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Electrician Question
mogley98
Member Posts: 18,291 ✭✭✭✭
Here's one to get your brain cells jumping early in the morning.
Heating circuit, 220vac, single phase (it's a 3 phase system with 3 heaters, one zone per phase)
Control is via a t-couple to a display/controler with a 0-10vdc output.
The output of the controler is switching 2 75amp SCR's wired in parallel (both the line/load and control are split), power side is protected by a 100amp fuse with a total load of 85 amps.
To detail the wiring configuration, from fuse 1 I'm hitting a junction block and comming off with 2 leads (one to each SCR). From the SCR's I'm hitting a 2nd J-block and comming off that with a single lead to one end of the heater element. The other end of the element goes directly back to fuse 2. From the controler + & -, I'm splitting each and feeding both SCR's with the same signal.
The problem is that just recently, on this one circuit only (I have a total of 9 of these circuits in 3 machines), it's running the entire load through just one SCR. If I disconnect the load side from that SCR, than the 2nd one will carry the entire load (IOW both SCR's are functioning properly). On the other 8 heaters, that are just like this one, each SCR is only handling 43 amps.
Why is just this one set acting this way, and what can I do to correct it?
Heating circuit, 220vac, single phase (it's a 3 phase system with 3 heaters, one zone per phase)
Control is via a t-couple to a display/controler with a 0-10vdc output.
The output of the controler is switching 2 75amp SCR's wired in parallel (both the line/load and control are split), power side is protected by a 100amp fuse with a total load of 85 amps.
To detail the wiring configuration, from fuse 1 I'm hitting a junction block and comming off with 2 leads (one to each SCR). From the SCR's I'm hitting a 2nd J-block and comming off that with a single lead to one end of the heater element. The other end of the element goes directly back to fuse 2. From the controler + & -, I'm splitting each and feeding both SCR's with the same signal.
The problem is that just recently, on this one circuit only (I have a total of 9 of these circuits in 3 machines), it's running the entire load through just one SCR. If I disconnect the load side from that SCR, than the 2nd one will carry the entire load (IOW both SCR's are functioning properly). On the other 8 heaters, that are just like this one, each SCR is only handling 43 amps.
Why is just this one set acting this way, and what can I do to correct it?
Why don't we go to school and work on the weekends and take the week off!
Comments
Therefore NO Motor loads.
The electrician made a big deal of the need to mark the phases and check the new wires when pulled with a phase meter.
I asked if since they were all serving single breakers of 110 did it really matter? He dismissed my question and said that if they were the wrong phase it wouldn't work.
I just don't get that, 208 3 phase L1 to L2 or L3 is 208 but ALL three are 110 to Neutral. Since you have no rotation of any motors how can phase rotation matter in this case other then being the right thing to do.
Also in a lighting circuit like this one if I understand correctly you should never add a motor to the circuit because it could cause flickering in the lighting circuit?
Please educate me.
And fiery auto crashes
Some will die in hot pursuit
While sifting through my ashes
Some will fall in love with life
And drink it from a fountain
That is pouring like an avalanche
Coming down the mountain
It might not matter this time, but it might matter the next time, and he might be the one called it to fix things.
And balancing the phases is always a nice thing to do.[:D]
For lighting you are correct. As far as the panel they have double up breakers now that allow for expansion without adding modules for most boxes.
Seruiously, Electricians are kinda * that way.
Someone should do a root cause analysis on the failed conductors.
Agreed so it doesn't matter in THIS case electrically, as far as balancing the loads if you spread the current draw across the three different phases of 120 regardless of the rotational alignment it is still spread out evenly right?
A balanced load is highly desired when a facility has 50+ panels and Desired if only one. Balanced loads are especially important when connected directly to generators and every offshore platform has generator sets.
3 phase 4 wire 208V panels are used in industrial facilities for lighting and receptacles.
Engineering produces PANEL schedules for their facilities/client. Not much doubt about what is connected where and the load is balanced.
On a three phase circuit you have a high leg. So not all three are 120. Don
WYE transformer should all be 120.
quote:Originally posted by dcon12
On a three phase circuit you have a high leg. So not all three are 120. Don
Then they megged the wires and found a short so they pulled them (Murderous job) and replaced them.
Lots of condensation inside the pipe.
quote:Originally posted by jimdeere
My dog had a high leg this morning after I let him out.
Seruiously, Electricians are kinda * that way.
Someone should do a root cause analysis on the failed conductors.