Tarm Solo Plus 40 Kettling

Hello All,

My new Tarm Solo Plus 40 has now been in service for approximately one month and I have burned approximately 3/4 cord of kiln-dried firewood so far. My wood boiler is plumbed in parallel with my oil fired boiler that is interlocked to fire based upon an aquastat. I am finally getting the hang of proper load size for the given conditions which up to this point in Upstate NY has been relatively warm. With that said I have only been running the boiler when temps are around 40 DegF or lower. About the only issue I am experiencing at this point is that on the hottest part of a burn cycle I am getting a 'heart beat' sound in my boiler accompanied by a clanking sound in my supply header copper piping. My first inclination was that by burning the extremely dry kiln dried wood (10% moisture or less by my meter) that I was overfiring the unit with the Tarm supplied Condar thermometer reading 800 - 1000 DegF. After seeing a post in the forum questioning the accuracy of this thermometer I ordered a thermocouple meter and confirmed indeed that the thermometer was reading anywhere from 200 - 500 Deg F on the high side! In addition, I bought a draft gauge and at this point I can confirm that on repeated measurements my flue temps just after the boiler flue collar are between 350 - 500 DegF at the hottest part of the burn and the draft is between -0.04 and -0.05 InWc. These measurements are exactly in line with what Tarm recommends. After inquiring with multiple people including tech support at Tarm, my conclusion was that I had air in the system and that the thumping sound in the boiler and the pipes was being caused by the water flashing to steam then back to liquid. I tried bleeding the boiler at the purge valve in top but of course made a huge mess having to remove the insulation to wick the water up with rags. At that point, I decided to purge the entire system including the two boilers and all zone piping in the house. I first isolated the wood boiler completely (shutoffs at the supply and return headers) then opened the drain valve slowly and allowed approximately 75 gallons of water to be exchanged in the system using the auto fill valve at the regulator (mounted in supply line in supply header by recommened Tarm direct plumbing method). My thought being that if any air was trapped in the top of the boiler that by draining/filling the boiler in this way I would add water from the top pushing out any air in the sytem while exchanging the entire capacity of the boiler (55 Gallons plus approximatly 10 feet of 1 1/4 inch header piping). With the wood boiler remaining valved out I then did the same for the oil boiler. I then did each of the two heating zones one at a time valving everything out as I did each zone. I am pretty confident that I removed all air in the system. Then valved everything back in and fired up the oil boiler to temp and everything seemed great with no water fall sounds in the piping as I know from previously having air in the heating zone lines. I next fired up the wood boiler and it came right up to temperature (oil boiler of course interlocked shut down above 160 DegF per aquatstat) with the no thumping or heartbeat sounds (kettling). Measured flue temps and draft perfect. After operating continuously now for two successive days I loaded the boiler this morning with coals with a small load of wood to get me through a couple of hours before the big load when leaving for work. About ten minutes later the kettling had returned and the copper pipes were rattling again. I am stumped to say the least as I was confident I had this figured out. Are there any members out there running a Tarm Solo 30/40/60 without storage who have had this same issue and know what might be going on? Any help would be much appreciated. Also, am running a Grundfos 3-speed circulator at medium speed. Tried high speed thinking that maybe I was pulling enought heat out of the boiler but this did not help. Am now back to medium speed. Help!

Ken

Clarkbug said:

Ken,

What are the pressures looking like when your temps get high? Do you have a new expansion tank that is connected to the wood boiler, or are you using the one on the oil boiler? I ask because when you have the oil boiler locked out, is there a zone valve that is preventing the expansion tank from accepting any more water? Does your relief valve ever open at all to spill any water? Did you purge your overheat loop also?

Just a few ideas to get things rolling along!

And welcome to the forums from another Eastern Upstate NYer!

Click to expand...

Thanks for gettings things rolling Clarkbug. Pressure with the temps at hottest part of burn are between 12-15 Psig and steady. I have a separate feedwater regulator, backflow preventer, and expansion tank on the new wood boiler arrangement with isolation via block valve (project piping and electrical schematic attached). Expansion tank can accept water in this arrangement even with oil burner locked out. No spillage from relief valve. My gravity overheat loop is plumbed through my upstairs heating zone and the 'bridge' between the zone valves is isolated via shutoff valves. I had the shutoff valves closed and auto-mag zone valves were ofcourse open with power removed when bleeding the system thus hypothetically unless there was already air right at or near the shutoff valves on either side the lines would have been bled I think. Bleeding the entire system with a parallel plumbed system is definitley more complicated.

Ken

jebatty said:

I tried bleeding the boiler at the purge valve in top but of course made a huge mess having to remove the insulation to wick the water up with rags.

Click to expand...

This is the easy one to address. I installed a shutoff valve, like the kind used for a sink, at the fitting on the top of the boiler, and then a short piece of tubing to the compression fitting on the valve through a vent slot of the 40 and about 6" out. If and when needed, which is very infrequently, simply open the valve, purge the air until water just starts from the tubing, and all is done. No mess, no fuss.

As to kettling, so far as I know kettling will not result in air at the top of the 40. Water flashing to steam and then condensing back to water produces no air. So don't try to vent the 40 to stop the kettling, unless you really have air at the top of the 40.

Originally and occasionally I would get kettling, which I just ignored. If it occurred, it typically occurred during the hottest part of the burn for a short period of time. Then three years ago, out of an abundance of caution, I drained and refilled my system using chemical treatment from a supplier. The kettling then disappeared, or at least I no longer hear kettling. I really can't say for sure, but I am assuming that the water treatment had something to do with eliminating kettling. I am assuming that the boiler water treatment produced a more uniform protective coating on the inside of the boiler which enhanced heat transfer and/or eliminated scale deposits inside the boiler which can be a cause of kettling

My suggestions are: 1) use less dry wood, which may produce a slightly cooler fire, 2) increase the velocity of the water moving through the 40 to shorten the time that any water molecules are in contact with the hx tubes or other hot metal surfaces. I use a 007, which has about the same performance as the 15-58 on M, but perhaps H will be somewhat better, and 3), anecdotally, consider an appropriate boiler treatment.

Click to expand...

Thanks for the feedback Jim. I see your posts regularly and they are always informative. Tried running 15-58 on H and same issue persists. I have been theorizing whether the kettling and pipe clanging are somehow related to whether one or both of the heating zone circulators are running, or both stopped, when the hottest part of the burn is active. Essentially, if one or both circ pumps are running at this point I am pulling more BTUs out of the boiler than if they are both stopped at this point. Just a theory but I have not tested it yet. Have tried smalled loads thinking this might make a difference but it does not.

Your fitting/tubing arrangement at purge valve sounds interesting but I could not completely envision what you were suggesting. Do you by any change have a picture. Incidentally, as you have a Solo 40, has your firebox always been glazed black, scaly, and sticky when not. Tarm manual says to expect creosote deposits in firebox but have had this black glazing in their from day one. bypass damper occassionally sticky as well. Suspect this depends on idling period duration. Have taken damper door out and scraped inside of door and am good for a while.

Thanks,
Ken

huffdawg said:

Here is something that might be a possibility. I dont know if your system is similar but maybe.

Hot water heat water hammer with Honeywell zone valves
I’m posting this here to hopefully save someone else the trouble I went through trying to correct a water hammer problem on a hot water heating (hydronic) system that uses Honeywell V8043 F 1036 zone valves. In my case the zone valves (4) are on the supply side manifold and the single circulator pump (Grundfos) is on the return side manifold. A water hammer would almost always occur when one of the zone valves closed especially if the circulator continued to run because more than one zone valve was still open. Adding more tie down clamps to the pipes on each zone and insulating the heating elements in the baseboard registers with EDPM rubber gaskets offered no improvement. Experimentation with closing the ball valves that isolate each zone indicated that if the zone valves were moved from the supply manifold to the return manifold, the water hammer problem would go away - but to move them would be a lot of work. Other options I investigated were switching to Taco “slow closing†zone valves, adding a zone valve controller, putting each zone on it’s own circulator, or adding a water hammer arrestor to each zone on the supply side. I finally decided an easier and cheaper approach would be to try to use weaker springs to force each zone valve to close at a slower rate when the power was removed from the power head. Before replacing or stretching any springs, I noticed the V8043 zone valves have 2 springs and that when the short spring was disconnected, the valve still closed but at a much slower rate. Hence I disconnected the short spring on each of the 4 valves and have been running the system that way for a about a month and have had no problems with a water hammer or with de-energized zone valves being stuck in the open position.

Click to expand...

huffdawg, I am actually using circulation pumps in my heating zones as opposed to zone valves. Thanks for the input.

Ken

Squeezle Bob said:

Is the boiler level, on top. You want the air vent to be @ the highest point. If not, then air can remain on the top of the boiler an then you will get thumping and it is almost impossible to get rid of the air.

Click to expand...

Just checked and the boiler top is exactly level side to side and front to back.

Tarm Sales Guy said:

Hi KenLockett, while there might be some air in your system still, I doubt it. I think the thump you are experiencing is a result of your excellent firewood. With super dry wood like you have, your secondary burn is almost surely more intense than what the boiler is designed around. As a result you are getting a very hot (hotter than "normal") exhaust stream getting to the heat exchange tubes at the back of the boiler. The rate of heat transfer is so great at the bottom of the tubes where the exhaust gas first enters them that you can get micro-boiling on the water side of the tubes. Bubbles form on the surface of the tubes and then as the bubble moves away from the tube the lower temperature of the water combined with the boiler pressure cause the bubble to collapse. Thump.

A couple of ways to address this: first, raise your boiler pressure so that it it maxes out at around 20psi instead of 15psi. This will make it more difficult for the bubbles to form in the first place. Second, you could consider mixing some more traditional firewood (around 20% moisture content) with your super firewood. This will drop the temperature of your exhaust gas a bit and reduce the micro-boiling as a result. I think the only negative consequence of this type of burning is that you will likely go through tunnel stones and insert (slot) stones sooner than normal because your secondary burn is so intense. Seems like a good trade-off to me.

Your stack temps are still relatively low because you are transferring most of the heat to the boiler water as you should. I would even suggest that you are running the boiler at higher than rated efficiency. Outstanding! Just as a side bar, I wonder if the addition of boiler treatment actually impeded the heat transfer in Jim's boiler and that's why the thumping stopped? Just wondering. I know that adding anti-freeze to a system reduces efficiency so maybe the same with boiler treatment?

The black creosote glaze that you see is normal and it really sounds like you are burning the boiler correctly - dry wood (!) and only when it is cold enough outside. What you don't want to see is a molasses type creosote running down the firebox wall.

The big lesson to take away from all of this, I would suggest, is that the number one thing you can do to increase/optimize boiler efficiency is burn dry wood. Although all the other stuff we talk about on here is maybe more fun!

Hope this helps, keep us posted. Chris

Click to expand...

Chris,

Thanks for the suggestions. The interesting thing is the only initial firewood I could find on short notice when comissioning the boiler was the kiln dried stuff from a wood processing facility here in town. As this first cord is almost burned I will most likely try to find a seasoned batch as opposed to the kiln dried stuff and see if that makes a difference. In addition I am going to bump the pressure up to say 20 psig as you as well as others have suggested. Just now fired up the boiler again as I gone all day. With regard to your statement that I should not have molasses like creosote running down the sides please take a look at the attached pictures I just took prior to firing the unit back off. Does the interior of this firebox look normal? I suppose this could be construed as molasses like?? In addition, as I mentioned my damper has been sticking again over the past two days while not sticking prior to the cleaning of the damper door. As I am burning super dry wood as you put it is this the result of idling too long. What do you consider too long of an idling period? I have more photographs if these are not conclusive. I will keep you posted on this run with pressure raised.

jebatty said:

Ken: has your firebox always been glazed black, scaly, and sticky when hot. Tarm manual says to expect creosote deposits in firebox but have had this black glazing in their from day one. bypass damper occasionally sticky as well.

Click to expand...

Yes, the firebox has always been pretty much as you describe, but I do not get any running creosote nor has my bypass damper ever gotten stuck. I have storage and idling is about as close to none as one could get.

Ken: Your fitting/tubing arrangement at purge valve sounds interesting but I could not completely envision what you were suggesting. Do you by any chance have a picture.

Click to expand...

Click to expand...

Thanks for the info and pics Jim. May even try an auto-bleed valve as was mentioned in another post. For now trying suggestions of less dry wood and higher system pressure. Thanks.

Clarkbug said:

Ken,

I would agree that if you had a pressure of 12 to 15 psig when you were at operating temp, you were probably a little too low. Most fill pressures are 12 psi, so bumping that up should help you out.

On an unrelated note, how close are you to Albany?

Click to expand...

Clarkbug,

I am in the town of Petersburgh, NY drectly west of Williamstown, MA. I would say I am about 45-60 Minutes slightly NE of Albany.

Ran the unit last night with pressure between 20-22 Psig and so far so good. At least I haven't heard anything at this point. Have been using the smallest splits I can find in my pile and relatively small loads.

KenLockett said:

Tarm Sales Guy said:

Hi KenLockett, while there might be some air in your system still, I doubt it. I think the thump you are experiencing is a result of your excellent firewood. With super dry wood like you have, your secondary burn is almost surely more intense than what the boiler is designed around. As a result you are getting a very hot (hotter than "normal") exhaust stream getting to the heat exchange tubes at the back of the boiler. The rate of heat transfer is so great at the bottom of the tubes where the exhaust gas first enters them that you can get micro-boiling on the water side of the tubes. Bubbles form on the surface of the tubes and then as the bubble moves away from the tube the lower temperature of the water combined with the boiler pressure cause the bubble to collapse. Thump.

A couple of ways to address this: first, raise your boiler pressure so that it it maxes out at around 20psi instead of 15psi. This will make it more difficult for the bubbles to form in the first place. Second, you could consider mixing some more traditional firewood (around 20% moisture content) with your super firewood. This will drop the temperature of your exhaust gas a bit and reduce the micro-boiling as a result. I think the only negative consequence of this type of burning is that you will likely go through tunnel stones and insert (slot) stones sooner than normal because your secondary burn is so intense. Seems like a good trade-off to me.

Your stack temps are still relatively low because you are transferring most of the heat to the boiler water as you should. I would even suggest that you are running the boiler at higher than rated efficiency. Outstanding! Just as a side bar, I wonder if the addition of boiler treatment actually impeded the heat transfer in Jim's boiler and that's why the thumping stopped? Just wondering. I know that adding anti-freeze to a system reduces efficiency so maybe the same with boiler treatment?

The black creosote glaze that you see is normal and it really sounds like you are burning the boiler correctly - dry wood (!) and only when it is cold enough outside. What you don't want to see is a molasses type creosote running down the firebox wall.

The big lesson to take away from all of this, I would suggest, is that the number one thing you can do to increase/optimize boiler efficiency is burn dry wood. Although all the other stuff we talk about on here is maybe more fun!

Hope this helps, keep us posted. Chris

Click to expand...

Chris,

Thanks for the suggestions. The interesting thing is the only initial firewood I could find on short notice when comissioning the boiler was the kiln dried stuff from a wood processing facility here in town. As this first cord is almost burned I will most likely try to find a seasoned batch as opposed to the kiln dried stuff and see if that makes a difference. In addition I am going to bump the pressure up to say 20 psig as you as well as others have suggested. Just now fired up the boiler again as I gone all day. With regard to your statement that I should not have molasses like creosote running down the sides please take a look at the attached pictures I just took prior to firing the unit back off. Does the interior of this firebox look normal? I suppose this could be construed as molasses like?? In addition, as I mentioned my damper has been sticking again over the past two days while not sticking prior to the cleaning of the damper door. As I am burning super dry wood as you put it is this the result of idling too long. What do you consider too long of an idling period? I have more photographs if these are not conclusive. I will keep you posted on this run with pressure raised.

Click to expand...

Chris,

I think the kettling has stopped at least for now and I am keeping my fingers crossed. Have been mixing some 15-18% MC pine with the hardwood and pressure now between 20-22 Psig. Thanks for the suggestions. Any thought on the firebox pictures that I sent in the previous post? Does what appears in my photos apear to be molasses type creosote running down teh firebox sides?

Thanks

Tarm Sales Guy said:

firebox looks fine, glad things have improved.

Click to expand...

Chris,

Glad to hear the firebox looks fine. On another note, the boiler is thumping/clanging like crazy this morning after putting in wood this morning. Interesting thing is that the boiler temperature for the first time in over two days actually fell low enough (wood exhausted earlier last night than I planned for) to fire back up the oil boiler and heat it up. Loaded the wood boiler back up this morning as I still had coals in the wood boiler with a relatively small load (mixed batch again pine/hardwood). Thumping/Clanging is happening on every burn cycle even louder this time. At this point not sure if increased pressure had any bearing or not over past two days. Maybe it is the particular wood I am loading. Also now wondering if it could have something to do with the water in the oil boiler being warmed as well. I will have to keep studying this I suppose. Will post updates as I continue to attempt to figure this out.

Thanks

OK, here's my update. Installed the Auto-Bleed valve in the top of the boiler, am burning a combination of red oak, cherry, and locust at 15-25% moisture content and mixing in a bit of the kiln-dried stuff here and there, and pressure is now at 22 Psig. Two full days now and NO kettling and flue temps 400-500 DegF and amazingly less ash. Also, damper handle appears to no longer be sticking. This seems counter-intuititve to me but it's true. Combustion is much different than strictly with the kiln-dried stuff.

I'm keeping my fingers crossed and hoping the issue has been solved. Thanks again to everyone who provided feedback. Will follow-up again after running a few more days.

My advice to anyone out there considering kiln dried firewood. It burns TOO HOT on its own. If you are inclined to purchase any or come across any be aware that it must be tempered with your typical 15-25% cord wood. Lesson learned on my part.

Ken