Need advice: Adding wood-burning boiler to OHW system

Hello to all:

First post for me, & glad to find this www.hearth.com website & forum. I could use some info from those with experience, as follows:

We want to add an INDOOR, add-on wood fuel boiler system to our existing Hydrotherm Oil Hot Water boiler (baseboard heat). Friends tell us we have the "perfect" basement for this kind of wood add-on system that will likely take over as our primary/main heating source. We're tired of paying for rising oil prices & don't want to participate in that part of the economy anymore.

Our house/set up:
- The new, wood fired boiler will sit nearby the existing oil hot water Boiler, and will share the same chimney (since they won't run at the same time. Need
to check building code & Insurance to be sure its OK).
- 2300 SQ. ft. house, 100 years old, moderately insulated (Attic & walls have had additional insulation blown-in, newer windows in most of the house).

Initial web searching and found just a few options ...
* The Alternative Fuel Gasification Boiler (Dunkirk, NY) appears to be the "Cadillac" system out there. This seems to be the best technology
(cleanest & most efficient burning, low emissions, etc.). I phoned & they say this "gasification" system burns 2/3rds LESS wood than other wood fired
boilers. The downside of this system appears to be that it is quite expensive ($6500-100K-BTU, to $7500/150K-BTU unit). It is also extremely heavy,
and at 1500 lbs., I don't know what I can use to wheel this thing into my basement. I guess we can figure that part out ... if I can afford this thing.
* Another we've seen for sale is a Thermo-Control Model 500 Wood Burning w/Hot Water Coils, about $2100. 125K BTU is adequate for 2300 s.f. house.
* Another we've seen for sale is an "Dakon FB 42 Cast Iron Boiler". It appears to be a Czech manufactured unit. Found it on eBAY, Min. bid $3350.
Not much info provided otherwise, so applicability to our house & set up is unknown.
* Also found from same seller on eBAY is "EKO Line Orlan Boilers". This appears to be another wood gasification unit, though not much info provided.

Is anyone familiar with these, or are there other recommended wood-boiler add-on units you can offer info on? Many thanks.

Welcome to the Boiler Room, altabugs. I think if you look around a bit, you'll find some discussion of most of the boilers you mentioned, plus quite a few that you didn't.

First things first: You can't use the same chimney for two different appliances, even if one is not being used. Your best bet would probably be to power vent your oil boiler out the basement window and use the existing chimney for the wood boiler, depending on its type and condition.

You're looking at two fundamentally different types of boilers. The gasification units, as you mentioned, are more expensive, but they burn with virtually no smoke or creosote and consume about 1/2 as much wood. That's because they're about twice as efficient. So you need to consider long-term costs and consequences in any decision you make. Gasification boilers work best with hot water storage, but it's possible to run them without it. At the moment, that's what I'm doing and it works fine, but it uses more wood and requires more tending and planning than simply heating the water in a tank at your convenience. Because they contain a lot of refractory material, gasification boilers also tend to be heavy, as you point out. My EKO 60, for example, tips the scales at more than 2,000 pounds.

Of the 120 or so posts here in the Boiler Room, I'd guess that at least half contain useful information pertaining to your plans.

Eric and I have similar installations, except that I'm on my third season now. I have the smaller EKO 25 (80,000 BTU) and I ran my first season without heat storage. I'll second Eric's comment about the efficiency as well as the percentage of boiler room threads that are relevant to your issue.

The gasification units seem to have a little more of a learning curve, but the results are pretty impressive. As I get older, handling half the wood seems more and more attractive. Eric, on the other hand, loves handling wood and is going to have to keep his house at 90 degrees to get through the enormous woodpile that he's accumulated.

Lots of experience on the forum, and even more opinions. Enjoy your research.

That's an astute observation, nofo. Proceed at your own risk!

Wondered if you'd catch that ;-)

On the conventional side, Biasi is also a choice. Not much info available on the "3WOOD" boiler, yet, but it should be getting released soon. Very nice boiler.

I can vouch for the build quality of the Econoburn. It's not cheap, but it's less than some of the others (eg, Greenwood) and better quality than most I've seen. They even use steel pallets to deliver them, which is nice since you can leave it on that to keep it up off the floor.

Ignore the "square foot" ratings given by the manufacturers. The "right" method is to do a heat-loss analysis on the house. To keep things simple, since you're already heating with oil, see if you can find out what size oil nozzle is being used in your system, and what the pump pressure is. Both should be written on the service tag, if it's been serviced by a reputable company. If the pressure is not there, it may be because the manufacturer has listed it on the unit itself (often a sticker on teh burner's air tube). Nozzles are rated at 100 psi, so if that's what you have for pressure, the nozzle flow rate is the actual flow rate. If the pressure is higher (eg, 140 psi), I can convert it for you, since it will flow more at that rate than the number on the nozzle says it will.

The flow rate is in gallons per hour, and oil contains 140k btu per gallon. So, multiply that out. For example, if you have a .85 nozzle at 140 psi, you are actually flowing a hair over 1 gallon per hour. That means a bit over 140k btuh being burned. Your combustion efficiency with most oil boilers is probably in the 80% neighborhood, so that would be 112k btuh, for this example.

Assuming your oil boiler keeps up with demand, that number (or whatever number you get for yours) is the maximum you could possibly need, since you know that amount of heat supply is sufficient.

Given your square footage, though, I doubt you actually need more than 100k btuh. 40 btuh per square foot is the "sanity check" we usually use to make sure that our heat loss calculations are not goofed-up. In residential applications, I've never seen anything that needed more than 35 btuh per square foot, so 40 keeps us plenty safe as a quick "check."

Joe Brown
Brownian Heating Technology
www.brownianheating.com

Hopefully Brown was offering 'spert advice, not one of those opinions ;-)

I, on the other hand, am NOT a heating expert. I can only tell you what I know from My experiance. My heating contractor 'lost' my heat loss calculation on my 4,000[] new residence (100% pex radiant, 40% concrete floor). So I did as Brown suggested and went with my existing boiler - 116btu - when I ordered my GreenWood100. I can tell you that Central Boiler reps insisted I go with the 250 for their unit, despite whattheir own literature said. Anyway, I have no water storage yet, but even without, I think I made the right choice size wise.

Of course, I don't intend to let my wife read this post and find out Eric's Lady has her house at 80 deg, either :zip:

Jimbo

Bear in mind that permission to stack all that wood in the backyard was obtained at a price.

"That thar's money in the bank, Mrs. Johnson"

I'll agree with Joe's advice about the existing oil boiler being the absolute maximum that you could need. However, there's some advantage to getting a wood boiler that's sized a bit closer to your actual requirements. You'll need less heat storage and you'll build fewer fires if you can run the boiler longer - that is, if the boiler's capacity is just a bit more than your peak load. Gasification boilers are a little fussy and inefficient during startup, and really happy once they're going.

I did that analysis to arrive at my 80,000 BTU EKO sitting next to my 120,000 BTU oil boiler. In my case, 80,000 BTU is plenty.

Three factors to consider:

1) Steady-state heat losses at your coldest outdoor temperature, depends on how well insulated and airtight your house is.
2) Capacity to raise the temperature of your house reasonably quickly, depends on how large / heavy your house is.
3) Capacity to quickly heat hot water if you use your boiler for that purpose. My indirect hot water heater can absorb about 100,000 BTU/hr for short periods.

Some good advice and here's an opinion. I looked at several of the unit you mentioned and decided to go with an gasification boiler system for the lower smoke, lower wood use and longer burn times. Don't know how I would get it into the basement at 1500lbs but it's going in a outside shed. Some of the most popular units are the EKO, Tarm, Garn, Econoburn, Seton and Woodgun and you will find alot of firsthand info on all on these here. I will be running without water storage to start with and possibly adding it later.

spoke to dave today at cozyheat. nice guy and Im leaning toward a eko. the question is size . dav sized me with a 40 . can I get away with a 25? my home is only three years old ,so buy way of code in ny it has to be Efficient. I also did use high quality windows doors etc.so My oil fired boiler is rated at 150 max BTU.I burn 1000 gal a year. my home is about 2500 sq' .I use 8 zones including garage and hotwater. so a good part of the house is kept cool.Just looking for some knowledgable opinions. $ 1000 cost diff. thanks

That's a really good question, verne, that I don't really have an answer for. But I think it's a great one to toss out to the group.

In general, are you better to oversize or undersize a gasifier? Nofossil has three good items on his checklist above that would appear to argue in favor of the smaller unit in your case. Based on my limited experience with a much bigger boiler, I'd say you're probably better to buy a smaller one and run it hard, vs. trying to balance the load on a bigger one. That's not to say I made a mistake, because I have a huge heat load and I use it. And I look forward to really using it when the weather cools off next week.

Another big factor to consider is hot water storage, or lack thereof. I would think, without the benefit of any experience, that decent hot water storage would tend to compliment both a boiler that is undersized and one that is oversized. You'd simply run the smaller boiler longer to get the same result. In both cases, you're probably starting it cold on a regular basis in any event, though you could (or would have to) fire a very small boiler around the clock, which may or may not suit your lifestyle.

For what it's worth, Dave, Zenon and one other EKO dealer all tried to downsize me from the 60 that I said I wanted to the 40, until I showed them a picture of my greenhouse. So I don't think Dave is trying to upsell you.

Bla, bla, bla. Anybody else?

The 'longer burn times' isn't a given on these systems. They seem to like to run flat-out, although the EKO can idle when there's no demand. I don't know about the idling capabilities of other gasifiers, but the consensus seems to be that they're happier running at full throttle which will not give you a great burn time. Mine usually runs 3-4 hours on a load, for instance.

So let me say this about that - the $1000 should not be the deciding factor. You're going to live with this thing for a long time, and you'll forget the $1000 long before you're done with the unit.

I'm heating 3500 square feet configured as 3 heat zones, hot water, and a hot tub with heat storage and an EKO 25. Works for me, but no garage. My pre-wood oil consumption was a bit less - around 750 gallons/year, of which about 240 was for hot water.

Based on all of this, the EKO 25 might be marginal - you certainly wouldn't have the capacity to raise your house temperature much during the coldest weather. On the other hand, it would run more continuously with less idling, probably being more efficient in the bargain. Could you sacrifice the garage when needed to divert more to the house zones?

Here we go, one by one:

RE: Econoburn
They are an extremely well made unit with a bit heavier gauge steel used than most comparable gasifiers. In a conversation with a person from the factory, who will remain nameless, he flatly stated that given decent care and maintenance, the boiler should outlast the homeowner. Said a tad tongue in cheek but you get the jist of their build quality and engineering goals.

The weight issue is indeed something to consider but what's the difference between moving 800 pounds or 1,500? Our modus operandi is to hire a moving company when we have something like that to move. They have the expertise and the equipment to handle loads like that and the insurance to cover any "accidents" that may occur. Do yourself a huge favor, hire it done and don't worry about it. It'll be the best $250 you spend on the whole project.

The chimney issue is indeed a problem as it is a violation of any and all codes to vent solid fuel appliances in the same flue as oil or gas equipment. Power venting is an option but adds another piece of equipment that requires maintenance and repair. If it were my house I would explore and exhaust all other options including running a second, all fuel chimney for the wood or oil boiler. Once it's up and your through the mess you'll have lower long term costs than a power venter.

Piping of the wood boiler will probably be very simple if you choose a "sealed system" type like the Econoburn or the EKO. Most times it's just a matter of piping the wood boiler in series with what you already have, "upstream of the oil unit. That way, the return water from your zones is preheated before it gets back to the " main boiler" If you leave for a weekend or longer the oile unit will automatically take over.

I'll voice a STRONG second on doing a Manual J heatloss for you house. Calculating heating loads for years has taught me one of the immutable laws of the heating trade and it is this. "The urge to oversize any type of heating equipment is stronger than the sex drive." I would be very surprised to see a calculated load above 75,000 btu's at design temp......unless you have huge windows or live in Alyeska. You can visit www.heatinghelp.com and download a free heatloss program for your own use, run it and then you'll know.

Of the brands you mentioned, Econoburn and EKO would be my only recommendations. The Econoburn is, or will shortly be, ASME rated which may eliminate a code issue depending on your jurisdiction. The Eko meets tough German TUV specs but they are not recognized here in the USA.

Jeez ... leave for a few hours, and a wealth of info is here when I returned. I've read through all the posts and all I can say is, many, many thanks to all of you for your info and for pointing me in the right direction. In a strange kind of way, I'm really enjoying this kind of research as I know that when a decision is made, it will be with pretty good confidence. I'll continue to watch the posts/replies and will post again when needed to update.
- Paul