Safe solution or not

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Another C10

Another C10

Electrical Contractor 1987 - present
Location
Southern Cal
Occupation
Electrician NEC 2020
I'm thinking there is no real issue with this, what's your thought .
There is no need to create a full scenario of this installation other than the concept.

Just asking to maybe save me hours of research.
Basically I would like to use the neutral of the 480 panel so I can create a 120/240 condition after the secondary
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Thank you Tom - Electro,
I'm thinking I'll have to research some other options. This is for 4 Receptacles 80 ft apart from a source roughly 150ft from the 1st recep. basically 400' For portable warehouse fans roughly 8A each. The problem is the voltage drop , just trying to utilize as much of the existing infrastructure as possible.
 
synchro said:
The neutral for a 120/240V output would be provided at the X2,X3 connection. It would need to be bonded to the EGC and connected to a GES.
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Thank you, although Im trying to achieve both 120 or 240, I believe this configuration is for one or the other
 
Another C10 said:
Thank you, although Im trying to achieve both 120 or 240, I believe this configuration is for one or the other
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There are two 120V secondary windings: one between X1 and X2, and the other between X3 and X4. At the bottom of the wiring diagram, on the left it shows the two windinngs in parallel for 120V, and on the right in series for 240V. However, 120/240V providing both 120V and 240V are available from the series configuration at the bottom right. Electrically, the connected X2 and X3 would be the equivalent of an X0. The only issue is if the transformer cannot provide an output from X2 and X3, but only a jumper can be used there. That might be the case given how the diagram is drawn.
 
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synchro said:
There are two 120V secondary windings: one between X1 and X2, and the other between X3 and X4. At the bottom of the wiring diagram, on the left it shows the two windinngs in parallel for 120V, and on the right in series for 240V. However, 120/240V providing both 120V and 240V are available from the series configuration at the bottom right. Electrically, the connected X2 and X3 would be the equivalent of an X0. The only issue is if the transformer cannot provide an output from X2 and X3, but only a jumper can be used there. That might be the case given how the diagram is drawn.
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If you can switch the windings from series series to parallel then you have access to all the leads and enough length and flexibility or compartment space that there should be nothing restricting you solely to a jumper between X2 and X3.
 
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synchro said:
The only issue is if the transformer cannot provide an output from X2 and X3, but only a jumper can be used there. That might be the case given how the diagram is drawn.
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Great input thank you, I'm pretty sure there is only one X4,X2,X3,X1 being the left option or the right.
I know I should of studied transformers more in class.

There's a safe solution out there somewhere, just need to keep trying, There's another good thread in this forum
I found I'm reading for ideas as well.
 
ActionDave said:
If you can switch the windings from series series to parallel then you have access to all the leads and enough length and flexibility or compartment space that there should be nothing restricting you solely to a jumper between X2 and X3.
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so are you considering the idea that the connected X2 - X3 of the 240V configuration would be a neutral point being a measured voltage of120V at X2-X3 jumper to X4 as well as X2-X3 to X1. .. that would be nice.
 
All you need(ed) is a 1ph 480 (or 240/480) primary (leave H2-H3 unconnected!)) and a 120/240v secondary, connected for 240, and simply ground the new neutral, X2-X3 (or center tap) as a separately-derived system.

No need for the 480/277 neutral at all. A 3ph unit is overkill, in my opinion, unless you foresee a use for 208v.
 
The whole transformer idea might be overkill. By the time you buy the transformer, buy the wire and conduit to feed the transformer, buy wire and conduit for the secondary, set up your secondary disconnect/overcurrent protection, secondary connection to a grounding electrode, buy some breakers and somehow finally get power to some fans it might turn out to be easier to run some bigger wire at 120V instead. Even better run a MWBC.
 
Another C10 said:
I'm thinking I'll have to research some other options. This is for 4 Receptacles 80 ft apart from a source roughly 150ft from the 1st recep. basically 400' For portable warehouse fans roughly 8A each. The problem is the voltage drop , just trying to utilize as much of the existing infrastructure as possible.
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So you have 8A loads at 150 ft, 230 ft, 310 ft, and 390 ft from the source. For a 2-wire circuit, the voltage drop at the end will be the same as a single 32A load at 270 ft from the source (average distance). Southwire's VD Calculator says that at 120V with a 0.9 PF, #2 Cu will give you a VD of 2.8%.

For a 3-wire 120/240V the exact math is a bit harder, but just treating the system as a 240V load instead of 120V is not far off. [It would be exact if it was pairs of 8A loads at 190 ft and 350 ft.] Then the Southwire VD calculator says #4 AWG would give you 2.2% VD.

IIRC, for the 3-wire case, the size of the neutral has a bigger impact than of the ungrounded conductors. So with extra math, you might find that #6 AWG ungrounded and #4 AWG grounded would give you a VD under 3%, not sure.

Cheers, Wayne
 
wwhitney said:
So you have 8A loads at 150 ft, 230 ft, 310 ft, and 390 ft from the source. For a 2-wire circuit, the voltage drop at the end will be the same as a single 32A load at 270 ft from the source (average distance). Southwire's VD Calculator says that at 120V with a 0.9 PF, #2 Cu will give you a VD of 2.8%.

For a 3-wire 120/240V the exact math is a bit harder, but just treating the system as a 240V load instead of 120V is not far off. [It would be exact if it was pairs of 8A loads at 190 ft and 350 ft.] Then the Southwire VD calculator says #4 AWG would give you 2.2% VD.

IIRC, for the 3-wire case, the size of the neutral has a bigger impact than of the ungrounded conductors. So with extra math, you might find that #6 AWG ungrounded and #4 AWG grounded would give you a VD under 3%, not sure.

Cheers, Wayne
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I would go ahead and figure that the fans will not have any trouble if the voltage drops to 110V and just run some 8 AWG.

Where does the notion that a neutral has a bigger impact on voltage drop in a MWBC? It's only carrying a couple of amps.
 
ActionDave said:
Where does the notion that a neutral has a bigger impact on voltage drop in a MWBC? It's only carrying a couple of amps.
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Well for alternating 120V 8A loads, it will be carrying 0A or 8A in the idealized case of all loads being on. But there's also the case that just the loads on one leg are on, which will be the worst case VD for those loads. And upsizing the neutral will reduce the VD for both of those cases (the two legs), so it gives you more benefit.

Cheers, Wayne
 
I decided to try this route, Under the circumstance I believe this is my best solution. Any thoughts from the group experts is welcomed.
Plan A.png
 
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