what is the death of an OWB?

I would think water treatment would be very important for longevity.

Return temp protection.

Dry wood.

Is it a steel tank, or stainless steel? Open system steel tanks need some chemical protection.r

Thermal shock is another concern. Try not letting it get real cold, then fire to 180. Thermal expansion on the metal takes a toll.

Fill it with good quality water, hard water will coat out some of the heat transfer surfaces.

In a nutshell: you want to keep water returning to the boiler above 150* to prevent local corrosion of the steel. You can do this with a thermic valve or circulator loop to bleed supply water into return.

My dads CB5036 rotted out in 7 years from the inside because he refused to clean out the ashes over the summer. I reminded him just about every spring.
You could see a line of pitted steel right at the ash level from front to back.

warno said:

does creosote build up in the fire box hurt anything over time?

Click to expand...

I've always assumed that the creosote is not a problem, it's probably not too different than a "cured" frying pan. But anything resembling ash is definitely a problem since it will pick up moisture and promote corrosion. I just wash my boiler with a garden hose and stiff brush, let it dry and then apply fresh engine oil. It would probably be a good idea to run a 20 watt incandescent bulb or a gun-safe type heater to keep it above dew point at all times spring, summer, and fall.

A good share of it is simply the nature of the beast. Internal temperatures in the fire box never get high enough to "self clean" so they are constantly coated with wood tar/creosote which is acidic. Metal type doesn't make much difference from what I have experienced. The mild steel corrodes and the stainless will get brittle with time and crack. Both are caused by the same caustic action of creosote and ashes.
Probably the number one reason for failure is the seeming insistence of many OWB users in burning green unseasoned fuel. I don't mean to offend anyone but this is just plain dumb on so many levels it shouldn't even be part of the discussion. Efficiency, emissions and life expectancy of the equipment all take a serious hit with green wood.

Some of the newer EPA rated units have some design issues which need to be resolved through changes in the product but that's a whole 'nuther topic.

Keeping return temp elevated does help to slow the buildup and also protects against thermal shock to which some types are susceptible. Central Boiler does a good job clearly stating this in their manual.

warno said:

So I'm getting some good info. Thanks everyone.

Let me know if I'm missing anything, Basically do a good clean out in the spring time to remove all ashes and try to scrap off as much creosote as possible. Keep a small light bulb lit in the fire box through the off season to keep humidity out of it. Keep return water temps as high as possible while running. And, the well known, burn only seasoned wood.

Click to expand...

I'd definitely oil it to. I oil the chimney and the firebox on my indoor furnace every spring .
Clean out the T where it comes out the back of the boiler and put a bucket over the chimney.

Keep in mind you are probably looking at a heat exchanger efficiency in the mid 40% with most OWF's. That's with dry hard wood.

They are built with a "sloppy" heat exchanger so they can operate at low temperatures without condensing and corroding away quickly.

Same concept in a gas fired water heater, not so great HX design , promotes high flue temperatures and inefficient fire to water heat exchange.

warno said:

I was looking into the bl series from P&M. I just want to know everything I can do to keep it alive as long as possible.

Click to expand...

Whoa, hang on. I think perhaps there was an assumption that you already had an OWB and you were looking for ways to make the best of it. Since you haven't yet committed to getting an OWB this would be the point in the thread where the alternative of an indoor gasifier in an outbuilding is explored, although the P&M BLxxxx units certainly look like an exceptionally good design for an OWB.

Number one killer used to be poor build quality and fundamental flaws with the design. There used to be several companies that had slick ads and changed names whenever warranty claims built up. I think they have been shaken out of the industry but some of them may still be around used.

warno said:

I did explore that possibility, I looked into the gasifier units. I simply don't have the funds to get a gasifier. That's why the BL from p&m looked like the best option. Seems to be the most efficient of a "conventional" OWB. But this vs that is not the point of this thread.

Click to expand...

My suggestion is to wait until you do have the money rather than regret the decision for many years of excessive wood use. If I may ask, how much is the boiler you currently plan to buy?

I bought my eko for less than owb's were selling for. I'd look into indoor boilers in a shed if you want it outside. Econoburn sells one in an enclosure also.

Last summer a dealer had P&M BL displayed at a flea market. I think the model was 2840, the small one. The price was $8995 for boiler alone.

gg

A gasser , at least an EKO is no more expensive than a Central Boiler. Also, to answer your Question, I think moisture is a killer. When I start a fire form a cold stove you can see moistures dripping down the side walls. No doubt a bad thing. Once the water temp hits 140 or so the moisture quits. I believe My EKO 25 ( $4500 today) will last a long time cause it rarely cools off cause I run it all winter without storage. The water temp stays at 165 for four months and I only shut it down a few times to clean it. SHoulder season is a bit different but really only start a fire in it 50 times a year or so and then water temp is ussually 100-130. This keeps the metal from shrinking and expanding. I recommend a gasser but you do what ya want.