RUUD Funace - Won't stay LIT

Reply

  #1  
Old 11-11-07, 07:44 PM
Member
Thread Starter
Join Date: Nov 2007
Location: Mid TENN
Posts: 3
Received 0 Votes on 0 Posts
RUUD Funace - Won't stay LIT

Furnace Info - RUDD Model UGED - 10ERAJS SERIAL BU5D707 M5092 4609

BTU 105,000 Natural Gas , It's an Upflow Furnace , 90 Plus High Efficiency.

Thermostat in house - Honeywell , Small rectangular, manual (no high tech digital or programmable) , one side has Heat / Cool / Off switch , other side has Fan switch ON or Auto. Just basic thermostat.

Furnace in basement of house. Uses outside air for combustion , Exhausts to outside as well. Furnace is 15 years old, installed new when house was built. NO modifications to furnace in any way such as lengthening or shortening of air inlet or exhaust.

2 years ago a furnace control board (printed circuit board) was replaced , 1 year ago the Hot surface igniter was replaced. Last Friday the gas valve was replaced , and the pressure or vacuum (don't know correct name) switch was changed to no avail. This pressure / vacuum switch senses difference in pressure / vacuum of the main combustion chamber where gas burner is and the secondary (exhaust) heat exchanger. Checking this switch with a Digital Voltmeter , and visual inspection it is working, lines (clear tubing) not clogged.

Symptoms - Thermostat calls for heat , Secondary heat exchanger (exhaust) motor comes on and runs, after about 20-30seconds the Hot surface igniter comes on and glows fire red , Gas solenoid valve energizes and gas flows to combustion chamber , Gas ignites , BUT Gas only stays lit maybe 2 seconds, or a brief flash, and extinguishes , All of the above is a normal sequence of events except flame is not maintained , operating temp is never reached and main blower motor is never called upon to run , which it should not as there is no heat to distribute. Given about 1 1/2 minutes the sequence will start again with same results. Furnace will not stay lit. The Furnace Control Board does not flash any error codes on the LEDS ( 2 green , 1 Yellow ) whatsoever.

The Main Gas valve has a vent tube (clear tubing) that runs to the gas inlet on the combustion chamber , which is common to the outside combustion air inlet. Thru experimentation if this vent tube is removed from the Gas/Outside combustion air inlet and a slight pressure is applied (blowing by mouth on tubing) I can get the burner to light and stay lit with a little careful manipulation. This tube I am blowing on is still connected to the main gas valve (which is new) and disconnected from the combustion air inlet. Flame will be maintained , main blower motor comes on , Heat is distributed thru house until Thermostat setting is satisfied , and then furnace is shut down. If while furnace is operating , blowing heat , and I try to reconnect the vent tube from the main gas valve to the Gas / Outside combustion air that leads directly to the main burner the flame in combustion chamber immediately goes out , and back to original problem ....

As I said previously the main gas valve , and the pressure/vacuum switch between the combustion chamber and the secondary (exhaust) chamber are new. Same results/symptoms with new parts as with old parts ??

I have not physically checked the air inlet pipe , nor the exhaust pipe for obstructions. I believe both are 3" or 4" PVC. These pipes run up inside the basement at about a 45 deg. angle with some bends so I can't SEE thru them to determine if blocked. From outside where both pipes are and both intake and exhaust running on the furnace there is good suction on the inlet , and good pressure on the exhaust. On Monday morning I shall rig some device that I can pull / push thru these pipes to insure they are not blocked.

If anybody needs clarification please ask. If you need pictures just ask. If you prefer I call you or send you direct email just PM me at this site. Any help appreciated...
 
Sponsored Links
  #2  
Old 11-12-07, 01:29 PM
Member
Join Date: Aug 2007
Posts: 2,021
Received 0 Votes on 0 Posts
Hi dp:

Tell us about the old and new gas valves- brands, part numbers and also about the ignition system. Also, did you clean the flame sensing rod? They get an oxidized coating that you can't see. Steel wool works best.
 
  #3  
Old 11-13-07, 07:26 AM
Member
Thread Starter
Join Date: Nov 2007
Location: Mid TENN
Posts: 3
Received 0 Votes on 0 Posts
daddyjohn
Update.

This unit does not have a Flame Sensor.

It appears the combustion chamber has cracks , therfore altering the internal pressures the gas valve senses, therfore will not stay lit....

Ruud no longer makes replacement combustion chambers.

Still exploring options.
 
  #4  
Old 11-13-07, 07:43 AM
mattison's Avatar
Member
Join Date: Mar 2003
Location: Cinti, OH
Posts: 5,549
Received 0 Votes on 0 Posts
Your furnace has a cracked heat exchanger and you're trying to get it to operate ?
 
  #5  
Old 11-13-07, 07:48 AM
Member
Thread Starter
Join Date: Nov 2007
Location: Mid TENN
Posts: 3
Received 0 Votes on 0 Posts
mattison

Not only tried , but was successful. I'm sure this is not S.O.P. and may be slightly dangerous?? Trying to get it to light came before I knew it had cracked combustion chamber.

All experts admonish me as you see fit - amazing what you'll do when you get cold - or hungry.
 
  #6  
Old 11-13-07, 07:51 AM
mattison's Avatar
Member
Join Date: Mar 2003
Location: Cinti, OH
Posts: 5,549
Received 0 Votes on 0 Posts
I'm not going to say anything to put you down like some sites or people may do. I understand where you are coming from but this can kill you and your family. If you insist on using it please get some CO detectors. Good ones.
 
Reply

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


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: