I replaced this disconnect to a 12.5 ton condenser last year at a large church. There is another Fused disconnect on the other side of the wall with 60 amp fuses. Anyways, Get the call for no AC and before I can get out of the truck I see the soot on the disconnect and the unit looked oddly out of place. I stood there looking over the situation and realized the grass looked freshly cut… I don’t have before pictures of the unit but there were at least 4-5 rigid straps holding the conduit on top of the pad. I obviously assume mower crew but tell them to check the cameras and decide what they want to do before I touch anything. I asked who mowed the place and they said another member does it for free but he’s honest and would’ve said something if he did that… my reply was “nobody could’ve made a mistake like this without seeing/hearing the fireworks nor realize their dragging a 12.5 ton unit off the pad” but they still denied the mower man and ironically enough the whole weekend of footage on that camera was “somehow gone”
Yep! That lawn tractor took ahold of it for sure! Lol
That was too long of a wiring job inside the liquidtite….
Agreed, I made it clear before getting power back to it that if something happened to the compressor during this “mysterious mishap” it’s going to go from hundreds to thousands really quick lol. The units are pushing 20 years
Agreed, I made it clear before getting power back to it that if something happened to the compressor during this “mysterious mishap” it’s going to go from hundreds to thousands really quick lol. The units are pushing 20 years
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My biggest concern is that high voltage flash mark where the wiring is leaving the building into the inside of the disconnect…that disconnect had to go sideways cutting into the wiring insulation and the high voltage wiring should be replaced …I don’t think silicone will work as a permanent fix..
I think the flash burn is the from the locknut not making a good ground connection.
The disconnect became energized from the shorted load wires and the ground path back to the panel was not secure.
Unless the locknut was tightened to where it cut into the paint on the box then it was not effectively bonding/grounding the box.....good reason to always run a green grounding wire.
Was the breaker inside tripped or were the fuses quick enough?
Also are the low voltage wires run thru the sealtite?
They could have been shorted to the high voltage during the break away action and take out the 24 VAC transformer in the air handler....or worse.
Another reason they are supposed to be separated.
I think the flash burn is the from the locknut not making a good ground connection.
The disconnect became energized from the shorted load wires and the ground path back to the panel was not secure.
Unless the locknut was tightened to where it cut into the paint on the box then it was not effectively bonding/grounding the box.....good reason to always run a green grounding wire.
Was the breaker inside tripped ?
Also are the low voltage wires run thru the sealtite?
They could have been shorted to the high voltage during the break away action and take out the 24 VAC transformer in the air handler....or worse.
Another reason they are supposed to be separated.
I think the flash burn is the from the locknut not making a good ground connection.
The disconnect became energized from the shorted load wires and the ground path back to the panel was not secure.
Unless the locknut was tightened to where it cut into the paint on the box then it was not effectively bonding/grounding the box.....good reason to always run a green grounding wire.
Was the breaker inside tripped ?
Also are the low voltage wires run thru the sealtite?
They could have been shorted to the high voltage during the break away action and take out the 24 VAC transformer in the air handler....or worse.
Another reason they are supposed to be separated.
That would not make any sense since the copper lineset is there and typically where the low voltage wiring would be..especially since I see separate smaller liquidtite next to it
That picture was the way it looked a year ago when I replaced the disconnect. It was grounded properly but when the #2 wire got broke loose from the lug it landed on the ground lug along with the lock nut therefore shorting out on the EMT conduit through the building from one disconnect to another until Two of the 100 amp fuses were blown, one leg was still hot when I got to it. They all got replaced with 60s when I ran all new wire/conduit. I agree low voltage isn’t good to be ran with high voltage but I checked the twined furnaces and there wasn’t even a blown fuse, both furnaces still had the blowers running. I Didn’t take a picture of the final outcome, I was more than less dumbfounded from the ignorance of the whole situation. I personally saw the camera footage of Thursday/Friday, motion activated with moths and wasps all day long but somehow Saturday and Sunday footage was blank..
IMO, the lineset would only ground the outside unit, however...the inside coil could be sitting on a plastic drain pan with grommets isolating the lineset from the furnace metal. If that were the case, then the lineset and coil were "hot" until the fuses blew.
I see only 2 sealtites, one for each disconnect. There is another disconnect to the left of the burned one for the second unit.
Yup.. Reason why the code now requires a separate ground!
“A dying culture invariably exhibits personal rudeness. Bad manners. Lack of consideration for others in minor matters. A loss of politeness, of gentle manners, is more significant than is a riot.”
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IMO, the lineset would only ground the outside unit, however...the inside coil could be sitting on a plastic drain pan with grommets isolating the lineset from the furnace metal. If that were the case, then the lineset and coil were "hot" until the fuses blew.
I see only 2 sealtites, one for each disconnect. There is another disconnect to the left of the burned one for the second unit.
How do you figure the line set is the ground when there are separate ground wires from each power source? If the line set was “hot” then how’s come the bent panel on the unit against the line sets didn’t arc and short out the system or blow a hole through the old coils? One condenser is for the 1st floor with twined furnaces and the exact same setup for this damaged one on the 2nd floor. Once the disconnects go through the wall into the mechanical room there are separate power sources and grounds for each system
Well sealtite or metallic liquid tight is only approved to be used as a ground if the whip is 6ft or shorter. Why are the black line wires taped with a band of green? To be legit, here anyways. You have to phase tape those wires. Any color except green.
But yes it looks like mower man chopped a little more than he intended.
I did not mean to imply that the lineset is the ground, it is merely secured solidly to the cond unit and if the other end was well bonded to the air handler then the fault current would pass thru the lineset.....but the plastic drain pan and coil grommets may have allowed it to "float hot".
I do not see a bonding wire coming out with the line conductors to the disconnect, I am assuming that the raceway (EMT) is the bonding method. I believe the locknut on the connector was not solidly hammered into place to cut thru the paint of the disconnect. Even the concentric KO's are taken into question at this point, although they all seem to be intact.
So the "loose" locknut was trying to pass the fault current of 100 amps before opening the fuse. Without a secure connection this would produce some arcing at that point (and anywhere along the home run to the panel that was compromised with loose connections).
Some of the fault current flowed into your green ground wire to the unit, but it had nowhere to go to return back to the panel ground, some may have tried to get back thru the lineset but as said above it may have been somewhat insulated from a true ground path. Maybe some thru the unit cabinet to the concrete pad. Most went into the disconnect box and tried to go thru the locknut.
You can see the lug for the green wire has arcing behind where it was as it spun around as the wires were pulled out, as I said, a fraction of a second....did the hot get cut first or the ground?
All of this happened in a fraction of a second, fuses are quick to open....CB requires perhaps 2 cycles of the 60 cycles per second. (there is a reason fuses are still used, when you need serious protection a fuse is probably involved)
I assume the bent panel you refer to is on the outside cond unit, which all was at the same potential of voltage for that moment.
Yes, if at the inside coil and the air handler was grounded I could well imagine copper tubing burned thru or welded to the cabinet.
I have seen loose locknuts produce the same arcing on a simple 20 amp circuit for a switch, not as severe but proportionally equal.
A grounding wire in every pipe and box is a great idea.
Well sealtite or metallic liquid tight is only approved to be used as a ground if the whip is 6ft or shorter. Why are the black line wires taped with a band of green? To be legit, here anyways. You have to phase tape those wires. Any color except green.
But yes it looks like mower man chopped a little more than he intended.
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Yeah I know the green tape was supposed to be temporary (only other color I had with me besides black) for my own mindset but afterwards I figured it wouldn’t hurt to leave it there “in case something was to happen”
I did not mean to imply that the lineset is the ground, it is merely secured solidly to the cond unit and if the other end was well bonded to the air handler then the fault current would pass thru the lineset.....but the plastic drain pan and coil grommets may have allowed it to "float hot".
I do not see a bonding wire coming out with the line conductors to the disconnect, I am assuming that the raceway (EMT) is the bonding method. I believe the locknut on the connector was not solidly hammered into place to cut thru the paint of the disconnect. Even the concentric KO's are taken into question at this point, although they all seem to be intact.
So the "loose" locknut was trying to pass the fault current of 100 amps before opening the fuse. Without a secure connection this would produce some arcing at that point (and anywhere along the home run to the panel that was compromised with loose connections).
Some of the fault current flowed into your green ground wire to the unit, but it had nowhere to go to return back to the panel ground, some may have tried to get back thru the lineset but as said above it may have been somewhat insulated from a true ground path. Maybe some thru the unit cabinet to the concrete pad. Most went into the disconnect box and tried to go thru the locknut.
You can see the lug for the green wire has arcing behind where it was as it spun around as the wires were pulled out, as I said, a fraction of a second....did the hot get cut first or the ground?
All of this happened in a fraction of a second, fuses are quick to open....CB requires perhaps 2 cycles of the 60 cycles per second. (there is a reason fuses are still used, when you need serious protection a fuse is probably involved)
I assume the bent panel you refer to is on the outside cond unit, which all was at the same potential of voltage for that moment.
Yes, if at the inside coil and the air handler was grounded I could well imagine copper tubing burned thru or welded to the cabinet.
I have seen loose locknuts produce the same arcing on a simple 20 amp circuit for a switch, not as severe but proportionally equal.
A grounding wire in every pipe and box is a great idea.
Just my observation.
I understand your logic and theory and wasn’t trying to criticize that, the locknut was secured and bonded but within that quick of a motion I think it’s obvious everything got loosened and the falcons had to be upsized to 3/8. The line sets got bent and cut the insulation into the top panel. Was able to move the condenser back on the pad without and creasing or further damage to the copper. No restrictions as well, thank goodness they weren’t strapped to the wall
I wish there was evidence of a mower wheel since I seemed to be the only person on-site that could picture the obvious but unfortunately that is a trash can wheel lol
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Originally Posted by Unlimited1
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