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Author Topic: Heat options  (Read 4202 times)
belfert
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« Reply #15 on: December 19, 2010, 02:24:08 PM »

The problem with most water heaters is they don't have near the BTU capacity of a boiler.  A lot of water heaters for RVs have 1,500 watt elements which produce very little in the way of BTUs when considering heating a bus.

I'm not saying you shouldn't try this, but don't be disappointed if the results aren't great, at least in a real cold climate.
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« Reply #16 on: December 19, 2010, 02:53:30 PM »

Check out the Aqua Hot propane system there are others the market with better propane useage but even theirs are better on fuel than the diesel fired systems they manufacture and they don't stink , smoke,they are quite and don't exhaust at 500 degrees draw back 2 different fuels aboard 


good luck
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« Reply #17 on: December 19, 2010, 05:29:58 PM »

Hay Dude when you talk about 40 year things let's show a little respect!!!!!!  The 40 year old furnace are  the best ones if they are not rusty.  They are very simple to repair and have no printed circets. Just get no smaller than 30,000 BTU unit.
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« Reply #18 on: December 19, 2010, 09:30:25 PM »

Trucktramp, 30,000 BTU is about the equivalent of six portable electric heaters, if that's any help. It would take about nine KW to run all of them at one time. And a 30 amp shore cord is only 3.6 KW, so you would need a 50 amp shore setup; if you did that, you would only have about 6 KW left for everything else on your coach.

When you realize that you should not use a portable electric heater for permanent heating, it becomes obvious that another solution is needed.

Bob's use of a heat pump is one way to go, because they are now available to work down to -4 F, and on average, you should be able to get 12,000 BTU per KWH until the temperature drops into the freezing range. Some of these that I have checked on were rated to produce around 8,000 BTU at 17 F, so it has to be cold before they will not do the job.

Just for comparison purposes, one golf cart battery stores about 1 1/3 KWH, so you would be able to take from it around 2/3 KWH or about 3,400 BTU safely. On the other hand, 1 ounce of propane will produce 1,000 BTU of heat after allowing for a furnace's loss of 25%.

The big advantage of carrying a liquid fuel is the storage capacity of your energy. Trading 3 ounces of fuel for 65 pounds of battery makes sense to me. That concentrated energy is exactly why it can be dangerous if uncontrolled.

I don't think that it pays to choose a fuel based on it's price because they are all based on the BTU available from each. I think that finding a way to reduce the BTU usage by using insulation, and using heat pumps for primary heating and fuel for backup heating makes for a solid setup for cold weather and dry camping.

Good luck in your choices.

Tom Caffrey

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« Reply #19 on: December 20, 2010, 10:24:10 AM »

The problem with most water heaters is they don't have near the BTU capacity of a boiler.  A lot of water heaters for RVs have 1,500 watt elements which produce very little in the way of BTUs when considering heating a bus.

I'm not saying you shouldn't try this, but don't be disappointed if the results aren't great, at least in a real cold climate.

  If I were starting from scratch building a Bus, I would rather shoot myself than use RV equipment. There are shorty residential electric water heaters, but there are also small fuel oil boilers that would easily fit in a bay. Better would be a pot type oil burner boiler, and gravity heat. The idea would be to use shore power in the park, engine heat on the road, and boondock with as close to zero electrical load as possible. If you trade a little furnnace efficiency for lower electrical loads, not needing to run the gen to charge batteries, etc., the actual net loss/gain could come out much higher.
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« Reply #20 on: December 20, 2010, 05:21:41 PM »

Not trying to muddy the waters here (well, ok, maybe just a little), has anybody considered something like these?
Eden Pure Heaters

It seems I read a lot of discussion about these not too long ago, some think they are good, some not, but it is a heat source. Any experience with this type of heater and are they adequate to use for heating a bus? You could also use it as a nightstand and/or small end table by your sofa, so they would serve double duty.  Smiley

Mike
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« Reply #21 on: December 20, 2010, 05:40:47 PM »

I've got a couple of these built in under the cabinets:

http://www.ronthebusnut.com/detailDisp_10032.html

They probably would be running full time at 18 degrees and not keeping it very warm, but they are great to take the chill off in the morning or when you are not paying for the electricity.  Regardless of what you choose, diesel or propane, you might want to consider some type of electric heating as a backup in case you are out of/low on fuel, or have a problem with the main heater....

Steve
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Sean
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« Reply #22 on: December 20, 2010, 05:43:42 PM »

 If I were starting from scratch building a Bus, I would rather shoot myself than use RV equipment.

Not to start a debate (but it will, I'm sure), you are actually required by law to use RV-approved equipment for certain systems.  For example, inverters, converters, and generators must be "listed for use" in an RV.

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There are shorty residential electric water heaters, but there are also small fuel oil boilers that would easily fit in a bay. Better would be a pot type oil burner boiler, and gravity heat. The idea would be to use shore power in the park, engine heat on the road, and boondock with as close to zero electrical load as possible. If you trade a little furnnace efficiency for lower electrical loads, not needing to run the gen to charge batteries, etc., the actual net loss/gain could come out much higher.

It's not a "little" furnace efficiency, it's a lot.  You just can't completely combust diesel without atomizing it under pressure and forcing air into the combustion chamber.  Modern diesel boilers and furnaces achieve efficiencies in the 90s -- gravity-feed oil burners are on the close order of half that.

When you do the math, the tiny amount of energy required to pressurize the fuel and force air into the chamber is de minimis compared to the fuel energy wasted by not doing so.

Not trying to muddy the waters here (well, ok, maybe just a little), has anybody considered something like these?
Eden Pure Heaters

Snake oil.  Resistive/radiant electric heat is ~100% efficient -- this device is no better than any other electric heater on the market.  About the only thing any given electric heater can do better than any other is distribute the heat where you want it.  That's a matter of preference, so "better" is subjective.  If you want heat directed in one place or towards an object, a radiant model with a parabolic reflector will seem to be best.  If you want even heat with no hot spots, one with a good circulating fan and diffuser will seem best.

This unit provides the same 5 kBTU/hr for $300 that a $12 unit from Wal-Mart will provide.  Period.  Save your money and buy a couple of decent compact models for $20 apiece.  You could go through a dozen of them and still not spend what one Eden Pure will cost you.  FWIW.

-Sean
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« Last Edit: December 20, 2010, 05:48:47 PM by Sean » Logged

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« Reply #23 on: December 20, 2010, 06:07:43 PM »

I run 2 wave8 propain heaters in my mc5 and it stays between 60 and 80 in the snow I run them on a 10 gallon propain tank and have left them running for 5 days straight and never run out of propain Amazon have the ceepest price JPULLEN
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« Reply #24 on: December 21, 2010, 08:30:52 PM »


It's not a "little" furnace efficiency, it's a lot.  You just can't completely combust diesel without atomizing it under pressure and forcing air into the combustion chamber.  Modern diesel boilers and furnaces achieve efficiencies in the 90s -- gravity-feed oil burners are on the close order of half that.

When you do the math, the tiny amount of energy required to pressurize the fuel and force air into the chamber is de minimis compared to the fuel energy wasted by not doing so.


  I dont believe you looking at this the same way that I am.

  Lets say I need 20K BTU of heat. Lets use your figures that a pot burner is only 50% efficient. From a gallon of diesel we get 145K BTU. At 50% efficiency, I would have to burn 40K BTU to get 20K BTU out. If I dont need any other energy to use that heat, that is the total cost.

  The smallest motor ive seen on a fuel oil burner atomizer pump is 1/4 HP. 1/4 HP is 186 watts out, at 90% efficiency its drawing over 200 watts load. Then you have the ignitor transformer, between the two components you could easily have over a 1000 watt draw, and you would kill batteries in no time. Either way youll be running the gen or the engine sooner or later. And then you have the noise.

  If have to run my generator to operate the furnace, and my Gen burns a minimum of about 1/3 gallon diesel per hour doing almost nothing, that adds an additional 45K BTU to any efficiency equation. If im burning 85K BTU to get 20K BTU out, I achieve an effective efficiency of only 23%. Even using a 95% efficiency oil burner, if I have to burn 65K BTU to provide 20K BTU of heat, I only reach 30% efficiency. In either situation, 50% is much higher.

  When they issue an RV plate for a bus, they generally only ask if it has a crapper, a sink and a fridge. I have never heard of any required inspection or any requirement to use specific RV equipment, or any particular product for that matter, any particular heating system, specific manufacturers, etc.. AFAIK, Manufacurers that produce and sell RV's commercially are under different standards than DIY'rs. I have seen homebuilt Buses with everything from pot belly wood stoves, to electrical wiring hung like Christmas tree lights wire tied to gas lines, and everything in between, etc., etc.. If there were any laws or standards everyone was supposed to be following, I havent heard or seen much of it.
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Sean
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« Reply #25 on: December 21, 2010, 09:41:50 PM »

  I dont believe you looking at this the same way that I am.

Clearly not.  Let's see where:

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  Lets say I need 20K BTU of heat. Lets use your figures that a pot burner is only 50% efficient. From a gallon of diesel we get 145K BTU. At 50% efficiency, I would have to burn 40K BTU to get 20K BTU out. If I dont need any other energy to use that heat, that is the total cost.


Well, first off, 20,000 BTU is a tiny amount of heat.  Unless you actually mean 20,000 BTU/hr.  I get that much heat out of my diesel boiler in just half an hour, and I can't keep the bus warm very long on just a half hour of boiler run time.

So let's say you mean 20,000 BTU/hr.  My boiler would run less than 50% cycle to do that and would use about 0.17 gallon of diesel.  So if you had a non-electric furnace that was only 60% as efficient, you'd be using an extra tenth of a gallon per hour.  That can make a lot of electricity to run the efficient pressure pump and fan in a modern marine/RV boiler like a Webasto or Espar.  If you ran that heater for ten hours, that would be a gallon of diesel, and with a typical RV generator you can easily generate 15-20 kWH of electricity with that.  That's enough to run my whole coach for two days, including the boiler.

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  The smallest motor ive seen on a fuel oil burner atomizer pump is 1/4 HP. 1/4 HP is 186 watts out, at 90% efficiency its drawing over 200 watts load. Then you have the ignitor transformer, between the two components you could easily have over a 1000 watt draw, and you would kill batteries in no time.


Umm, my 45,000 BTU/hr boiler system draws perhaps 100 watts when it is running, so I don't know where you are getting your numbers.  Maybe from a residential system?  I mean, you are off by an order of magnitude here.  And this is not theoretical -- I live in my bus full time and when it is below freezing I run the boiler plenty, and the batteries are just fine with it.

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Either way youll be running the gen or the engine sooner or later. And then you have the noise.


Well, OK, if your goal is to never have to listen to the noise, then wasting diesel is the price you'd pay for that, although I would think in that case LP would be a better solution, as the pressure is conveniently provided for you.  Direct-burn LP heaters are very efficient.  I will also point out that there are other ways to charge batteries, and generators can be made silent or nearly so, especially the small one you would need for this purpose.  And "sooner or later" can be as late as you want -- that's what batteries are for.  We need to run our generator an average of one hour per day, but a more efficient generator could halve that average.

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If have to run my generator to operate the furnace, and my Gen burns a minimum of about 1/3 gallon diesel per hour doing almost nothing, that adds an additional 45K BTU to any efficiency equation.


Well, the trick is not to run the generator when it is doing almost nothing.  As I said earlier, a typical RV generator can produce 15 kWH from a gallon of diesel.  If you can't use that energy while the unit is running, then you need to be storing it in batteries.

Your argument here seems to be that you have a really inefficient generator/charger setup and/or insufficient battery capacity, and therefore it makes sense to make up for it with an also inefficient diesel heater.  Although I suspect it is really just that you are seriously overestimating the electrical needs of a diesel boiler.

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If im burning 85K BTU to get 20K BTU out, I achieve an effective efficiency of only 23%. Even using a 95% efficiency oil burner, if I have to burn 65K BTU to provide 20K BTU of heat, I only reach 30% efficiency. In either situation, 50% is much higher.


Again, I don't believe these numbers as they just do not jibe with my real-world experience.  In sub-freezing weather we burn perhaps three gallons of diesel per day in our boiler, and we use about another half gallon per day to keep the batteries charged; even then, the boiler accounts for a tiny fraction of that charge and our generator is only half as efficient as it should be (it's way too big).  But even if you assumed that entire half gallon was necessitated only by the boiler, that's 3.5 gallons, compared to roughly 5-6 gallons to get the same heat from an unpressurized system.

Quote
AFAIK, Manufacurers that produce and sell RV's commercially are under different standards than DIY'rs.


Sorry, this is not correct.  The NEC is law in all 50 states and has specific provisions applicable to RVs, whether you do it yourself or not.  NFPA 1192 has similarly been adopted by most states and applies equally to DIY as to manufactures.  Remember, the code is not just there to protect you, but also your neighbors, passengers, service personnel, and even the rescuers who might have to come into your rig.

Where you are correct is that there is almost no enforcement.  And yes, I too have seen hokey DIY coaches that wouldn't pass inspection by my grandmother let alone a code enforcement official.  But I've also seen DIY home additions with the same problems -- just because someone did it and got away with it does not mean it is legal.

As is often the case in such matters, no one will be the wiser if you don't follow the codes, right up until someone gets hurt or killed, and the lawyers get involved.  At which point your willful neglect to follow the established codes can incur civil penalties and even criminal charges.

That particular debate, however, is very old ground on this board -- search the archives.  Many opinions on both sides.

I think it behooves you to take a closer look at where your numbers are coming from before dismissing modern heating appliances out of hand.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #26 on: December 21, 2010, 10:46:28 PM »

Forgot to mention in my last post that if you really want to go with gravity-feed diesel and no electric power, the Dickinson units that I mentioned way back up several posts ago are probably the most efficient.  They make a gravity-feed unit that, once started, uses some of the heat to vaporize the diesel at the burner.  The unit does have a 12-volt draft-assist fan, and with the fan running and proper draft they are about 84% efficient.  They work without the fan, too, at some penalty to efficiency.

They have the same drawbacks that all hydrocarbon-burning appliances located in living quarters have, which is that they need a proper fresh air supply.  They also need positive pressure in the cabin and a good draft up the flue, which needs to go direct to outside somehow.

On the plus side they have a sort of homey fireplace appearance.

-Sean
http://OurOdyssey/BlogSpot.com
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Nick Badame Refrig/ACC
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« Reply #27 on: December 22, 2010, 02:58:01 AM »

Hi Sean,

Again, you are spot on with all your points. I wish I had the time to put more info into words as you do so well.

I'm glad we have you here!

Thanks Sir! Wink
Nick-
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« Reply #28 on: December 22, 2010, 07:24:20 AM »

No fair using Latin, though - "de minimus"   Shocked  What does de minnie-mouse have to do with heaters, I mean she and Micky live in Florida!

OK, real stretch, I am just in an oddly good mood for one, give me a break...   Grin
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« Reply #29 on: December 22, 2010, 08:05:49 AM »

O sibili, si ergo
Fortibus es in ero.
O Nobili! Demis trux
Vat es inem,
Caus in dux.


-Sean
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