Fire in chamber and smoke in basement
2019 Spirit VHF-ABT oil fired furnace with Beckett AFG burner. Last year the pump went. Replaced it with new clean cut pump and it worked fine for a few months, then same problem. Limped it through and now here we are with this heating season. First fire up of the year (early Sept) and burner went into lockout because the pump was seized up. Did a service on it - filter, nozzle, electrodes, coupling, freed up the pump and cleaned exchanger. Start it up and it ran, but a fire burned in combustion chamber after shut down for almost 10 minutes. Pulled it apart, checked everything, reassembled and did same thing. Combustion analyzer said everything was in check. My buddy who’s a tech recommended just running it and burning off any residual fuel inside. It was warm so a few days went by, go to start it and pump is stuck again. Spun it free by hand, reset it, burner lit and again a big fire after shut down. After talking to Beckett tech support they assured me the oil pump failure was from sludge in tank. I removed the two pipe system that fed off the bottom of the tank and changed it to one pipe off top. I installed a Tiger loop/filter to go along with new filter in the original filter housing as extra insurance. Installed new pump, bypass plug installed, set to 120 psi my unit called for, new nozzle, bled the air, start it up and once again big fire. Over the course of a week I’ve tried many things. I adjusted the Z dimension per Beckett manual. I confirmed solenoid is shutting off fuel instantly upon shut down. I completely disassembled the furnace and removed the heat exchanger for visual inspection. Still shiny and new looking. I also burn wood so this furnace gets little use. Only burn 100 gallons or so a season. (Also probably reason sludge in tank.) I smoke tested the heat exchanger. Slowly heated it with a large weed burner torch in the dark in hopes the metal would expand and a crack would appear and then smoke tested it again. I stuffed flashlights into every opening hoping to see light. Nothing. I reassembled, blocked the air tube and tried to use the blower to get any air back through the heat exchanger out the flue. Nothing. I adjusted the barometric damper while running to try and set it at -.03. The Klein manometer I bought isn’t the best, but I definitely seem to have a positive pressure coming down the flue and also out of the inspection cover. So as it sits right now I can’t get that -.03 -.04 in the flue and when I pull the nozzle assembly out it seems to always be soaked in fuel. I also removed the nozzle adapter and installed a new one with a new, correct size nozzle, measured the distance from nozzle to head with straight edge and ruler and set to manufacture specs which I believe was 1-3/8” with the heat shield which my burner has. I also replaced the original retention head due to cracks on it. I had my chimney repointed last year and new clay flues installed. The old ones were even in height. The new ones are offset with the upstairs fire place taller than the flue for furnace in basement. Research seems to say this is normal. I’m also a sinner and have the wood stove tied into same flue as furnace. I sweep the chimney every season and haven’t had a problem since installing the furnace in 2019. I did for the first time today though have some of the smoke from furnace exiting from the door on the wood stove. So there is a definitely a draft issue as well as a combustion issue in the chamber. But why all of a sudden? Sorry so long just trying to cover all bases. I am a licensed tech, so I’m knowledgeable, but limited as I do commercial ac/refrigeration. Any ideas?
Thank you
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First thing to do is fix the illegal venting. Second thing to do is address the quality of the fuel oil and tank. You have serious problems if you are going through oil pumps like that. No filter or tiger loop is going to solve the problem of a badly contaminated oil tank.
What is this "heat shield" ? Are you talking about the flame retention head? Those usually last a very long time. If yours cracked within five years that's a major red flag that you are back drafting the chimney and overheating the chamber, which takes us back to the first thing I mentioned. Separate the flues, it's not a sin to combine them but it's against code and unsafe to vent them together.
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Yes first thing I planned to do today is remove the wood stove from the equation. The heat shield is part of the retention head. So could the back draft be the reason I am finding unburned fuel in the air tube? Poor combustion preventing proper air/fuel mixture and not all the fuel is burning? Thanks for your advice
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Are you absolutely positive the chimney is clear and sound?
It's the correct firing rate for the boiler? Nozzle and pump pressure?
"Combustion analyzer said everything was in check." Really?
You're stuck on the pump seizing, but it could be the motor, or the coupling is too long. But none of that explains a saturation.
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Back drafting over heating the chamber can cause the nozzle to drip but I don't think it would completely explain what you described. I'd check combustion, draft over fire and draft in the stack. I would be suspicious of an ignition issue as well. Check the resistance to ground on each spring of the igniter and between the springs. Double check the electrodes.
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I am positive chimney is clear I swept it like 3 days ago and cleaned everything out from clean out. I’m positive the fuel pressure is set to 120 psi and it has correct nozzle. I bench tested the motor and it was perfect. I replaced coupling with exact one I removed. I have a new set of electrodes I’ll put in and I will check resistance on springs. I like that idea. Thank you
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Springs were 670 to ground with nothing between them. I read the reading between springs should be less than 2000 ohms, which technically it is and the measurement of each spring to ground should be 1/2 the spring to spring reading. Which would still fall under the 2000 ohms. Is this correct?
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The resistance of each spring to ground should equal the total resistance when measured across the two springs.
Your combustion test results look decent, I only see one draft reading and I assume it was taken in the stack. I don't measure draft in mbar, I measure it inches of water column so I can't comment on the draft measurement. You need two draft measurements, one in the stack and one over fire. Hopefully oil pump pressure and the same nozzle was in the burner when these measurements were taken. Even so, a combustion analysis needs to be done anytime anything is changed, even the burner nozzle. I have had different results when installing new nozzles even when I put in the same exact size and spray angle nozzle from the same manufacturer. I've also measured higher and lower oil pump pressure on equipment that was supposed to be set from the factory. Gotta check this stuff every time you work on a oil burner. The tools are expensive, that's why it's usually best to call a professional.
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Do an over fire draft test.
Check draft over fire while system is idle. With the tube still inserted, turn on the fan only (not the heat) and look for a change in draft. Going from 0 to negative with the fan off, to positive or heavily fluctuating with the fan on is an open heat exchanger.
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Ya I’ve reached my limits today. I have an oil burner guy coming tomorrow. I’ll let you know what he says. Thanks for all the help.
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The tech today tested the pump (and everything else) and says the seal appears bad as it was losing over 20% of the pressure after shut down. He also suggested adding an oil safety valve to prevent siphoning from the over head oil line. He seems to think the oil is siphoning, filling the chamber and then causing the fire. Also causing the bad seal. Another combustion analysis proved to be in spec. There was still a positive pressure at fire box but he suspected it was from the fuel burning within. Thoughts ?
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Last year the pump went. Replaced it with new clean cut pump and it worked fine for a few months, then same problem.
I find it impossible to believe that a brand new Clean cut pump has failed after less than one year of use. If this is the true situation, the source must be found.
BTW, if the pump loses "20%" at shutdown………..and HOLDS pressure after that point………..the pump is perfectly fine. If it loses 20% and continues to drop, the tech has a valid argument.
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ya it was continuing to drop
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Yeah it's quite normal for the pump to drop pressure after shutdown like that. You gotta watch it for a while and see if it continues to drop. A pump seal leak will give you obvious visual indication when you remove the oil pump. You will see oil on the pump shaft, on the air band, air shutter, air guide and burner chassis. The drop in pressure test is to check if the internal cutoff in the pump or solenoid valve is not holding and allowing oil into the nozzle line when it shouldn't.
I agree that you would have some serious issues if you are going through pumps like that. And oil siphoning and filling the chamber? A dripping nozzle is one thing, filling the chamber is another. I have a hard time believing that.
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yes it’s dripping. Not physically filling it. As for the solution to the bad pumps, that’s why I added tiger loop and switched to one pipe from top of tank. Hopefully no more sludge
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He was saying seal, but I’m wondering if he meant the solenoid valve stem not seating. Is this a possibility?
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It's very easy to see if you get oil out of the nozzle line after shutdown.
Where is the oil tank, and how are the oil lines run? On the floor, over head, both?
In you're first post you mentioned installing a bypass plug, but now you're saying a tech suggested and OSV. So…? As far as I know, an OSV doesn't get used on a 2 pipe system, so what exactly are we looking at here? Might I suggest we have a bypass plug in a one pipe system? Because that makes as much sense as anything else here.
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Tank is in basement with furnace. As I mentioned in the first post, I converted it from a 2 pipe to a 1 pipe. The line is ran off the top of tank, strapped to the joists for about 20 feet and then it drops down to the tigerloop which is mounted next to the furnace/burner 18” off the floor. The bypass plug is installed in the clean cut pump when using a return line on a 2 pipe system OR with a tiger loop.
Also as I mentioned I pulled the connection tube off the assembly side of the burner, put it in a water bottle and called for heat to test the solenoid. Oil flowed and once the call for heat was terminated, the solenoid closed and the oil stopped instantly. That test was performed per the Beckett tech support phone call I made. The oil burner tech who came yesterday was concerned that although the oil stopped when I did that, it wasn’t under “pressure” because the nozzle was removed. Then, when we did a pressure test with the gauge, the pressure reached 120 and continued to drop past 80. The recommendation was a faulty seal or seat in solenoid and OSV to prevent the gravity/siphoning from the one pipe overhead oil line.
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Combustion analysis would have shown the difference btw afterdrip vs. a leaking pump. You should still have it done.
If the chimney isn't relined, get it done separating the woodstove from the heater and the fireplace. Each wood fire requires its own separate suitable flue and all flues must meet NFPA 211. You cannot legally reline with terra cotta btw.
If you're getting oil fumes recirculating down another flue you have pressure issues. Usually, the fumes of the upper backdraft down into the basement because it is more depressurized unless you have other factors shifting the Neutral Pressure Plane. What has changed? Was there a mechanical exhaust running when it backed up? Someone leave a window or attic access open upstairs? Is there ductwork in the attic where a supply duct could have separated? Alterations to the structure?You can tinker with equipment until you prove you have the proper venting and expect positive, reliable, repeatable results. Get a new sweep and have him perform a level II inspection on the whole chimney. There is probably a shunt btw the oil flue and stove flue. Regardless, the flues need to be relined. Next, conduct a Worst Case Depressurization Test to see what is or can interfere with draft. It will indicate the depressurization limits of the house, too. Correct the venting, makeup air (MUA) and CAZ issues THEN adjust the appliance THEN prove it's set up properly by combustion analysis. While you're at it, make sure that furnace is really scrubbed out and the fire chamber in proper condition. Part of running CA including recording the delta T because that affects combustion and efficiency. You may need to change out or modify the duct work. Measure the TESP for starters. CA will show if there's interference when the blower kicks in.
Pics?
Please use paragraphs on long posts. Now, what was that about burning weeds? 😁
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