Stack temp

[Richie]

I have a firechief FC 500. I like it however I am am having trouble getting my stack temp over 220. I would like to see it between 300-350. I can only achieve those temps with the blower going. If I did that I would be feeding the furnace every hour and I fear that I would over fire. Any input would be welcome.

 

[maple1]

How are you measuring the stack temps?

 

[Richie]

How are you measuring the stack temps?

I have a magnetic rutland thermometer that is about 15" from the furnace/15" up the stove pipe. I checked the accuracy of the thermometer in my new bosch stove and it was dead on.

 

[flyingcow]

I think a magnet type unit reads at least 100f less than actual internal temp? My internal probe type unit reads about 400f when burning right.

 

[maple1]

I have a magnetic rutland thermometer that is about 15" from the furnace/15" up the stove pipe. I checked the accuracy of the thermometer in my new bosch stove and it was dead on.

Those magnetic stick-ons will read way low. I have one next to my internal probe thermometer - the stick on reads 100°c less than the internal one.

 

[imaddicted2u]

I'm glad I found this discussion. I have been having a hell of a time keeping the stack temp up on my old boiler. I was fearful of generating creosote. I had to have quite a fire going to keep the temp up as indicated by the magnetic thermometer on my flue pipe and I've been reloading it way more often than I expected. I used another thermometer to measure the temp of the smoke in the pipe and found it to be reading more than 100 degrees F higher than the magnetic thermometer. The house would get so hot that I had to let the fire go out for a few hours to let the place cool down. Then I would have to reheat all that water. I'm going to try running to the smoke temperature and keep an eye out for creosote build up. I brushed out the chimney before the heating season and twice since. I found it was staying clean. Hot fires will do that I guess...lol
I'm burning wood for the first time this year. The house we bought has a 1957 gravity feed cast iron coal boiler and cast iron radiators throughout the house. Probably not the most efficient wood burner but it's what I have. I added rope seals to the doors to make it more air tight which certainly made it more controllable. I'll probably try burning some coal in it when the weather stays colder.
As you can see, it's an OLD beast. I use the draft regulator that feeds air into the back of the ash pit, under the fire. I played around with feeding air through the slots in the loading door, over the fire, but found it cooled the smoke going up the flue. I'm not sure if over or under the fire draft is preferable when burning wood. There is a damper in the smoke pipe too. I'm gradually learning how to use them. Anyone got any tips?

 

[Coal Reaper]

Holy moly!

 

[imaddicted2u]

Holy moly!

LOL, I found it amazing that I could still buy parts for it. I ordered an ash door hinge from a hardware store in Pennsylvania. It ain't pretty but it's heating this old 2500 sq ft house with ease and no pumps to fail or require electricity. The supply and return headers are a hefty 2 1/2".

 

[maple1]

Holy dinosaur Batman!

I think about the only thing you can do with that is keep a very close eye on creosote buildup, and feed accordingly.

It's basic construction would lead to quite poor burn efficiency (the fire is surrounded by water - so rather than think about the fire heating the water, think about the water cooling the fire), and there's not likely much you can do about it aside from replacing it all together. Although, if the fire box itself is really big, you might try adding some firebrick around it in a way that would insulate the fire from the water jacket yet still allow the gases to get to the chimney. If it's too warm in the boiler room, maybe some exterior insulation might help.

What part of the province are you in?

 

[imaddicted2u]

Holy dinosaur Batman!

I think about the only thing you can do with that is keep a very close eye on creosote buildup, and feed accordingly.

It's basic construction would lead to quite poor burn efficiency (the fire is surrounded by water - so rather than think about the fire heating the water, think about the water cooling the fire), and there's not likely much you can do about it aside from replacing it all together. Although, if the fire box itself is really big, you might try adding some firebrick around it in a way that would insulate the fire from the water jacket yet still allow the gases to get to the chimney. If it's too warm in the boiler room, maybe some exterior insulation might help.

What part of the province are you in?

The boiler heats the basement quite nicely. I know the old timer lacks in looks and efficiency but it sure is killing the oil bill and also reducing my power bill by providing some of my hot water.
I'm in Sydney, where are you?

 

[tom in maine]

Hey, it works, that is important. If you are watching stack temps and the flue for creosote, you are on top of the game.
Keep us posted on how much wood you burn vs. how much oil you had used.
If you can operate this boiler without smothering the fire to control things, you should be okay.
I love passive systems. With radiators, they can't be beat. You have some built in storage there!

Depending on your experience and how warm the basement is, you might consider insulating the boiler shell, but in this
case cheap looks good.
10F at my house this morning. Burned last night and will be able to skip tonight.

 

[imaddicted2u]

Hey, it works, that is important. If you are watching stack temps and the flue for creosote, you are on top of the game.
Keep us posted on how much wood you burn vs. how much oil you had used.
If you can operate this boiler without smothering the fire to control things, you should be okay.
I love passive systems. With radiators, they can't be beat. You have some built in storage there!

Depending on your experience and how warm the basement is, you might consider insulating the boiler shell, but in this
case cheap looks good.
10F at my house this morning. Burned last night and will be able to skip tonight.

I notice a big difference since I stopped trying to keep the stack temp up based on the reading of the magnetic thermometer. House is a comfortable 70F while outside it's 25F and I'm using less wood. I threw in 2 sticks at 4am this morning. At 8 am, I threw in another stick but probably could have waited another hour. I'm using a wireless remote bbq thermometer probe in the flue pipe to watch the smoke temp, best 12 bucks I ever spent. I'll continue to watch for creosote and run the brush up the chimney next week.

 

[Clarkbug]

I just think its a testament to those old systems that you can still get parts and its still keeping you comfortable today!

I would love to design an all gravity system if I could. KISS principle at work.

Just make sure your wood is dry, and that will help you keep your temps up, and creosote down.

 

[maple1]

The boiler heats the basement quite nicely. I know the old timer lacks in looks and efficiency but it sure is killing the oil bill and also reducing my power bill by providing some of my hot water.
I'm in Sydney, where are you?

I'm at the other end, 1/2 hr. from NB border.

I'm thinking that thing used to burn coal at one time? Maybe you could get some of that too if the wood ever runs out?

You're doing good displacing the oil & bills that go with that, no doubt - just make sure you get a handle on the creosote thing.

 

[woodsmaster]

Thats what I like about a good pressurized system. They last forever !!

 

[imaddicted2u]

I'm at the other end, 1/2 hr. from NB border.

I'm thinking that thing used to burn coal at one time? Maybe you could get some of that too if the wood ever runs out?

You're doing good displacing the oil & bills that go with that, no doubt - just make sure you get a handle on the creosote thing.

That's the plan. I've got a couple of tons of coal in the basement.

 

[imaddicted2u]

Holy dinosaur Batman!

I think about the only thing you can do with that is keep a very close eye on creosote buildup, and feed accordingly.

It's basic construction would lead to quite poor burn efficiency (the fire is surrounded by water - so rather than think about the fire heating the water, think about the water cooling the fire), and there's not likely much you can do about it aside from replacing it all together. Although, if the fire box itself is really big, you might try adding some firebrick around it in a way that would insulate the fire from the water jacket yet still allow the gases to get to the chimney. If it's too warm in the boiler room, maybe some exterior insulation might help.

What part of the province are you in?

I get your point about the water jacket cooling the fire. So far, the only place I've seen any signs of creosote buildup is on the walls of the firebox.

 

[imaddicted2u]

Here are a couple of pics I took inside the firebox of my old boiler, just before adding fuel. You can see creosote buildup on the water jacket and the cooler parts. I guess if you are going to have creosote, the firebox is the best place for it....
I plan to sweep the chimney tomorrow and have a look to see if there is any building up past the boiler. Perhaps it's all condensing out inside the boiler since I didn't find any creosote 2 weeks ago when I last brushed out the chimney.
Door opening left side:

Door opening right side:

Firebox:
Interesting that the back has no water jacket, it's exposed to room air. Creosote seems to build up at the bottom of the water jacket, I assume because of the return water enters there.

 

[BoilerMan]

My guess is that was for cola use as well. There are still quite a few old boat anchors like that around here......with plates over the doors and an oil burner in them . Seems everyone abandon coal when oil was cheap........... For the most part, anything that can burn coal you can burn wood in, but not vice versa. Coal needs underfire air, wood does better with overfire air.

TS

 

[imaddicted2u]

My guess is that was for cola use as well. There are still quite a few old boat anchors like that around here......with plates over the doors and an oil burner in them . Seems everyone abandon coal when oil was cheap........... For the most part, anything that can burn coal you can burn wood in, but not vice versa. Coal needs underfire air, wood does better with overfire air.

TS

Yep, this boiler spent most of its life burning coal. I read somewhere that wood prefers to have its draft over fire but, on this boiler at least, if I close the under fire draft and open the slots in the door to feed air over the fire, the flue temp drops like a rock and the fire dies down. Consequently, I open the under fire when I start a new fire. After startup my best results have been with both the drafts closed and controlling the flue temp with the stove pipe damper. Even then I get more heat then I need. The over and under fire draft regulators are never truly closed. They are cast so they always pass some air. I can't load the thing up for an overnight burn or it would drive us out of the house, even with everything closed up. Two splits at a time will last 3-4 hours. With the drafts closed and the flue damper open the added wood fires up and once burning well I set the draft at the breech using the flue pipe damper using my Dwyer manometer. The fire begins to die down and the flue temp gradually decreases. Longest burns are at .01" on the Dwyer. If I close the flue damper much below that and I get smoke out of the slots in the loading door. Water temps run 95 to 105 degrees F. Flue temps range 250F to 450F. I aim to keep it above 300F but have to let it fall below sometimes before reloading to avoid overheating the house. Do you see anything I may be doing wrong? It is better since I stopped relying on the stove pipe thermometer and started going based on the temp in the pipe.

 

[maple1]

You can improve the creosote buildup in the boiler itself with return temp protection - basically a thermostat on the return line just outside the boiler tied also to a bypass loop that will keep your return water above 140c. And you could improve it a TON by doing that AND adding some storage, whatever you have room for. Then you could just burn a fire wide open until storage gets hot. But, the way things are going now with it, sounds like you're doing fairly good. My firebox looks kinda like that too - it just builds up a bit, gets kind of flakey, and burns off. So it only gets so thick. If you're not getting creosote outside your firebox, or not much, that's good - the main thing I would be worrying about then would be if the creoste buildup in the firebox gets to prompting some corrosion under it where the buildup is most heavy. That's the main reason for +140° return temp protection, to avoid that. If you make sure your wood is dry that will help with that a bit.

Sure don't build them like they used to - that thing is stout.

 

[imaddicted2u]

You can improve the creosote buildup in the boiler itself with return temp protection - basically a thermostat on the return line just outside the boiler tied also to a bypass loop that will keep your return water above 140c. And you could improve it a TON by doing that AND adding some storage, whatever you have room for. Then you could just burn a fire wide open until storage gets hot. But, the way things are going now with it, sounds like you're doing fairly good. My firebox looks kinda like that too - it just builds up a bit, gets kind of flakey, and burns off. So it only gets so thick. If you're not getting creosote outside your firebox, or not much, that's good - the main thing I would be worrying about then would be if the creoste buildup in the firebox gets to prompting some corrosion under it where the buildup is most heavy. That's the main reason for +140° return temp protection, to avoid that. If you make sure your wood is dry that will help with that a bit.

Sure don't build them like they used to - that thing is stout.

There are 2 supply headers and 2 return headers coming out of the boiler, one set feeds half the house the other pair feed the other half. All are header pipes are 2 and 1/2" threaded schedule 40 pipes. Would both return need to have a bypass? It's not a job I could tackle in the heating season. There are no isolation valves in the entire system so it has to be drained to be worked on. These old gravity systems had huge pipes and few manual valves and no zone valves to minimize the pressure drop so the heat/water could be moved by gravity without any pumps.
Also, I could never get the return temp above 140 given that the highest I've seen the boiler water discharge temp so far has been 105. It has typically operated at 95 to 105 degrees to keep the house between 70-75 depending on outdoor conditions. Due to their large surface area the cast iron radiators require low temperature water.
I installed a manual bypass on my oil boiler to keep the return temp up for similar reason, sulphuric acid was condensing out from the flue gas and coating the boiler tubes due to the low return temp from the cast iron radiators, but it has 1" copper pipe and has isolation valves so it was a relatively easy soldering job and didn't require draining the system or threading schedule 40 pipe.

 

[imaddicted2u]

Here is a short video, taken through the sight glass in the loading door, of the fire right after loading in 2 sticks of wood. The draft was completely closed and the flue pipe damper was closed to obtain .01" on the Dwyer manometer.

Another video taken half an hour later. You can't see it in the video but there is blue flame dancing all over the wood. It's 75F in the house, boiler water temp is 100F and the flue temp is 300F. Draft and flue damper still closed.

 

[imaddicted2u]

Chimney cleaned, a hour and a half well spent. I didn't see any new creosote formation. There was none in the smoke pipe either, only soot. I brushed a couple of cups worth of soot off the walls. I tried to burn a sample with a propane torch, it doesn't burn. I see a coupe if cracks in the liner. Who ever did the work beat out the holes for the flue pipes rather than cutting them and cracked the liner. They didn't bother to align the liner tiles when they put them in either, all around...a crappy install.
I took these pics through the oil boiler flue opening. It enters about 18" above the Coal/Wood inlet pipe.
Before: After:

A look through the heat exchanger door, before I brushed it out. Quite a bit of creosote buildup on the front water tube and on the inside of the door, only a little further back. With the door closed I think there is a dead air space that gives time for creosote to condense. Note the rope gasket I glued on to seal up the doors.

 

[Clarkbug]

There are 2 supply headers and 2 return headers coming out of the boiler, one set feeds half the house the other pair feed the other half. All are header pipes are 2 and 1/2" threaded schedule 40 pipes. Would both return need to have a bypass? It's not a job I could tackle in the heating season. There are no isolation valves in the entire system so it has to be drained to be worked on. These old gravity systems had huge pipes and few manual valves and no zone valves to minimize the pressure drop so the heat/water could be moved by gravity without any pumps.
Also, I could never get the return temp above 140 given that the highest I've seen the boiler water discharge temp so far has been 105. It has typically operated at 95 to 105 degrees to keep the house between 70-75 depending on outdoor conditions. Due to their large surface area the cast iron radiators require low temperature water.
I installed a manual bypass on my oil boiler to keep the return temp up for similar reason, sulphuric acid was condensing out from the flue gas and coating the boiler tubes due to the low return temp from the cast iron radiators, but it has 1" copper pipe and has isolation valves so it was a relatively easy soldering job and didn't require draining the system or threading schedule 40 pipe.

I dont think you can install any sort of bypass on that particular boiler that is going to be of much use for you during the heating season. Maybe one for a complete cold start, but otherwise the gravity just does what it does. All of the bypass devices I have seen have too much pressure drop to be used in a gravity system. I would say if it has worked this long without it, why mess up a good thing?