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Portable propane heaters, Mr. Buddy, others? Moisture issues
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61Scout
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PostPosted: Mon Jan 09, 2012 11:37 pm    Post subject: Portable propane heaters, Mr. Buddy, others? Moisture issues Reply with quote

So, this post is not to talk about various heaters and their advantages/disadvantages. That said, I was in Lowes tonight and they had a couple of Mr Buddy heaters for sale. I've heard others comment on moisture (and oxygen) concerning using these and other portables.

As I was studying the Mr Buddy it seems as though the "intake" for combustion was from underneath. My thought is that if you could control the intake to pull from the outside that one would esentially get rid of the moisture and oxygen problems. What do ya'll think?

Design wise, and not wanting to modify the heater itself necessarily... I was thinking of a more passive intake. It could be as simple as a small metal box the same dimensions as the base, Drill holes on top of the box nearest the intake to the heater. Then from the side of the box, connect a hose that leads to the outside. Maybe a panel to place in the silder and run the hose through that. In this way, one could direct fresh outside air straight to where the heaters intake is located.

Thoughts?
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Timwhy
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PostPosted: Tue Jan 10, 2012 6:16 am    Post subject: Reply with quote

Pretty sure any moisture from the heater will be caused by the exhaust. You would probably need
to bring in air for the intake and also need some way of venting the exhaust to the outside.
One way I have found to cut down on the moisture, and you won't be able to get rid of it entirely.
Is to have a window cracked open (for the heater buddy) and I use a Damp Rid canister. It collects
alot of the moisture but doesn't get it all.
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PostPosted: Tue Jan 10, 2012 6:39 am    Post subject: Reply with quote

I've always been under the understanding that the burning of the propane creates the water vapor. I don't think there's any way to stop it. The only thing you can do is to ventilate properly by cracking a few windows open (which should be done anyway).

Here's a related article:
http://www.ehow.com/about_6635338_burning-propane-water.html
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gl98115
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PostPosted: Tue Jan 10, 2012 6:41 am    Post subject: Reply with quote

There are three sources of moisture in a campervan.

Standing water evaporating (cooking, is the worst).
Combustion from an unvented heater (oxygen and propane combine to create carbon dioxide and water while releasing heat).
You sweating and breathing (when you exhale, your breath is at 100% relative humidity).

Modding the heater only addresses the second.
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PostPosted: Tue Jan 10, 2012 8:11 am    Post subject: Reply with quote

> it seems as though the "intake" for combustion was from underneath. My thought is that if you could control the intake to pull from the outside that one would esentially get rid of the moisture and oxygen problems. What do ya'll think?

The incoming air is not the problem.

The moisture comes from the flame of the heater. There is nothing you can do with a heater buddy to change the fact that heat and moisture come off the flames together.

It is not safe to use a Heater Buddy in a sealed van, you should have a window open. This will let the water vapor, and the heat, out.

Heater buddy is fine for warming your hands, but if you leave it running in a closed van, you risk death.

Do a test, run the heater in the van, with you outside the van, say for 30 minutes. Then get in the van and smell the air. I dont think you will love it.

It is as unsafe to run a heater buddy in a sealed van, as it is to cook with the westy stove, in a sealed van. Both create tons of moisture, consume oxygen, and smell unhealthy.
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ragnarhairybreeks
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PostPosted: Tue Jan 10, 2012 8:18 am    Post subject: Reply with quote

Here are some calculations i did a while back. The respiration portion is, I think, conservative.

First the unvented propane heater, lets make assumption that no CO is produced, ie the heater is working perfectly, and that there are 16 oz to the lb bottle of gas (454 g).

combustion equation:

C3H8 + 5O2 -----> 3 CO2 + 4H2O

so for every mole of propane burned, we get 4 moles of water.
molecular weight of propane = 44 g/mol

moles per 1 lb bottle = 454/44 = 10.3 moles

therefore burning the entire bottle would produce 4(10.3) = 41.2
moles of water

molecular weight of water = 18 g/mole

therefore 18(41.2) = 741.6 g of water produced.

A respectable, almost 3 cups of water, into the van when you burn a one lb bottle of propane.

Now respiration, and lets do a sleeping human...

Assumptions:
160lb human, breathing in/out 6l air/minute (reflects slower resp
rate when sleeping)
ambient temp -5 deg C (chilly van!)
70% rel humidity

At this humidity there'd be 2.4 mg H2O/l of air inspired.
Exhaled air would be heated to body temp / 100% humidity

Heat up for 49.3 mg H2O / l
"Humidity deficit" = 49.3 mg H2O/l MINUS 2.4 mg H2O/l = 46.9 mg H2O/L

At 6 L air /minute there would be 281.4 mg H2O / min expired.

This works out to 135 ml H2O over 8 hours.

Respiration minor compared to burning propane it seems, but take that calc. as very conservative. Add to both is water (snow) brought into van on boots and clothing, and as mentioned in other post, cooking.

alistair
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PostPosted: Tue Jan 10, 2012 8:32 am    Post subject: Reply with quote

ragnarhairybreeks wrote:
Here are some calculations i did a while back. ... A respectable, almost 3 cups of water, into the van when you burn a one lb bottle of propane. ...

alistair


Great info, thanks for posting!
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indytriple
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PostPosted: Tue Jan 10, 2012 8:40 am    Post subject: Reply with quote

Great info. Thanks!
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PostPosted: Tue Jan 10, 2012 8:46 am    Post subject: Reply with quote

I have a heater buddy and I have always used it with the pop top up and moisture was not a problem. Also I have a CO detector and the heater buddy has a low oxygen detector neither go off, but in a hard top I would crack a window. The problem would be fuel use, it does go through propane canisters in 4 hours. If the price is right get one.
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PostPosted: Tue Jan 10, 2012 2:22 pm    Post subject: Reply with quote

To continue on with the geekyness, let's calculate the volume of air required to burn a bottle of propane.

As Alistair illustrated above, a mole of propane requires 5 moles of oxygen. Each mole of oxygen occupies 22.4 liters at standard pressure and temperature. But, air is only about 21% oxygen, so we need

(5 * 22.4) / .21 = 533 liters of air per mole of propane.

As above, there are 10.3 moles of propane per 1 lb bottle, so

533 * 10.3 = 5500 liters of air per 1 lb bottle of propane.

The interior volume of a tintop is about

1.3m (high) x 1.4m (wide) x 4m (long) = 7.3 m^3 = 7300 liters, so it takes 3/4 of the oxygen in a tintop Vanagon to burn a 1 lb bottle of propane.
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PostPosted: Tue Jan 10, 2012 3:56 pm    Post subject: I am making power vents for my Mr Buddy Reply with quote

I have to (2) 12 volt computer fans from my old pc that I am going to use to vent the camper. I have one mounted in the fridge vent after I took out the fridge ( have a TF fridge now) and I mounted the other on the pass. side door in that intake vent. (the blue one) both are switched and run off the dash solar panel that tickle charge my second battery. this is a work in progress, I'll post some pictures when I'm done.
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61Scout
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PostPosted: Tue Jan 10, 2012 9:25 pm    Post subject: Reply with quote

Certainly lots of information to consider. I suppose a real world test must be done.

Anyway... seems to me the moisture is really the only problem. I still think my intake idea would benefit those who use a portable heater. Drawing outside air decreases the amount of inside air used for combustion and occupants.

I've personally always cracked the window open... but for sake of this discussion, let's consider a closed loop. I'm curious as to the propex design, and would love for those who have one to comment on their construction. I'm going to make the assumption that there's a heat exhanger, thus forcing the exhaust outside the van.

So let's say I've got the passive intake in place, Mr Buddy sits on top, draws air from the outside. Let's say a window is NOT cracked open. So what to do with the exhaust? A cracked window or skylight would certainly allow the exhaust to vent, but also the heat to escape...

What about having an exhaust vent on the bottom of the van? Thus the Mr Heater would draw from the outside and essentially push out the exhaust out the bottom of the van because it has no where else to go.

Does anyone know of a way to measure the oxygen and monoxide levels? I'd be willing to do a live test and record the results. I don't personally want to be the canary Confused
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PostPosted: Tue Jan 10, 2012 9:41 pm    Post subject: Reply with quote

gl98115 wrote:

533 * 10.3 = 5500 liters of air per 1 lb bottle of propane.


And just for comparison, a a 175-lb. person consumes 120 L. of oxygen during eight hours of sleep which is

120 / .21 = 570 liters of air per person during 8 hrs of sleep, which is about 10% of the air required to burn the bottle of propane.

http://www.livestrong.com/article/513676-how-much-oxygen-do-we-consume-while-sleeping/
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PostPosted: Tue Jan 10, 2012 11:36 pm    Post subject: Reply with quote

Only slightly related to the discussion, but worth noting. I recently used my Mr. Buddy heater to spend a couple nights in my LandCruiser as the Syncro isn't ready for prime time yet. I brought an indoor/outdoor thermo and duct taped the sensor to the windshield wiper. It was 16 out and I turned on the heater on low. In just a few minutes it was 60 inside. I had a window cracked and insulated panels on the windows. After a couple hours of reading, I turned off the heater for the night and it got down to 31 inside by morning - still comfortable with winter camping gear. In the morning the interior did not have a "wet" feel. Can't speak for several nights in a row or several people or the added burden of cooking. The interior volume is about 2/3 that of a Vanagon hardtop if I recall.

So the reality of winter camping means you need a heat source, but I agree with Allistair and others that there will be considerable condensation with continuous heater usage with a portable propane type. A necessary evil, I guess. There will be water vapor produced.

As for sucking in air to use in a portable heater - same thing. You will not reduce the amount of combustion-related condensation. I think the only way to do that is to use an exhaust on the combustion process, which means it would need to be surrounded by a heat exchanger. Combusted air goes back out of the van, and the heat of the exhausted air is captured on the way out and directed into the van. Doable, but the ducting and such would be quite bulky and would not be a modification an amateur should carry out where safety is paramount.

Doug
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PostPosted: Wed Jan 11, 2012 1:07 am    Post subject: Reply with quote

Propane? We don't need no stinking propane!


Link

Calculations for this are as follows:

Ingenuity + Mini Keg + Wood = HEAT

Just one's body heat in cold temps alone will make plenty of condensation. No way around it. Towels on the dash and wipe the windows regularly.

Happy heating Wink
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PostPosted: Wed Jan 11, 2012 10:06 am    Post subject: Reply with quote

No way...pretty cool! Does it keep it warm?
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PostPosted: Wed Jan 11, 2012 10:25 am    Post subject: Reply with quote

Thanks for the air consumption info!

> Vanagon air space

1929 gallons

> air [used] per 1 lb bottle of propane, in 4 hours

1453 gallons

that leaves 476 gallons of air for people.

> air per person during 8 hrs of sleep,

151 gallons.

So one propane bottle and 3 people sleeping overnight, can consume the entire volume of air in a vanagon.

Turning off the heater when sleeping is a no brainer. It means 3 people sleeping overnight will only use 24% of the air in a Vanagon.

To put it differently, it would take 20 sleeping people, to equal the amount of air a 1gal propane tank uses per hour.

> the reality of winter camping means you need a heat source

Heater Buddy is great when awake, WITH a window open, not safe when asleep.

Safe heat to sleep by requires a Propex or similar heat exchanger with dedicated intake and exhaust air from/to the outside
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PostPosted: Wed Jan 11, 2012 11:01 am    Post subject: Reply with quote

61Scout wrote:
...So let's say I've got the passive intake in place, Mr Buddy sits on top,
draws air from the outside...and essentially push out the exhaust out the bottom of the van...

You're mixing modes here. No matter how hard you think about it, the buddy heater
isn't going to PULL or PUSH anything, much less hot moist air DOWN through the floor.

There is only one sure way to keep the moisture from a Buddy heater
condensing inside the van: burn it outside.

(Not very thermally efficient, however...) Wink

Buy a Propex...
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PostPosted: Wed Jan 11, 2012 11:04 am    Post subject: Reply with quote

b00t wrote:
No way...pretty cool! Does it keep it warm?


It raises the temp about 10-15 degrees. I use it all winter long. Wink

Thanks CJ,,,, I am pretty Smucking Fart!!!
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Last edited by VanWilder on Wed Jan 11, 2012 11:44 am; edited 2 times in total
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PostPosted: Wed Jan 11, 2012 11:10 am    Post subject: Reply with quote

Wowzer, we have some very smart people on this forum. Thanks for the posts, propane geeks!

-CJ
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