|
DO owners manual (pdf)
DO Series brochure (pdf)
DO series
Add-on wood hot water boilers
DO110 & DO180
The DO add on wood boiler can be added to your existing oil boiler.
Click here for DO Installation. Click photo to enlarge.
The Benjamin line of ADD-ON units, when used properly, will increase the convenience and
pleasure you receive from heating your home with wood, and yet still give you the convenience
and reliability of heating with fuel oil.
Because of the unique Benjamin wood burning design, which will utilize more of the BTUs
available from each stick of wood, you will soon discover that you can reduce the amount
of wood that you use to heat your home.
How does the Benjamin DO Add-on Boiler do this?
In several ways..
- The unique combustion chamber.
- Hand welded steel construction.
- The "DUTCH OVEN" design.
- DO Series operational procedure.
1) The DO's unique wood combustion chamber.
- It's oval shaped.
- It's lacks firebricks or wood grates.
- It's thoughtful design and construction.
Hand welded, and constructed of 3/16" and 1/4" thick steel, the combustion chamber is the heart
of the unit. It measures 20" in diameter and is 23¼" long on the DO110, and 23½" in diameter
and 35" long on the DO180.
As you may already know, smoke contains much of the wood's total energy, and it wants to spiral by
it's very nature. Benjamin has built a uniquely different combustion chamber and heat exchanger that
facilitates that effect. A conventional square combustion chamber, or box frame heat exchanger restricts
this natural flow. The smoke will rise up to the corners and swirl around there, cooling as it does so.
This cooling process allows creosote and soot to form on these surfaces. They act as an insulator, and
restrict the ability of the combustion chamber and heat exchanger.
The oval design also eliminates the need for firebrick or wood grates. These were also found to reduce
efficiency. Wood grates will allow too much combustion air to enter under your burning wood. Your wood
will be consumed ineffectively and the heat will go up your chimney, instead of into your home. Firebrick,
in essence, will do the same thing. BTUs and time will be lost as the unit is forced to heat the unneeded
thermal mass.
Benjamin has a better idea.
Benjamin wants you to always keep a layer of coals and ash in the base of the wood burning combustion
chamber. These are to be used in place of the conventional wood grates or firebrick. This will slow your
wood burn down to a manageable level, allowing you to effectively remove heat from all three of the stages
of combustion, and it will allow the smoke to do what it wants to do naturally.
The door to access the chamber is made out of cast iron. Benjamin is one of the few remaining wood burning
manufacturers that still utilize a cast iron door. They do this because the cast iron will not flex the way
a steel door will. This ensures a tight gasket seal and a reduction in lost BTUs due to a constant air leak draft.
2) Hand welded steel construction.
The one piece, hand welded design of the Benjamin DO line of Add- On boilers is constructed of 3/16" and ¼"
thick steel. The 3/16" steel thickness extends all of the way out to, and includes, the exhaust collar. Let's
put it this way, the collar on the unit will probably be more rugged than the smoke stack it connects to.
Benjamin's safeguards the DO's consistently high degree of product quality, because each weld is individually
inspected by the welder after it is created. Benjamin uses thicker steel than many other manufacturers. Because
of this, they have been able to extend their product line's life span beyond that of which is expected.
Thanks to it's revolutionary design, the Benjamin DO line is classified as
an "ADD-ON" appliance. This enables it to be connected to an existing oil or
gas boiler.
To learn more about why Benjamin uses steel see our article "Steel Vs. Cast Iron".
3) The "DUTCH OVEN" design.
The "DUTCH OVEN" or "WET LEG" design is a concept where you completely surround the firebox with the cooling
water heat exchange medium. This will:
- Eliminate the need for firetubes.
- Prevent damage from overheating.
- Increase efficiency.
Firetubes
Firetubes can be very effective on a conventional oil fired boiler like the Benjamin OB1000, but on a wood
burning boiler a firetube design can quickly evolve into a nightmare. Because soot and ash are a constant
part of the wood combustion process, firetubes can easily become dirty, or worse yet plugged completely.
This means that the unit will require constant attention and care to keep it operating effectively. Because
of its "wet leg" or "dutch oven" design, the Benjamin DO line of ADD-On boilers does not require firetubes.
The "firetube wood combustion application" headaches are eliminated, making it much easier to clean, and a
delight to operate.
Damage from overheating.
Because the wood firebox is completely surrounded with water, the temperature of the steel can never
really exceed that of the water on the other side. This prevents a dangerous overheating condition that can
potentially damage your boiler, your entire system, or possibly even your home.
Increase efficiency.
If you were going to heat water on your stove top how would you go about it? I suspect that you would put it
into a container, and then set that container over a flame. You can't get much more efficient than that...Unless
you could figure out a way to contain the fire inside of the water, then you would have something, as very few
of the BTUs from the flame would be able to escape to the ambient air.
That is the idea behind the Benjamin Dutch Oven.
4) DO operational procedure.
The Benjamin DO line of ADD-ON boilers operate using one thermostat, but the unit itself requires a triple
aquastat, and a single aquastat.
The oil side of the system will be set at your "set-back" temperature. This is the temperature that you want
the boiler maintained at when you aren't around, typically this will be a low limit of 150°F and a high limit of 170°F.
Now, let's say that you want to fire up the wood heat portion of your boiler when you get home from work.
You go down to the basement and start your wood fire. (If you want to preheat the chimney to achieve a better
draft for the wood fire, turn a wall thermostat up while you are loading the wood firebox. This will create a
demand from the boiler and will fire the oil burner.) Once you have a wood fire running that you are happy
with, go back upstairs and go about your normal activities. Your boiler was being maintained within the oil
set-points, but the wood triple aquastat, set at a low limit of 180°F and a high limit of 200°F, has taken
over and will maintain these boiler temperatures by opening and closing the air draft control on the wood
combustion chamber. (The silver box and chain connected to the top left corner on the front of the unit.)
When the wood fire goes out, the temperature of the boiler will start to drop. The wood aquastat will be calling
for heat, but there is nothing on the other end to provide it. The temperature inside the boiler will continue
to drop. When the boiler reaches the low limit oil set point of 150° the unit will automatically switch
over to the oil burner and it will resume and maintain the oil aquastat set-points, until you reload and light
another wood fire.
These set points are fully adjustable and can be set anywhere you want them to be. With the automatic switch
over from wood to oil, you no longer need to worry about "rushing home to stoke the fire". The Benjamin will
take care of everything for you. Go out with your friends, stay late at work, relax, and enjoy a slower pace
to life. When you come home, the heat will still be on.
With a Benjamin in the basement, these are no longer concerns. You can remain toasty warm inside without the
fear of frozen water lines, as both the DO line, and the CC500 combination fuel boiler, when properly installed,
can still operate effectively without power. They were designed to utilize gravity flow convection, if the need
arises.
|
