Was good for sure, however I wouldn'tcall that fan a safety feature....maybe, but more essential than anything, when that thing quits and all the exhaust s8de down stream is full of gas and oxygen....ya, yall kno whathappens next. Its a purge fan glad he didn't blow his head off. Very cool video though, we need more people with the pioneering mind!
I have a Lennox pulse in my home and yes its loud but I keep up with service and maintenance. Its got an updated heat exchanger and has been very reliable. Very efficient for its age which is the reason I haven't replaced it yet. I'm an hvac/ sheet metal mechanical contractor, so I see this unit as an old classic car. Its no trailer queen though. It won't quit pulsing and keeps my home nice and warm in the cold winter here in Boston. Love your video. 👍
Im getting a gas smell during the purge sequence especially if its real cold outside an the unit cycles back on pretty quickly. Any idea what that could be?
@@philb707 check your inducer motor with front plate removed. If it's spinning freely and pressure switch closes then check sensor, spark plug and wire.
@@williamfabiano543 Maybe you could help. I'd greatly appreciate it. My pulse wasn't starting consistently. An HVAC tech tried different things and replaced the control board. It would run for a few weeks, then wouldn't start unless it was powered off for a while. After the 6th visit or so, they said there wasn't more they could do, so I tried taking the flame sensor out hoping to replace it. The techs didn't want to take it out. The threads are galled on the sensor and the chamber. Do you think it's repairable? I thought maybe the chamber could be retapped.
@@justinmcgrath753 how did the threads get galled? Anyway have you changed your flapper valve? Check for blockage in the venting. Someone should have already checked gas pressure on both sides of the gas valve. Sometimes gas street pressure or gas meter regulator pressure can make a pulse missfire. Very sensitive. So check gas pressure, should be 3-4" w.c. i believe. very simple design, assuming the control is fine and F.S. is fine it should be easy to diagnose your problem.
@@williamfabiano543 I think they're galled just from removing the sensor. I used a ratchet and it only took moderate pressure. I didn't have to force it. When I got it out though, the threads were ruined. Maybe the chamber threads are OK, but it's hard to see. I can't get the sensor back in though. He said he checked the flue and I assume he checked the gas pressure. The first visit he cleaned the flapper, and that seemed to help for a while. I don't know if he later replaced it when it stopped working again. I'll double check the flue and ask them whether they checked the pressure. I don't know what F.S. is - flue size? Thanks for your help.
Great video, it is nice to see the distance between the flame and spark plugs are before taking everything apart. Our three units are 32 years old (21's) and they always run like brand new. Never an issue, ever.
lennox pulse furnace was great when they first came out. you are supposed to replace both flapper valves once a year. lennox discontinued all the parts for those furnaces. johnson makes controllers for them still. the failure in those furnaces is the brazing on the coil heat exchanger. it breaks from vibration and leaks into the home. the flame sense probe actually picks up the milivolts produced by the flame. if the unit isn't properly grounded the controller should shut down the unit due to not having a ground to compare the milivolts to. it would be a lockout due to no flame sensed. the combustion blower is only used to purge the combustion chamber for initial startup. those furnaces like to run at 2.5 to 4" of water column for natural gas. because its a pulse you have to measure the differential pressure from supply to manifold pressures across the gas valve, there should be some ports on the plumbing for measuring the pressures. for propane you need close to 9' of water column on the manifold side. also a different size orifice due to the different btu output of the fuel. when the units run to rich they sputter but don't miss a burn, to lean they sputter and miss. i work for a lennox dealer in reno nv. i've worked on quite a few of those furnaces. however i condemn more than i fix due to the failing heat exchanger. i am actually surprised to see someone with one apart, most people are happy to get rid of them. i enjoy you eagerness to explore!!!!!
My 33 year old Lennox Pulse G14 100k btu furnace has been nearly trouble free for the last 16 years in my home. Keeps my 4900 sf home warm for under $100/mo in Jan and Feb in Northern Colorado. I will continue to maintain and repair this awesome furnace as long as I possibly can. Absolutely no good reason to replace it. The cracked welds on the heat exchanger occurred in a relatively short run of production which resulted in less than 2% of replacements under warranty. I keep multiple CO detectors in my home just in case anyway. Best furnace ever made!
Im getting a gas smell during the purge sequence especially if its real cold outside an the unit cycles back on pretty quickly. Any idea what that could be
Principle of a German V1 rocket motor sitting right in front of you. Really cool. Thanks for taking the time to show it and explain how it works. Too bad these are so noisy.
I love this thing. I can see it should be extremely efficient. it appears that all most every bit of heat will be converted in this system. like a well built pulse jet. :) ~Russ
+rwg42985 Yeah it is really great! A lot of people didn't like it though because it sounds like a big truck running outside your window! :P The other reason was that the constant vibration would cause the brazed joints in the radiator to crack and leak carbon monoxide into the house. It is a positive pressure system unlike the newer ones that are negative pressure. So if the newer ones get a leak in the heat exchanger they will simply suck in air from the house, not leaking any CO into the house. Other than that they are great units. Our house has 2 furnaces and the other one is the same type and it runs on!
+Makerj101 every time I build a zvs driver I get a little bit use of it, and then it quits, I checked my mosfets after that and I find out some how, the voltage killed them, do you have any idea why this is happining?
+Owen Chase science channel Well it's probably inductive feed back voltage spikes from the transformer. You could try increasing your capacitors. That may absorb some of the voltage. Apart form that I can't really help that much because I have the same problem.
That air (and gas) flapper assembly is extremely critical. It controls airflow and just a few thousands change in the spacer will change the way it fires. We had trouble with these when I first went to work for "the outfit." Especially on the older ones, gas pressure was critical, and often "had" to be run out of spec to get them to fire. Read my comments your other post. Sensor is an insulated rod, this is common known as "flame rectification." The controller feeds a fairly high (around 100v) limited AC to the rod, and when it is "in a flame" it actually rectifies a tiny DC current, sort of like a crystal radio. The controller detects this current and as long as that is present locks the box for operation, until the stat or other control opens. I don't remember current on these, but generally around 1/2+ to as much as 4-5 microamps DC current on a working sensor.
@@ahmalcunningham7809 If you do not know how to troubleshoot it you need to call a Lennox dealer who does. There are many problems that can prevent firing, some simple, but they require a knowledge of the operation and safety concerns of the equipment. I used to maintain/ repair these and others when they "were"
The sensor is not a "thermocouple." It is a flame rod, flame detector, flame rectification. It works on the principle that the controller supplies a fairly large AC voltage, the sensor sits in the flame and is rectified by the flame to a tiny DC current. This varies with design of the unit, but generally is from 1/2 to 5 microamps or so. That's right.......microamps. The ignition control detects this tiny DC current and that "proves" the flame
@@chrisnichols9830 @fourfortyroadrunner it's ac to dc rectification by flame. the carbon molecules in the flame allow the ac current to flow from the probe, thru the flame, to ground (the burners are electrically grounded) and that creates a voltage drop, (dc offset), the ignition control microprocessor reads that voltage drop to confirm there is a flame present. If no flame is detected, it shuts off the gas for safety.
Our Pulse G21 is 24 years old and runs great. Easy to troubleshoot and repair if you know the basics of how to use a multimeter. Service manual has detailed troubleshooting diagrams. If heat exchanger cracks, its garbage. I have 2 CO sensors near the furnace room (which also has 2 gas hot water heaters in it) in case the furnace or water heaters have problems..
Mine was installed in 1996. Just had it pressure tested last year. I have had to replace the purge motor and the control board but did those myself. (my brother is an HVAC tech and helped me out on the board diagnosis). Flapper valve/etc. maintenance done last year with the pressure test too. Only issue I have is the occasional non-start-up even when the thermostat is calling for heat.
Tyler G, our G21 is starting to have a problem, doesn’t always kick on when the thermostat says to. I’ve changed the flapper & poked around. I’m interested in pulling out the spark plug, either replacing or cleaning it. Any advice on how to get it out would be appreciated. Socket size, type of wrench? Happy Thanksgiving 2019!
I have two in my home. Both are twenty one years old. There is one in the attic for the upstairs. I don't worry about CO as it will directly vent out of the roff. I do have one in my basement and I also keep two CO detectors nearby. I have not had either pressure tested in over ten years as it is hard to find a tech that will do this. Most companies will tell just tell you to toss the furnace I yearly take the air flapper apart and clean it. The media flappers for the 100,000 btu units are getting hard to find. The 80,000 btu and lower ones seem available (they are the same size for 40/60/80 btus).
@@raquelpolson3691 if you can't feel any heat from the outside surface of the ductwork at top, even a rubber fabric flexible membrane boot between the furnace and ductwork, then there is no flame and possibly bad spark plug or dirt flame sensor. if there IS heat but the unit only runs 15-20 seconds, then check air intake & exhaust tubes for blockage, and listen for excess water bubbling sounds in the lower exhaust pipe. use a shop vac to suck out the excess water formed from many false starts, there should be a small thin pipe to drain the water to floor / ground.
These were normally fussy on gas pressure and venting. Just like a two stroke expansion chamber, the venting affects overall operation. In some cases we used undersized vent tubing with very short vents on the larger 100K furnaces which were even more fussy.
Cool video. Just found a G21 pulse bad tonight. 27 years old. My co dectector showed 35 ppm when I walked in the door. I'm anxious to see where exactly it cracked or separated. Guess I'll find out tomorrow.
Lennox Pluse (10/1987) G1404/5-100-6 still chuging along. Replace flapper about every 4 years. Had to change Fan Limit switch - HOWEVER generic limit switch cause Blower to short cycle. So had to add Delay -Off-Relay set to 4 minutes (that feature was built into original fan limit switch).
The Pulse was in theory and even practice the most efficient furnace ever made, and pretty durable. The problems came when these heat exchangers cracked and they refused to run. Owners swore by them as they were 97 percent efficient.
Makerj101 I worked in the heating, ventilation and air conditioning industry for number of years and also performed energy efficiency tests on individual pieces of equipment to show the customer. These were done with a combustion analyzer and many of these were 97 to 98% efficient. This is really good for a furnace that's about 20 years old. The downside is that they need to be tested EVERY YEAR and scrapped if they fail. These can develop cracks, especially units built before 1990. Problems with starting, water leaks and even carbon monoxide are the result. Personally, I'd just bite the bullet and replace it.
+Walter Grace Interesting thanks! We did replace the one unit that I show in this video. That's why it's all taken apart. We have another unit that is exactly the same and we will keep using that unit until it needs replaced.
Walter Grace Thank you! I should probably do a service on our other furnace like this and pressure test it. It's been a couple of years since it's been pressure tested last.
6:10, it's missing the sealed chamber around the combustion chamber. it purges that chamber before ignition so the flapper chamber has to be sealed for it to pass that part of the start up process.
Talked Dad into getting one of these back in 1985 or so after I saved the family by smelling the combustion products of the old 1969 era gas furnace. HVAC guy didn't believe I could smell the CO. I have always been able to detect it. Anyway, I remember it working quite well back in the day. Certainly antiquated by today's standards. Was funny how the neighbor complained about it rattling his windows, so HVAC company had to come out and put auxiliary mufflers on the exhaust and inlet.
I just worked on one these for the first time ever in 20 years a week ago a bird was stock in the forced air motor. Got it cleaned and and running and immediately cut it off thinking something else was wrong because of the noise. These are pretty loud
+sporadic -Z Actually, I still have one, which unfortunately I a;m replacing, because it needs a few parts and it;s not worth buying new NLA stuff for $$$... In any case, they were well over 90% efficiency delivered to the vents. Mine tested 97%. The new lennox 90%+ going in is actually an efficiency downgrade. Don't forget, all those hot parts are mounted in the air stream- the fully boxed, operating unit barely gets warm externally. Even with all the mufflers and stuff that went on them though they still were a bit grumbly and I won't miss that part. Still, I will miss having my house heated by a pulse jet. :)
Have had mine for 35-years. First time replacing the ignition controls (Elite Parts $85). New flapper & intake gasket ($26). Best $1000 upgrade made during construction in 1984. Noisy, heavy beast but efficiently ahead of its time.
The noise was another complaint from customers, the temps were -20 C for months where I lived, the furnace would come on every 15 minutes, the pulse furnace sounded like a Vulcan cannon going off every 15 minutes for 5 minutes LOL
Cool! I just can't understand the advantage of a pulse combustion like this versus just a simple, constant burner. Seems more complicated and the noise is just aweful.
+ch300fnqi Yeah me neither. But it works! LOL It's one of the first high efficiency furnaces that used PVC plastic pipe for the exhaust vent. So for some reason that was the only way at the time that they could make it that efficient. When it was all hooked up to the vent pipes it wasn't that loud. However it did kinda sound like a truck idling out side hahaha
+ch300fnqi Don't quote me on that but I think it has to do with the turbulences created by this particular combustion mode. The turbulent flow is more efficient at transferring the heat to the pipes so you get a colder exhaust and more heat into the water. So it improves the efficiency of the furnace.
+stefantrethan Yeah me too... kinda wish I would of done more experiments with it. But my parents wanted it gone. It sat in the drive way for too long in their opinion.
if you havent already, get your heat exchanger inspected. they crack at the braze joints and leak CO into the house. if your capable of checking it, unplug the fan connector, remove the 2 3/8" screws on the blower housing. slide it out of the way and look at the joints on the coil. you would see white crusty building up from moisture escaping. if you see the white crust, time for a new unit.
+MrJohhhnnnyyy Well it was used for heating my house for the past 25+ years. And the down stairs part of the house is still heated by another one exactly the same. With the exhaust pipes on it's not as loud.
yeah everytime I see one of these I say get rid of it. Now I have a video to use to scare people into pulling the trigger. Looking at the guts of this thing really drives it home how absurd it is.
60Hz flyback? Why not just use a standard transformer? O.o I donder unserstand the point of this furnace, it's so damn loooooooooooud, what's it even used for? It's basically just a pulsejet xD
+Jordan O'C (Xenro66) Yeah IDK what I was saying there LOL. It's much higher frequency than 60Hz. Well it's one of the first high efficiency furnaces that used PVC plastic pipe for the exhaust vent. So for some reason that was the only way at the time that they could make it that efficient. When it was all hooked up to the vent pipes it wasn't that loud. However it did kinda sound like a truck idling out side hahaha
Makerj101 I don't even know the optimal frequency for a flyback is haha. Ah right... Jesus dude, I couldn't put up with it. What's wrong with a good ol' normal flame? xD
I was a helper for a plumbing and heating outfit in the late 80s , these things were really efficient and high tech but as far as reliablity they sucked , they failed so often it was embarassing.
Carbon dioxide and water are the byproducts of combustion anytime you burn natural gas and are vented to the outdoors. Neither is toxic. You do the same thing with your gas stove and oven and don't even think about it. You should run your vented range hood when cooking but many people don't.
Serviced these from the first models to the last. Basiclly they became to expensive to manufacture due to all the hand welded parts. Some are over 30 yrs old,you won't get that out of your new furnace,or anything even close to that. I'm wondering if your Dad has your life insurance paid up,your lack of knowledge is going to get you hurt some day. You know just enough to be dangerous.
"It's missing all the safety features but we don't need those, it works fine without em". Probably my favorite thing you've said.
+nekocal LOL
My favorite part too
Was good for sure, however I wouldn'tcall that fan a safety feature....maybe, but more essential than anything, when that thing quits and all the exhaust s8de down stream is full of gas and oxygen....ya, yall kno whathappens next. Its a purge fan glad he didn't blow his head off. Very cool video though, we need more people with the pioneering mind!
I have a Lennox pulse in my home and yes its loud but I keep up with service and maintenance. Its got an updated heat exchanger and has been very reliable. Very efficient for its age which is the reason I haven't replaced it yet. I'm an hvac/ sheet metal mechanical contractor, so I see this unit as an old classic car. Its no trailer queen though. It won't quit pulsing and keeps my home nice and warm in the cold winter here in Boston. Love your video. 👍
Im getting a gas smell during the purge sequence especially if its real cold outside an the unit cycles back on pretty quickly. Any idea what that could be?
@@philb707 check your inducer motor with front plate removed. If it's spinning freely and pressure switch closes then check sensor, spark plug and wire.
@@williamfabiano543 Maybe you could help. I'd greatly appreciate it. My pulse wasn't starting consistently. An HVAC tech tried different things and replaced the control board. It would run for a few weeks, then wouldn't start unless it was powered off for a while. After the 6th visit or so, they said there wasn't more they could do, so I tried taking the flame sensor out hoping to replace it. The techs didn't want to take it out. The threads are galled on the sensor and the chamber. Do you think it's repairable? I thought maybe the chamber could be retapped.
@@justinmcgrath753 how did the threads get galled? Anyway have you changed your flapper valve? Check for blockage in the venting. Someone should have already checked gas pressure on both sides of the gas valve. Sometimes gas street pressure or gas meter regulator pressure can make a pulse missfire. Very sensitive. So check gas pressure, should be 3-4" w.c. i believe. very simple design, assuming the control is fine and F.S. is fine it should be easy to diagnose your problem.
@@williamfabiano543 I think they're galled just from removing the sensor. I used a ratchet and it only took moderate pressure. I didn't have to force it. When I got it out though, the threads were ruined. Maybe the chamber threads are OK, but it's hard to see. I can't get the sensor back in though.
He said he checked the flue and I assume he checked the gas pressure. The first visit he cleaned the flapper, and that seemed to help for a while. I don't know if he later replaced it when it stopped working again. I'll double check the flue and ask them whether they checked the pressure. I don't know what F.S. is - flue size? Thanks for your help.
Great video, it is nice to see the distance between the flame and spark plugs are before taking everything apart. Our three units are 32 years old (21's) and they always run like brand new. Never an issue, ever.
lennox pulse furnace was great when they first came out. you are supposed to replace both flapper valves once a year. lennox discontinued all the parts for those furnaces. johnson makes controllers for them still. the failure in those furnaces is the brazing on the coil heat exchanger. it breaks from vibration and leaks into the home. the flame sense probe actually picks up the milivolts produced by the flame. if the unit isn't properly grounded the controller should shut down the unit due to not having a ground to compare the milivolts to. it would be a lockout due to no flame sensed. the combustion blower is only used to purge the combustion chamber for initial startup. those furnaces like to run at 2.5 to 4" of water column for natural gas. because its a pulse you have to measure the differential pressure from supply to manifold pressures across the gas valve, there should be some ports on the plumbing for measuring the pressures. for propane you need close to 9' of water column on the manifold side. also a different size orifice due to the different btu output of the fuel. when the units run to rich they sputter but don't miss a burn, to lean they sputter and miss. i work for a lennox dealer in reno nv. i've worked on quite a few of those furnaces. however i condemn more than i fix due to the failing heat exchanger. i am actually surprised to see someone with one apart, most people are happy to get rid of them. i enjoy you eagerness to explore!!!!!
My 33 year old Lennox Pulse G14 100k btu furnace has been nearly trouble free for the last 16 years in my home. Keeps my 4900 sf home warm for under $100/mo in Jan and Feb in Northern Colorado. I will continue to maintain and repair this awesome furnace as long as I possibly can. Absolutely no good reason to replace it. The cracked welds on the heat exchanger occurred in a relatively short run of production which resulted in less than 2% of replacements under warranty. I keep multiple CO detectors in my home just in case anyway. Best furnace ever made!
Im getting a gas smell during the purge sequence especially if its real cold outside an the unit cycles back on pretty quickly. Any idea what that could be
@@philb707 Poor diet?
@@basketballjones6782 possibly
Principle of a German V1 rocket motor sitting right in front of you. Really cool. Thanks for taking the time to show it and explain how it works. Too bad these are so noisy.
+Lidmotor Yes exactly! You're welcome!
@@makerj101 Mine not ingniteing ,what can I do to have it working? It's- 47C right now as I speak. Would really appreciate your help.
Canada!
I love this thing. I can see it should be extremely efficient. it appears that all most every bit of heat will be converted in this system. like a well built pulse jet. :) ~Russ
+rwg42985 Yeah it is really great! A lot of people didn't like it though because it sounds like a big truck running outside your window! :P The other reason was that the constant vibration would cause the brazed joints in the radiator to crack and leak carbon monoxide into the house. It is a positive pressure system unlike the newer ones that are negative pressure. So if the newer ones get a leak in the heat exchanger they will simply suck in air from the house, not leaking any CO into the house. Other than that they are great units. Our house has 2 furnaces and the other one is the same type and it runs on!
+rwg42985
Just a pulse jet engine! And yes, they are efficient at producing heat and noise.
+Makerj101 every time I build a zvs driver I get a little bit use of it, and then it quits, I checked my mosfets after that and I find out some how, the voltage killed them, do you have any idea why this is happining?
+Owen Chase science channel Well it's probably inductive feed back voltage spikes from the transformer. You could try increasing your capacitors. That may absorb some of the voltage. Apart form that I can't really help that much because I have the same problem.
Makerj101 ok thanks, I have not been using any capacitors.
That air (and gas) flapper assembly is extremely critical. It controls airflow and just a few thousands change in the spacer will change the way it fires. We had trouble with these when I first went to work for "the outfit." Especially on the older ones, gas pressure was critical, and often "had" to be run out of spec to get them to fire. Read my comments your other post. Sensor is an insulated rod, this is common known as "flame rectification." The controller feeds a fairly high (around 100v) limited AC to the rod, and when it is "in a flame" it actually rectifies a tiny DC current, sort of like a crystal radio. The controller detects this current and as long as that is present locks the box for operation, until the stat or other control opens. I don't remember current on these, but generally around 1/2+ to as much as 4-5 microamps DC current on a working sensor.
Mine not kicking in, just the fan. What can I do to make it work. Thanks for the help
@@ahmalcunningham7809 If you do not know how to troubleshoot it you need to call a Lennox dealer who does. There are many problems that can prevent firing, some simple, but they require a knowledge of the operation and safety concerns of the equipment. I used to maintain/ repair these and others when they "were"
Ahh yes, the Direct Current Current. Those are used in PIN Numbers (Personal Identification Number Numbers) too, aren't they?🤣
@@basketballjones6782 No idea what you are talking about, an I don't think you do, either.
The sensor is not a "thermocouple." It is a flame rod, flame detector, flame rectification. It works on the principle that the controller supplies a fairly large AC voltage, the sensor sits in the flame and is rectified by the flame to a tiny DC current. This varies with design of the unit, but generally is from 1/2 to 5 microamps or so. That's right.......microamps. The ignition control detects this tiny DC current and that "proves" the flame
because the plasma of the explosion is conductive?
@@chrisnichols9830 @fourfortyroadrunner it's ac to dc rectification by flame. the carbon molecules in the flame allow the ac current to flow from the probe, thru the flame, to ground (the burners are electrically grounded) and that creates a voltage drop, (dc offset), the ignition control microprocessor reads that voltage drop to confirm there is a flame present. If no flame is detected, it shuts off the gas for safety.
Likewise, ignition is only for startup. After combustion starts, residual heat of the pulse action maintains the combustion.
Our Pulse G21 is 24 years old and runs great. Easy to troubleshoot and repair if you know the basics of how to use a multimeter. Service manual has detailed troubleshooting diagrams. If heat exchanger cracks, its garbage. I have 2 CO sensors near the furnace room (which also has 2 gas hot water heaters in it) in case the furnace or water heaters have problems..
Mine was installed in 1996. Just had it pressure tested last year. I have had to replace the purge motor and the control board but did those myself. (my brother is an HVAC tech and helped me out on the board diagnosis). Flapper valve/etc. maintenance done last year with the pressure test too. Only issue I have is the occasional non-start-up even when the thermostat is calling for heat.
@@tylerg3423 What do you do when you have the non-start up? Ours starts the rumbling like it's going to start and then it kicks off.
Tyler G, our G21 is starting to have a problem, doesn’t always kick on when the thermostat says to. I’ve changed the flapper & poked around. I’m interested in pulling out the spark plug, either replacing or cleaning it. Any advice on how to get it out would be appreciated. Socket size, type of wrench? Happy Thanksgiving 2019!
I have two in my home. Both are twenty one years old. There is one in the attic for the upstairs. I don't worry about CO as it will directly vent out of the roff. I do have one in my basement and I also keep two CO detectors nearby. I have not had either pressure tested in over ten years as it is hard to find a tech that will do this. Most companies will tell just tell you to toss the furnace I yearly take the air flapper apart and clean it. The media flappers for the 100,000 btu units are getting hard to find. The 80,000 btu and lower ones seem available (they are the same size for 40/60/80 btus).
@@raquelpolson3691 if you can't feel any heat from the outside surface of the ductwork at top, even a rubber fabric flexible membrane boot between the furnace and ductwork, then there is no flame and possibly bad spark plug or dirt flame sensor. if there IS heat but the unit only runs 15-20 seconds, then check air intake & exhaust tubes for blockage, and listen for excess water bubbling sounds in the lower exhaust pipe. use a shop vac to suck out the excess water formed from many false starts, there should be a small thin pipe to drain the water to floor / ground.
These were normally fussy on gas pressure and venting. Just like a two stroke expansion chamber, the venting affects overall operation. In some cases we used undersized vent tubing with very short vents on the larger 100K furnaces which were even more fussy.
The blower is only for starting purge. It does not run under normal use, only at the first of the startup cycle
Cool video. Just found a G21 pulse bad tonight. 27 years old. My co dectector showed 35 ppm when I walked in the door. I'm anxious to see where exactly it cracked or separated. Guess I'll find out tomorrow.
Lennox Pluse (10/1987) G1404/5-100-6 still chuging along. Replace flapper about every 4 years. Had to change Fan Limit switch - HOWEVER generic limit switch cause Blower to short cycle. So had to add Delay -Off-Relay set to 4 minutes (that feature was built into original fan limit switch).
I hope you mean a 4 minute delay during the cool off cycle. Can you share your delayed relay part number, I'm interested in this modification?
That's a really cool design. I never knew such a furnace even existed
The Pulse was in theory and even practice the most efficient furnace ever made, and pretty durable. The problems came when these heat exchangers cracked and they refused to run. Owners swore by them as they were 97 percent efficient.
+Walter Grace I would think burning the fuel in pules like that would actually not be all that efficient at combustion. But I could be wrong.
Makerj101 I worked in the heating, ventilation and air conditioning industry for number of years and also performed energy efficiency tests on individual pieces of equipment to show the customer. These were done with a combustion analyzer and many of these were 97 to 98% efficient. This is really good for a furnace that's about 20 years old. The downside is that they need to be tested EVERY YEAR and scrapped if they fail. These can develop cracks, especially units built before 1990. Problems with starting, water leaks and even carbon monoxide are the result. Personally, I'd just bite the bullet and replace it.
+Walter Grace Interesting thanks! We did replace the one unit that I show in this video. That's why it's all taken apart. We have another unit that is exactly the same and we will keep using that unit until it needs replaced.
+Makerj101 As long as you can do that, save some money. Your channel is very interesting. This is why i subbed.
Walter Grace Thank you! I should probably do a service on our other furnace like this and pressure test it. It's been a couple of years since it's been pressure tested last.
6:10, it's missing the sealed chamber around the combustion chamber. it purges that chamber before ignition so the flapper chamber has to be sealed for it to pass that part of the start up process.
So cool I wondered what was going on downstairs and now I understand more 😃 great video!
Thanks for doing this-very helpful really appreciates it. You put it into a language that I can understand!!!
Talked Dad into getting one of these back in 1985 or so after I saved the family by smelling the combustion products of the old 1969 era gas furnace. HVAC guy didn't believe I could smell the CO. I have always been able to detect it. Anyway, I remember it working quite well back in the day. Certainly antiquated by today's standards.
Was funny how the neighbor complained about it rattling his windows, so HVAC company had to come out and put auxiliary mufflers on the exhaust and inlet.
I just worked on one these for the first time ever in 20 years a week ago a bird was stock in the forced air motor. Got it cleaned and and running and immediately cut it off thinking something else was wrong because of the noise. These are pretty loud
thank you for running it as a pulse jet
Cool! It runs great! still crazy that people put this in their houses :D
+Triangle_DIY Hahaha yeah!
+sporadic -Z But it was super high efficiency for the time!
+sporadic -Z
Actually, I still have one, which unfortunately I a;m replacing, because it needs a few parts and it;s not worth buying new NLA stuff for $$$... In any case, they were well over 90% efficiency delivered to the vents. Mine tested 97%. The new lennox 90%+ going in is actually an efficiency downgrade. Don't forget, all those hot parts are mounted in the air stream- the fully boxed, operating unit barely gets warm externally.
Even with all the mufflers and stuff that went on them though they still were a bit grumbly and I won't miss that part. Still, I will miss having my house heated by a pulse jet. :)
Have had mine for 35-years. First time replacing the ignition controls (Elite Parts $85). New flapper & intake gasket ($26). Best $1000 upgrade made during construction in 1984. Noisy, heavy beast but efficiently ahead of its time.
Thanks for explaining! Very cool.
Nice, I want see it glowing red hot ;)
Thumbs up :D
Alex
The noise was another complaint from customers, the temps were -20 C for months where I lived, the furnace would come on every 15 minutes, the pulse furnace sounded like a Vulcan cannon going off every 15 minutes for 5 minutes LOL
Cool! I just can't understand the advantage of a pulse combustion like this versus just a simple, constant burner. Seems more complicated and the noise is just aweful.
+ch300fnqi Yeah me neither. But it works! LOL It's one of the first high efficiency furnaces that used PVC plastic pipe for the exhaust vent. So for some reason that was the only way at the time that they could make it that efficient. When it was all hooked up to the vent pipes it wasn't that loud. However it did kinda sound like a truck idling out side hahaha
+ch300fnqi Don't quote me on that but I think it has to do with the turbulences created by this particular combustion mode. The turbulent flow is more efficient at transferring the heat to the pipes so you get a colder exhaust and more heat into the water. So it improves the efficiency of the furnace.
Michel PASTOR That's totally possible. Thank you!
Over eighty percent failed
They used a muffler just upstream of exhaust termination to mitigate the noise issue
Still can't believe you scrapped it all.....
+stefantrethan Yeah me too... kinda wish I would of done more experiments with it. But my parents wanted it gone. It sat in the drive way for too long in their opinion.
Nice little tear down of your old furnace. Not something you get to do everyday. Really cool.
Also, you misspelled furnace in your video title.
+Harry of All Trades Yeah! Thank you! Just fixed it!
used to have one, great furnace Wish I hadn't replaced it.
Love your video. So this is just a pulse jet that some madman thought he could use as a heater, am I right?
Pretty much it was a very odd furnace even at the time
I'm wondering if it will run without the noisy fiberglass gasket thing,
That's not the thing that makes noise, and no, it wouldn't work without it.
it would if the intake was extended, search valveless pulse jets.
nice run
My pulse is 21 yrs old still works
if you havent already, get your heat exchanger inspected. they crack at the braze joints and leak CO into the house. if your capable of checking it, unplug the fan connector, remove the 2 3/8" screws on the blower housing. slide it out of the way and look at the joints on the coil. you would see white crusty building up from moisture escaping. if you see the white crust, time for a new unit.
thank you Aaron for the info i will get that checked i have many co monitor in the house
monitors are great!!! they will save your life, however i hope you never have to hear them go off!! cheers!
The grand daddy of noise knockers.
You should only need spark for about 20 seconds. After that spark is not needed. It will fire just off compression. No electricity needed.
Very interesting, I wonder what other types of fuel could be used. Stay safe!
+shazizz It would probably run on gasoline too but you would need to vaporize the fuel first.
where do you get all this stuf?
+petacreepers23 It's our old furnace that we were replacing
Can't quite get what this is for, it's so loud that I doubt its use for heating
+MrJohhhnnnyyy Well it was used for heating my house for the past 25+ years. And the down stairs part of the house is still heated by another one exactly the same. With the exhaust pipes on it's not as loud.
Makerj101 Wow, what a fancy furnace :) Never have seen such a beast before, just boring conventional furnaces, like new one that you told about
Are you a combustion tech?
So can you make your own pulse jet from this valve???
No, it's a normal gas valve.
how do i get to the spark plug and the flame igniter to change them....
I hated dragging them old dogs out of the basement . Heavy
Run it without a regulator and a bigger washer. It'll probably get red hot ;)
+Anton Babiy Yeah that might have done it!
Good job, thanks
Been in HVAC in the Midwest my whole life and we don’t work on them, replace them.
yeah everytime I see one of these I say get rid of it. Now I have a video to use to scare people into pulling the trigger. Looking at the guts of this thing really drives it home how absurd it is.
60Hz flyback? Why not just use a standard transformer? O.o
I donder unserstand the point of this furnace, it's so damn loooooooooooud, what's it even used for? It's basically just a pulsejet xD
+Jordan O'C (Xenro66) Yeah IDK what I was saying there LOL. It's much higher frequency than 60Hz.
Well it's one of the first high efficiency furnaces that used PVC plastic pipe for the exhaust vent. So for some reason that was the only way at the time that they could make it that efficient. When it was all hooked up to the vent pipes it wasn't that loud. However it did kinda sound like a truck idling out side hahaha
Makerj101 I don't even know the optimal frequency for a flyback is haha.
Ah right... Jesus dude, I couldn't put up with it. What's wrong with a good ol' normal flame? xD
+Jordan O'C (Xenro66) Engineers gotta be engineers! :D That's the only reason I can think of!
We want FLAMES! lol
Nice.
volume warning in the beginning! wha!
that thing is basically a pulse jet with a heat ex changer
+joe muncey Exactly
I was a helper for a plumbing and heating outfit in the late 80s , these things were really efficient and high tech but as far as reliablity they sucked , they failed so often it was embarassing.
The main complaint on these was it being so noisey.
it kinda sounds like a weed Wacker
I know right , actually I said chain saw
Carbondioxide ??????
Carbon dioxide and water are the byproducts of combustion anytime you burn natural gas and are vented to the outdoors. Neither is toxic. You do the same thing with your gas stove and oven and don't even think about it. You should run your vented range hood when cooking but many people don't.
Sounds kinda like a dirt bike.
Put a diode to ground.
I've got one under my house in Oregon if any one wants to come and get it for me! Free free free!
The farting machine!
he fixin furnaces n sounds like he's 12yo
They don't make quality stuff today to dependably last, even aluminum foil computer controlling computer with plastic cars (Mv) . Failure Engineering.
The only furnaces that killed their customers.
Except for every other gas furnace made up to that point.
Serviced these from the first models to the last. Basiclly they became to expensive to manufacture due to all the hand welded parts. Some are over 30 yrs old,you won't get that out of your new furnace,or anything even close to that. I'm wondering if your Dad has your life insurance paid up,your lack of knowledge is going to get you hurt some day. You know just enough to be dangerous.
Lennox could’ve kept this BS 😂😂😂😩