Lennox Pulse exhaust problem

______________________________________________________________________ Recently, I have had problems with my circa 1990 Pulse furnace. It will try to start up and sputter like it is chocking on water in the exhaust, drip leg area. Then it will cut out. It will do this over and over until it finally clears things out enough to work, but it will still have a sputtering, inefficient burn. I have cleaned and checked the condensate pump and the pipes seem clear. After calling Lennox, they said to hacksaw off the bottom of the drip leg and clear out any crud that might be blocking the inside pvc pipe that leads to the drain. Did that (there was crud!) Sealed that back up, but still have problem. Maybe a sag in my exhaust PVC pipe (horizontal)? Should I snake that to see if there is a blockage? Service man came and did a pressure test (fine) and changed the sparkplugs $$$ and made sure the pvc pipes were angled correct, but just scratched his head over the problem. Air filter is clean. Any help? Replies: Xenos Webmaster “Re(1):Lennox Pulse exhaust problem” , posted Sun 29 May 10:01 ______________________________________________________________________ Since your furnace is that old I would recommend that the first 2 elbow where its enters the primary heat exchanger be checked for cracks or a break on the weld and I would also have the gas and air flapper valve replaced. Xenos. The best way to escape a problem is to solve it. niko851 “Re(1):Lennox Pulse exhaust problem” , posted Sun 29 May 09:17 ______________________________________________________________________ That’s ridiculous that this technician just ‘scratched his head’ after socking you with a bill for (probably) items you didn’t need, i.e. the ignitor. The indications of ‘gurgling’ and your diagnosis appear accurate, i.e. water is not draining, getting up into the components, and probably going out on a pressure cut-out. Also, the ‘pulse’ is designed to have intermittent operation. The easiest way to describe is that there is not a ‘constant’ flow of gas for combustion, and the burners ‘cycle’ to improve efficiency. Given that you’ve cleaned out about all that you could do, now the question is why wasn’t the pressure switch changed out? While the pressure test may have come back “normal”, this could be because at that time, there was not enough water backed-up for the unit to ‘act up’ and give a lower than normal reading. Finally, whenever a tech. comes out and walks away without solving the problem, it’s time to get stern. Demand, from the same company, that you want another tech out, at their expense, since the other one was not competent to correct the problem. You shouldn’t have to pay for service when you (in actuality) did not get service. Sure he swapped some parts, but that’s not a techician, that’s a parts-swapper. I can’t say for certain that the ignitor(s) were justified in replacement, but the problems you’ve mentioned (the water gurgling) has nothing to do with the ignitors. Again, tech. should have known this and troubleshooted appropriately. This “scratching of head” BS is just that – BS. No offense intended to you, but this tech did a ‘dog & pony show’ for you. Sounds like you are competent/knowledgeable enough to re-address the problem yourself, if you want. However, given you’ve spent $$ on this already, I say to get them back out as I mentioned before, telling them that there’s a drainage problem and the other tech decided to swap an ignitor, charge you for that, which in my opinion wasn’t even necessary. I could go on and on about this, so I”ll just cut myself off now…. SO – now it is your call; you’re on the right track by ensuring that there is proper drainage, however it is undisputed that you’re still runing into a drainage problem somewhere, somehow. You found ‘crud’ as well, which means there is probably more. The 90+ efficient furnaces have as many components as a computer; they have ‘motherboards’ even. Last, the control board (if i am not mistaken) has a self-diagnosing light which will flash a certain # of times to let the tech (and homeowner) know what the problem is. Doesn’t appear that this tech paid attention to that…. Hope this helpsand have a good holiday, despite the problem you’ve run into. Niko Check your circuit breaker or fuses before calling for service – it could save you $$!! dmacfadden “Re(2):Lennox Pulse exhaust problem” , posted Sun 29 May 17:06 ______________________________________________________________________ Thanks for the knowledgable replies. I will take these to the owner of the dealership and keep you posted! mechacc “Re(3):Lennox Pulse exhaust problem” , posted Sun 29 May 20:55 ______________________________________________________________________ When you cut the cap off the bottom of the drip leg did you also clean out the 1/2″ diameter pvc inside the 1-1/2″ drip leg? This is where the condesate water rises to go out the tee drain on the side of the drip leg. The air diaphragm that was mentioned is to be replaced every 4 years as well as the heat exchanger pressure leakage test being performed. Sagging vent pipes will collect water and cause a problem. Any debris in the pipe can also cause a lockout problem as well. If this has a concentric vent termination there is rubber insulation covering on the 1-1/2 inch pipe inside the concentric housing. There have been incidents where the rubber has torn loose and blocks the combustion air opening causing sputtering and shutdown. Another possible cause is vent gases recirculating into the combustion air intake. The gas pressure should have been measured.Too high or too low gas pressures can lead to lockout problems. Large amounts of pressure fluctuations indicates that the gas diaphragm is not properly seating. The exhaust gases should also be tested for the amount of carbon dioxide and carbon monoxide being produced. MechAcc niko851 “Re(4):Lennox Pulse exhaust problem” , posted Mon 30 May 08:35 ______________________________________________________________________ Thanks Mechacc for mentioning the concentric venting. Totally flew over my head since I haven’t run into a Pulse in a while.. In actuality, I should have ‘known’ it at least since they (similar ones I should say) are still in use today w/other units. Maybe I misinterpreted the ‘sputtering’ as solely water-related, not considering other factors. Given the verbiage of the post, I concentrated on the one aspect. Nice job, thanks again for the ‘re-cap’ 🙂 I do appreciate it and I’m sure the Owner does too… Have a good Memorial day, Niko Check your circuit breaker or fuses before calling for service – it could save you $$!! mechacc “Re(5):Lennox Pulse exhaust problem” , posted Mon 30 May 09:14 ______________________________________________________________________ Thank goodness the newer concentrics no longer have the rubatex insulation. But, there sure are enough of the ones that do that are installed that are just waiting out there. Have a good Memorial Day weekend. Especially to those that are now serving and have served in uniform. MechAcc dmacfadden “Re(6):Lennox Pulse exhaust problem” , posted Wed 1 Jun 16:32 ______________________________________________________________________ Bad news. A different serviceman came out and is saying that there is a “crack in the furnace where it ignites”. Now they are talking about us needing a new furnace due to the furnace not holding pressure where it ignites. The furnace does work, though poorly. Any thoughts. MechAcc “Re(7):Lennox Pulse exhaust problem” , posted Wed 1 Jun 22:44 ______________________________________________________________________ If you are the original owner, ie. the one who had installed. Check with the a Lennox company depending upon serial number you may be lucky. I am just guessing but it sounds like the first tech was looking for only corrosion on the secondary heat exchanger. A leading cause of Pulse failure but not the only cause of leaks. Cracks in different locations will cause excess sputtering and lock out. Hopefully the first tech will get the word and be a little more thorough in the future. MechAcc Xenos Webmaster “Re(7):Lennox Pulse exhaust problem” , posted Wed 1 Jun 17:56 ______________________________________________________________________ IT may not all be bad as it may be under warrantee, 20 year was standard on that model and if there is a recall witch there may be the labor will also be included. Xenos. The best way to escape a problem is to solve it. dmacfadden “Re(8):Lennox Pulse exhaust problem” , posted Thu 2 Jun 19:25 ______________________________________________________________________ You were right! The warranty is still in effect, though I will have to pay the labor for the installation. The dealer offers the G51 single stage high efficiency Lennox as a replacement. Should I consider offering to pay the difference and get a 2 stage unit like the G61? Xenos Webmaster “Re(9):Lennox Pulse exhaust problem” , posted Sat 4 Jun 15:04 ______________________________________________________________________ I guess it really depends on the costs and if this cost justifies the additional comfort you may gain. Xenos. The best way to escape a problem is to solve it. dmacfadden “Re(10):Lennox Pulse exhaust problem” , posted Sat 4 Jun 20:50 ______________________________________________________________________ Oops. Hit return on the blank message. The dealer said it would cost an extra $600 for the 61. The efficiency is the same (virtually) so it is just the 2 stage advantage. We are leaning toward the 51. MechAcc “Re(2):Re(10):Lennox Pulse exhaust problem” , posted Sat 4 Jun 21:06 ______________________________________________________________________ With the two stage you will get a little more comfort by running on low fire. MechAcc dmacfadden “Re(10):Lennox Pulse exhaust problem” , posted Sat 4 Jun 20:48 ______________________________________________________________________