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Lennox L Series RTU giving me troubles

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Bombboy90

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Discussion starter · #1 ·
I am an hvac tech and am going on 3 years experience. I have this Lennox rtu Model- LGA120ss1Y Serial- 5600D04459.

It has tons of issues, some history: Another technician went to it and replaced the ignitor, flame sensor, and gas valve. Worked for about 2 days and I got called out to it and it was flashing code 56, air proving switch didn't make or high limit tripped. So I took out my U tube manometer and stuck it right to the draft inducer, had 0"w.c. Took the draft inducer off of the unit and retested 0"w.c. Again. Wheel is fine and not rotted, and secured. So I took a torch tip cleaner and poked out the hole of the inducer housing where the pressure switch hose goes to, then I got 1.5" w.c. Hooked back up and fired every time. Then a few days later another tech went out and not sure what he found then another tech went out and put a washer on the ignitor because he said it wasn't close enough to ignite the flame.

So after that I went back out, about 2 weeks from my original call and had the same exact thing happen, 0"w.c. On the draft motor. I pulled the blower out checked the heat exchanger saw no cracks and I tensioned the belt, etc. Poked a torch tip cleaner all the through the port again and made sure it was open again, checked the hose and all of that and it fired up every time after that. I told the customer and he doesn't believe me at all of what's happening even after he had an employee out there watching over my shoulder.

So the customer said he is going to have his employee pull the heatexchanger and wash it out, blow it out, etc. My opinion is the baffles are rotted and causing debris to get in the port and clog it up but he wasn't buying that argument.

Any tips would be appreciated.
 
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#2 ·
So the customer said he is going to have his employee pull the heatexchanger and wash it out, blow it out, etc.[/QUOTE]

Really ? Well then I guess you'll be off the hook and no longer married to it.
 
Discussion starter · #4 ·
VTP99 said:
So the customer said he is going to have his employee pull the heatexchanger and wash it out, blow it out, etc.
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Really ? Well then I guess you'll be off the hook and no longer married to it.[/QUOTE]

I agree! I told him to please do it!
 
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Discussion starter · #5 ·
id86bc said:
inducer housing metal? is the paint flaking off the outside? perhaps the inside looks the same? hopefully this isnt another cliff hanger
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Inducer housing is metal, still in decent shape. Inside is rusty though, looks like normal combustion to me hence why I feel it's baffles rotting and clogging the fitting. But according to the customer "it hasn't acted up for 10 years and now it has been a problem since January, your explanation about rotting from the inside doesn't make sense to me!"
 
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#6 ·
Sounds like you solved it really. Keeps getting clogged up from debris of some sort in HX. Just because the customer has said it doesn't make it true. People lie. Only way is to pull HX and see how rusty it is. See if it has had water damage from condensate off AC or other water issues lately. Maybe insulation is gone somewhere creating condensate. Or maybe it is 10 years old and needs replacing.

Good luck
 
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#7 ·
I'm thinking if you look hard enough the heat exchanger might even be cracked somewhere. L series arnt bad units in my opinion, they have their fits at times but all in all a decent unit. But when they throw their fits it can be quite a battle.
 
Discussion starter · #8 ·
I believe it's the heat exchanger but customer said he is going to rip it out and fix it himself so I'm done with it! I just wanted to make sure I wasn't going bat s**t crazy!
 
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#10 ·
First of all, a 10 year old heat exchanger on a Lennox10 ton B box unit is probably near the end of its service life. I would actually have to be there and look at this unit for myself to give you a better idea.

The chances are very good when he goes to pull this thing out of there that part of that heat exchanger is going to come apart.

Just for your own personal reference, if his employee has been working on this thing and it has "tons of problems," then you're going to have to consider the fact that that inducer is not rotating in the correct direction every time it receives power.
 
#11 ·
One follow-up note, since I see that you're still logged in to the site.

I've been working on these for a long time (and their predecessors) and this is one of the few models that I have never had to use anything to clear out the pressure port on the induced draft assembly. I've had to do it on a couple of residential units that had condensate water running back down the tube, and the hole would rust closed...but on a Lennox rooftop unit? That has never happened to me.

No, I'm not saying it's impossible, and I don't know what area of the country you're in, and different weather conditions and maybe even the different qualities of fuel gas could certainly affect the way that this unit is responding.

But my first thought would not be that you have a real issue with that hole. It's much more likely that you have a bad induced draft assembly and a case where that motor starts up in the wrong direction, and the cause could simply be a bad capacitor strapped to that motor.

You have three years in the business, so these are things that you need to file away in your head for the next time you see a problem like this.
 
Discussion starter · #12 ·
timebuilder said:
One follow-up note, since I see that you're still logged in to the site.

I've been working on these for a long time (and their predecessors) and this is one of the few models that I have never had to use anything to clear out the pressure port on the induced draft assembly. I've had to do it on a couple of residential units that had condensate water running back down the tube, and the hole would rust closed...but on a Lennox rooftop unit? That has never happened to me.

No, I'm not saying it's impossible, and I don't know what area of the country you're in, and different weather conditions and maybe even the different qualities of fuel gas could certainly affect the way that this unit is responding.

But my first thought would not be that you have a real issue with that hole. It's much more likely that you have a bad induced draft assembly and a case where that motor starts up in the wrong direction, and the cause could simply be a bad capacitor strapped to that motor.

You have three years in the business, so these are things that you need to file away in your head for the next time you see a problem like this.
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I greatly appreciate your response and I failed to mention that I checked rotation each time the draft motor turned on and still read 0"w.c. I even pulled off to check the wheel direction, etc. I told the customer the heat exchanger is probably bad but since I can't see the other half and bottom because the duct goes off the access port I don't know for sure. I, 9 times out of 10, see the seams rust out and these seams were bad, so maybe when it gets good and hot it expands and creates a hole. Anyways, have yet to hear from him!
 
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#13 ·
I hate it when they side duct these units.

The larger 156 units get the blower drawer pulled for inspection, then I literally climb in past the blower with a mirror, a flashlight, and my camera.

You can do the same thing with the 120's. It is just a bigger pain.

You may have an issue in your area, as I have never cleaned a pressure port on these units. Best I can do from where I am sitting.
 
#15 ·
You can't do most customers a favor. Repair it once and mark that if it occurs again you recommend replacing the heat exchanger and all ancillary components. That way if it reoccurs you can fall back on the ticket. You try to do the right thing and it can bite you in the but. If they are wanting to pull and "clean" a heat exchanger doesn't sound like a customer you want anyway.
 
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#16 ·
ZeroCool said:
You can't do most customers a favor. Repair it once and mark that if it occurs again you recommend replacing the heat exchanger and all ancillary components. That way if it reoccurs you can fall back on the ticket. You try to do the right thing and it can bite you in the but. If they are wanting to pull and "clean" a heat exchanger doesn't sound like a customer you want anyway.
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Especially when the customer has "my own maintenance staff."

That one ALWAYS leads to problems, and they are deaf to anything you try to tell them about that dynamic.
 
#17 ·
One thing I've been running into lately is they want to have their maintenance guy assist you with what is a two man job. Hell with that. You want the same guy to help me that led it be the reason for my being here now.

My response. Your worker isn't covered under our insurance, and we are the ones who you called here to perform the work. For liability reasons that will not work.
 
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