Fire creep …I have my boiler set for 170 /10 …trouble is the "heat creeps up " after shut down, and makes my boiler blow off ! ( always at 4 am in the morning when I fine it btw), LAST nite> outside temp at 5 pm was 27 degs and my "zones" had just finished called for heat and were closing. Weather was a wind of 9 ta 16 mph Boiler water, after all day was 140 with only a oilcan size of wood/coal left = GOOD! I load 1, 6" log and 3, 2" and a 4" dry azz spruce and a couple 2by construction stud cut off’s of 2by6/8 . I close the door a turn on the blower and the fire gets a ripping and 20 min latter I’m at 170 deg /boom off goes the AQ-s . then the creep starts/ slow …the stove and fire brick in this 1200lb monster holds the heat well …..all the lines are insulated and I get NO temp change in the 120’ 1 ¼ of line in the loop GF alpha is running 6 gpm with the no call for heat. So last nite, while we were a sleep, the wind stopped and the outside temp went to a toasty 37 . So am I’m building a fire to big?? I’m at a ¼ load…AQ--s is good ….there is no leaks of air etc…the heat from the 20 min run ….just crept up till boom…(210) and it only happens < once a week thus far. My thinking to fix this is to place a AQ-s on the supplyline coming out the top of said boiler "set on" something like 200 with a diff of 15 or 20 ,which would turn on/open a zone valve and dump the spare 15 of heat into a unini heater /something till it hits <185 deg then close OR how’s about setting my AQ-s @t 150 / 5 leaving room for 50+degs of creep < cheap 2 !!
fire + heat + creep = boil over
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You need dump zone with gravity feed using a normal open valve like an automag with a break on rise AQ.
What would happen if your main circ failed at the start of a burn or you lost power?
Most dump zones are fin tube mounted above the boiler so it will thermosiphon when the valve opens. The say 10% of the boiler rating and find tube is about 550 btus per ft. I have 24 ft for a 30kw boiler. The automag opens whenever power is lost and the AQ is set to also open the power circuit to the automag whenever the temp is too hot. Taco and Honeywell make normal open valves that apparently work too because the automag brand might be harder to find.
What would happen if your main circ failed at the start of a burn or you lost power?
Most dump zones are fin tube mounted above the boiler so it will thermosiphon when the valve opens. The say 10% of the boiler rating and find tube is about 550 btus per ft. I have 24 ft for a 30kw boiler. The automag opens whenever power is lost and the AQ is set to also open the power circuit to the automag whenever the temp is too hot. Taco and Honeywell make normal open valves that apparently work too because the automag brand might be harder to find.
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yes to which onelol
I just looked for the question mark - so yes to that.
(Don't think we know what you have for a boiler for one thing - but sounds like you don't have any dumping capability which I would think is a must. Which may or may not be what you were talking about towards the end there.)
![[Hearth.com] fire + heat + creep = boil over](https://www.hearth.com/talk/data/attachments/145/145080-f8b2c60c571b778e7be983b54814ac5b.jpg?hash=5HIQKok3IC "[Hearth.com] fire + heat + creep = boil over")
I just looked for the question mark - so yes to that.
(Don't think we know what you have for a boiler for one thing - but sounds like you don't have any dumping capability which I would think is a must. Which may or may not be what you were talking about towards the end there.)
The SlantFin is the right idea. To me it looks considerably undersized to do its job. It then also needs to be activated as you start to come close to your overheat temperature.
You might get a better handle on when and how much wood to add by weighing your wood and the multiplying the weight in pounds by 6050 to get the heat btu content of your wood. Then take the difference between the average temperature of the water in your boiler and the maximum boiler temperature, multiply by # gallons x 8.34 to get the btu's to bring your boiler temperature up to the maximum, divide that by 6050 to get the maximum # pounds of wood you can add without putting the boiler into overheat and boil over. If you have a good coal bed or other unburned wood, you also need to factor that into the computation.
Otherwise, the simple fact is that you are overloading your boiler and the creep and boil over is caused by the overloading. Don't overload, no worry about boil over.
You might get a better handle on when and how much wood to add by weighing your wood and the multiplying the weight in pounds by 6050 to get the heat btu content of your wood. Then take the difference between the average temperature of the water in your boiler and the maximum boiler temperature, multiply by # gallons x 8.34 to get the btu's to bring your boiler temperature up to the maximum, divide that by 6050 to get the maximum # pounds of wood you can add without putting the boiler into overheat and boil over. If you have a good coal bed or other unburned wood, you also need to factor that into the computation.
Otherwise, the simple fact is that you are overloading your boiler and the creep and boil over is caused by the overloading. Don't overload, no worry about boil over.
I only have 12 feet or so of s-fin as the dump 
...another thing is my boiler is in a walk in cooler, in gets no "winter" air when it fires all the heat that bleeds off the boiler stays in "in the building"... all of it ...blowers are tied to a Honeywell damper / make up air device that opens and mixes air "to the boiler"/shed. I real don't get coals the ash is a fine azz powder that I take out once a week, which barely fills that foil tray in the pic. COULD it be 
>this thing is lined on each side of the grate wit 3"fire brick for use with coal....I think maybe the heat of a rip roaring fire bleeds thru the brick. After shut down.... thru to the "wall/water" after the blowers come down???
...another thing is my boiler is in a walk in cooler, in gets no "winter" air when it fires all the heat that bleeds off the boiler stays in "in the building"... all of it ...blowers are tied to a Honeywell damper / make up air device that opens and mixes air "to the boiler"/shed. I real don't get coals the ash is a fine azz powder that I take out once a week, which barely fills that foil tray in the pic. COULD it be >this thing is lined on each side of the grate wit 3"fire brick for use with coal....I think maybe the heat of a rip roaring fire bleeds thru the brick. After shut down.... thru to the "wall/water" after the blowers come down???
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I'm sure you do get residual heat from the brick. They are there to protect the boiler. That is all good!
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