I've always hated having to fix things that someone else screwed up not knowing what they are doing. Just came across your channel. I use to fiddle with a large absorption system in a high school I volunteered at back in the 70's. Never knew what the tonnage was but the water/lithium bromide chiller was about 30 feet long and a good 10 feet in dynamiter. Really big school built for 5000 students. Those were the days. Amazing how technology has advanced.
IIRC, you can set a parameter in those ABB drives that electrically swaps the motor rotation in FWD mode so wire swapping isn't necessary. That parameter was buried pretty deep in the settings menu...
I am glad you settled on changing the output on the drive, because changing the input to the drive will not change the output direction. The three inputs are individually rectified to DC and sent to the DC bus. Then the bus is taped three times and run through three large transistors to form the three output phases. The three transistors are driven by the control logic to create the sine wave of the needed Hz.
@@subcoolHVAC Puzzling indeed! That system was quite a mixed bag, antique Carrier AHU, Barber Coleman chill water valve, what is left of a Honeywell pneumatic t-stat, an ABB drive feed by a T775. The lack of cooling I think came from the blown pneumatic tube. The drive appears to be the newest part of the control system, maybe it has always run the AHU in reverse. Or someone has been into the motor wiring or service disconnect. The AHU will move some air running backwards and the air being super cold and dry with low air flow might have cooled the space. You just found the AHU fan issue first. My $0.02😊
Also begs the question as to why the wires from the drive to the conduit were all wire nutted and not directly connected to the drive? Bearings don't sound like the best in the world either.
Im curious how all that was messed up. Wonder if it was a case of "i know a guy" who doesn't actually know jack squat. Good job on getting to the bottom of it.
My first time seeing that unit, looks like it’s been limping along awaiting replacement. There’s crews on site replacing ahu’s. I just get sent out to troubleshoot
@@subcoolHVAC i hate to say it.....but these installers nowadays dont seem to know how or what itnis they are doing. I've had my share of going behind them for something that is simple......and was in the manual....they didn't bother to read or open. I may be a grumpy old salty guy....but it isn't that hard to do.
Awesome work. New sub here from West Palm. I'm enjoying watching your channel . No BS and experienced. I'm a welder/fab guy and like learning new stuff. Cheers...
Thanks for the comment. I had an incident many years ago resulting in second degree burns because I couldn’t get the glove off ( refrigerant burn ). I wear silicone ring since too. I don’t always wear gloves but when I do it’s nitrile coated 👍
Correct, pneumatic thermostat was missing . The T775 stat controls drive speed. This ahu is scheduled to be replaced with new controls from what I was told. Thanks for watching
I've always hated having to fix things that someone else screwed up not knowing what they are doing.
Just came across your channel. I use to fiddle with a large absorption system in a high school I volunteered at back in the 70's. Never knew what the tonnage was but the water/lithium bromide chiller was about 30 feet long and a good 10 feet in dynamiter. Really big school built for 5000 students. Those were the days. Amazing how technology has advanced.
Thanks for watching Cowboy Frank, that was a big school. Welcome to the channel!
IIRC, you can set a parameter in those ABB drives that electrically swaps the motor rotation in FWD mode so wire swapping isn't necessary. That parameter was buried pretty deep in the settings menu...
Yep 👍
I am glad you settled on changing the output on the drive, because changing the input to the drive will not change the output direction. The three inputs are individually rectified to DC and sent to the DC bus. Then the bus is taped three times and run through three large transistors to form the three output phases. The three transistors are driven by the control logic to create the sine wave of the needed Hz.
Puzzling how it got that way, Thanks for watching
@@subcoolHVAC Puzzling indeed! That system was quite a mixed bag, antique Carrier AHU, Barber Coleman chill water valve, what is left of a Honeywell pneumatic t-stat, an ABB drive feed by a T775. The lack of cooling I think came from the blown pneumatic tube. The drive appears to be the newest part of the control system, maybe it has always run the AHU in reverse. Or someone has been into the motor wiring or service disconnect. The AHU will move some air running backwards and the air being super cold and dry with low air flow might have cooled the space. You just found the AHU fan issue first. My $0.02😊
@@subcoolHVACUnless the motor was changed recently and connected wrong? Strange because of the wire colors were matching before you changed them.
Also begs the question as to why the wires from the drive to the conduit were all wire nutted and not directly connected to the drive?
Bearings don't sound like the best in the world either.
There’s currently a replacement project in process throughout the buildings so it looks an update is imminent.
Im curious how all that was messed up. Wonder if it was a case of "i know a guy" who doesn't actually know jack squat. Good job on getting to the bottom of it.
My first time seeing that unit, looks like it’s been limping along awaiting replacement. There’s crews on site replacing ahu’s. I just get sent out to troubleshoot
@@subcoolHVAC i hate to say it.....but these installers nowadays dont seem to know how or what itnis they are doing. I've had my share of going behind them for something that is simple......and was in the manual....they didn't bother to read or open. I may be a grumpy old salty guy....but it isn't that hard to do.
@jasonjohnsonHVAC you’re not alone, I find myself doing a lot of follow up .
Interesting one tech professionally solved
Thanks much !
Awesome work. New sub here from West Palm. I'm enjoying watching your channel . No BS and experienced. I'm a welder/fab guy and like learning new stuff. Cheers...
Welcome to the channel neighbor 👍
Nice work!
Thank you
what a mess/air control with modern speed control...in reverse. your a patient man. enjoy your workmanship all the best and thanks for sharing
Thanks for watching, it was an interesting find for sure.
Good video, I like the fact that you never wear gloves! 😂
Thanks for the comment. I had an incident many years ago resulting in second degree burns because I couldn’t get the glove off ( refrigerant burn ). I wear silicone ring since too. I don’t always wear gloves but when I do it’s nitrile coated 👍
Excellent trouble shooting
It was a fun one 👍
thank
I did a dental lab once. I worked all day cleaning the coil. That crap turns to stone with a bit of water.
Yep, that dust was all over this ahu
👍👍👍
Civilian here, what the hell was the little pneumatic line that was keeping it from cooling? Am I misinterpreting that?
IMHO it was for the pneumatic Cold water valve.
Correct, pneumatic thermostat was missing . The T775 stat controls drive speed. This ahu is scheduled to be replaced with new controls from what I was told. Thanks for watching
Switching input phase will not change rotation of output (only in bypass will that work)
Correct
are they pwm drive units
Yes