cable.

I'm using the 25W, 15 Foot long cable, running inside the hose from the humidifier output all the way to the end of the Breeze mask's small diameter hose, just before it connects to the plenum shell. The Repti-Cable is connected thru a Lutron lamp dimmer and a plug-in digital timer. I've removed my hose covers. I also modified an oxygen hose fitting to serve as an air-tight entry for the cable. About 8 - 10" of the heated portion of the cable is exposed outside the hose at the humidifier. It serves to let me gauge the cable's temperature by touch. It's also unavoidable when using a 6' hose, as you don't want to coil any cable inside the hose for safety reasons. There is no other exposed cable.

I plan on gluing a stop to lamp dimmer slide control to limit the power to the cable to the maximum I anticipate needing. So far, I have not needed more than the 50% setting provides. At that setting, the exposed portion of the cable is warm, but not hot, and the hoses are best described as "not cold", even with the CPAP off for an extended period. The hard plastic plenum shell of the Breeze is also "not cold". Inside the tubes, with no added insulation, the cable loses heat rapidly thru convection and radiation, which I think is far safer than the between the hose cover and tube approach. I can also inspect the hoses and cable without effort. Maximizing the length of heated hose also allows a lower cable temperature. Cleaning the hoses and cable is pretty easy without the covers.

Last night was my first night with the Lutron dimmer which provides greater power reduction than the Repti-Temp control unit I initially tried, and consequently lower temperatures. I slept straight thru with no awakenings until 3:30 AM when I was water-boarded by my rig. Seems that I had an unseen program setting on the timer which shut off the cable. Wiped my nose and mask, clicked the timer to manual-on and slept straight thru 'till 7:30. Best sleep in weeks!

Many thanks to p2pjunkie for the brilliant idea, Bert_Mathews for having the guts to put the cable inside the hose and Snooze_Blues for the valuable info on the 15 foot cable and control devices.

Despite living in Aridzona I've always had rainout issues, i can't get the dial past 2.5.

I've ordered the Repti Cable 50W - 23ft and look forward to getting it soon.

Uncle_Bob wrote:Despite living in Aridzona I've always had rainout issues, i can't get the dial past 2.5.

I've ordered the Repti Cable 50W - 23ft and look forward to getting it soon.

I have to limit my 15w repti cable bc it is way too hot for me - you better order a fire extinguisher too.

Ever consider sticking your tongue on a 50W bulb?

GumbyCT wrote: - you better order a fire extinguisher too.

FYI.....and entertainment pleasure.

viewtopic.php?f=1&t=33702&st

Uncle_Bob - I have to agree with Grumpy_CT. I'm using the 25W cable at 50% power, or 12 - 13W. With a 6' hose and an 18" (?) mask hose, I still have 8 - 10" of excess heated length, which I can just manage to keep from contacting anything. Even if you throttle down the power using a dimmer (the Repti-Temp control won't let you cut enough power), you'll have to deal with the excess cable length. As others have advised, don't coil it around the hos or coil it inside the hose or let it contact itself. Furthermore, there's no need to overdo it. 15W will solve your rain-out issue. My rationale for the longer length is to keep the mask warm to avoid c0ndensation issues from breath exhalation. With longer length comes higher wattage.

BTW, I dissected one of the cables to see if the length can be reduced. The short answer is no. I'm very impressed with the cables' construction and design and think that any modifications would result in safety compromises.

GumbyCT wrote:

Uncle_Bob wrote:Despite living in Aridzona I've always had rainout issues, i can't get the dial past 2.5.

I've ordered the Repti Cable 50W - 23ft and look forward to getting it soon.

I have to limit my 15w repti cable bc it way too hot for me - you better order a fire extinguisher too.

Ever consider sticking your tongue on a 50W bulb?

Mmm i might return it and get the 15w version or i suppose i could purchase a Lutron dimmer

sronsen wrote: BTW, I dissected one of the cables to see if the length can be reduced. The short answer is no. I'm very impressed with the cables' construction and design and think that any modifications would result in safety compromises.

Based solely upon observation, the exterior appears to be silicone, but I can't verify that in any literature.

What's inside that thing, anyway?
And what's with the elongated, bulb-like terminator at the posterior?

I'm tempted to try the "in-the-hose" configuration myself since silicone should produce FAR less phthalates than the CPAP hose. My one bug-a-boo is if something "shorts out" that produces smoke inside the hose. High heat-related accidents should have roughly the same outcome, whether the cable is inside or outside the hose: hose breach, fanning of flames, nocturnal cremation.

Inside what I too assume to be a thick silicone sheathing, is a coaxial assembly consisting, at the center, of a stranded conductor surrounded by a very flexible, thick plastic insulator around which is wound a very thin gauge (30+?) conductor. At the heated end of the cable, it's wound around the conductor at a pretty high pitch, I'm guessing 25+ windings per inch. At the unheated end, the pitch is a few windings per inch. It appears that each length is wound separately, as there are no changes other than wound conductor pitch at the heat/no-heat marking. The bulb at the end covers a crimp connector which connects the core conductor to the wound conductor. The crimp connector is actually smaller in diameter than the insulation around the core, so the bulb walls are quite thick at this point, probably to prevent any possibility of the rigid connector from piercing the insulation. Given the disparity of diameters between the core and wound conductors and their unknown composition, I don't feel comfortable cutting the end and replicating the crimp connection, even though I think I can substitute for the bulb. Cutting the other end of the heater cable is even more difficult, as both conductors would require splicing.

There's not much to short out. If, under some very strange circumstances, a portion of the winding contacted the core conductor, the result would be a shorter heated length with the same unit heating characteristics. Much more likely is that any failure would result in the breaking of the wound conductor and the loss of heat entirely.

Snooze_Blues - Thanks for agreeing that any problem with the cable bursting into flame is no worse if it's inside the hose than along side it. My point is that the cable loses heat more rapidly when placed within an uninsulated hose and it is further protected by the hose if it is left under a pillow. In any case, as you originally suggested, running at reduced power by means of a dimmer and controlling the cable with a timer are absolute necessities for safety.

Marvellous discussion! Many thanks for the technical information.

My only question would be to wonder about the intended goals of "in-the-hose" vs. "outside-the-hose" placement.

The "advantage" of "in-the-hose" placement would be warming of the humidified air itself. But if the primary goal is rainout reduction or prevention, I'm not sure what the target temperatures would be, or whether such temperatures compatible with comfort requirements. If, as I understand, the key to rainout control is whether the tubing inner wall is below the dewpoint temperature of the air in the hose, "in-the-hose" heating will help by raising the dewpoint.

The "advantage" of "outside-the-hose" placement would be warming of the tube wall itself, particularly if the heating element is covered by a tubular blanket. This may or may not significantly affect the temperature of the flowing air, which may or may not be a good thing.

By the way, I use a medical-grade thermostatically controlled "in-the-hose" humidifier / heating system at home, and an "outside-the-hose" Repti-Cable system (25w, spiral wrapped with cable-ties, covered, with dimmer switch) for travel.

Again, many thanks for the research and thoughts. Velbor

New postby Velbor on Sun Nov 22, 2009 10:31 am

My only question would be to wonder about the intended goals of "in-the-hose" vs. "outside-the-hose" placement.

In my case, condensation in the hose has not been an issue. I'm trying to address condensation in the mask and sensitivity to cold air in my nose by, as you state, warming the air. But, I really want to minimize the temperature of the air so that it doesn't feel like I'm in a hothouse. I also think the in-the-hose without any hose cover is inherently safer. The in-the-hose solution has been 100% successful, but, I never tried the outside-the-hose approach. Maybe Snooze_Blues will give us a definitive comparison?

Velbor wrote:Marvellous discussion! Many thanks for the technical information.

My only question would be to wonder about the intended goals of "in-the-hose" vs. "outside-the-hose" placement.

Velbor

My goal would be to see, empirically, if I could eliminate rain-out in my mask (CL2) at a lower wattage with, hopefully, a lower inside-the-hose air temperature to breathe. Currently, the wattage required to eliminate rain-out in my mask heats the air inside the hose close to what I find uncomfortable in the Fall and Spring, and definitely uncomfortable in the Summer. I'm consuming ~13 - 14 watts in the Fall, Spring, and Winter with minor to moderate moisture accumulation in the mask and an occasional rain-out event that wakes me. I reduce the output to ~6 - 7 watts in the Summer, resulting in random moisture accumulation and random rain-out events, and occasionally, uncomfortably warm air to breathe (we sometimes use A/C, sometimes not; bedroom temps can vary quite a bit).

I like the idea of rapid heat dissipation (for safety) when the Repti Cable is exposed to moving air inside the tube. I speculate the inside tube walls might get heated more evenly and efficiently with the Repti Cable radiating heat in all directions inside the tube as well as convecting heat into the air stream. I can only wonder if this means hotter or cooler air to breathe.

The outside-the-tube solution I'm using now would seem to depend more on convecting heated air within the hose-cover than any radiant heat (or conducted heat where the cable contacts the tube), which I'd think would be less efficient per watt and provide less even heating than radiation inside the tube.

BTW: I currently use the nightlight version (dim, red LED) of the Lutron table lamp dimmer, with the wattage continuously displayed on a "Kill-a-Watt" meter next to my CPAP machine. I also found the Repti rheostat didn't go below ~13 watts at the lowest setting, which was too high for comfortable Summer breathing.

A couple days ago I ordered a second Repti Heat Cable as a backup and for travel. I might use it to try the inside-the-hose solution, depending on how much effort is required to get it inside-the-hose with a good seal and how great the risk of trashing a hose.

SRonsen -- Can you post a photo of your modified oxygen tube connector hose penetration?

Snooze_Blues wrote:
Can you post a photo of your modified oxygen tube connector hose penetration?

Sounds dirty. Give me a day to take a photo.

It certainly sounds like we're both on the same wavelength. I don't have a watt meter, but I think I'm using the same dimmer as you and it's at about the 50% position, although I have no reason to believe there's a linear correlation to output voltage. We're both using 25W cables, but I'm using an unwrapped 6' hose to your wrapped 10' hose. Then again, some portion of yours is wrapped around the mask and all of mine is internal.

At this setting, the air at the mask is warmer than the room air, but noticeably so. Most importantly, it doesn't "feel" like I'm breathing warmer air after the air is flowing for a few seconds. (Because of the timer contriol, it usually pre-heats for some time before I start the CPAP.) I'm hoping that I can keep the dimmer in a constant position during the winter, as my bedroom temperature will stay in the 60 - 68F range, and so far I haven't needed to change the setting since I found what seems to be optimal.

I overslept this morning, later than my timer which turns off the cable. Within 15 minutes I was awash in rainout, so it surely is working. If my alarm clock fails. . .

This isn't an obsession with me. In fact, I've been on CPAP almost ten years without tinkering with anything other than some clips to keep my hose in place. However, this project has been lots of inexpensive fun with a practical benefit.

Ok. So I ordered the 11.5 ft 15w cord. I already have a lutron dimmer from another project. What other issues will I have to deal with? Is it about right at 1/2 dimmed?

Snooze_Blues wrote:
Can you post a photo of your modified oxygen tube connector hose penetration?

Here's the finished product:



Using these parts:



Cut the oxygen tube nipple off and use the resulting hole to center a 3/8" drill into the adapter body. Insert a short length of 3/8" OD styrene tubing into the adapter and glue with plastic solvent cement. The styrene tube is available at hobby stores and has a very thin wall. Insert the heater cable into 3/4" lengths of 3/8" and 1/4" heat-shrink tubing. You'll need soap and water to lubricate the bulb at the end of the cable as it's a really tight fit into the 1/4 heat-shrink. Heat-shrink tubing is available at Radio Shack , Home Depot and Lowes is small packs of assorted diameters. Insert the cable into the modified adapter and determine the required cable length. I plugged the styrene tube with a piece of polyfoam caulking backer rod, but any similar foam should work, or none at all, since the heat-shrink is probably adequate by itself. I slit the foam, placed it around the cable and forced it into the tube. Then place the 3/8" heat-shrink over the styrene tube and shrink with a heat gun. Then slide the 1/4" heat-shrink over the other piece of heat-shrink and heat it. The result is totally air-tight Cost: $5 for the adapter and $2 for 2' of styrene tubing. Everything else is incidental in my workshop.

YawnGirl wrote"
Ok. So I ordered the 11.5 ft 15w cord. I already have a lutron dimmer from another project. What other issues will I have to deal with? Is it about right at 1/2 dimmed?

I suggest that you add a timer to turn the cable off when it's not expected to be used. 1/2 dimmed is a good place to start. A little adjustment makes a big difference.

I applaud all of the ingenuity and craftsmanship displayed in this thread in the name of saving $140 for a boxed solution. You make us 'wrenchs' proud.