Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: NHmtndad on March 21, 2014, 08:08:08 PM
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What a week...I woke up at around 1:30am Monday morning to my OWB screaming at me from my barn. I ran down to the basement and my gauge was reading 240 degrees. When I went out to the barn the unit was blowing steam out of the pressure relief valve. The main circulator pump was fried. In the end I had to manually remove the coals from the firebox which was sketchy to say the least. Pushing a wheel barrow full of hot coals through a barn full of wood was far from a good time.
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Goodness! I imagine you had a little trouble falling back asleep after all that excitement!
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Sure glad the relief valve worked! any reason found why it overheated? please replace the relief valve for future safety before refiring the boiler, at those temps I would be surprised if you didn't damage the pex.
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To say the least...I tried to trouble shoot it the next day but my experience is limited. I wasn't sure what caused it to overheat...I suppose I still don't know why. The main circulator off of the unit was toast at that point. I suspect that either the pump failed, which caused the overheating, or the unit was somehow allowing air to leak by through the ash door or main door. Does anyone have any other insight?
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Was the forced draft fan running when it was overheating? The aquastat could have failed in the closed position which caused it to leave the fan running. Door gaskets could definitely be a culprit, how do they look?
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I don't believe the fan was running but I could be wrong. Gaskets on the door look in decent shape and have held a tight seal all season. That morning I did notice that the Ash door seemed to be a little loose which was never the case. So On Monday I immediately replaced the main 007 taco pump and I also had to replace a handful of fittings because they had been leaking through the compression fittings after the incident. I then proceeded to refill the boiler and thought that I was bleeding the air correctly. After the pump was full to 10 PSI and held for a couple hours, I felt like I had a no more issues. Unfortunately this was not the case. I started a fire in the firebox at around 530 6 o'clock and by 8pm I was not showing an increase in temperature on the gauge located in the house, I was not getting proper circulation which was definitely the case as I believe the system was airlocked and overheated once again. At this point I'm not sure if I damaged the pump or anything else. I decided to wait till this morning to try and refill the boiler.
Being a novice at these types of things I do have some concerns. How do I test to see if the aquastat is performing properly? Also, I'm not sure how to properly test the system to see if it is circulating so I don't run into the same issue?
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My Aquatherm has overheated 3 times in the 16 years I've owned it (it's 18 yrs old). First time my son left the ash door open after cleaning. Second time I was away at a trade show in January and it happened to my wife in the middle of the night. That was fun trying to tell her what to do on the phone. Never did determine the cause of that one. The last time was this winter. The drive belt on the HX fan motor broke and wasn't blowing the hot air into the house, so it kept calling for heat and kept the aquastat fan blowing on the fire.
Thankfully the temp relief valve worked each time. And the pump kept working. All 3 times had to shovel out the wood/coals in order to cool it down enough that the relief valve (I keep a spare on hand) would hold so I could fill it again and restart. There's always a reason, just sometimes difficult to diagnose.
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Sure glad the relief valve worked! any reason found why it overheated? please replace the relief valve for future safety before refiring the boiler, at those temps I would be surprised if you didn't damage the pex.
Why he need to replace the relief valve? It worked..Which its designed to do.. Relief valves aren't a ,once they pop they aren't no good.. I pop mine at times when refilling the boiler with wood, when the fan just shut off and the fire is going good..No need to replace..Only time to replace when its leaking or has a constant drip..
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240 degrees is awfully hot, it should have popped before that, I would look for one that pops at a lower temp to protect the piping is all i'm saying, perhaps adding another would be in order as well, one may not have been enough to drop the pressure fast enough to protect the pipe, better safe than sorry!
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240 degrees is awfully hot, it should have popped before that, I would look for one that pops at a lower temp to protect the piping is all i'm saying, perhaps adding another would be in order as well, one may not have been enough to drop the pressure fast enough to protect the pipe, better safe than sorry!
of course it popped before the 240 f degree..and besides how he gonna ruin his piping when there's no flowing water.. It's the boiler itself was that hot not the water in the pex al pex.. I would stick with what the factory installed for the relief valve
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It very well might have popped before that...should pop at 210 if I'm correct. But the heat kept rising b/c the pump failed and the temperature didn't start coming down until after I shoveled all of the coal out of the fire box.
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Matty read post # 5, the heat obviously compromised the pex or the fittings would not be leaking, perhaps a lower temp relief valve or a second relief valve would have kept this from happening, without pressure the water would have a very hard time to go above 213 degrees much like boiling water in a pan on a gas stove, pressurize it and it will climb in temp very fast, remove the pressure and it will very quickly drop back to 212 degrees, It's called latent heat. NH, you posted your last comment before I finished, was there steam / water still coming from the boiler at that temp, if so then the damage to pipes and fittings possibly could have been avoided by a second relief valve, the boiler temp would certainly have still climbed in temp but the pressure and extreme temp of the water / steam would not have damaged the piping and fittings, would you rather that steam vent from a safe pressure relief valve or burst a fitting possibly in your home with your children in the basement playing, I am in no way bashing pressurized systems, all I'm saying is make it as safe as possible, steam is not something to be taken lightly, IT CAN KILL YOU OR YOUR LOVED ONES if done incorrectly!
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If the EPA regulations go through, then the gasification boiler will be the only choice on the market. It's also bad this will also put Americans out of jobs who manufacturer conventional OWB's.
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Slim I agree but the compromised fittings needed to be replaced anyhow. Doesn't surprise me that they leaked. The pipe had multiple older compression fittings and it was at a funny angle so it was due to fail at some point. Lots of steam came out of the boiler for well over an hour after I discovered the issue.
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Do you understand my concern for safety, If those fittings were to pop at a point where a person were standing, they would have been hurt, is it not worthwhile to be a bit redundant about safety?
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Yes I understand and agree. How would I go about being redundant with two relief valves? Is it as simple as putting in a tee where the existing valve is with a valve on each side?
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Anyplace in the line or preferably on the boiler, vent it to within 1 foot of the ground and if you use a ball valve to shut off water before the relief valve take the handle off the ball valve in the open position to ensure that it does not get shut off by accident, THANK YOU for listening to my concerns.
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Looks as if the isolation valve between the pump and the OWB has a weeping leak. Is it possible to just replace just the recessed screw? See pics.
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No they have no packing nut that can be tightened, You will more than likely break the stem before you can even close it. Replace it with a real watts isolation flange, the set should cost you about $40
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The pipe/fitting may be toast because liek all things metal (think OWB/most fittings) they transfer heat. Like I learned in Engineering class - everything in nature want to be equal - so heat will actaully travel down the metal fittings to the plastic pipe.
***This is also why you are supposed to plumb 18" away from DHW and other such heat sources before you transition to PEX - the whole heat transfer
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PRV's -pressure relief valves don't have temp ratings, only 30 psi relief and xxxx btu ratings. They must be located on the heat source without isolation. Normal routine maintenance includes replacing them annually. Steam is very damaging to any rubber or plastic components in the system. They should be tested manually or by cycle once a year, cuz they like to stick , turning a 30psi relief into a 50-60psi relief and thus a violent dump when they do go.