Lennox Pulse

[toyotatech]

I have a Lennox pulse manuf in 12/89 and according to Lennox, it does not fall under the recall on the heat exchanger. I have never had any problems with it other than sometimes it will come on for 10 sec and then shut off. I have not had it serviced in a while, so I am having someone service it soon. Per Lennox I am having the gas flapper and air flapper serviced, and pressurizing the heat exchanger to ck for leaks. Can anyone think of anything else that I should have done when the tech comes to service it?

Also, can someone give me an idea of how long this furnace might last, and whether it is worth keeping it? I have kept the air filters changed religiously.

[Toolpusher]

the only other item to service is the drip leg on the drian line,
Some have a rubber cap at the bottom, if it yours doesn't he'll need to cut the PVC and glue back a 1 1/2 " coupling.
The air flapper is the main cause for concern.

As far as lentgh of service, my brother and uncle both have one. I keep an eye on them. But they are both running as factory intended today. If it passes the test, keep it.But have it checked every yr.

Also another thing to have your guy look at is the secondary heat exchanger.
Have him pull the blower and see if it needs cleaned. This will only take about 15 minutes of his time.

good luck,

[markwolf]

Toolpusher has it covered,good advice.

[toyotatech]

Thanks a lot for the information.

Bill

[MikeJ]

Make sure the intake and exhaust do not recirculate. Both pipes should be at least 12" apart. The exhaust should have a reducer on it and you may have/put a 90° elbow on the intake. Also make sure the holding straps stay secure so there is slope back to the furnace on the exhaust and there are no leaks at any of the joints. When in the intake chamber, put a drop of oil on the motor shaft to prevent rust. Check gas manifold pressure.

[HvacBob]

Hire a lennox technician and not a carrier or york.
They probally don't have the proper tools to test heat exchangers.

[mark beiser]

I did hundreds of the pressure tests on Pulse furnaces for the last company I worked for, I found 8 or 9 that leaked. I think the total failure rate was less than 3% last I knew.

If your furnace was built after the cutoff date, the proccess for attatching the the stainless and mild steel parts of the heat exchanger was different and shouldn't be a problem. Unless something new has been found out in the last 3 years or so.

If furnace hasn't had the gas and air diaphragms changed, or the spark plug and flame sensor, its definatly a good idea to go ahead and do that now. There used to be an update kit that changed the gas oriface and pressure regulator along with the diaphragms, but you may not need one if its a G21, GS21, or GS21V furnace. All G14 and GS14 furnaces should have the update kit installed if its still available. The revised gas presure regulator and oriface make the units operation quieter.

Just about every problem with a Pulse furnace can be diagnosed by listening to the unit. ;)

Your best bet is to find a Lennox dealer that services them, as there are a few special tools and knowledge involved that you are unlikely to find from other dealers.

The problem with the fan coming back on briefly after a heating cycle is usually caused by a dirty secondary heat exchanger, but any restriction to the airflow can cause it, dirty blower, coil, filter, poor duct system, etc. The heat exchanger isn't cooling down enough, so the air temperature goes back up inside the furnace and the thermostatic fan control turns the fan back on.

The problem can also be caused if the heat assist in the fan control has failed, someone monkied with the settings of the control, the fan control itself is going bad, or if someone installed an incorrect fan control that doesn't have heat assist.
The unit should have a 7" insertion ChamStat fan/limit control or a 5" insertion Honeywell fan/limit control. They are interchangable, the opening in the unit is shaped to talke either one and there are predrilled screw holes for both. The important thing is that it MUST have heat assist for it to work correctly.

Overall, I would have to say that the Lennox Pulse furnace is the most reliable resadential furnace I have experience with. Most of the problems I have seen with them were due to lack of maintenance or incorrect installation of the vent and drain systems.

[toyotatech]

Thanks for the insight. The service tech could not get the gas flapper to come off. He said it was attached to the heat exchanger and if he put too much force , that it might break the heat exchanger, so he left it in. This is a propane system and might be contributing to it being frozen. Would Lennox provide a furnace to me if the gas flapper was not able to be removed to do the pressure test, or would they require the tech to test the heat exchanger with the gas flapper still installed. Do you suggest that I not worry about the gas flapper valve since the furnace works fine? Would Lennox provide a free replacement furnace if the Lennox recommended routine maint., like replacing the gas flapper every 4 years was not possible without breaking the heat exchanger? What would Lennox do if my heat exchanger broke while trying to replace the gas flapper valve?

Thanks

[ken from nw ohio]

...All you have to do on the gas diaphramn is back it up with a wrench and use an electric impact. It will pop right off with no damage.

ken

[toyotatech]

Originally posted by ken from nw ohio
...All you have to do on the gas diaphramn is back it up with a wrench and use an electric impact. It will pop right off with no damage.

ken



The tech had the large 1/2 inch drive socket on what he said was the gas flapper valve. I looked at it again today, and there is nowhere that a wrench could fit onto behind it. There is a big red grommet directly behind what he had the socket on.
He took off the 90 deg elbow that has the square drive service plug installed in it for a gas pressure guage to be installed into, and then a 2-3 inch straight piece of pipe, to the left of the elbow was unscrewed from what he said was the gas flapper valve. Then he put a large socket on what the short 2-3 inch pipe had screwed into. On the left side, there is a big red rubber grommet where this pipe enters the inner cabinet. This is what he was trying to remove with the big socket. It appeared to be part of the heat exhanger assy, not a removable part. I saw a sticker on what looked like a condenser, that said to use 2 wrenches when removing the gas flapper valve. I am not so sure he was trying to remove the gas flapper.

I have a pic of the heater I would post, but I can't figure out how to post it.

Do you have any ideas about what he had the socket on?

Bill

[mark beiser]

He had the socket on the correct part, he just lacked desire to get it off...

[ken from nw ohio]

...very true Mark !

[jlkelly]

Trust the advise of the pulse experts. Lack of desire is correct. He's probabily not experienced with a pulse and is afraid of damging it.

[prestiege]

if you want i can host the picture for you for a while, just email it to me prestiege@midnighttokers.com : you have to upload your picture to a web site that hosts images, you then just copy the web address and paste it between {img}webaddress{/img} but instead of {} use the straight brackets[ ] [ / ]

http://img12.imageshack.us/img12/8171/peeing.gif

http://ai.pricegrabber.com/product_images/843000-843999/843998_125.jpg

i guess the center tabs dont work on these forums, its posed to center the image on the page, oh well

[Edited by prestiege on 08-23-2004 at 10:19 PM]

[prestiege]

http://www.cyberonic.com/~gbanks/gallery/lennoxpulse.jpg

sorry i dont know what to do with the flapper i never worked on one of these before

[i_got_ideas]

Have the tech back over.......

tell him....

"get outta my way boy!"

Crank on that baby and break it loose.

I only weigh 135 pounds and those puppies cause me a BUNCH of grief, and busted knuckles :( everytime cause I have to litterally put ALL of my weight into it. :D

Even if you do break the heat exchanger...well, you have clearly been considering replacement anyhow. However, if you do break it, I'd hate to ever have to go a round with you :D .

[mark beiser]

Bleh, a GS21, not getting a backup wrench on that. Tell him to try tightening it a little and/or tap on it(NOT HARD) with a small hammer. It should break free. The things definatly are not fragile, but you certainly don't want to jump on the end of a breaker bar.
Once the rust deathgrip is broken, they usually come out easy, or have for me. I wouldn't use penatrating oil of any kind.

[MikeJ]

Anyone ever seen the limit located down there? Seems strange. Seems like most are up top near the pressure switch.

[i_got_ideas]

Originally posted by MikeJ
Anyone ever seen the limit located down there? Seems strange. Seems like most are up top near the pressure switch.

It appears to be horizontal.....that is a stange locale for that though. It must be limit only with the fan timer.

[mark beiser]

Originally posted by MikeJ
Anyone ever seen the limit located down there? Seems strange. Seems like most are up top near the pressure switch.

Thats an early GS21 horizontal Pulse furnace installed in the left hand discharge position.
That fan control is a 5" insertion heat assisted (time delayed) fan/limit control. Note that it has 6 wires running to it. 2 for the limit, 2 for the fan, 2 for the resistance heater in the control.
If I remember correctly, some of the later G21, GS21 and all the GS21V furnaces had a fan control board, so the limit control was just a standard 2 wire limit.

If you ever look inside the cabinate of a Pulse furnace, you would understand why it kinda has to be there, and why its so short, lol.

Its location, and the way pulse furnaces work, is why its critical to always use a fan/limit control with the built in heat assist(time delay) if you ever replace one.

If you ever replace one with an aftermarket fan/limit, don't forget to break off the jumper between the limit and fan side of the control. The limit side is 24v and the fan side is 115v, I got called out to clean up the mess a couple of times at my previous employer because other techs forgot the jumper. :(

[Edited by mark beiser on 08-26-2004 at 01:00 AM]

[toyotatech]

Thanks prestiege for posting my pic. Thank you all for the advise. I think I will run the furnace until it gives trouble and then consider more drastic measures on removing the gas flapper valve. The furnace runs good and who knows, it might run fine for many more years. Maybe not also. I just wanted to replace it because Lennox recommended it. I was able to replace the air flapper material and gasket though.

Thanks again to all!

[mark beiser]

The gas diaphragm usually announces its failure fairly noticably. If your unit starts making a lot of noise in the heating mode, firecrackers in a pipe kind of sound, it is usually the gas diaphragm leaking.

[hockey]

I am working on a Pulse 21 and cannot get gas. There are three connections on the gas valve. Two are spade connections and the lowest one is a screw. Can anyone tell me what these connect to? The schematic does not tell me the specific gas valve symbols. I know one of them is 24v common, another goes to the control board (that has high voltage for spark plug) and the third goes to "Valve" on the circuit board, but which goes to which?

[t527ed]

can't get into davenet on this old puter, believe power comes into gas valve from module then sends signal down to circuit board for fan on delay. have had a lot of bad ign modules could be cause of problem. think i have only had 1 bad gas valve in over 20 yrs of pulse.

[ken from nw ohio]

Do you have 24 V at the valve when it is trying to run ??


ken

[hockey]

Yes, I get 24V on the wires but i don't know which wire goes where. there's 3 terminals on the gas valve.

[t527ed]

if you have 24 volts you have bad gas valve. 24 volts comes in from module, hot leg goes down to valve terminal on circuit board to energize blower control. you did check gas pressure right???

[hockey]

Yes, I am getting gas. Once again, there are three contacts on the gas valve (labelled 1,2,3). Which wires go where on the gas valve?

[hockey]

My Pulse 21 project is now working fine. The gas valve is now wired correctly. Gas pressure is 2.4" water, unadjustable, except to turn plug around for LP. I've never seen a "Pulse" design!? Whassup wid dat? On for 8 seconds, off for 30?

[markco]

Originally posted by mark beiser
[QUOTE]If you ever replace one with an aftermarket fan/limit, don't forget to break off the jumper between the limit and fan side of the control.This is something most techs do once...and hopefully only once. For some reason, stats, tranformer secondarys, gas valves, etc. don't take 120 volts very well.:) If you get the flapper off, make sure that you put the little washer back in the same spot that it was in before, or you will have problems.

[hockey]

What's a "Flapper"?

[t527ed]

do you mean pulse is firing for 8 seconds and off for 30 every time it runs? and you don't know what the flapper is.
shut the switch off put your tools in the truck. find a lennox dealer that was trained for the pulse furnace cause you don't know what your messin with!!!!!

[hockey]

I connected the 24V Common to chassis ground (per schematic) and now the furnace runs coninuously. No more cycling: "On 8 seconds, off 30 seconds".
This is one cool baby to work on!
As far as "Qualified" techs go: every licensed "Professional" I have been forced to work with in the past month has over-charged me AND mickey-moused the quality. I am licensed (and poor).