Don't laugh too hard: Firewood boiler or Propane?

farmerzeek

Hello all, currently I have a 1998 Hardy H4 that has been patched and mended a few times. At some point, it will need to be retired. Currently, my house is forced air with a water to air exchanger. I am slowly converting to hydronic.

I was thinking about going with a propane combi, condensing boiler because I am sick of dealing with firewood, but not sure if I can afford to buy propane. I tried to calculate the cost but that seems like a futile effort since it is all so personal to your home and climate. I can buy a Central Boiler for about xx,xxx and they say it will burn less wood, so that means I may only need 5 cords. If I buy firewood it will be about x,xxx. Is it possible to heat my home for less money than with propane? Can I ask that?

House is 1870, being remodeled, windows and doors being replaced, moderate insulation, and I live in Ohio (zip code 43964).

I may always have a fuel bill....propane or firewood, but which one should I go with?

I am open to all lines of thought and on the surface I realize this may seem like an easy choice, but I am willing to pay for the convenience of not having firewood. I know all the pros of firewood and not relying on anyone as I can always go cut firewood. I will always have 2 ways to heat my house, right now my back up is an oil furnace and it will stay since I just did a bunch of work on it.

Ok well let it rip......thanks!

EdTheHeaterMan

How do you get the firewood out of the LP tank? How do you get it in the tank in the first place?

But seriously, you don't want to cut, split, and lug wood into the boiler anymore. There is your answer. Now the ModCon boilers are very efficient with fuel. And that is a good place to start. If you want to reduce the fuel bill start with the fuel burner. once that is as efficient as it can be, then you can start on the other stuff. Insulation, windows, caulking... will all help over time. The nice thing about the ModCon boilers is the fact that, as the load gets less and less over time, the boiler actually gets smaller. (not really but the modulating input gets smaller) In 15+ years or so when you have made all the energy-saving upgrades, you can purchase a smaller replacement boiler.

@hot_rod posted this calculator that may help. since you know what you use in oil and wood already, you can plug those numbers in and see what other fuels would cost to do the same thing.

https://coalpail.com/fuel-comparison-calculator-home-heating

BTW we don't put prices in our posts. it's in the rules. we can say numbers of gallons or number of cords of hardwood or stuff like that. but quoting equipment prices and dollars per gallon is a no-no.

Yours Truly,
Mr.Ed

hot_rod

If you need to buy firewood, I doubt that is the least expensive fuel. Call around and see what LP is running currently. I filled up for as low as .99/ gallon, it is at $1.75 currently.
The biggest issue with wood boilers is coming up with actual efficiency numbers. I've worked on some Hardys I suggest they run 40-45% efficient, enter that number into the calculator.
The newer gasification wood burners maybe 75%. IF you have dry, hard wood.

Jamie Hall

First, off, please edit your cost figures for the equipment out -- one of the rules of this site is that costs or equipment and installation or maintenance aren't to be posted. Thank you!

It's not hard to compare fuel costs. The heat content of good, dry ash is somewhere around 24 million BTU per cord. As noted, a good modern wood-burning furnace may be as much as 75% efficient. The heat content of LP is around 100,000 BTU per gallon, and a modern mod/con boiler will run at least 86% efficient and, in some situations, up to as much as 96%. Just run the numbers using what you are paying for wood and what you might pay for LP.

A note about wood, though -- of which you are probably aware. First, ash is about the highest heating value per cord. Second, that figure assumes that it is dry, and dry means cut, split, and stacked under cover for at least a year. Green or wet wood will be quite a bit less.

EBEBRATT-Ed

I would start by tighting up the house, windows, insulation etc. Then do a heat loss and calculate your yearly use. There is plenty of resources to do this.

Then you have to decide between LP and oil which you already have.

Then there's the wood issue which only you can decide.

Larry Weingarten

Hi @farmerzeek , My climate is warm compared to yours. The coldest I've measured here was 18 F. I built a very well insulated and snug house and my average wood usage is 1/4 cord per year. Termites eat my firewood faster than I can burn it. So, whatever you can do to make your place efficient will minimize the wood vs propane fuel question. Best might be to go with a boiler and hydronics along with a wood stove using outside air. That gives you options.

Yours, Larry

Robert_25

The cheapest btus are the ones you don't need to buy.  Spend the $$ on the house instead of a wood boiler and you will easily be able to heat it with any fuel...and be more comfortable.  This is coming from someone that lives in an old house and has burned LOTS of wood.  I switched to coal 10 years ago, and have done considerable work to the house since then (which has cut my coal consumption in half).

OWB are very inefficient.  

GroundUp

In your situation with only one building, there isn't a chance I'd ever consider buying a wood boiler. Personally I heated a 2800 sq ft house for several years with propane forced air then built a detached 1600 sq ft shop with an electric boiler running the in-floor radiant electric. The electric bills were pretty obscene (so I thought) so I bought and installed a new Cozeburn wood boiler to heat both building s and save money. The poor thing could never catch up when below zero (in MN that's pretty common) as it was too small for the 4400 sq ft load. After a few years I saved up and bought a new Heatmaster thinking it was the proper route to save money in the long run. Then 2 years ago I built another 1600 sq ft detached garage and connected it to the OWB as well but also have an electric boiler for the in-floor, so I have a 6000 sq ft load plus DHW on the OWB. I run through about 10 cord of oak per season, which is pretty economical, but last year I added up the actual expenses of burning wood (fuel, chains, saws, splitter, the occasional punctured tire or twisted sheetmetal, etc) and came to find out that based on the BTU output of my 10 cord of wood, I am only saving about $500 a year after everything is said and done; compared to burning propane in the house and electric in both outbuildings. Simple depreciation on a new OWB costs you $500-1000 per year right off the bat, they still take quite a bit of power to run a larger circ pump 24/7 and all the modern units have a draft fan which takes some juice too. The biggest factor though, is TIME. Between cutting, splitting, hauling, and stacking 10 cord of firewood (my wooded acreage is only 3 miles away) I was spending roughly 150 hours per year for those 10 cord of wood. Add in another 50 hours a year feeding the stupid thing twice a day, taking ashes out, cleaning, etc. A few years ago I had a spinal injury and have trouble wrestling a saw for an extended period of time so I started buying a 10 cord semi load every year and hiring a guy with a firewood processor, then loading my trailer with the skid steer so the only times I handle it is from the trailer to the stack in my wood shed, then from the stack to the OWB so I've cut out more than half of the time- maybe have 80-100 total hours in it now. Even at that, take the $500 a year savings and divide it by 100 hours of time spent. My time is worth more than $5 an hour. Even a minimum wage job pays better than that and you don't wreck anything including your body. Burning wood sucks, and it's expensive.

farmerzeek

Mr.Ed, thanks for the reply, very helpful.. What is a ModCon boiler?

Hot_Rod...I agree the Hardy is not efficient. My thought is the price of propane will change, so then when it goes up and I can't afford I am stuck.

Jamie, good numbers and I will do some math and see what it costs per BTU for wood.

Larry and the others that recomended tightening the house, Iam working on it and totally agree.

Groundup, thanks for the pot..sorry you had such a time. I have to read your post again and think on it.

I guess my ultimate question is if I can afford propane and also if a hydronic systems would use less LP than if I keep the system forced air with water-to-air exchanger.

Thank you all for great information, keep it coming.

Robert_25

I guess my ultimate question is if I can afford propane and also if a hydronic systems would use less LP than if I keep the system forced air with water-to-air exchanger.

All other things equal, you probably would not see any difference in LP consumption.

What WOULD make a difference is if your hydronic system was multiple zones, and you kept the parts of the house you were not actively using at a cooler temperature. It is also really nice to have cool bedrooms, warm bathrooms, etc.

Have you considered a modern woodstove for the house to supplement your heat? The newer units are very efficient and burn clean.

farmerzeek

Robert_25, I am definitely doing zones and am slowly in the process of getting the in-floor Pex installed, well at least for the first floor since I can access from the basement. One I figure my zones I will figre out what is the best manifold, well I will try because everybody has an opinion.

By modern woodstove do mean an insert that burns wood? We are hoping to install an insert where the old fireplace was, is that what you mean?

It seems that the OWB is not the best idea, even if I buy firewood, but if the LP and firewood cost is the same, or say the LP is a little more by even 25% I may be willing to pay just to have the convenience. But I do use the current OWB to heat my DHW and that is nice because I can shut off my electric hot water tank.

Zman

If you adjust the calculator to represent your wood boiler efficiency to 50% and the propane boiler to 90%, it looks like wood at $200 per cord and propane at $1.80 per gallon are about the same.
I would go with propane and save yourself the work.
Whatever you do, don't leave the wood boiler in the loop and pipe the propane boiler in series. This makes the propane boiler heat the outdoor boiler (turned radiator) all year. I had a customer do that, once they complained about their gas bill, we repiped it and cut the as bill in 1/2.

farmerzeek

Zman, thanks and I will be sure to keep thinigs separate when needed and I know my limitations and have problem calling a professional to help me out. I think there is this idea that wood heat is free or cheap, but now that I am thinking about things as have been explauined here it seems that wood is sometimes not the best option. Sure if I can't get propane or oil delivery then the choice is made, but I can get LP and oil. I even considered an oil boiler but decided that if I did a boiler it would have to me LP and as high efficiency as possible. SOmeone mentioned a Mod/Con....does that mean Modern COndensing boiler?

Larry Weingarten

Hi @farmerzeek , Mod/Con means modulating, condensing. Modulating means it can cut down the burner flame to 1/5th or 1/10th, or whatever the boiler spec is. Condensing means it grabs so much heat from the fuel that flue gasses are cool enough to allow water to condense from them. Often these boilers use a plastic vent pipe.

Yours, Larry

farmerzeek

So is a Mod/Con also a condensing unit? Can I vent a Mod/Con with plastic? I will do my homework for sure, but I have not come across Mod/Con before.

Robert_25

Yes.  The Con in Mod/Con means condensing.

Check out section III in this report by NYS:  https://shwec.engr.wisc.edu/wp-content/uploads/sites/711/2015/08/NYRptRev08.pdf

Jon_blaney

I have always thought that a wood boiler only made sense if your son-in-law ran a tree service and would fill you yard with two foot wood chunks.

EdTheHeaterMan

To expand on your question about Mod/Con boilers. Let us first look at the condensing aspect. Over 30 years ago the condensing furnace became very popular in the residential HVAC industry. 50 years ago the most efficient burners were about 80% with the majority being closer to 68% efficient. About 400°F gasses were released from the furnace up the chimney. When the energy crunch made it economical to add more cost to the equipment, the condensing section was added to take the 400°F exhaust and run it through a second heat exchanger to reduce the exhaust temperature to well below 200°F. This caused the water vapor in the byproducts of combustion to condense allowing more heat from the fuel to stay in the heater to be distributed into the home.

More recently, a new technology became affordable to place into residential heating equipment. The modulating feature for the gas input. Think of it like cruise control for your heater. Since the beginning of automatic heating in the late 1800s and early 1900s, the burner was controlled by a thermostat that was basically an on and off switch based on a set temperature. When the home was cold the burner turned on full input. When the home was comfortable the burner would turn off completely. The off-cycle was wasteful and the startup-cycle was inefficient. So when the burner operated for about 5 minutes it was at its most efficient operation.

Modulation makes the burner operate at something less than full-on. So there are never any wasteful off-cycles during the coldest time in the winter. No off cycles mean no wasteful downtime and no inefficient startup-cycle. As we get closer to the fringe seasons, the burner never reaches full-on because the burner operates at a reduced input making the on cycle last longer and the off cycles happen much less. So when you look at the cost of the propane you should enter an efficiency of 90% to 96% when comparing the amount of fuel to the Wood Burner that you have at less than 70% efficiency.

Downtime on your oil burner will use more fuel because the vent pipe is connected to a chimney. When the burner is off it is still connected to the exhaust vent (chimney). After the burner shut off, the chimney does not stop drawing air from the home. It is still drafting. The air that is leaving your home up the chimney is coming from your home, and you paid to heat that air to 68° or 70° Furthermore, the heated air that is leaving your home is being replaced by air that is leaking in thru the cracks and crevices of your home. That air is from the cold outdoors. This also happens at a greater rate during burner operation.

Most of the ModCon boilers are able to use outside air for combustion. This will greatly reduce the infiltration of outside cold air during the operation and any downtime of the gas burner

I hope this puts a little more light on the Mod/Con boiler

Yours truly,
Mr.Ed

EdTheHeaterMan

farmerzeek said:

So is a Mod/Con also a condensing unit? Can I vent a Mod/Con with plastic? I will do my homework for sure, but I have not come across Mod/Con before.

Condensing unit is a term we use in the HVAC industry for the outdoor section of an air conditioning system. So to answer your question literally... NO.

But I believe you might mean: Does the boiler produce condensation of the flue gas while operating? The answer to that is YES.

farmerzeek

Ed your explanation was the best thing I have read all week. Looks like I will start researching Mod/Con LP boilers.   Are you allowed to talk about brands and such in here?  Like many people I am a DIY kind of guy and will do all the work myself. If I get over my head I have access to HVAC guys and a plumber.  I still have to complete my heat loss calculation before moving forward.  

flat_twin

Toronto OH eh? I'm a couple hours west of you. Get your water tested for hardness and chlorides. Stainless steel modcons don't like chlorides, combi's don't like hard water. Consider a modcon plus indirect water heater instead. Less btu required with a heating only modcon.
Get familiar with your hydronic piping layout. Research "pumping away", primary /secondary piping schemes. Look for Hot Rod's Coffee with Caleffi videos on youtube. Tons of good info about hot water heating systems.
Check out the Slant Fin app for calculating your homes heat loss. Don't go by the size of your previous boiler especially since you're doing a lot of remodeling.
We replaced a fuel oil boiler / electric water heater with a modcon and indirect WH. Very happy with the performance and savings.

hot_rod

The key to Lp as a fuel is to buy a few 500 gallon tanks and load up in summer. Properly piped you can have both Lp and a wood fired ready to go. I have a wood boiler in my shop been running it for about 15 years, every year it get less and less use, already switched to Lp.
In the house we had a small wood fired parlor stove

farmerzeek

Jamie Hall said:

First, off, please edit your cost figures for the equipment out -- one of the rules of this site is that costs or equipment and installation or maintenance aren't to be posted. Thank you!

It's not hard to compare fuel costs. The heat content of good, dry ash is somewhere around 24 million BTU per cord. As noted, a good modern wood-burning furnace may be as much as 75% efficient. The heat content of LP is around 100,000 BTU per gallon, and a modern mod/con boiler will run at least 86% efficient and, in some situations, up to as much as 96%. Just run the numbers using what you are paying for wood and what you might pay for LP.

A note about wood, though -- of which you are probably aware. First, ash is about the highest heating value per cord. Second, that figure assumes that it is dry, and dry means cut, split, and stacked under cover for at least a year. Green or wet wood will be quite a bit less.

Ash? There are many other species that have a higher BTU...so not sure what to make of your comment. What did I miss?

Jamie Hall

I prefer ash -- or hickory (yeah right, try to find that!), or oak -- low residual ash, very low smoke and creosote. Apple, beech, honeylocust and black locust, maple (but not silver maple), osage orange, and pinyon are also higher than ash in terms of BTU per cord (not per ton; that's a different measure, as the density of the various wood species is different.

EdTheHeaterMan

I like to get a little piece of ASH once in a while too. But enough about "Boiler Porn"

About brand names... you can mention the pros and cons of the brands you are considering. Most of those discussions come down to the fact that the brand is less important and the installing contractor is more important. Since you are a DYI then your discussion of a brand should be looking into the best Tech Support and repair parts availability. I like Bosch Greenstar, but I have also installed Navian. I like Bosch tech support better. If you can get Velocity Boilers (formerly Crown Boiler) where you are, I like them the best for price and tech support, Bob M. in tech support used to work for my family's business years ago. He remembers me as the boss's kid and still calls me Eddie.

Don't make the mistake of using a water heater in place of a space heater. Water heater control systems are a bit different and don't adapt well to space heating systems. There are several discussions herein that try to address that problem after the fact. The best advice is to get a boiler designed for space heating. They are a litter more expensive compared to water heating boilers but are worth the difference. There are also combi boilers that will do both if you are interested in making hot water more efficiently. I am not a fan of that because when there is a failure of one system, you usually have a failure of both.
like putting all your eggs in one basket. I prefer to have separate devices to generate hot water and space heating.

Yours truly,
Mr.Ed