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Old 11-07-2008, 12:02 PM   #1
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Rollout on Goodman Condensing furnace


My 14 year old Goodman GUN125-5B Condensing propane furnace is tripping the rollout switch.

For testing purposes I jumped the switch and observed the burners and the last chamber sporadically does rollout a bit. All burners have a nice blue flame except for one that is more yellow but the rollout is not ocurring on that burner. I could also detect the odor of the flue gases. There is some surface rust noticeable in the bottom of the chamber having rollout. Light or no rust in the other chambers. I shut it down for safety and am hoping to fix the problem this weekend.

The furnace uses room air for combustion and the room and house are not any tighter than they've been for 14 years. Filter was replaced recently and is clean. Airflow through the ductwork seems normal.

My research so far indicates that I should look at the airflow through the combustion chamber, primary and secondary heat exchanger, draft motor and vent pipe since an obstruction there could cause rollout. And also inspect the heat exchangers for cracks that would allow circulating air to enter the combustion chamber and also cause rollout.

I could sure use some advice from the pros on here. Here is my plan so far:

1. Remove the burners and clean them out, remove any scale etc. (I don't think this will help the rollout but may help the "yellow flame" burner???)

2. Clean out the primary and secondary heat exchangers and examine them closely for cracks.

3. Check the vent pipe for obstructions.

4. Check the draft motor/fan. It's running well enough that the sensors indicate it's working (and I hear it running).

Here are my questions:

1. What is the best way to clean primary and secondary heat exchangers?

2. Is there a way to check to see if the draft motor/fan is blowing enough air besides relying on the pressure switch?

3. What else should I be looking at that could cause rollout?

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Old 11-08-2008, 01:00 AM   #2
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Rollout on Goodman Condensing furnace


The cell has a perforation. You'll have to replace the heat exchanger,

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Old 11-08-2008, 11:46 AM   #3
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Rollout on Goodman Condensing furnace


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The cell has a perforation. You'll have to replace the heat exchanger,
Thanks hvaclover. How were you able to conclude that the cell was perforated?
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Old 11-08-2008, 12:29 PM   #4
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Rollout on Goodman Condensing furnace


Generally, a clogged secondary effects all the cells/burners.
Since your is only effecting on cell mostly.

95% probability its a bad HX.

Does the flame jump more when the blower turns on. Then before it turns on.
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Old 11-08-2008, 01:44 PM   #5
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Rollout on Goodman Condensing furnace


It seems to roll out after the blower has been on for a couple minutes. I don't notice the roll out or any change when the blower kicks on then after a couple minutes it starts to roll out.

I just got the burners out and vacuumed the rust from the bottom of all cells. The bottoms actually look like they are in pretty good shape. Most have no or very very light rust on the surface. One cell has a bit more surface rust but isn't the one that rolls out and doesn't appear to be near enough rust for perforation.

Where should I be looking for perforation?
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Old 11-08-2008, 02:29 PM   #6
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Rollout on Goodman Condensing furnace


Open the plenum, and look at the crimp rings.
You might find some missing.

Or pull the blower, and look from teh bottom up.
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Old 11-08-2008, 04:37 PM   #7
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Rollout on Goodman Condensing furnace


From what has been said so far, and my experiences with older 'clam-shell' type ht exchgrs, especially Goodman, I'd place a bet on a cracked heat exchanger. Most of the one's I've seen crack at the rivets, some crack at the 'flame intake' area of the mounting plate. The ones that crack at the rivets can easily cause the flame to 'dance' when the blower is running. Many of the cracks I've investigated can be seen by using a telescoping mirror tool, accessed from the top of the unit. I hate to say this, but being an older Goodman with a clam-shell, 10 bucks says I could find at least 5 cracks. And of course, one is too many.
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Old 11-20-2008, 05:16 PM   #8
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Rollout on Goodman Condensing furnace


Thought I'd give you guys a follow up. I didn't attempt removing the heat exchangers because they were sealed with some kind of sealant and I didn't want to cause more problems. So I visually examined the primary heat exchanger as best I could in place. I couldn't find any cracks or perforations so I cleaned everything up and reassembled. The flame quality of the orange cell seemed better after cleaning and there actually seemed to be less roll out - in fact the roll out sensor didn't ever kick out.

But I know that nothing I did should have affected the rollout and I noticed that as the furnace ran for an extended time to heat up the house from 55 to 70 the burners kicked off once for a couple minutes and then kicked back on. I interpreted this to be the Hi temp switch in the upper part of the heat exchanger. During this run I set up a digital CO detector in the furnace room and it went from 0 to 35 ppm during this extended run.

I came to the conclusion that you guys were correct and the heat exchanger was bad so I shut her down and broke out a couple electric baseboard heaters to get by on.

I found out the good news that the heat exchanger was under a lifetime warranty and the bad news that the warranty didn't cover labor - and of course the labor is the biggest expense. I figured I could replace it myself but they required a licensed HVAC guy to make the heat exchanger transaction.

Not many HVAC guys wanted to deal with replacing the heat exchanger - they all wanted to sell a new furnace. One guy said he would but it could be $500 to $1000 or more. Finally a Local HVAC guy said $650 labor. I told him to go ahead. The new exchanger finally arrived yesterday and he sent out a youngster to install it. He about finished in 3 hours but told my wife that he had to come back this morning for about an hour to finish up. I got home and looked at his work. Everything was done and wired up and the gas and power were on. I wondered why he didn't fire it up??? But I did notice that he had wired it slightly wrong. He had a yellow wire hooked to the rollout sensor instead of the red wire that had been there forever. I figure he tried to fire it up and realized he'd done something wrong and it would take a while to trace.

So I couldn't resist. I turned on the thermostat with it wired his way and - nothing. I swapped the red wire for the yellow wire and tried again. She fired right up. And boy did it stink!!! Filled the house with smoke. The wife was not happy. I figure the new exchanger would smell some but was worried the kid left some packing material in the heat exchanger. So I shut it down, swapped the wires back and aired out the house.

I stuck around this morning for the kid cause I figured I'd end up paying for his education if it took him two hours to figure out his wiring error. When he started looking at it again I said -"Looks like you got it ready to fire up. I notice you hooked that yellow wire to the rollout sensor instead of the red wire that use to be there." He said "you sure?" I said, "Yeah, you see that tape residue on the red wire. When I took the burners out to clean them I had to disconnect it and I always put tape on them and write on it where they go. It's a lot faster than looking at a faded wiring diagram" (hint, hint). So he swapped the wires and I left him to finish up.

Few minutes later he comes up and switches on the thermostat and goes back downstairs. I hear the heat kick on and the house fills with smoke again. He said that's normal it's the oil on the exchanger. (The wife and I are relieved.) He watches it run through a whole cycle and monitors it and the registers with a high dollar CO detector - everything zero. He also used a combustion analyzer. My CO detector stayed at zero. He says everything looks good. I'm glad cause the temp is suppose to plummet tonight to 13.

By the way, He and I looked at the old exchanger and couldn't find any crack or hole. He said that it's actually pretty common to not be able to see the cracks. I hope he's right.

Thanks again to you all for pointing me in the right direction.
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Old 11-20-2008, 06:17 PM   #9
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Rollout on Goodman Condensing furnace


Might be missing a couple of crimp rings.
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Old 11-20-2008, 08:19 PM   #10
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Rollout on Goodman Condensing furnace


Good thing it was not my job..I would have let you know what I think.
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Old 11-20-2008, 08:43 PM   #11
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Rollout on Goodman Condensing furnace


Quote:
Originally Posted by hvaclover View Post
Good thing it was not my job..I would have let you know what I think.
yea but you woulda wired it right the first time so the customer wouldnt have had to be noseing around in it assuming thats what you meant
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Old 11-20-2008, 09:30 PM   #12
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Rollout on Goodman Condensing furnace


GUy fired that furnace with out the tech finishing the job and making sure it was good to go.

he took a big risk regardless of weather he found wiring you thought was not right.

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Last edited by hvaclover; 11-20-2008 at 09:34 PM.
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