Calling Stove Engineers!

I removed the natural gas manifold off so I could access the inner portion of the burn chamber and found that it is blocked by a radiator surrounding a coil of copper water pipe. So now I go to plan “B” to use the propane weed torch. In one photo see the torch head positioned toward the burn chamber containing the radiator heat exchanger.

@davidinkenai,

Okay, I might be done on the heater/HX part.

 

$119, 34,000 BTU/hour, 1.34 gpm, 10.8 pounds, 2-110 psi water pressure, includes regulator and propane hose. The “20-minute safety shut off” is slight downside, but for this app, I can set a timer on my phone. Other models don’t have the time limit, but are 22 pounds. Also, it’s the sort of thing I like I have in my arsenal of equipment and a canoeing or rafting trip, hoisting a water bag in a 10 feet in a tree (or sitting on a water bladder) would give hot showers in remote locations. And for those times, professionally, when someone calls in a panic for some toxic-waste site solution and wants it tomorrow.

So I’ll order it up and update you guys when I’ve fired it up. Size and weight are compatible with checked bags (if TSA doesn’t freak out).

Next item: a 5-gallon, 20-pounds-of-propane, (plus 20 pounds of steel) BBQ grill tank is the obvious answer and easy to borrow in the SF area. But that’s 40 pounds (although plenty of fuel for two nights of soaking). Maybe I’ll stop there. But an aluminum tank of 10-15 pound capacity would be more style points. Thing is, while this event is in CA, future uses of the heater would be back home in Alaska and once the tank is filled, I could only drive it back, not check on an airline. And they are $150-$250.

I saw a lot of composite (fiberglass? FG-wrapped aluminum?) tanks used in Iceland and when I search for that, I see 10-pound-empty tanks that hold 17 pounds of propane on Amazon for $119.

Or just use another one-pound cylinder every 40 minutes and leave them in a bucket of water so they don’t ice up. Spendy on the road ($3-4/pound = $15/gallon) if I’m not at home to refill them from bulk ($2.89/gallon).

Jul 21, 2017 at 3:16 pm

David, gut feel is that your heater may be under powered to heat the amount of water in your inground hot tub. (to heat 300 gallons (2500 pounds) of water from 60F to 104F (plus conduction to the ground, the air and evaporative losses).

Dan, I agree it is a bit on the small side.  And the longer it takes, the more losses there are.  And net output is only 79% of 34,000 BTU/hour.  So about 4 hours with no losses.  The small unit was attractive for its weight, and usability back home as a hot shower in remote settings.  For the hot tub, I’d couple it several single-burner stoves with HX pots on top of them, manually transferring the contents.

But when I read the manuals and double-checked the details, I found the overview had a typo in it.  Min water pressure isn’t 2 psi but is 20 psi.  That takes some power for a pump of that size (versus dumping water in a bucket 6 feet higher up).  So now I’m trying to research the water spigots at the campsite – distance and pressure.

But when I read the manuals and double-checked the details, I found the overview had a typo in it.  Min water pressure isn’t 2 psi but is 20 psi.  That takes some power for a pump of that size (versus dumping water in a bucket 6 feet higher up).  So now I’m trying to research the water spigots at the campsite – distance and pressure.

Not ideal, you’ll need a 12 volt battery…

http://shurflo.com/rv-products/rv-pumps/rv-fresh-water-pumps/revolution-4008-pumps/130-shurflo-revolution-pump-12-vdc-2-3-gpm

50 psi, 2.3 gallons per minute.

I found this piece interesting for my heater:

<span style=”text-decoration: underline;”></span>That’s a pretty standard burner. Looks identical to both of my large Camp Chef stoves. Keep in mind it’s low pressure so you need to reduce the pressure to 11″ WC. I didn’t look at the specs, but all of mine are 30K BTU each.

Thanks Nick. I’ll be sure to reduce it with a standard regulator. I’ll be able to place this reducer over the burner and attach it to where the 6×12″ burn chamber opening is. Things are falling in place. I like when that happens :-)

I gave the unit to my neighbor. He stripped all unnecessary parts off and mounted it over the fire ring in his yard to preheat water being circulated going into his 12 foot diameter swimming pool. He uses a dc pump to direct water from pool to heat exchanger and return to pool. He says the heater produces 112 degree water out of the hose going into the pool.

Intriguing.  He stripped away everything but the HX and left the shroud around the HX?

Am I seeing the water piping bonded to the shroud and also going through HX fins across the flue pipe?  I’m guessing the fins tube is at the tube, farthest from the flame and that the water piping affixed to the shroud/flue pipe is downstream of the fin tube?  (counter-current has the potential to be more efficient, and it subject the tubing and HX fins to less demanding conditions.

For $100-ish, it might be totally worth it to order a unit and strip out the HX section.  And then just gravity feed through it.  Or maybe leave it all together but hot-wire the water-pressure switch.

Anyone coming to Alaska in the next month?  They won’t deliver to AK, but I see no reason one couldn’t check in baggage.  Only if it’s easy, I’m in OR and CA soon enough and can bring one back.

Yes, the water piping is bonded(aluminized maybe) to the shroud.

I’m going to strip out the one I have remaining and see what it looks like without the soot :-)  Better photos coming in the future.

This is the set-up he uses with propane:

David,
Have you thought about using a large coffee percolator?  It could heat and circulate your water.  Connect the outlet to the stem of the percolator tube and the inlet to the base of the pot.  I would image that a large old fashion coffee maker would be pretty cheap.  If not, the concept of super heating water as your pump source might be interesting.  You might be able to use a big style alcohol stove like they use on the Iditarod race as a lightweight & cheap heating source.  Just a thought.

Jon,

I’ve long appreciated the elegance of some percolator set-ups.  There are some thermal solar panels that use alcohol so it boils in the tubes and collects in a higher header pipe above thereby providing enough head to circulate the alcohol through the system down to a heat exchanger.  Propane refrigerators use a percolator scheme to move fluids around without any electricity.  Heat = recirculating flow would make for a more “set it and forget” operation.

I really like the concept of an Iditarod-style alcohol stove.  Thanks!  Very light (an aluminum baking pan and a handful of FG batting).  Not a very hot flame, but that makes it tolerant of low water flow without melting soldered pipes.  Alcohol fuel is a little spendy, but there’s no heavy fuel container as with propane.  Any Home Depot has denatured ethanol and any auto parts store has HEET.  And all fuel (butane, alcohol, white gas, esbit) is expensive except for motor gasoline and bulk (refillable) propane.  Not that I’m worried about fuel expense for this event, but I pride myself on economical designs.

I’ve committed to resurrect my original backpacking hot tub from 1993 for a 20-ish-year reunion gourmet backpacking trip of the UC Berkeley Hiking Club (“Cal Hiking And Outdoor Society” = CHAOS”).

How is this little project coming along? September is right around the corner. What is your latest economical design?