Sorry about your frustrations.
I am a wood burner with a Wood Doctor converter.
My opinion is that if your air flow thru your boiler is roughly correct
and its gasifying near its rate output, then its other factors causing the oscillation in temps.
Burn rate is important as it helps with tank storage sizing. not the manufacture's but with your wood
and the winter cold etc...
if you don't know the math here it is (always time your charges)
Use the boilers temp gauge as its consistant etc.
Your temp change(finish-intial temp) x the pounds of water in your system = btu's average output
140 to 180 = 40 degree change
say 600 gallons x 8.4lbs/gal = 5040lbs in your system
5040lbs x 40 degree change = 201,600 btu's and it took a total of say 130 minutes
130/60 = 2.167hrs
201,600/2.167 = 93,032 btu/hr average burn rate
Weight your wood
say 75lbs weighted @ 6050btu/lb = 453,750btu's in 75pounds of wood @ 20% moist.
again your Delta Temp(finished-intial temp) say 600gal x 8.4lbs/gal x 70 degree rise = 352,800 btu absorbed.
353/454 = 77.7% boiler efficient
And if you timed the burn cycle you would have an average burn rate @ 77.7% efficiency.
Storage sizing
Lets say your firebox size holds 10 cubic ft of wood and we now a cord is 128 cubic ft
10/128 = 7.8125% of a cord
0.78125 x 6050 btu/lb x 3680 lbs aprox wt of oak = total full firebox should contain 1,739,375 btu's
1.739 mbtu x .777 efficiency = 1,351,494 btu available to the water.
130 degrees to 180 degrees is 50 degree change
1,351,494 / 50 = 27,029 lbs of water or 3000 gallons
Reality should say if your firebox burns for 7 hours(which you have tested) at say 93,000 btu/hr* thats 651,000 btu to
the water
* you have to measure the actual burn rate.
651,000/50 degree change = 13,020 lbs of water (13,020/8.4 = 1,550 gallons)
You could possibly go bigger say closer to 2000 gal and fill the firebox in the evening and turn down your thermostat and
you could/would heat successfully with a smaller boiler to your btu load, because you will have stored 651,000 btu's during
the late night firing.
During the morning and day the boiler is heating the loop.
Just some Ideas test your burn rate and boiler efficiency and seriously look at storing more water as it would also reduce your
boiler cycle times/day, increasing the boiler's life(your investment).
Food for thought; 2000 gallons stored, your house etc at 60,000/hr to cooling, and the water will take 14 hrs to reach 130, and
conversely it would take 9 hour to reheat the 2000 gallons back to 180. And the cool part is thats 23 hours, Hence firing once
per day!
2000g x 8.4lbs/gal = 16,800 lbs; 16,800 x 50 degrees change = 840,000 btu
840,000 btu / 60,000 btu/hr = 14 hrs (ignoring system heat losses)
840,000 btu / 93,000 btu/hr = 9 hrs
Plumbing
you may have to make plumbing adjustments and ensure that your existing water storage receives the boiler water directly then the loop start to
supply all your heating appliances from the storage unit.
And lastly fuel is never the same twice and if stack temps are keep around 320-340 degrees will turn into good fuel... just need
alittle more of it. lol when stack temps drop you increase efficiency but risk tar buildup and too hot your wasting 3-4% of you load maybe more.
Good luck and work on getting hard facts you can make smart decisions with.
doug