Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 01-29-2013, 06:37 PM   #16
Newbie
 
Join Date: Jan 2013
Posts: 8
Rewards Points: 0
Share |
Default

Lennox Whisperheat runs normally but shuts off after 5-30 minutes


This is what I hate about discussions about furnaces (be it here on web forums, or on usenet in alt.hvac or alt.home.repair).

Every discussion ultimately focuses on the heat exchanger. It's probably cracked - you need a new furnace. Your air filter is clogged - you need a new furnace. Your drum-humidifier motor burned out - you need a new furnace. Your thermostat's battery is dead - you need a new furnace.

Doesn't matter what the problem is - you probably have a cracked exchanger, so you need a new furnace.

Fer cryin out loud - gi'me me a break already.

Does anyone know when Lennox started selling this model: G20Q5/6E-150-5 ???

sumguy is offline   Reply With Quote
Old 01-29-2013, 07:42 PM   #17
how
Member
 
Join Date: Feb 2011
Location: Vancouver BC
Posts: 1,492
Rewards Points: 8
Default

Lennox Whisperheat runs normally but shuts off after 5-30 minutes


I also hate the sales kool aide as well but you should still get the exchanger checked out by someone who knows what they are doing. Ask your neighbours who they use that they are satisfyed with.

Trying to convince us here that your exchanger isn't cracked will not help you or your family if it is.

Last edited by how; 01-29-2013 at 08:05 PM.
how is offline   Reply With Quote
The Following User Says Thank You to how For This Useful Post:
hvactech126 (01-29-2013)
Old 01-29-2013, 08:28 PM   #18
Member
 
Join Date: Jul 2012
Location: Toronto ON
Posts: 599
Rewards Points: 0
Default

Lennox Whisperheat runs normally but shuts off after 5-30 minutes


Did you check posts 2 and 11..and follow up? Also, some where I noticed someone gave you the correct milliamp/millivolt reading you should get from the flame sensor..some also sense DC volts..I think...

It is good advice to observe operation of pilot flame because, if it does start to waver and stopos impinging on the sensor the furnace will shut down

You haven't indicated how long you have observed the operation ..in one sitting..However from reading your description sure seems like the pilot flame could be flickering..OR intermittent signal..did you clean up those connections AND sensor..it could look clean but still require a cleaning..also ceramic holder for sensor/igniter could be cracked. Cracked igniter could be the cause of those arcs you described) Cracked sensor would intermittently short out causing failure. LET US KNOW how you make out
techpappy is offline   Reply With Quote
Old 01-30-2013, 06:24 AM   #19
Member
 
Join Date: Oct 2009
Location: Nebraska
Posts: 2,362
Rewards Points: 0
Default

Lennox Whisperheat runs normally but shuts off after 5-30 minutes


The year your furnace was made will be the third and fourth digits of the serial number.
Marty S. is offline   Reply With Quote
Old 01-30-2013, 08:19 AM   #20
Newbie
 
Join Date: Jan 2013
Posts: 8
Rewards Points: 0
Default

Lennox Whisperheat runs normally but shuts off after 5-30 minutes


Quote:
Originally Posted by techpappy View Post
Did you check posts 2 and 11..and follow up? Also, some where I noticed someone gave you the correct milliamp/millivolt reading you should get from the flame sensor..some also sense DC volts.

You haven't indicated how long you have observed the operation ..in one sitting..However from reading your description sure seems like the pilot flame could be flickering..OR intermittent signal..did you clean up those connections AND sensor..it could look clean but still require a cleaning..also ceramic holder for sensor/igniter could be cracked.
I have been in front of the furnace watching it a few times and have observed it shut off. It just abruptly turns off the main gas and the green LED on the ignition module goes out. The fan continues to run for a short time and then turns off. The thermostat is still calling for heat. The intake vent remains open (it does not close).

In those situations when I'm there and see this happening, I turn off the power to the furnace for a few seconds and then turn it back on. The vent door opens, the green light comes on for a few seconds, it might blink very quickly once or twice, then goes out without even trying to turn on the pilot gas or spark it up. I can repeat this maybe 5 times over the course of the next few minutes before it starts normally (green light comes on and stays on, pilot-gas comes on ignition is sparked, burners come on, etc).

So when the furnace shuts down for some unknown reason, that reason persists for a few minutes after the shutdown even if the furnace is power-cycled, and prevents the normal startup cycle from happening.

Unless I'm there when the shutdown happens, those few minutes have passed by the time I go back to the furnace and power-cycle it, and by then it always starts right back up.

The problem is not in the two over-temp sensors or the intake-gate switch (I temporarily bypassed those and the problem persisted).

By the time the ambient temperature is 61 or 62f, the furnace will run normally, continuously for hours without experiencing this shut-down problem. This problem only seems to happen when the furnace is started and the ambient temp is 55-60f.

To respond to a few other comments in this thread, you can drop the "your furnace needs to be checked - think of the children" comments. This furnace heats the basement of a small 2-story commercial building. I turn this furnace off when I leave between 5-6 pm, and turn it back on at 10 am the next morning (that's why the temperature drops to 55-60 by the time I get around to turning it on).
sumguy is offline   Reply With Quote
Old 01-30-2013, 10:20 AM   #21
Member
 
Join Date: Jul 2012
Location: Toronto ON
Posts: 599
Rewards Points: 0
Default

Lennox Whisperheat runs normally but shuts off after 5-30 minutes


OK that eliminates the igniter, sensor and some of the safety limits. For some reason there is an open limit at lower temp. Could be a set of contacts OR a crack in a control board OR just a loose connection. I would start by disconnecting power, removing all wire connections at termination points (one at a time) clean and re tighten. Try that. Not sure if you have an electronic control board but, if you do then the lower temp may result in open circuit, particularly at connectors. ALSO lower temps could cause some condensation that may affect electrical somewhere.

When unit refuses to cycle on it would be best to check all limits with a volt meter to see where the break is. Start at either side of the control board to determine where limit is interrupted. OR Perhaps at burner control module. Not sure of your set up but, that's the nub of it. Trying to find the dead spot in the limit circuit. Could take a few trie because it might just make the circuit when you touch whichever wire is loose.
techpappy is offline   Reply With Quote
Old 01-30-2013, 11:22 AM   #22
Roofmaster
 
Join Date: Oct 2012
Location: Maryland
Posts: 3,621
Rewards Points: 22
Default

Lennox Whisperheat runs normally but shuts off after 5-30 minutes


The burners on my furnace shut down in about 8 minutes if I have the lower blower door off.
__________________
" A lot of men build things, and a lot of things fall down "

jagans is offline   Reply With Quote
Old 01-30-2013, 11:29 AM   #23
Hvac Pro
 
Join Date: Nov 2008
Location: Winnipeg, Canada
Posts: 9,420
Rewards Points: 60
Default

Lennox Whisperheat runs normally but shuts off after 5-30 minutes


BCause the direct drive blower needs to have the door on to suck against a closed box/ductwork in order to get up 2 speed. Unlike a belt drive motor.
__________________
"Cut it twice and it is still too short".
yuri is offline   Reply With Quote
Old 01-30-2013, 11:51 AM   #24
Newbie
 
Join Date: Jan 2013
Posts: 22
Rewards Points: 0
Default

Lennox Whisperheat runs normally but shuts off after 5-30 minutes


>> OR a crack in a control board ...

FWIW, my furnace exhibited the same symptom of not turning on when cold as yours. I learned on a forum that my control board was subject to cracks so I replaced it. Haven't had a problem in 8 years.

BTW, how many posts do I need before I'm not a newbie anymore? :-)
bausin is offline   Reply With Quote
Old 01-31-2013, 07:52 PM   #25
Newbie
 
Join Date: Jan 2013
Posts: 8
Rewards Points: 0
Default

Lennox Whisperheat runs normally but shuts off after 5-30 minutes


Quote:
Originally Posted by Marty S. View Post
The year your furnace was made will be the third and fourth digits of the serial number.
So the model number is G20Q5/6E-150-5, and the serial number is 5897D 079NN (where NN are numbers). Which means according to your information, this furnace was made in 1997, making it 14-16 years old, which to my thinking is not terribly old.

What I did today is take the ignition module out of the furnace and have a good, close look at the circuit board. I re-soldered the connections to the spade terminals and the ignitor transformer a couple years ago, and these connections still look just fine. I washed the board in alcohol before I re-installed it in the furnace.

On several of the spade lugs that plug into the module, I applied solder to where the wires are crimped to the spade lugs just to insure a good connection. This includes the flame-sense wire. There is also one wire that goes to the gas valve, and I soldered the wire on that lug at the valve as well.

I also checked out the limit switch (removed it completely) and manually turned it while checking it with a meter. This appears to be a simple switch (normally closed) that opens when it reaches an adjustable temperature. No problems noted with it.

So after re-installing and re-connecting everything, the furnace powered up and ran all day. I'll know for sure tomorrow morning when I turn it on if this turn-off problem still exists.

Question: Can the flame sensor be involved here in any way if when I apply power to the furnace, the intake gate opens, the green light comes on - and then blinks off, with no attempt to light the pilot?
sumguy is offline   Reply With Quote
Old 02-01-2013, 12:20 PM   #26
Member
 
Join Date: Jul 2012
Location: Toronto ON
Posts: 599
Rewards Points: 0
Default

Lennox Whisperheat runs normally but shuts off after 5-30 minutes


The flame sensor shouldn't be involved at that point however, there may be an interlock switch on the intake door to ensure that it is open.

techpappy is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Lennox Merit watchguard boorahbill HVAC 6 02-04-2012 01:04 PM
Electric heater runs for 10 minutes, goes off for 2 abefroman HVAC 3 01-28-2011 07:06 AM
Lennox furnace blower runs slow ventport HVAC 9 02-21-2010 04:42 PM
Heil 80% EFF--- Fires, runs, Shuts off!! mrfyvie HVAC 4 02-09-2009 10:21 PM
furnace cycles, runs for 45-60 seconds shuts down and recycles again ronsmoneypit HVAC 4 02-03-2008 01:46 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.