This was a service call on a Lennox rtu with a duct detector trouble condition. I found that the unit had a bad condenser fan motor that caused the main breaker to trip. I replaced the motor and the unit is now working properly.
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So today's call is on an RT: u unit, not working the actual complaint. The customer didn't even realize that the unit wasn't working their alarm company called them and said that they had a trouble condition from their duck detector and, like I've, explained in other videos. These duck detectors if they're wired up a certain way, they can tell you if they've had a sudden power loss at the RTO unit or air-conditioning unit, so we're gon na open this up and see what we can find here. Opening the unit up.

The first thing I see is that I don't have any sort of a display and no control voltage power. I have not gotten my meter out yet come to the disconnect switch and the disconnect switch is on. This is going to indicate to me that we probably tripped a main breaker, assuming that you know we check power and there's no power at the disconnect switch. So before we turn anything on or off we're gon na go ahead.

I shouldn't say: we're gon na turn that off just to be safe, open this guy up and just do a visual inspection to see. If we see anything jumping out us, I don't see any terminals blown out on the compressors, nothing jumping out of me yet so we're gon na go ahead and test voltage coming into the unit. Okay, I got our disconnect switch meters set to volts testing. Nothing, nothing! Nothing 11 volts some trace stuff going on there yeah, so we don't have any voltage so far.

I'm gon na get this electrical disconnect, opened up and then inspect in there and then we'll go downstairs and see if we can turn on a main breaker or something nothing too out of the ordinary in here before I turn on main power, we'll go ahead and Just double check the tightness of those screws on the top of that disconnect switch just because I've seen them come loose, but since we got no power, it's even better everything's, nice and tight. So it's interesting is uh yeah they're, going they're using that disconnect the opposite direction, so main powers coming into t1, t2 and t3 and then AC powers coming out of load, one load two and load three. I believe that's what we're doing here and let's go over here and check and see yeah me and power. Is this big wire right here kind of hate when they do that? I mean it still works the same, but I just like things to be correct.

As far as labeling on the disconnect switch all right well, I'm gon na just double check the tightness of those and then we'll leave this off and then we'll go downstairs and turn on the breaker and investigate down there as I'm leaving and walking by something quipment. That's being installed and this units not sitting level it's pitch to the left. I see some problems there doing an installation on this stuff right now kind of messy. I mean it's not sitting level, that's going to be a problem.

Okay, so this is like a storage room and they have their electrical stuff and they sometimes I've had them bump these circuit breakers before. But if you look at this one, this is in the tripped position. Your position is in the middle okay, so you try to turn it on and it won't turn on. You have to turn it off and then on so now our powers energized, but because I shut off the breaker on the roof.
We're gon na be able to troubleshoot that unit and figure out what's going on okay, so we got power back on now. So we're good got the disconnect off. So what we're gon na do is we're gon na troubleshoot everything beside we're gon na check everything to ground we're gon na see, if there's anything in here that could have caused this breaker to trip we're not just gon na turn it on and test we're gon Na do our best to make sure we're going to start with the compressors, because that's a very common place and then the blower motor and then go from there. Okay.

So to start we're gon na go to line and load to ground on each contactor. Just a confirm, you haven't, got my meat on audible tone and I'm just going to continue this all the way through the process all the way through each one to see. If we see anything and we'll do the same thing for the condenser fan motors also so I went through all the contactors, nothing gave me an audible tone to ground or resistance to ground. So then, what I started doing was checking all these contactors.

Are these relays up here? Okay, these are all different ones, ones for a combustion motor, two of whom are for condenser fan motors, so they've got all kinds of stuff in here, and I was just testing the power wires to ground and I got an audible tone on convince our family. Our number two to ground, but what was weird was then it went away, but immediately I got it so we're gon na investigate that a little bit further and go from there. So we're just checking looking for anything jumping out at us, nothing's jumping out at us. Looking good so far, we're gon na investigate that condenser fan motor wiring, see what's going on over.

I take the condenser covers off, so I can get in here to these fan motors and I check the other side nothing. But right when I get to this side, I could smell a burnt motor. I can smell an electrical connection and when I pulled the leads off they're melted, it's hard to see they're just kind of melted and deteriorated, so the motor itself isn't giving me a reading to ground, but you can see up in that terminal. It's just burnt out.

So we're gon na start by changing a condenser fan letter and troubleshoot the rest of the unit. What I will do right now, temporarily, I'm gon na get this unit operational. I will disconnect the wiring to this. Condenser fan motor and power the unit up and let it run with only one condenser fan motor while I'm gone, and then that way I can verify because I'll be gone for about an hour getting apart, I can verify that the unit works everything else.

You know I'll, let it run and then we'll go from there. You can see. This is a really bad location. They did a horrible job installing this, this close to this wall.
We have a lot of problems with this condenser plugging up. I myself just clean this about a month ago or less so I know it's clean, but yeah. This thing is horrible man. It gets so dirty so fast.

We actually have to do their preventative maintenance more often than any other of this particular restaurant, because we do a few of them for this chain and we have to clean this one more often than every other one, because it just gets so much lint from all The palm trees we're at a shopping mall, so so yeah we're gon na pick up the motor and then go from there. Okay, I got everything: buttoned up panels are buttoned up. The condense fan covers are put back on temporarily. I put the other side on disconnect to the motor taped up the wires.

We're gon na go ahead and turn on power. You always want to stand back, don't put yourself in between the device you're turning on and you know it. Basically, don't you don't get in the way of it and the same thing? You don't want to stand in the middle of the controls panel and have something bad happen, so I'm gon na power it on okay units powered on we're just gon na kind of stand back and see what happens. Let's let the unit run so I'm getting ready to change the motor.

I picked it up most of the time when I change these motors, I like to change the blade. Also just my experience. It seems to be easier. The blades are cheap enough, just as part of my price as a condenser family.

I throw a blade on there. Why not so before I do that I'll, usually just lube it with some lubricating stuff, it's just rest Buster from Mars, but wd-40 whatever works. Fine, let that sit on there for a few minutes and it'll usually break that free, nice and good. If you have problems, sand up the shaft and then put a crescent wrench on the top and spin the blade and you'll break it free, you can sand it pull it out, but most of the time you just put that rest Buster on there and it just Pull right off so a little tech tip here when you're tightening these on you tighten them snug like so then you loosen, then you tighten and you'll notice.

Each time you do that, it'll tighten a little bit more. You go in out in out a couple times and what you're doing is you're actually scoring your place in the chef's you're you're, setting that set screw in there nice and good. I call that running it in and out so you're gon na run the screw in snug, then out, then in and every time you do, that you'll notice it'll go a little bit tighter and just kind of in out in out and out two or three times Until it's nice and snug so that way, you know it won't back out and so everything's running, and then I got in here and I amped both of the condenser fan motor we're allowed to run 1.5. So we at one point: that's one I believe is out 1.2 now 0.2.

So both my condenser fan motors are running properly now she's gon na let the unit for a few minutes make sure everything else is cool, so I am wrapping it up. Everything's working on this unit, refrigerant pressures, look okay, nothing major to be worried about with that motors are running. Amp draws are good. I'm gon na go ahead and clean up my messes and get on downstairs alright, so that wasn't too difficult service call was on a duck detector that was thrown a trouble condition.
When I arrived, I found that the kitchen a/c number four had a tripped main breaker before I reset the breaker I shut off the disconnect at the unit on the roof and then went downstairs and reset the breaker. That way, I didn't you know, have a direct short or something like that when I wasn't there to view it. Okay, then, on top of that, before I reset the power to the unit, I checked everything to ground to see. If I could maybe find the problem before, I turn the power back on.

Sometimes it doesn't work out that way, but whenever you can you want to try to do that, because if we can find the problem without potentially tripping a circuit, breaker again and/or overheating the wiring. You know - let's, let's do so so I always like to try to troubleshoot everything as much as possible before I reset power to the unit, and I actually found the problem. Okay. It was weird, though, because my meter toned out to ground on the condenser fan motor, but then it stopped and it didn't tone out again so there must have just been a wire that was floating around and that who knows but anyways that ended up being the Problem picked up, the condenser fan motor changed it.

Everything was working great after that the units refrigerant pressures were decent, no problems, nothing to be worried about with that unit was you know doing everything it could I checked the belt. You know made sure that was nice and snug, and you know everything else is good. Okay, alright guys. I really appreciate you taking the time to watch the videos I posted a video last night, a tool review or a tool.

Bag review pay attention. If you haven't seen that video go back and check it out because there's a giveaway associated with it, okay right now, you should see some other channels popping up give those channels a shot. Consider subscribing to them check them out. They've got some great content and I will see you guys on the next one: okay,.


47 thoughts on “Lennox rtu duct detector trouble”
  1. Avataaar/Circle Created with python_avatars Alex Richardson says:

    What if you have a tripped breaker and when you turn it back on everything has power except for the duct detector. I have no lights lite but, on the fire panel is says duct detector. So everything seems to have power except for the duct detector. I checked all the wires. Everything is connected, nothing is visually wrong with it.

  2. Avataaar/Circle Created with python_avatars Bruce T says:

    You're like a teacher, first you tell us what you'll cover,
    then you cover it, then you tell us what you covered.

  3. Avataaar/Circle Created with python_avatars John Walker says:

    Boy, you look even younger in this video. Good job.

  4. Avataaar/Circle Created with python_avatars Volactic says:

    This guy can see problems with the units before they've even been fully installed

  5. Avataaar/Circle Created with python_avatars jarhead shooter says:

    We are fortunate in my area. The fm requires the duct detectors be serviced by the alarm company. We mount them to the ducts and all wiring is the responsibility of the alarm company.

  6. Avataaar/Circle Created with python_avatars Joseph M Orost says:

    Wow – that’s a whole lot of volts – very dangerous!!

  7. Avataaar/Circle Created with python_avatars Just Ali says:

    Wait did you say the disconnect works the same I am usually not going to be the electrician in the chat but I have abb training and the switch can only break faults in the forward direction hence the breaker tripping and it also has thermal protection in the forward so let me know how it works the same .::?

  8. Avataaar/Circle Created with python_avatars deineroehre2012 says:

    So you are troubleshooting the unit and another company installs another one right next to you (with a disaster waiting to happen)? Wouldn't it be much more easy to have only you on the roof and installing and PMing ALL the units up there? Or do the other units belong to another customer who shares the roof with your customer?

  9. Avataaar/Circle Created with python_avatars BigHuff2316 says:

    Scary voltage.

  10. Avataaar/Circle Created with python_avatars Joseph Ibarra says:

    Nice job man

  11. Avataaar/Circle Created with python_avatars Ed says:

    Looks like that condenser is too close to the wall

  12. Avataaar/Circle Created with python_avatars Claude Hayden says:

    I am not an electrician, meter says 490 make a 180 and call an electrician…. Service area Nepean??

  13. Avataaar/Circle Created with python_avatars djblackarrow says:

    It's always better to use circuit breaker and switch-disconnectors in the right direction. In circuit breakers and switch-disconnectors, there are often spark extinguishing chambers that only work properly if the power supply and load are connected in a specified direction. If you connect it the wrong way round, the contacts burns out faster or weld together. In the worst case the disconnector can blow up completely.
    I don't see extra fuses or circuit-breakers in the RTU for things like the fan motors. I think 40Amps (from the tripped circuit breaker) are way to much for the fan-motors. The same thing for the compressors. Circuit breakers with auxiliary contacts could be used to switch off contactors and/or display error information on the controller display and/or, if necessary, to force the entire system to shut down, or to run in a emergency mode if it's possible. You could also use motor protection switches that switch off when a short circuit occurs and when the current rises over the adjustet value. Without tripping the main circuit breaker and stress the cables. There are motor protection switches that are screwed directly onto the contactor contacts. They have NO and NC Contacts for status-report function or other things.

  14. Avataaar/Circle Created with python_avatars Ben Kuxhouse says:

    nice technique on the set screws I'm going to keep that in mind. I still think you need to invest in a megaohmeter it will do a lot better job picking up shorts curious the true insulation tester. I've had it with my fluke 902 I can't pick up a short to ground but I can with a mega ohm meter. You are putting More Voltage through the windings with that insulation tester. Sometimes with the insulation tester you still won't pick up a short to ground in a winding but you have a lot better chance. You have great videos and I have learned a few things from you you're very thorough. I work for a school district in the Seattle area Renton School District we are going to have a few job openings in the HVAC department in 3 years if you're interested in relocating to Seattle and working for a school district that pays 80 grand a year plus benefits I'll make sure you know when it opens up. I really want to have some good help one of my co-workers is completely worthless.

  15. Avataaar/Circle Created with python_avatars mitch says:

    Those cube relays on the Lennox are terrible. I had one short and send 480v through the 24v circuit thus blowing the stat off the wall! Inspect one and you will see the coil and the line volt contacts are not isolated like most relays. That damn 480v still makes me nervous after all these years. Once you have it detonate on you, it is something one never forgets! It's comparable to a M40 Grenade. Service area Barrhaven??

  16. Avataaar/Circle Created with python_avatars Coach Chris says:

    Trumppppppppppp 2020 Service area Orleans??

  17. Avataaar/Circle Created with python_avatars Alexander Lewis says:

    just watched did again,, you had a continuity between a fan wire and earth,,, Okay

  18. Avataaar/Circle Created with python_avatars Alexander Lewis says:

    Did you check if the condenser fan motor if it was good? Continuity, and earth test,,,If it was good all that was needed was to cut the wires back and make new connections,,, .. But if the customer was not worried about the cost too much, its okay.

  19. Avataaar/Circle Created with python_avatars Alexander Lewis says:

    Thank you for another intersecting video,,, it seems easy when the cause of the problem is pointed out..,,, However it is not always so,, Most enjoyable,. Service area Kanata??

  20. Avataaar/Circle Created with python_avatars HVAC REPAIRS & INSTALLS says:

    what’s that putty called you use for brazing? What’s the brand name? thanks in advance

  21. Avataaar/Circle Created with python_avatars Marlun Sides says:

    Great video! I'm hvacr contractor but I use to work in the field for a company doing commercial work. I use to make videos of my work just to show the news how its done the right way. Im a stickler for detail and uniformity when installing anything contractors to ductwork. When you mentioned the line side of the disconnect was reversed I thought about myself, even though it doesn't matter in this case, it could matter in another situation. I've watched a ton of videos on youtube and you're by far one of the best. You're very informative and straight to the point without all the unnecessary useless information. Some people on youtube talk entirely too much before they make their point. Thanks for the video.

  22. Avataaar/Circle Created with python_avatars Ronald Zeigler says:

    Right I always change the blade to but I carried a lot of motors on my truck

  23. Avataaar/Circle Created with python_avatars siempre positivo says:

    Everyone does horribles job .
    Just do the job with out talking crap like a racist woman.

  24. Avataaar/Circle Created with python_avatars Hassan Bah says:

    How are you doing

  25. Avataaar/Circle Created with python_avatars Younis Layth says:

    Thanks for Ur hard work, I just got graduated and passed an EPA test, and now looking for work, BUT, every company are looking for 2-10 years experience 😭. It's been two weeks

  26. Avataaar/Circle Created with python_avatars 001tracker001 says:

    I’ll disconnect all the contractors and reset the breaker. Then go thru engaging each contactor manually to isolate the issue. Usually a fast way to find the issue.

  27. Avataaar/Circle Created with python_avatars xbreaselx814 - says:

    I will be troubleshooting a Lennox tomorrow with smoke detector problems allegedly thanks for the great video!

  28. Avataaar/Circle Created with python_avatars walt radcliffe says:

    They don’t have breakers on the unit that blow before the mains?

  29. Avataaar/Circle Created with python_avatars YouKnowItsLiam says:

    Why were there 500 volts coming into the disconnect Are you in Barrhaven ?

  30. Avataaar/Circle Created with python_avatars Brian Martinez says:

    I like ur videos👌😎

  31. Avataaar/Circle Created with python_avatars Donnie Robertson says:

    Great job again

  32. Avataaar/Circle Created with python_avatars Luwam Debas says:

    how can I contact you? I really need your help in this profession.

  33. Avataaar/Circle Created with python_avatars Bill Noller says:

    Lennox schematics…..🤯

  34. Avataaar/Circle Created with python_avatars JAMES MOSHIRI says:

    Good job! Are you in Kanata ?

  35. Avataaar/Circle Created with python_avatars Moe Whitfield says:

    I subbed, I've become so nosey watching and learning here and there and I promise I will not do repairs or work myself as I am not licensed to do so.

  36. Avataaar/Circle Created with python_avatars Sean Michael says:

    Gotta love the easy money condenser fans provide. I see you're growing the fan base! Pretty badass, duder 🤙 I'm not sure where you were at when I started watching not too long ago, but you're channel is growing.

  37. Avataaar/Circle Created with python_avatars Dan TX says:

    That's a crazy install how did they how do they expect that to breathe properly I guess they had to mount it that way possibly because of the ductwork? I love your videos you're a very good teacher looking forward to more

  38. Avataaar/Circle Created with python_avatars Alexander's Refrigeration & A/C Videos says:

    Good find… Them Lennox relays sometimes take a dump.. but the fan wires are notorious for that specially Lennox Are you in Ottawa ?

  39. Avataaar/Circle Created with python_avatars HVAC Slayer says:

    Good advice on standing not indirect of the disconnect when getting power back, but when you flipped that breaker look like you were standing right in front of it. Guess some people don’t understand fan blades come balanced from factory, you’ll notice on some blades there’s weights on them and any type of alignment from the blades or balance issue kiss your bearings goodbye. I knew about balancing through the field but I watched a grayfurnaceman video and he actually talks about the weights being on the blades.

  40. Avataaar/Circle Created with python_avatars Jeffrey Biberdorf says:

    Use your refrigeration wrench to tighten/loosen the nut on the fan blade. Also, be sure to set the fan blade at the correct height.

  41. Avataaar/Circle Created with python_avatars mc20855 says:

    very good video, thank you as usual.

  42. Avataaar/Circle Created with python_avatars HVAC/R KNOXVILLE says:

    great video….. tkxs

  43. Avataaar/Circle Created with python_avatars GREGO B-TEAM says:

    Man I love your videos, very thorough explanation. Keep up with your videos I look forward to watching them and gaining knowledge as I myself am in my first term of HVAC school at a local community college in Albuquerque.👌🏽👍🏼✊🏽 Are you in Orleans ?

  44. Avataaar/Circle Created with python_avatars DJSubAir says:

    Thanks for the tip regarding the shaft scoring when tightening the set screw by going back and forth, just used the same trick 😀 thank you 😀

  45. Avataaar/Circle Created with python_avatars TEXAS STAR HEATING AND COOLING says:

    GREAT FIND CHRIS HAPPY THANKSGIVING

  46. Avataaar/Circle Created with python_avatars ZuffaLtdDanaWhite says:

    9v to ground doesnt always pick up a short. when my meter picks it up then disappears, it's time to take out the megger.

  47. Avataaar/Circle Created with python_avatars kd9bwi says:

    Cool. I bet they had some high head pressure before that tripped the breaker. Luckily it shorted and tripped the breaker or else you'd be dealing with a burnout.

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