Auto ignition/torch control

[MadScientist267]

Looking into doing a thermostatically controlled system for the hybrid torch idea...

Need/want it to do the following:

1 - Valve control (very fine adjustments), probably opened by either friction drag, or highly geared motor pulling against a spring that continuously tries to close the valve. In the event there is a failure in control power or the fan stops, unit gets knocked over, the valve slams shut.

2 - A thermistor or equivalent overtemp sense device placed along the portion of the tube where heat would be expected to be highest in the event of fan failure or intake blockage, which would trigger shutdown.

3 - Anything other than a normal shutdown initiated by the thermostat would cause a lockout relay to interrupt power to everything until manually reset.

4 - Ignition to be carried out by a pulsing ignition coil around 5Hz (similar to a gas grill), and give up after 10 seconds if ignition is not detected (via thermistor on tube). This also triggers lockout for safety reasons.

5 - If ignition is successfully detected,  an "allowance" delay to briefly disable lockout, the fan would
start, followed by the allowance delay expiration. If anything in this phase is not in parameter, lockout occurs and the unit cannot be attempted to be operated again until manually reset.

6 - Possible integration into CO/Smoke detector as well?

7 - At first connection to power, the unit starts in lockout.

Sound viable?

Steve

[ghurd]

Dude...  I dunno about that.

Therm-anythings are likely to be far too slow reacting to do much good.

Even if they were fast enough, the propane is not?
(I have stories, but they all boil down to "propane does NOT shut Off very fast", and thats all I am sharing)
G-

[Wolvenar]

Also sounds dangerous.
IF the ignition fails,  the van turns into a gas chamber ready for ignition if the fuel to air mix is within range and there any kind of ignition source becomes available.
Gas and oil heaters have light sensors for this.
If the ignition fails after a given time the system and fuel is shut down.

[MadScientist267]

Anything other than successful ignition with unit upright and combustion chamber within proper parameter, triggers lockout which removes power from everything, slamming the valve shut via spring action, and requiring manual intervention to return the unit to operational state.

Ignition detection can be a challenge, I agree. Light sensor difficult due to the part of the spectrum and intensity. Any suggestions there?

Steve

[WooferHound]

http://www.amazon.com/Texsport-14215-Propane-Heater/dp/B000P9GZSW/ref=sr_1_3?s=hi&ie=UTF8&qid=1349302572&sr=1-3&keywords=propane+heater

[MadScientist267]

Was that retrieved from the moon? LOL

I'm tending to lean away from any commercial versions for the simple fact that the output (and therefore input) are orders of magnitude higher than what the space demands for heat. They are great and all where "leakage" is an issue, or much larger spaces are being heated, but all I end up with is lack of sleep from excessive cycling, and a prematurely empty can.

The torch was the first propane heat source that could do the job, didn't require constant adjustment or cycling, and wouldn't burn up a cylinder in a single night (two if I was lucky). Thing is of course, that valve is extremely touchy, there's no kind of regulation device, and of course a completely open, unshielded flame.

I'm looking into a shielding device of some sort, thinking double insulated. Two different size tin cans, coaxial to one another? This would at least allow a shutdown mechanism enough time to kill the flame if it gets tipped over. A cage maybe as an additional barrier too.

I'm going to tend to agree that what I'm proposing isn't the safest way to heat a space, and while I don't know up close and personally what all can go wrong with propane devices, I can imagine. The 10 second ignition thing was more of a "right off" concept than an actual number. Probably more like 3. I don't let it vent any longer than that when I'm striking it with a lighter, and I've never even smelled the funk they add to the stuff.

I obviously want to be safe about this, which is why I'm not just doing it without checking around first. Is there a such thing as a small handheld torch that has a regulator on it so the valve isn't so damn sensitive?

Steve

[rossw]

and of course a completely open, unshielded flame.

I'm looking into a shielding device of some sort, thinking double insulated.

Recent thought.

I have a "Pyropen" soldering iron. It uses a flame to start, but once the catalytic converter is hot, you extinguish the flame and the cat converts gas directly to heat with no flame.

Have you seen or tried one? Can you get one?

Mine uses butane, but I'm sure they'd work just as well on propane. They're a small, low-wattage device, might even do you.

[MadScientist267]

Actually, yes. Used to use them all the time, but found that the valves would eventually get unstable and either lack power (usually) or go wide open and leak around the valve (less usually).

That's an interesting idea though... I briefly thought of something like that at one point when I was glancing over the catalytics, one in particular. Its some kind of woven mat that has platinum dispersed through it and the same lighting/operation attributes as the irons. I wondered if the mat could be taken out and somehow used on the torch head, but I'm not really super familiar with torch venturis and didn't want to destroy a good (but useless to me) heater just to find out that for whatever reason it wouldn't work with the torch.

If you've got any ideas there...

Steve

[bj]

  As a slightly related suggestion, catalytic alcohol burners.  The fuel is usually scented, which I usually find revolting, (someone gave us one), but you can
use unscented.
  Advantage--no flame.  But they don't have ignition systems, and don't put out a whole bunch of heat.  They don't burn a whole bunch of fuel either.  Probably
take three or four to equal your torch.
  Just an early morning thought.

[Rover]

"...and while I don't know up close and personally what all can go wrong with propane devices, I can imagine"

Here is a clue

http://www.wavy.com/dpp/news/local_news/va_beach/propane-explosion-in-van



Rover

[MadScientist267]

Damn.

Well, as I mentioned, I could only imagine.

I don't wish to tempt fate on this concept, particularly with the above story in mind. I just think there has to be a way of going about this that minimizes all of the dangers associated with doing so. I understand the physics behind an explosion, seen too many up close to not have grasped it, the only difference being the fuel source. Propane hasn't made it to the list yet (thankfully).

Propane (and its counterparts) are in too wide of use to not have been tamed. Sure, it demands respect. I'm fully prepared to throw all kinds of safety mechanisms at this, as required. I would even go with another fuel if there weren't so many cons in doing so (as far as I can tell). Propane has several benefits in this application, the top three being that its readily available, relatively cheap, and most importantly, burns cleanly. It also doesn't require a complex device to burn it.

The con of being so readily explosive is, no doubt, a very significant problem. I just think there has to be a way... And while now I feel I've been handed a challenge (and therefore offered a duel), I'm inclined to beat it, but obviously don't wish to die in the process.

I've been looking at how natural gas ovens keep the gas in check, as they are the most analogous appliances to what I'm trying to do. But electronic ignition modules for them are not cheap, and I think I see why. Hence the DIY approach here.

So, how to do it... ?

Steve