LENNOX VFD FAILURE 

Was waiting for a video today thank you!

In Germany we normally use ferrules. This makes it easyer to prevent arcs between the connected wires 😉

I suspect that the short you found is what blew the VFD. With that kind of power, the bang at the VFD is going to be big in quite a bit of the cases.

Chris, Nice job !! One thing, when you were transfering the wires on the green blocks ( wire for wire) those green blocks are called Euro-blocks, you should be able to pop the top of each section, there are pins under each block, and they plug into the base of each block, It's a time saver.

Gotta give you props on how you went about terminating the VFD. Basically the opposite of careless. Refreshing to see a tech soo methodical and conscientious about his work . These days the big push is "do it faster, just get it done, who cares how it looks" I refuse to work that way and it's good to see someone else apparently thinking along the same lines.

Thank you again the old videos are just as good !!!

I wonder if Big Clive would be interested in looking at those VFD modules? 🤔 Not sure what shipping would be like to the Isle of Man though lol

I'm taking a class on VFD's for my Automation program in school, and we just got to setting them up in the lab. Lots of reading the manual, and quick start guides and learning what to look for for troubleshooting, and how to program them right now. After 2-3 weeks doing the basics, learning error codes and things we're supposed to start wiring and interfacing with PLC's and networks and I'm really excited for it. We're going through a lot of troubleshooting, and it's one of the things we focus on a lot in this program. Having you going through this kind of stuff, and showing examples of it, and how to fix it really puts the theoretical into context. Even the practical stuff we do gets some grounding with real world and it makes me feel more confident. Some of the stuff we've had hit on us, is of course the importance of incoming power and power to the motor, not getting mixed up. Also have been told that you cannot have a drive fed incoming power through filter capacitors. Thanks for putting out a VFD video. Your troubleshooting and installation videos are always full of great tips and you have a really solid methodology.

You are starting to look very tired my friend. You need a vacation! Thanks for another interesting video for us HVACR enthusiasts

At my warehouse that I take care of I have a strapping machine that has vfd drives. It is also plc driven. This machine is what has taught me a lot about a/c voltage. The vfd's control the motors that feed the strap and tension the strap around the product. In my case we strap tires for the manufacturers ford,chevy, etc. I thank you for showing how you replaced it and using tech support. If I could teach someone about any trade, i would say don't be afraid to call tech support. Being self taught on a lot of things I would say that calling tech support will save you a headache and time. Trying to look things up for an hr when you can get the answer in a few mins is priceless. I found that if you know how to use a multimeter these guys can walk u through about anything electronic or electrical. Thank you for the great videos.

I am the same way when I'm installing and doing service calls. I also do dcommercial hvac and sometimes when people observe me they think I'm crazy or weird but I now that I'm not the only one that talks to himself as I'm doing the work

Your troubleshooting procedures should be the gold standard

Tip for using but connectors, use some silicone filled heat shrink over the top to keep moisture out and protect others if the plastic cracks.

My own OCD would probably not allow me to use the demolition screwdriver for anything else than beating on it , kudos for not letting it get to you , Chris !

Nice and simple explanation and thinking process 👊🏼

I really love your channel. I'm an electrical engineer from germany and your right, you have to show respect when you're facing a 480V 3phase system. I worked a lot with 690V 3phase here when i worked in automation for big industries like steel mills. Theese days mostly 400V 3phase, what is actually the supply for every private house over here. I wonder that you don't work with end sleeves on stranded wires in the US. Here in Germany you would never connect a VFD directly with stranded wires.

Very well done !

Dude, Greetings from Jersey! Excellent job on explaining how to troubleshoot and what not to do. Your on point with this stuff, keep up the great vids!

Great video and good way to approach the replacement

Sounds like they need a mechanical interlock to avoid that problem. Great video.

14:14 Not a HVAC guy but I was thinking the same. Both contactors should use an interlock, either mechanical or electrical. I mean, You CANT call both of them AT THE SAME TIME. Old relay boards with big three phase contactors used to invert rotation, both contactors were conected mechanically through a crowbar, so Its is one or the other, never both. Sensitive things like this, shouldnt be just SW controlled. A plan B for fail safe is required.

Thanks for the information. I work on a lot yorks that have a VFD and they can get tricky. Yorks VFD looks very similar to the one you changed out.

480 volts proceed with caution. Your a very smart tech, one wrong move and it will spell disaster. Great video.

Thank your for this Lennox video,,, i and probably most people of my generation , feel a bit nervous when it comes to working on units laden with modern electronic , inveters and such,,,,i know many of these units give a fault code which tells you what is wrong,, .......but....,,,,,,, Enjoyable video .....

Great job again like always

Great video, as always great content, I carry the the connectors for R290 units now instead of wire nuts I like the visual and locking the wire in place and preventing moisture. Those VFDS don’t look weather proof should be installed in a conditioned space

Also with VFD's there's capacitors that take about 20 minutes to drain out. So it's always a good idea to wait at least 20-30 minutes before interacting with it.

Great video Chris.

After your wrap up and i went back and looked at those contactors to see for myself. I can't believe Lennox isn't using auxiliary contacts to interlock those two. That is motor controls 101. I wonder how many VFDs they have had to replace under warranty that could have been prevented with a pair of $10 aux contacts.

Checking you out from Alabama ,thanks

Thanks, Great Info

Nice repair video 👍

Interesting design. Lennox should have used a reversing contactor setup. If one side is on there is a Electrical interlock using Auxilliary contacts, along with a Mechanical interlock between the contactors. Good practice with the 480 connections. I take a pictures using a cell phone of the connections at different angles as a backup. Regarding arc flash if low peak fuses are used with proper wiring I am more secure. With a breaker then watch out. Breakers can put out 12 cycles before tripping. Low peak fuses open at the first 1/3 of a cycle if shorted. They are also expensive. :-)

Good detail to attention and safety practice. Job well done. Yes I talk to my self as I work seams to help think things through

Thanks🙂nice video

I always talk to my self when do trouble shooting, so its pretty normal 😂

Nice weather for repair. I was rarely that lucky.

It is finally starting to get cold 🥶

VFDs are typically designed for 80 F ambient and start derating their output above this temperature. They should not be in a package unit on a 110F roof. Way over it’s specification. Look at the data sheet and you will be shocked! A 10hp vfd cannot output 10hp at 100f. VFDs also contain electrolytic capacitors which fail faster in proportion to their increase in temperature, higher ambient temps = significantly shorter lifespans. This is often a source of failure, as IGBTs are sensitive to dirty power

"Hooking them up wrong causes the unit to explode" Proceeds to hook up the new part in the same way. You are trusting.

It seems weird that Lenox would sell the VFD without the wiring attached. It also seems insane that they use the same colors and connectors for the input and output harnesses.

Just an observation looks like you’re using a Klein demolition screwdriver that end cap is conductive

Aaand you forgot the sticker..😂 8:15

I seen you check for no power before starting, but did you check your meter before on a know voltage?

Does the control use the pressure switch attached to the blower housing to determine if the blower is working?

i remember that you could pull out the entire green wire bar, the one with the push releases.

Just for those who are not aware, those vfd’s can hold a lethal charge up to 5 minutes. I personally usually wait about 15 minutes to touch any wires when changing one out. The manual always has the info about how long to wait when changing a vfd. Don’t want anyone out there learning the hard way

Yes amigo

I do have a question. Are outdoor condenser units on a drinks fridge/cool room suppose to produce / blow condensation and therefore create mould on the surrounding area?

Very smart great

Great job. Do you think that in the hot dessert area that you service in, it pays to have VFD's installed? I would guess that they run wide open most of the time. Thoughts?

Some VFDs will have stored power in the drive...They power down after short time main power off.. i also use a volt stick on the drive also..

I'm going to lose some sleep after seeing those white cable ties being uncut.

Those VFD's are a big money maker!

Still waiting for the Volunteer Fire Department to arrive!

it is sad to say but how long will it be before you are back replacing that or any new VFD agene?

I work on high voltage all the time up to 13800 volts. I respect all your videos and your OCD. The manufacturer has a torque spec for line connections. You turned in then turned out then turned in. Was the torque wrench in your arm clicking

First like and comment I wish VFDS were more durable

Just thinking you didn’t mention a lock out on the bypass Shouldn’t there be a lockout to prevent that on the contactor ?

That’s a WHOLE LOT of Volts!!

great video I love it ......is the allergy is killing you...lol.....I have the same problem

Wire termination is your friend ;-)

Interesting

I suppose the VFD feeding one phase shorted to ground is all that it takes to takes to spoil it's day. Ron W4BIN

Don't those green contact strips in the vfd just unplug? They should use a relay that opens the circuit to the vfd when it bypasses it. A 3 phase reversing contactor could be used with a slight modification.

Any condensation on connectors with 480 VAC might as well be a short!

can i have tho old vfd module???? but ur video is awsome.

You do some good work. However instead of using electrical tape on those butt connectors it would be better to use adhesive lined heat shrink. I also would have cut those wires back so that the insulation came all the way up to the screw terminals.

Why is it 480V, seems a weird voltage. Thinking about it, im guessing its a safety measure for the PCB. 🤔

I wonder if that short on the output of the VFD was what turned it into popcorn.

👍👍

If the bypass contactor can backfeed the VFD, then they did it really wrong! They may have used the wrong contactor type, or cheaped out or something... You should have a normally open and normally closed contacts... Motor should go to the common, VFD output to the NC and power to NO. This way, there is no way for the VFD to get backfeeded, the contacts will break before it make with the other, and you can not get a short between NC and NO unless the contactor melt down...

I'm changing a carrier ruftop unit bloower motor the new motor has its 3 hp. It's same model..and number. The blue wires 2 coming out fron the motor. Has fimale and male ..to connect the the red wires goit to the control .. but this red wires has only males..adaptes.... so only 1 gets conested quet about the other ..the old motor it wasn't this motor its fron marathon motors..like this. Any suggestions.?.?

why did they not use wire ferrules?

Can someone explain why you’d need a vfd for 59hz? When standard line voltage is 60hz?

I'm surprised that those run and bypass contractors are not electrically interlocked. A VFD out put is not a sine wave - if you ever look at a vfd output on an O scope it will scare you to death. A vfd not only varies the frequency of the output it also vary the voltage - so if your speed is 50% your motor will be turning at 30 Hertz your voltage will also be 50% - so you can see what would happen if you bypassed the drive that was running at a reduced speed not only would you be closing two electrical systems into each other at different frequencies they would also be operating at different voltages - and to add more destruction to the mix there is the phase relationship difference that the drive creates - when a drive takes its input voltage it converts it to DC- then the drive fires the triacs according to what the drive software is calling for - even if both systems are operating at 60 Hertz the drive input and output will not be Synronized - the more electrical degrees apart the two systems are determines the amount of fault current that will be generated. That is what blew up that drive I'm sure. I have seen huge breakers launch out of switch gear and hit the wall because phase rotation was not correct on a 4000 hp generator that generates 2.5 megawatts of power at 4160 volts. What they have designed is a bomb waiting to blow up in somebody's face. I would disable that bypass relay so there would be no way it could supply power to the output of the drive - I would mark the phase rotation and disconnect the power to the bypass relay - then if you need it you could disconnect the input from the drive and reconnect the bypass relay. And if you need the bypass relay I would also disconnect the output of the drive - you will be backfeeding into the drive when your bypass relay is energized... judging from this video I would not let any employees mess with it. Everyone needs to understand exactly what forces are in play with two out of phase power sources... if you want to verify what I'm saying next time you get around one of these drives put your meter on voltage and put one lead on A phase input and the other lead on A phase output - if they were in sinc the meter will read 0 volts - any voltage reading indicates how far out of sync the input and output are - with a little math you can figure out how many electrical degrees out of sync the two systems are. Good luck

Is it possible to bypass a VFD on a Lennox unit with a 3 pole contactor?

Bypass contactors should be both electrically and mechanically interlocked especially if used around a VFD - secondly is it possible that the original VFD was actually not faulty at all and the problem the motor supply cables that where shorted on the cover ?? Most VFD are very well protected for shorted output.

I have changed the same Mitsu VFD in a York. F700 I think.....

So... why didn't those wires have any ferrules or terminals on them?

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I would think that there should be interlock on bypass contactor that would take vfd out of the circuit. But it looks that manufacturers like to make better margin and leave that safety to software.

a bit late to the party maybe, but why are those contactors not wired like a logic XOR gate? basically like the cooler/defrost interlock, except on both contactors? If I understand those things correctly, that way they'd only allow one to be energized, and never both...

I like to install ferrules on this cables

Next time use your cell to watch the unit startup and stand aside from the access panel and the disconnect switch. In this case it would have been better to stand further down the side of the unit away from anything that could go boom. Backing up and turning your head will not help, if anything happens it will happen so fast that it is like dodging laser beams. Hopefully one day you be driving home with a destroyed cell phone and amazed at how fast the whole thing went sideways, but you are fine and just need to replace your cell. You have a tripod so you could have used it for keeping an eye on the startup.

Throw that skew driver almost eletrcuted myself with chisel driver easy to absent mindendly use on live circuit

i like those styled packaged units

Was the replacement part made by Mitsubishi Electric?

Auxiliary switch on vfd contactor wired nc to interlock with the bypass contactor. Advise Lenox.

I have the same screwdriver

Remember that you had to clean the coils on that unit?

How long did it take for the part to come in and does it need more volts the bigger the tons are

Smarter not harder

Even in residential applications i have a lot of problems with those drives. They are garbage

Maybe lennox should wire in a relay that would disable the drive contactor if and when the bypass energizes.

Why is it a Mitsubishi VFD?

You could strip the wires a little shorter.

#156 Thumbs Up

you did reveal something, but editing must take time

I bet the short is the reason tbe vfd went ... pop....