Hi... I'm new here.

[StihlYourFace]

Greetings to all,

I have just purchased a home with a Burnham MFB-301.

The boiler is a wood/coal burner with an oil backup. This is my first heating system of this kind.

Currently, I been burning primarily hardwood and bio bricks. I look forward to getting to know more about this unit and sharing my experiences with this forum.

Cheers!

-Casey

 

[3fordasho]

Welcome! We like pictures... lots of pictures

 

[peakbagger]

Wow nice to know there is at least one more of these out here and running. I have the SFB version which is the wood boiler only version. The rotary coal grate is in pieces and its supporting frame is not usable on mine so I burn wood or run my wood stove. The actual design of the wood side is a "tank" I think they over engineered the pressure side big time possibly because of the potential fireside corrosion from coal. I dont think mine ever ran coal but I got it from free and moved it from where it was installed. My upper baffle plates above the combustion pit are pretty bad, I had new set made up but the heat gets to them. I recently inquired on the forum for suggestions on better alloy but no responses. My turbulators are also a lot shorter than original, I have gotten around to chasing down a new source.

Cant help you with the oil side but if you have questions on the wood side let me know. I will guess that unless the oil gun has been upgraded the units heating oil efficiency inst great.

Mine is run with separate 500 gallons of storage. In general without storage running it as designed is going to be very frustrating as the damper arrangement means that when there is not enough demand for heat, it turns into a "smoke dragon" and a major producer of creosote. This is a big issue as the unit shares the flue with the oil boiler so a flue full of creosote with an oil boiler in operation is very bad thing. Make sure you have the chimney cleaned and inspected especially if there is hint that they actually burned wood.

One last FYI is the emergency dump zone is wired backwards to most newer design thinking. Unless its been converted it is normally closed and requires power to open. The current thinking is to install a normally open valve with a spring to return it open, when the power is turned on to the boiler the valve is powered open. If the power fails while using the boiler, the valve spring would open the valve and the boiler would thermosyphon heat through the dump zone by gravity circulation to cool things down. The air damper also shuts so the fire will go out eventually. With the original design the valve rarely if ever is exercised so it may not work when you need it. I had to replace the operator on mine. If it doesnt open there is still the 27 psi safety relief valve that should be plumbed into the side of the firebox so that if the valve opens it douses the fire.

 

[StihlYourFace]

Wow peakbagger, that’s a lot of information.

Truth be told this is my first boiler. My last home had a hot air furnace. It has been a rocky road thus far.

I have been figuring this system out bit by bit. When I first got it running, I was running it as solely on oil. It was grossly inefficient and actually caused the PSI to go above 27 which caused an emergency pressure relief valve to dump gallons of water into the firebox.

It pumped so much in that it started overflowing out of the ash catcher and got water all over the floor.

I let some water out of the boiler from the valve at the bottom and closed the automatic feeder it seemed to have helped.

That is until I came home one day and it was 53 degrees in the house. I went down stairs to discover that the low water cut off had tripped. So I opened the automatic feeder and filled the boiler back up, fired it, and everything seems to be fine.

Since then I have burning wood as often as I can and periodically opening the automatic feeder and watching the pressure gauge.

I have also installed WiFi thermostats and a water alarm in case it goes down or dumps water again.

Here are some pictures.

 

[maple1]

Sounds like an expansion tank issue there.

 

[StihlYourFace]

Sounds like an expansion tank issue there.

I tapped on it in several locations and it didn’t feel like it was full of water. I also verified the air bleeder was open a couple of turns.

 

[peakbagger]

Steep learning curve!

I would agree on the expansion tank. My system has two Amtrol 4.4 gallon bladder types tanks, one was on the boiler side and one came with the wood boiler. That capacity is borderline. You probably first want to take a tire pressure gauge and see if the bladders are still intact. If any water comes out the air vents then you need to buy new ones. The other thing you need to check is the pressure setting on the water makeup valve. It may be set too high.

The hassle you have is Burnham sold the boiler with a box of controls but every burner tech may have a different way of connecting them. I did the same and set up the controls to match my needs and its quite complex so I cant tell you to "connect wire a to wire b". If it was mine I would take a big piece of paper and draw up a diagram of the all the electrical components and how they are wired. It means tracing out every wire between every component. I will agree in advance that its PITA and probably best done in warmer weather as the system needs to be powered down to be safe.

Here are my guesses on what each component is . In the 5th picture I am guessing that the top square control is the low water cut off? The rectangular aquatrol on the left may be the air damper control? the aquatrol to its right (right side of the round dial) is the overheat switch? and the square box all the way to the right is the oil boiler controller. By the way aquatrol is just a fancy name for an adjustable water temperature switch. They come in all sort of configurations but the standard design has two switches that move when the setpoint is reached. One switch is normally open meaning no power is being conducted through it until the boiler water is over the setting on the dial. The other switch is normally closed which means power is being conducted through the switch until the temperature on the dial is met.

The low water cutoff is going to kill power to the oil burner (that is required by law in some areas) but I dont have one. It may also be shutting the air damper so that the wood boiler fire goes out if the water goes too low.

The air damper control aquatrol is a normally closed contact. If the temperature in the boiler is less than the setpoint on the dial, power is sent to the air damper motor (the box with the arm with the chain attached). On mine if the power is on the boiler, this damper is open. If the temperature in the boiler goes over the setpoint, the power is taken away from the air damper motor and it closes. Mine is set at 205 degrees F. I have an external hot water storage tank which complicates things for comparison. The tank has a PVC liner so I need to make sure that the tank doesnt go over 190 deg F. The tank is remote from my boiler so I had to slowly raise the air damper temp over a couple of days carefully looking at the supply temperature to the tank. It looks to me like the air damper aquatrol on yours is currently set at 140 degrees F so it is always closed if the boiler water temp is hot. This is not normal but may have been done to keep the air damper closed while the oil side is running. If you notice the lever arm is spring loaded, if you dont want to use the wood boiler you just push on the end of the arm sideways and that disengages the arm from the motor so that the damper stays shut without messing with the setting on the aquatrol.

The overheat aquatrol is normally closed until the boiler water hits setpoint. On mine its set at 210 degrees. This is related to my lack of expansion capacity and that I really dont want to send water that it too hot to my storage tank. If I set it higher the water pressure gets too high and I risk having a relief valve open. Incidentally, the safety relief valve for the fire box is a special order valve as its set at 27 psi. The other safety relief on the boiler that is plumbed to the floor is set at 30 psi. My 27 psi valve leaked when I got it and I could not find a reasonably priced replacement so I have a 30 psi on mine. The overheat aquatrol should be wired directly to the overheat valve that is connected to a dump zone or separate radiator. The dump zone has to be set up so that if the valve opens, heat is sent to somewhere it can be gotten rid of, if its not hooked up or valved off, the next protection is the 27 psi relief valves open and puts out the fire which should be a last resort as it could ruin the refractory in the fire pit.

The boiler control box looks standard but its settings have to be set to keep the oil boiler from running if the wood boiler is running. Since I have seperate oil boiler I have to guess on this one. The high setpoint looks to to be 180, when the burner is running if the water in the system is less than 180, the other dial is the low limit and looks to be set at 160, the burner will not run if the water temperature is less than 160. That implies that unless the water temperature in the boiler is over 160 degrees that the oil boiler is going to run to keep the water in the system hot. This is where the oil boiler efficiency is going to suffer as the physical size of the combined unit is much larger than a standard oil boiler. That means more heat is being radiated into the basement instead of into the house. I had to pull the sheetmetal on mine boiler when I rigged it in and the insulation under the sheetmetal is pretty thin compared to a newer boiler.

My guess is that the wood boiler circulator pump runs continuously as long as the power it on ?

Well thats my second data dump. I dont think anyone do do a lot more until you trace out the wires and post a system schematic.

 

[maple1]

Air bleeder? That perhaps should be closed all the time. Don't exactly know where it is & what it's doing though - but air needs to stay in the expansion tank and if that tank doesn't have a bladder (or has one but there is a hole in it), an open bleeder will usually let it out over time. Tapping usually won't reveal issues either. An oil burner won't cause pressure to go wild like that, which is what I read you as saying but maybe you didn't mean exactly that. There are really only two things that can do that - a faulty fresh feed circuit (maybe dirt in a regulator), or waterlogged/inadequate expansion.

 

[peakbagger]

Maple and I are posting at the same time. I too am confused on the bleeder but have a suspicion. Somewhere on the hot water piping is an air scoop that tries to remove air bubbles from the system. On top of it is little steel can with a very small threaded cap on top.This can is called a float trap. That cap should be lose to let air out. It normally only puts out air when the system is first filled. The suspicion is if the system is run too hot, it can put out a mix of hot water and steam. When a mix of water and steam hits a float trap, the float doesn't know the difference between steam and air and it will vent the steam. Float traps arent really designed for steam so the steam can erode the seats and eat the internal gaskets. This can make the trap to leak and many people just crank down the cap so it wont leak.