Don't mistake it for a bad control board Carrier rooftop

Learning experience for me I can't possibly know It all www.amazon.com/shop/miheatingguy
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#MIHeatingGuy

[@mattcummings8402]

Thanks so much for this! Saved me a huge headache.

[@Jremi95]

Appreciate this. Just saved me a load of time scratching my ass on a roof trying to figure out what was going on. Not super familiar with carrier equipment, especially the new stuff.

[@allanford1582]

I can tell you in the course of my 50+ years around this trade, we are in the era of rapid change to be gentle, there is no doubt the limit tripped in heating mode, due to the nature of the fan I always suggest maximum fan off delay and minimum fan on delays where possible, good luck to all service techs, the speed of change will require it.

[@Tom-l9z]

I know this is 4 years old, but they made an auto reset replacement for that limit.

[@HVACGUY]

Thanks for the video. You just taught me something.

[@andym7513]

Wish I had watched this before I ordered a board. Thanks

[@makeithotornothvac6347]

I work for a factory authorized dealer for carrier, they are rolling out replacement motors for certain models, call your local branch tech support for tips, wire nut the two red leads together, replace the blower limit with a auto reset, then wire the new limit and the heat exchanger limit in series so if the blower does fail to communicate it will reset on it’s own. Temporary fix

[@MiHeatingGuy]

Thanks

[@CarlosMendoza-yo8ul]

Just got off the phone with tech support and that is exactly what he told me to do. Told me to replace limit with #hh18a160
Thanks for the help

[@renj6531]

0:15 that fan reminds me of the one on the old porshce air cooled engines

[@jsfkdkjslfdslfkdj]

Cool tip thanks

[@steverosswog4926]

I had this same exact problem last week, had the same thought, bad board. Another guy went back to change the board and found that limit tripped.

[@stevenbennett9785]

I had one doing the same thing. Ended up being fan not moving enough air. Had to adjust blower on the board based on static, and dc voltage.

[@RJMaker]

That reverse vane (or whatever it's called) blower is great. Hopefully those units were commissioned correctly, if not you'll be back.. :-(

[@gregmercil3968]

I had a Carrier RTU do similar to me a few days ago, expect this unit was a little older (2015) and had the traditional belt driven blower wheel. The board got 24v but no 24v at the Tstat connections or anywhere else. I went through the whole system and when insane trying to figure it out, I ended up condemning the board. None of those limit switches felt like they were tripped either. Except I think this may have actually been the board, because nothing reset.

[@jonnymac31]

Nice. So now instead of just the heat exchangers dying every third year the fan will too. Fantastic.

[@MiHeatingGuy]

The only good thing is its going to be easy to change

[@sharky5570]

Limit trips cuz the fan stops running and found sometimes it’s the plug not making good connection to the controls

[@dwight.bennett]

Interesting ... Guessing the idea behind the new fan design to eliminate belt/pulley maintenance ... Seems like that got swapped for controls maintenance.

[@MiHeatingGuy]

The new fan is because of government regulations

[@AmericanFarmerHVAC2024]

Rooftop with an icp sticker? Must be a recent decision.. never seen any icp rooftops before.

[@jamesg9936]

Where in the world have you been

[@antoniosantiago2770]

Question why did it trip. Maybe in heating. That's what I want to follow up if it happens again. Great video

[@MiHeatingGuy]

I think it happened in heating with not enough delay for the fan on off cycle

[@capitolrefrigerationheatin7501]

@@MiHeatingGuy there is a service bulletin for that issue

[@guyguyguy2020]

Would there be a manual reset limit in a Carrier HVAC? No power to our Controller or boards. We swapped everything from boards to transformer and Controller. Everything works perfectly fine with an ac that is running.
Any ideas? Thanks

[@MiHeatingGuy]

Believe it or not, some of the older carriers when they switch to the little blue fan have manual reset high limits in that compartment and there is a service bulletin on them. I've done the same thing, changed every board out and still no power because of a limit

[@jwchicano]

Blower off delay isn't adjustable to my knowledge (please correct me if I'm wrong) and not sufficient to cool the heat exchanger. Been replacing those limits with automatic reset limit switches.

[@MiHeatingGuy]

I think your right

[@trinito97]

Now you have to find out why is tripping

[@MiHeatingGuy]

Filters

[@Jason-wc3fh]

What a POS. a heat related limit switch prevents the whole board from working and not even allowing you to have air conditioning. Does it not display the fault anywhere?

[@MarkCarpenterHVAC-me2jg]

In newer commercial units, most things including smoke detectors are now home run to the board. Trane uses Modbus, similar to the way cars use CANbus. It's nearly impossible to meet efficacy standards like California's Title 24, using electro mechanical controls anymore.
Newer Carrier units are going to Near Field Communications (NFC). You hold your phone up to the board similar to the way you tap to pay for things at the store. Haven't worked on one yet but it seems interesting.
Not to worry much of this is on It's its way to residential units. The normal progression is from Chillers > Commercial > lite commercial and finally on to residential.
There are some advantages to using DC reference signal to ground, it sure makes for some easy troubleshooting.

[@dennisduffy5678]

What caused the trip ? you just reset it ?

[@MiHeatingGuy]

Brown out

[@fastzombie1]

That is a really odd looking fan.

[@throttlebottle5906]

more great engineering by people whom can hardly wipe their rears and have zero field experience... yet a piece of paper says they're qualified, for what? :))