Oil furnace intermittent operation/ "nuisance lockout": Ideas wanted!

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Old 10-30-10, 05:55 AM
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Question Oil furnace intermittent operation/ "nuisance lockout": Ideas wanted!

My furnace, with a Beckett model AF burner approx 2 years old, is apparently possessed by demons or hates me or something. I have conducted what most people would call a very extensive search and have been unable to find anything that has helped.

Here's what happens:
1. "Call for heat" sent, unit fires normally and runs for a complete cycle.
2. When the next "call for heat" is sent, one of the following things happens:
a. The unit fires normally if it feels like it (about 20% of the time)
b. the unit fails to light and trips the lockout button (80% of the time)
3. Trudge down to the basement, press the button. Sometimes it fires right away. Sometimes it does not. If I wait a minimum of 30 minutes and press the button again, it fires normally.
4. Repeat until you're sick of it.

Steps taken:
- Inspect and replace filter. Fuel is clean and has no water present.
- Replace line between filter and burner. Bled the living hell out of it. As a side note, there is no air in the system and no leaks. Even when the unit won't fire, cracking the bleeder produces only clean fuel, no air, good pressure.
- Replace nozzle.
- Replace thermostat (I'm grasping at straws here).
- Called local heating co. Got charged $200 and it still doesn't work. Those boogers.
- Called Beckett. They wanted CO2 readings and stuff. When I told them I was the homeowner, they basically told me to shove off and call a heating co.

Steps I'm thinking of taking next:
- Replace line between tank and filter
- Call priest, shaman, or medicine man

Does anybody have an idea what could be going on with this thing? I'm completely stumped as to what could be wrong and I'd like to get some considered opinions before I just start throwing parts at it. The fact that it works perfectly when it wants to suggests to me that things like the transformer and pump are OK, but I really have no idea. I would appreciate any thoughts y'all might have. Thanks!
 

Last edited by Sporkupine; 10-30-10 at 07:19 AM.
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Old 10-30-10, 12:48 PM
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My guess is marginal spark or marginal primary system relay that sets any blower, motor, purge in motion, so it then allows it to fire.
 
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Old 10-30-10, 02:31 PM
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Interesting. So as a next step, would you recommend replacing the transformer (the one that supplies power to the igniter)?
 
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Old 10-30-10, 03:46 PM
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No. Just don't start throwing parts it at, based on what I or anyone says might be causing your problem. You will have to be able to check and/or test and maybe adjust those things that are mentioned as possibilties.

Grady, the topic moderator who is an expert with oil burners can help guide you better than I. I am sure he wil respond to this thread, so periodically check back.
 
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Old 10-30-10, 04:50 PM
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You call for an Exorcist?

The single hardest thing to troubleshoot is an intermittent problem.
I need you to help me help you but by working together we can chase the demons away without throwing part after part (dollar after dollar) at 'em.

1. The next time it fires normally I want you to look at the flame. Look for size & color (should be bright & light yellow).
2. When it misbehaves & you finally get it to fire, look at the flame again (the quicker after it fires the better).
3. If in step 2 the flame is big & dull yellow or orange, it tells me you are getting fuel & the problem is likely ignition but don't change that transformer yet.

Make & model of the furnace?
 
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Old 10-30-10, 05:23 PM
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Hi, Grady. I appreciate your taking an interest in my problem.

When it fires normally, the flame is indeed as you describe...bright yellow, filling the firepot properly.

When it finally lights after a failed attempt, the flame is large, orange and sooty. I presume this is from the extra fuel in there due to the previous failed cycle. However, it quickly clears up and is again bright yellow after about 45 seconds to 1 minute.

The furnace itself is a DMI "Highboy". The burner is a Beckett AF with a sunstrand pump and an old-style honeywell safety.

As a side note, this afternoon, I pulled the thing apart and looked at the electrodes. They were filthy. I gave the tips a quick sanding (just enough to get the soot/carbon off) and put it back together. It fired up right away, but it hasn't tried to cycle yet, so I don't know so far if that has helped. I'm also thinking that maybe I should check the electrode gap (don't ask me why I didn't when I had it apart the first time...I had a brain fart and forgot to check that ) and clean the porcelains.
 
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Old 10-30-10, 06:28 PM
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Set the electrodes as follows:
5/16" above nozzle center
1/16" ahead of nozzle face
5/32" apart

If it still gives you trouble, let me know & I'll tell you how to check the ignition transformer. Is it an old style iron core or electronic?
 
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Old 10-30-10, 06:41 PM
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OK, I will do that tomorrow. I think the transformer is an electronic one. It's a Beckett part, and it is smaller than the other ones I've seen...only sticks up about an inch or so. I have a picture of it if it helps.

Thanks again!
 
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Old 10-30-10, 06:44 PM
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It's electronic. The primary is an R8184G?
 
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Old 10-30-10, 06:54 PM
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The part number is 51838U, and you're right...it does say "electronic igniter" on it (I had to swing it up to see the whole label).
 
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Old 10-31-10, 07:06 AM
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All right, the furnace had the same problems as usual overnight, so I took the opportunity to reset the gaps on the electrodes. That was fun. It's one of those jobs that would have taken about two minutes with one of those gauge things, but doing it freehand takes...a while.

Anyhow, the gaps were reset precisely to Grady's specs. Here's what I found:

Distance from nozzle face: good
Distance from nozzle center: too high by about 1/16
Gap: at least double what Grady called for.

The unit fired up, ran through a cycle, then went through another cycle just fine. Now it's back to its old tricks. Next step?
 
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Old 10-31-10, 04:40 PM
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Before I can dig more deeper myself and Grady can dig into more deeper did your furance have one fuel line or two fuel line ??

And how far the fuel tank is from the furnace and which way the line run above the furance level or below furnce level { on the floor } ??

And did you check the chimmeny for any restrictions ??

The reason why I was reading thru and you stated it was bright yellow that is fine but as soon change to lazy orange colour check the damper on the flue to see if that is flipping properly if not moving at all either you have draft issue or airflowage issue.

{ do this happend during windy days or calm day or both ? }

Crap .,, Almost forgot this item did this oil burner pump have a electric shutoff valve between the pump and nozzle ?

Merci.
Marc
 
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Old 10-31-10, 04:54 PM
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Okay, let's see here...

It's a one-pipe system. The tank is about 10-12 feet away and the line runs on the floor. The fuel can push itself up to at least the level of the burner with no problems. The flue is not restricted at all (I can look straight up to daylight). The barometric damper works like it's supposed to.

Wind is no problems. Last week, our area of the country experienced record winds for three days (60+ mph/95 kph), and when it would light, it did so with no hesitation and had a good, strong flame.

As far as the flame colour, what I was trying to tell Grady is that when I would reset it after a failed start attempt, the flame would start off orange and dirty and then clean up to the proper bright yellow and it's fine after that.

I do not have a shutoff valve of the type you described, unless there's one in the pump somewhere.

Hope this helps.

votre bon cur !
 
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Old 10-31-10, 05:51 PM
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Ignition Problems

I strongly suspect a weak ignition transformer. Testing with a screwdriver can be dangerous. Please be very careful.

Be sure to use a screwdriver with a well insulated handle (adding a couple of layers of good electrical tape to the handle will hurt nothing).
Turn off the power to the burner.
Disconnect the 3/16" nozzle line & direct the oil into a suitable container.
Open the transformer & flip it back.
Start the burner.
Place the blade of the screwdriver on one spring & the tip on the other.
Draw the tip back toward the other spring.
The spark should have a sharp crack & be able to follow the screwdriver tip at least 1/2 way to the other spring before the arc breaks.

This test is by no means 100%. I've had more than one fool me.
 
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Old 10-31-10, 06:14 PM
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Wow.

Hey, doing that test sounds like good times and all (), but I've already absorbed a lot of voltage from my days as a lineman. Given that the test is not 100%, and that you strongly suspect it (and I trust your judgment), and the part is $25, I think that I'll just order one and swap it out. If nothing else, I figure that it can't hurt to have a spare on hand.
 
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Old 10-31-10, 06:20 PM
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Changing Parts

I absolutely hate troubleshooting by changing parts but sometimes, especially with an intermittent problem, I've had to resort to it. You don't by any chance have a high voltage (20Kv) milliamp meter do you?
 
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Old 10-31-10, 06:29 PM
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No, I don't. Even my "good" meter is only rated up to 2Kv DC. And I hear you about hating to just throw parts at something. In this case, though, the part is cheap enough, and it would give me a spare.

Plus, in any other set of circumstances I can come up with, I would gladly pay $25 to not have 20Kv applied to me, so there's that angle, too...
 
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Old 10-31-10, 06:46 PM
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10Kv

The 10Kv was for the old iron core transformers. These electronic jobs pack anywhere from 14 to 20Kv.
I got bit ONCE by an old iron core & man alive, it hurt. The muscles in my arm ached for days. Believe me, I have no desire to repeat the experience let alone get hit with one of the electronic jobs.

BTW: Where did you find one for $25? That's less than I pay at my supply houses.
 
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Old 10-31-10, 07:10 PM
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Here's the link:

Beckett Corporation 51838U Igniter for Beckett Less Base

They seem to have decent prices.
 
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Old 10-31-10, 07:37 PM
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"Less Base"

The "less base" is the key. I buy all of mine with the base. I never know what brand I'll be replacing.
 
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Old 10-31-10, 07:39 PM
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Originally Posted by Sporkupine View Post
Okay, let's see here...

It's a one-pipe system. The tank is about 10-12 feet away and the line runs on the floor. The fuel can push itself up to at least the level of the burner with no problems. The flue is not restricted at all (I can look straight up to daylight). The barometric damper works like it's supposed to.

Wind is no problems. Last week, our area of the country experienced record winds for three days (60+ mph/95 kph), and when it would light, it did so with no hesitation and had a good, strong flame.

As far as the flame colour, what I was trying to tell Grady is that when I would reset it after a failed start attempt, the flame would start off orange and dirty and then clean up to the proper bright yellow and it's fine after that.

I do not have a shutoff valve of the type you described, unless there's one in the pump somewhere.

Hope this helps.

votre bon cur !
Ok let do the Grady's part first to rule out the ingtion transfomer before I can get into this part once you pass Grady's test then I will go in next step but you will need pressure gauge on this one due majtory of resdentail oil burner pump are set at 100 PSIG give or take few PSI depening on setting Myself or Grady will fill you in how to do this part.

{ I know Brackett do use two verison of fuel pump so it will make the diffrence how to read the pressure }

Oh yeah Exepect the ingtion transfomer to run about 10 to 25,000 volts and with good transfomer you should have about 15mm gap with nice bleu spark that is good but any thing less or show orange colour that mean weak ingtion transfomer.

Merci.
Marc
 
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Old 10-31-10, 07:44 PM
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Transformer "Less Base"

Oh, right. I did see that. Since this is a direct like-for-like swap, this should not be a problem for me and I can just re-use the old base, right?
 
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Old 10-31-10, 07:47 PM
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Originally Posted by Grady View Post
The 10Kv was for the old iron core transformers. These electronic jobs pack anywhere from 14 to 20Kv.
I got bit ONCE by an old iron core & man alive, it hurt. The muscles in my arm ached for days. Believe me, I have no desire to repeat the experience let alone get hit with one of the electronic jobs.

BTW: Where did you find one for $25? That's less than I pay at my supply houses.
Try that with GM HEI coil they are the worst they crank about 40Kv That how I used on my burner to burn the stubborn fuel.

Merci.
Marc
 
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Old 10-31-10, 07:47 PM
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On a direct swap you should be fine.
 
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