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[F7JC]

I know their are a ton of factors with this, but I will ask anyway.... I have a Hawken 1100 and the last few weeks I load this thing hardly twice a day.  Once a day if it is in the 40's and twice when its in the 30's.   So far I have been pleased with the wood consumption.   
The past week end we hit the 20's, couple days went by and I still loaded twice a day.  The last two nights in the low twenties I have been getting 6-8 hour burn times.... Not real happy about it,  I dont want to load it in the middle of the night and nobody is home in the middle of the day. I do not understand why it suddlently started sucking the wood. 
My theory is because my bubble wraped, pvc sleeved pex lines are only buried 2 foot max and the ground started to freeze robbing the heat from my setup.   I have also noticed the fan in the house kicked on every 15 minutes at night, maybe its the cheep plumbing or maybe its the ineffecient house.  Any ideas??

[willieG]

the fan kicking on that often is a little high i think. on the other hand are you sure your bubble wrapped lines are dry, could your pvc have a bad joint and be letting water in and surrounding the bubble wrap. if your lines are dry, only being burried 18 inches shouldn't affect it so much that you would go from loading twice a day to three times. what did you heat with before this stove? what were your fuel bills for a winter with your last furnace.
has something esle changed? are you sure yoru damper is operating properly and not opening too far and you are losing too much heat up the stack?  there are many things that could h ave changed, you need to investigate them all. there will be more ideas come for you to consider..please do consider them all and do your best to check them all out.

[woodman]

I will try to help if I can as I have basicly the same owb. First we need to know more info. What exactly are you heating? How big is it and how warm are you keeping it? What did you heat with before and how much fuel did you use in a comparable month? What kind of wood are you using and how long has it been seasoned? How deep is your water table and have you noticed any snow melt above your underground pipe. How full are you filling your owb? When the draft fan is on are you getting any visible smoke from the stack or is it just heat waves?

I am heating a 3000 sq ft house plus dhw. My boiler is a he1000 (same size as yours). I live in Michigan (cold). My underground pipe is logstor. I keep the house 73 when we are here 71 when we are not. When it is in the teens my house blower cycles probably every 15-20 minutes for about 5-7 minutes. I have a 140,000 btu water-air hx. When temps are in the teen's at night 20's during the day I have no problem going 14-16 hours before putting more wood in. I normaly put in half loads twice in 24 hrs.

As far as I am concerned, 6 hours between fills is unacceptable and should not be occuring unless you are grossly undersized for your heating demand. Without knowing anything more I would be leaning towards your undergound line's as this is where a tremendous amount of btu's can go if things are not perfect. You need to measure the temp at the line before the hx to see what your ground loss is. This however is easier said than done unless you have a temp gauge installed in the line where it enters the house. Good luck and keep us posted. 

[MTJAG]

I have a CB5036 with Thermopex install about 1 foot in the ground.  My wood burning when the temps were in the 30's at night doubled when we started having consecutive nights in the single digits.  I was taken back a bit by the amount of wood increase.  Recently, we've had lows below zero and I typically load my unit up around 4:30pm just at dark and check it in the morning around 6:30 just before daylight.  The first night our temps dropped to -12 degrees and I had my OWB about half ful.  The next morning I heard my propane heater kick on, meaning my OWB was out of wood.  I went outside to find the temperature down to 154 and just white ashes.  That evening I loaded it full, which I hadn't done before.  The low for that night was -7 degrees and the next morning I found the OWB with some wood still to burn, but mostly gone.  That was nearly a 14 hour burn at a overnight low of -7 degrees burning mostly aspen with a couple of pieces of ponderosa pine. 

My point of laying that out is that our stoves are probably fairly close in performance.  Thermopex line is probably the difference in efficiency compared to your bubblewrapped pvc lines.  I used some bubblewrap foil insulation beneath my infloor heat water pex between floors in my house and it is not a very efficient form of insulation.   You can actually lay Thermopex on the ground for awhile and not loose any heat with freezing weather, unless of course it is well below zero.

[martyinmi]

 MTJAG and woodman
 20* earth temperatures won't bother Thermopex much at all. My stone foundation is right at about 2' thick, so I ran mine through a window to supply my heat exchangers, and the 4' of exposed line never even melts snow unless the sun shines on it. I wrapped one layer of foil backed(or faced) bubble wrap around my side arm heat exchanger and shot the temperature and it was around 115*-120*, so I added another wrap and it is still about 10* warmer than than the ambient temperature of by old basement. That stuff is better than nothing, but it's not Thermopex.

[MTJAG]

MTJAG and woodman
 20* earth temperatures won't bother Thermopex much at all. My stone foundation is right at about 2' thick, so I ran mine through a window to supply my heat exchangers, and the 4' of exposed line never even melts snow unless the sun shines on it. I wrapped one layer of foil backed(or faced) bubble wrap around my side arm heat exchanger and shot the temperature and it was around 115*-120*, so I added another wrap and it is still about 10* warmer than than the ambient temperature of by old basement. That stuff is better than nothing, but it's not Thermopex.

That's a good indicator of the difference between foil backed bubble wrap and Thermopex.  F7JC do you have a thermometer on your inbound OWB water pipe in the house?  If so, what is the temperature variance.  On my application, the temperature on the OWB at 175 is nearly the same or maybe a degree or two cooler.  Woodman suggested that you message that before your HX and that is sound advise.  That will quickly tell you if the problem lies in your lines.  Hope this helps, cause it would drive me nuts to not be able to figure out where all your btu's are going.

[jerkash]

Because you mentioned your fan inside your house is coming on about every 15 minutes since the outside temp dropped, I would have to say it is your house.  Like mentioned above, we need more info on your house.

[Sconnieman]

Because you mentioned your fan inside your house is coming on about every 15 minutes since the outside temp dropped, I would have to say it is your house.  Like mentioned above, we need more info on your house.

  Everyone seems to always jump to underground lines first. While it could be the issue, it is pretty easy to test. Get a barbecue thermometer and strap it to some copper on your incoming line in the house. Chances are it will only be a couple of degrees cooler than at your boiler. If the fan wasn't coming on every 15 minutes before and it is now, then that is why you are burning more wood. That fan is drawing BTU's out of that water and sending cooler water back to the boiler, which causes your draft fans to run more, which causes you to burn more wood. What's your differential set at on your aquastat? Try lengthening it to see if makes any difference. So if it's at 5, move it to 10, or if it's at 10 move it to 15. That way you will idle a little longer between burn cycles which should save some wood theoretically.

[Ridgekid]

Of course combined underground pipe used and how well a house is insulated are the keys to determine wood use.

Thermopex and well insulated house here= 1/4 cord so far in Dec.

[Sconnieman]

Of course combined underground pipe used and how well a house is insulated are the keys to determine wood use.
Thermopex and well insulated house here= 1/4 cord so far in Dec.

Thermopex, Logstor, or any underground pipe like them is the best you can buy. Still doesn't mean F7JC's problem is that he didn't use that pipe. Could that be the problem? Absolutely. It's more likely an inefficient house problem though.

[willieG]

onemore thing, i went back and re-read the original post..what are you calling a "filling" you say you were loading twice a day in the warmer weather and now you have to load three times?

when you loaded twice was it like ..twice 30 pounds of wood (example only) and now 3 times 30 pounds..how about now that it is colder you fill twice with 45 pounds?

just trying to make sure you understand that when the weather gets colder it will take more wood..most of us who are experienced with our own OWB  get to know about how much wood to put in on a mild day to get  us through until we want to add wood again..like, i like to add wood at 6 in the morning and 6 at night, depending on the forcast and the temp the air is when i fuel the stove is my gauge on how much wood to put in, as i am sure many folks here do teh same thing.

[F7JC]

Wow nice reply on this one.  I am leaning on the house being the issue.  The home is only 14 years old and a two story with 1200 square feet on the main, 400 on the second, and 1000 on the basement.  I have a foyer about 15 feet high in the front of the home (200 square feet maybe) and catherdal ceilings (300 square feet)  in the family room. I do believe alot of heat rises there.  The second floor atic has about 9-10 inches of celose and the rest of the main floor is about the same, not sure whats in the family room (catherdal ceilings).   Fiberglass insulation in the walls, maybe R-19.  I have been keeping the house 74 degrees.  As I remember I went through 1200 gallons of propane last year with my indoor wood stove running at night and weekends  (at 70 degrees).  I do believe the furnace kicked on frequently also.

I am heating with green oak, maybe and cherry,  I load about 5 to 7 6-8 inch logs anywhere from 2-3 feet long.  Wood has set pry 4 months.

As far as the pvc having a leak in the joints I really doubt it,  I pitched the line toward the basement so I could see if any water leaked in, so far no wet basement.
The little snow we had this year did melt above the lines, but at night it all freezes up again.

Not sure on the damper, the fan does make some strange noises once and a while,  just have to hit the door and it stops.
From the boiler to the home I loose about 3-4 degrees,  the differental is factory setting at 20 degrees I do believe,  kicks off at 175 and on at 155.

As far as the bubble wrap Im not sure thats the best insulator I should have choosen in my current situation,  Maybe I will spray foam around it next year or save up for the good stuff.

[rhugg]

Two things to look at:

1)  What is the difference in your heating degree days, that number should point to a related difference in wood usage.  Us a 65 degree base, it simply means that at 65 outside temp your house requires no heat due to solar and internal heat.  http://www.degreedays.net/  Degree days are the correct measure of heat load, not a rough temperature.

2) You are getting frost on the ground.  Is it melted above your piping and frozen everywhere else?  If you are keeping frost above your line it suggests your insulation is somewhat effective.  Burried 2' down is surely below the frost line?  Therefore the ground temp is above 32.  How long an underground run is it?  Short = less heat loss.  Had your ground gotten wetter due to rain?  Water can pull away heat, especially flowing water.

[F7JC]

My underground run is 110 feet.  I do notice when it rains I burn a little more wood.  But not as much when It snowed and was 20 degrees out.  I'm thinking about just runing the furnace with propane for a couple days, bypass the HX and let the boiler pump run and see how much I burn that way.  When we hit the 20's again that it.

[willieG]

1200 gallons of propane would equal about 109,800,000 btu plus any wood you burnt in your indoor unit.

lets say in mixed hardwood you have about 18,000,000 recoverable btu's in a cord. now lets say your owb is 60 percent efficient. you would recover about 10,800,000 btu per cord. you would need about 10 cords of wood for your heating season plus what ever amount of wood you burnt in your indoor stove.

most outdoor stoves i have seen (unless your unit is quite small) can achieve this number on 2 fills per 24 hours, but not knowing how much you burnt previously in your indoor stove i dont know what to say. it could be possable you may have nights that you can't get by on 2 fills. these nights in my opinion would be severly cold and windy if your house is an average insulated house.

do you know what your OWB is rated at in btus per hour and what was your propane stove rated at per hour.  this may help you in knowing if your OWB is rated for what you really need. if yoru propane stove could keep your hose warm without the indoor wood stove then you have a good start in knowing how big of OWB you need. I am not quite sure how to size the OWB but perhaps some dealers here could tell us. you must remember as long as you have propane in teh tank your stove can output the max it is rated for, with the OWB its rating may not be wuite true as your fuel supply wanes as it burns. I am not sure if OWB are rated on a burn of say one hour burn of a full load of wood or a 4 hour burn, this would change the btu output. perhaps a dealer could tell us how the btu output is calculated?