Lennox Pulse 21 Fan Control

[gofish]

by golly Bob finally posts something I totally agree with.

it must be the season. :)

[Bob_Loblaw]

[e-mail] wrote

If you're agreeing with me, then you're smarter than I've given you credit for! Cheers

[Bubba]

Yes they were something, werent they? Lets just quickly go over a few items of that marvelous wonder.

1) The sonz-a-biatch was heaver than a small car 2) It had 6 or 8 big bolts hiding that inducer motor you say wasnt there to allow changing of a flimsey paper flapper 3) and on the subject of those bolts.......those damn things NEVER freely turned out of there by hand. You had to ratchet ever single inch of that thread to get that bolt out. 4) How about that wonderful vibration pad the whole unit had to sit on. 5) How about those lovely canvas connectors you HAD to install on the supply and return ductwork. 6) How about that lovely flexible gas connector you had to use. 7) What did you think of that HUGE muffler that had to be installed on the pvc exhaust just to keep the noise down enough outside so that you could only hear it running 3 houses away. 8) So what did you think of all that spacious room to change the spark plug and flame rod with only a sense of feel and no visual. 9)and lastly that lovely water test of the heat exchanger. YES, that Lummox Pulse was a true marvel. It earned the recognition of placement in a museum. I've heard "Daves" ass is up for the challenge. Bubba

[Bob_Loblaw]

Bubba wrote

Aha! Gottcha! :-) It wasn't a ventor motor. It was a purge blower. It only ran on start-up to get fresh air into the chamber, then it shut off for the rest of the heating cycle. If it was a windy day, it sometimes wasn't needed for ignition due to the venturi effect.

I never found them flimsy. Those air flappers needed to be changed every 5 to 7 years.

All the rest is true, as far as mufflers and vibration connections,but they were still pretty impressive for their day, including the ignition system, which only ignited the first couple of pulses, after which the ignition was caused by the refraction of the combustion gases. One thing that was very poorly designed was the access, or lack thereof, to the spark plug and sensor. I bought a special tool for around $50, that was no more than two socket heads welded onto a bar with a half-inch drive hole in it for your socket wrench that made the job a little easier, but what a pain in the ass it was. If you ever come across one that seems to light intermittently, and you've ruled out a bad exchanger, try removing the ignitor, then take a 1/4" drill bit and insert it through the ignitor opening, straight across to the other side of the exchanger, and ream out the gas eustation tube.It will get a build-up of crud on the lower edge of the tube, which deflects the gas upwards and away from the ignitor. Of course, all of this is done using the Braile method, because you can't see any of it inside the access panel! :-) Built to work , not to work on!

[Bubba]

Vent motor, purge blower......its still a 2nd motor on a furnace that goes bad. So you're saying that on a windy day your purge motor doesnt come on? Hmmm, I seemed to miss the pressure switch that controlled that feature. Maybe it has a hidden misting feature for cool heat that I didnt read about too? :-) Bubba

[Bob_Loblaw]

Bubba wrote

Nope.Not what I said. I said it isn't necessary for ignition if the wind is right.

Nope. It's a normally CLOSED pressure switch, the only one that I know of. I'll let you figure out the rest. :-)