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Originally Posted by VTP99

Jason, did you look at the date of this thread ?

🤔

Jason, did you look at the date of this thread ?

Originally Posted by jeremyhall.tech.sc

thanks to everyone for their help this one was a pretty bad foul-up on my part.

i checked the temperature with a probe and seen the temperature rising when in reality it was getting high temp readings from radiant heat . . . stupid stupid stupid me . . . the HX cracked from short cycling since the hls was faulty...


i still have the issue with a small amount of roll-out im not happy with, nothing i cant fix with a tune-up kit im sure.

Ok, now wait A minute. I understand what you’re saying about taking that temperature right there, but if you think about it that’s exactly where the high limit senses its temperature as well, so whatever temperature you got on your digital thermometer is the same temperature that high limits going to get and if your high limit is rated at 160 and you’re getting 200 and something then there’s an issue there. So, I don’t think that u screwed up there. You’re not supposed to be checking supply air temp or anything. You are SUPPOSED to be checking the temp right there where the HL is located, because the HL cutting out due to excessive heat ISSS the problem after all, correct?

Well, what I say is true and correct, UNLESS you just stuck your probe in there any which way and possibly had it going in at an angle and way too dam close to or even touching the HE, OR were you careful to ONLY put it in straight and level and at the correct depth matching the length of the HL?

Lol, sorry, I know that you basically called this one “solved” and you “that’s a wrap!”ed it, but I was reading the thread and that’s what it made me think when you said you screwed up. Only way u may have, is if u did what I said above. With the prove angle and depth, etc. Anyways. Be safe snd take care everyone!

I had the SAME exact thing happen on a 11 yr old goodman furnace. I did everything you did and still could not figure it out. She ended up wanting a new unit anyways but it bothers me that I could not figure it out.

Originally Posted by jeremyhall.tech.sc

you really helped me here pal thanks.

i checked the temp at the return and supply plenums and it was 69 degrees incoming 138 degrees supply , well with in the 40-70 range...

i changed out the hi limit L-160 for a L-190 and all seems well .

almost well i should say its still got some small roll-out on the start-up . im going back with a combustion analyzer and my tune up kit to get it under control.

Glad I helped there, since the airflow theory sucked... I'd have bet money on that one. Still, 69 delta T says the air volume is minimum. Oh well, that's the downside of troubleshooting over cyberspace...

thanks to everyone for their help this one was a pretty bad foul-up on my part.

i checked the temperature with a probe and seen the temperature rising when in reality it was getting high temp readings from radiant heat . . . stupid stupid stupid me . . . the HX cracked from short cycling since the hls was faulty...


i still have the issue with a small amount of roll-out im not happy with, nothing i cant fix with a tune-up kit im sure.

Originally Posted by Saturatedpsi

"Stickin' the probe into the hi-limit hole" might not give you a realistic air temp value, due to radiant heat.

I didn't see an actual measured temperature rise through the furnace. You could confirm low air another way:

CFM = BTU output / 1.08 X temp rise

= 60000 / 1.08 X 70 (max) = close to 800 CFM, the minimum you would need for design operation.

you really helped me here pal thanks.

i checked the temp at the return and supply plenums and it was 69 degrees incoming 138 degrees supply , well with in the 40-70 range...

i changed out the hi limit L-160 for a L-190 and all seems well .

almost well i should say its still got some small roll-out on the start-up . im going back with a combustion analyzer and my tune up kit to get it under control.

Originally Posted by rundawg

My parts list for this unit shows the Primary Limit Switch to be 220ºf.

Send me an email (it's in my profile)and I will send the manual back to you.

I still think you have airflow issues too. I'll give you the service manual too so you can check the airflow after you do a static pressure test.

on the spec plate it says temp rise 40-70 degrees, hi limit 160 degrees, and MAX output 170 degrees ......

i called tech support and they told me that it could handle up to 220 degrees as well . . .


the supply air sp is .37 ...

i changed the limit to an l-190 and it seems to be fine except for that small amount of roll-out on start up....

You mentioned it had a slight rollout. You should check the orifice sizing and make sure the correct gas valve is installed. i have seen people install a snap action, when a slow open was OEM. Also, make sure the insulation hasnt fell down inside the unit and block air flow. We are talking about a Goodman here!

Whats the Static pressure in the duct system S.and R. that should tell air flow. I would bet its an air problem

Afterthoughts

"Stickin' the probe into the hi-limit hole" might not give you a realistic air temp value, due to radiant heat.

I didn't see an actual measured temperature rise through the furnace. You could confirm low air another way:

CFM = BTU output / 1.08 X temp rise

= 60000 / 1.08 X 70 (max) = close to 800 CFM, the minimum you would need for design operation.

We're all still hanging at the edge of the cliff...

Problem #1 - With 12" supply, and 14" return duct, the blower is not moving much air @ 1 amp. What speed is the motor on, low? Try switching to high speed for heat and see what that does to amp draw and your temperature issue.

Problem #2 - Still keep going back to that roll-out condition you observed. Something is not right with the inducer air circuit from what you described. All the gaskets for the collector box sealed airtight? Any leaks through the HX reduce the volume/velocity of the air entering the HX tubes, creating rollout. Which is why I was curious if you 'leak' tested the HX with water before you installed it. BTW... I got that idea from recent posts here at H-Talk. I did it the other day to an old HX, and water poured out of it. Considering the quality of things nowadays, I'm going to do more leak searches from now on - even with new HX's.

I remember some GM package units had a stainless steel screen in each tube to decrease laminar flow for better heat exchange. Were they there, and are they needed?

Saturated makes a good point, and I don't know if anyone else has mentioned it yet or not, but is this thing on Gas company gas or well gas? we see some here on well gas and they are running hot and need the Gas pressure adjusted accordingly.

Originally Posted by jeremyhall.tech.sc

im going to check the indoor blower wheel and make sure its tight and not slipping on the shaft , also im not sure i want to start changing orifices even though ill check it.

i did kind of deal every one here a dead hand though i didnt get my SP readings ...

The blower motor's rated 2.5+ and pulling 1.0. It's not moving air. You already disconnected the ductwork, and it still didn't move air. Supply and return static pressures will be low, only confirming it's not moving air.

I don't know what's causing the problem, but it's got to be a restriction, slow motor, reverse rotation motor or restricted blower wheel...If the blower wheel was slipping, you'd hear an abnormal noise. It is a PSC motor, right? Every now and then you run across a Goodman with an ECM type , which could be running slow.

We're all assuming it was running "normal" yesterday, or the day before or last week. Be sure and confirm that. It it was, something broke.

My parts list for this unit shows the Primary Limit Switch to be 220ºf.

Send me an email (it's in my profile)and I will send the manual back to you.

I still think you have airflow issues too. I'll give you the service manual too so you can check the airflow after you do a static pressure test.

Originally Posted by jeremyhall.tech.sc

tell me more . . .

where do i find this info? what is the purpose of this metal "baffle" ?

when you pull the blower assembly it is the small curved piece you have to remove in order to get the wheel out of the throat of the housing.
usually held in by 2 screws & a couple of tabs
ill find a picture of it tomarrow.

Originally Posted by jeremyhall.tech.sc

i dangled my probe into the exhaust box and it read 239 degrees and was still rising. . .

im going to check the indoor blower wheel and make sure its tight and not slipping on the shaft , also im not sure i want to start changing orifices even though ill check it.

i did kind of deal every one here a dead hand though i didnt get my SP readings ...

ill keep you guys posted , im tired, im frustrated , and the wife is about to sling my laptop out the window . . .

No I didnt mean that. I meant verify their size by markings AND visually to see if they are too large.

Originally Posted by hvacvegas

I can never remember which is bigger orfice, propane or NG?

LP burns hotter , there fore smaller hole . . .

hope i helped you my freind.

Originally Posted by stickinit2thman

You could also check your vent temp to see if its the firing or airflow.Also check the venter fan flue to ishure no blockage.Then proceed from there. Did you verify the correct orafices are installed and even compare them to a known correct size to see if they were stamped wrong or are just too big. Sounds like youve checked about everything else, id start looking for factory or tech screwups.

i dangled my probe into the exhaust box and it read 239 degrees and was still rising. . .

im going to check the indoor blower wheel and make sure its tight and not slipping on the shaft , also im not sure i want to start changing orifices even though ill check it.

i did kind of deal every one here a dead hand though i didnt get my SP readings ...

ill keep you guys posted , im tired, im frustrated , and the wife is about to sling my laptop out the window . . .