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Old 12-05-2003, 12:40 PM   #1
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LP consumption by the furnace?

I just got my 2 30# tanks filled with LP. Actually I was told that they take 6 gallons each.

I have been running my main Suburban furnace these last two nights in an attempt to keep things from freezing, though I wasn't staying in it. I set it first to 60F, then 55F which is the minimum.

I have also been running my catalytic heater, the which is set up right by the door. I understand there is an issue with it, it consumes oxygen and produces carbon monoxide or something toxic. But again, I haven't stayed in it.

The temperature inside is a comfortable 50F, while outside it has been fluctuating between 23-28F at night and about 30-35F during the day. If the temp. gets above 32 during the day, I turn the furnace off.

I want to get a general idea how much LP this will consume -- I think that the catalytic heater is pretty economical, but the Suburban furnace?

I will be full-timing in it so winterizing won't be a real option, rather keeping things warm is the viable solution.
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Old 12-05-2003, 12:44 PM   #2
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I assume you are running the heat to keep pipes and tanks from freezing......

.....be aware that the catlytic heater is doing you NO good in this regard, for it is heating areas where there are no pipes or tanks.

Further, it is preventing the thermostat from activating the forced air furnace, which WILL heat the pipe and tank areas by design.
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Old 12-05-2003, 12:50 PM   #3
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Good point, I will cut off the catalytic heater.
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Old 12-05-2003, 12:59 PM   #4
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IPSO,

This may or may not be of an help, but here it goes......

I picked up my Bambi in Feb of last year. I too have 2 30lb LP tanks. I used the furnace (before it stopped working in the spring) about 25 hours of use. I also used the oven, stove and LP fridge settings. The fridge alone I would assume I have at least 100 hours on as of today.

Thing is that I still have about 1/4 of a tank of LP....I haven't even switched to the new tank since it was new.

I would guesstimate that using the furnace only at the lowest setting in cold temps would most likely use about a 30# tank of LP every two weeks maybe a bit more (depending on outdoor temps).

Keep in mind that is only an estimate.

Eric
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Old 12-05-2003, 01:06 PM   #5
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Here is a thread on the topic. It covers it about as well as can be:

http://www.airforums.com/forum...light=lp+usage

In comparing lp usage you need to distinquish whether the coach is sitting empty or occupied, and if so, by how many people. The human body throws off 400-500 btus per hour, which adds up.

Mark
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Old 12-05-2003, 01:08 PM   #6
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There are 91,500 BTU's per gallon of propane. So, if you have a supply of 12 gallons, you have 1,098,000 BTU,s of energy available. With that in mind, figure if you have a Suburban NT30 furnace, it uses 30,000 BTU of fuel an hour. You have 36.6 hours of runtime available from the 12 gallons of propane. So if your furnace runs 30 minutes out of every hour you have 73.2 hours of "real time" heat. 20 minutes an hour, 109.8 hours, "real time" etc.

Just divide BTU usage of device into 91,500 to find your run time per gallon.
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Old 12-05-2003, 02:07 PM   #7
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Pick, one thing I get a bit confused about - is that 30,000 BTU rating for the furnace input or output?

I had thought is was output but I have seen some things that make me think it is input.

At 70% or so efficiency for the furnace, it wouldn't make much difference for calculations such as yours, though.

If somebody wanted to get a real engineer's cap, they could keep careful temperature and fuel use records to determine the effective R ratings for the entire rig. Then calculate fuel use for each storm coming in ...
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Old 12-05-2003, 05:17 PM   #8
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this is my rule of thumb for propane useage.

about ten pounds per day.

with the thermostat set at 68 outside temps ranging from the teens to mid 40's.

i get about 3 days out of each thirty pound bottle.

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Old 12-05-2003, 05:26 PM   #9
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My 2 cents

Leave all of the closet doors, draws, cabinets cracked open. This helps to circulate that warm air in and around the plumbing.

Count on using at least a 30# tank per week running the furnace only at night. More if used during the day.
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Old 12-05-2003, 07:16 PM   #10
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Re: LP consumption by the furnace?

Quote:
Originally posted by ipso_facto


The temperature inside is a comfortable 50F, while outside it has been fluctuating between 23-28F at night and about 30-35F during the day. If the temp. gets above 32 during the day, I turn the furnace off.
It gets that cold in the "City of Solitude"?


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Old 12-08-2003, 11:43 AM   #11
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The BTU rating for furnaces and water heaters is always the "input."

The output at a register can vary considerably depending on how the heat may be ducted, etc.

Andy
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Old 12-08-2003, 12:33 PM   #12
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thanks Andy.

that means a 30,000 btu furnace is delivering maybe a bit over 20,000 btu heating to the rig. It also means that the furnace ratings can be directly related to propane consumption.

thanks also as to the "why" for furnace ratings being input. The losses in air delivery outside the design of the furnace makes sense.
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Old 12-08-2003, 10:00 PM   #13
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I'm full time in mine and I just emptied a 100 lb tank. I got about 5 weeks out of it. We did get some cold weather for about 3 days in the single digits. I thought the popane consumption wasn't bad. During this time I also used the water heater and stove/oven sometimes. I have AC so the fridge runs on that. I do use a small electric heater though. If you have electric, buy one. Wal-Mart, 12 bucks, "small milkhouse heater." I use mine on low (750 volts) and place it in the back compartment to keep the pipes and valves warm. It's cool to the touch and only comes on when it's set to. A fan is hard to find this time of year, unless you live in Florada but a small fan on low can circulate the air around the pipes and along the pipes for some distance. I just froze up my toilet with the heat ON. It got down to zero outside and the thermostat was set to 55. The pipes froze a little too. Also seal up your side compartments if the gaskets are bad, even if you have to put regular foam on them to seal them up. Mine had frost on the inside of the doors when I opened them up! So far I think living in the Airstream in the winter time sucks. I just winterized everything and so I'll be milk-jugging-it till spring. A problem I ran into also was the holding tanks got a little icy. Good luck.


Brian
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Old 12-10-2003, 12:19 AM   #14
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overlander76,

thanks for sharing that. I too lived in the region, near fort collins which is also next door to Wyoming. The temperatures didn't strike me as particularly cold, but definitely colder than here in the South. Though it can rarely get to low teens even here, which is what worries me. Water freezes at 32 - theoretically, in practice it seems I have some room until maybe 25-27F when I begin to worry and cut my heat on. 0F outside is an interesting or should I say challenging phenomenon.

I am glad these pipes are polymer and not old copper - last winter I had pipes in the residence burst when it hit an unusual 9F. I couldn't believe it - water stronger than thick looking copper metal pipe.

Anyway, 20 lbs / week is not bad, I thought it would be worse than that.
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