Voltage Drop Distance
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justdavemamm
Senior Member
- Location
- Rochester NY
Re: Voltage Drop Distance
Is electricity carried by crows or wires ?
Is electricity carried by crows or wires ?
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Voltage Drop Distance
Perhaps it will help if you recall that limiting voltage drop is not an NEC requirement. It is a design consideration only.
You can start with a quick estimate of the distances from panel to load, without calculating the distance along the exact routing. This would give you a general idea of the amount of VD. If you could quickly tell, for example, that the VD is somewhere in the order of 1% to 2%, you do not need to get a more precise answer. It is not important to know that the VD is "exactly" 1.734%. If you know that VD is well below 3%, you can walk away from that question.
On the other hand, if your quick estimate tells you the VD is on the order of 2.5% to 3.5%, you might want to do a more precise calculation. It may be important to learn whether the VD is above or below 3%, because it may influence your choices of wire sizes.
Perhaps it will help if you recall that limiting voltage drop is not an NEC requirement. It is a design consideration only.
You can start with a quick estimate of the distances from panel to load, without calculating the distance along the exact routing. This would give you a general idea of the amount of VD. If you could quickly tell, for example, that the VD is somewhere in the order of 1% to 2%, you do not need to get a more precise answer. It is not important to know that the VD is "exactly" 1.734%. If you know that VD is well below 3%, you can walk away from that question.
On the other hand, if your quick estimate tells you the VD is on the order of 2.5% to 3.5%, you might want to do a more precise calculation. It may be important to learn whether the VD is above or below 3%, because it may influence your choices of wire sizes.
Re: Voltage Drop Distance
CharlieB.... I do believe there IS an article that states that VD must be within 3% on branch circuits. I will look for it and give you an article # if I can find it. If you read the archives you will see a problem I encountered with a "house inspector" on exactly this issue. The "house inspector" had a fancy $500.00 circuit tester that tested for >3% VD on a circuit, he called a circuit in a 1 year old house as "failed"the current test. Come to find out his $500.00 checker was doing a VD test. It was a can of worms. Lou
CharlieB.... I do believe there IS an article that states that VD must be within 3% on branch circuits. I will look for it and give you an article # if I can find it. If you read the archives you will see a problem I encountered with a "house inspector" on exactly this issue. The "house inspector" had a fancy $500.00 circuit tester that tested for >3% VD on a circuit, he called a circuit in a 1 year old house as "failed"the current test. Come to find out his $500.00 checker was doing a VD test. It was a can of worms. Lou
Re: Voltage Drop Distance
I have a 208V/20A receptacle that is 520' away from the panelboard. Unfortunately this is the closest panelboard to the room needing this receptacle. The voltage drop calculations yield a #3 to achieve a 3% voltage drop. I know this is a bit ridiculous and not practical. I was thinking of using a buck/boost transformer at the load. However, does anyone else have any ideas?
I have a 208V/20A receptacle that is 520' away from the panelboard. Unfortunately this is the closest panelboard to the room needing this receptacle. The voltage drop calculations yield a #3 to achieve a 3% voltage drop. I know this is a bit ridiculous and not practical. I was thinking of using a buck/boost transformer at the load. However, does anyone else have any ideas?
bphgravity
Senior Member
- Location
- Florida
Re: Voltage Drop Distance
You are refering to the FPN's to sections 210.19(A)(1) and 215.4. FPN's are not enforceable.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Re: Voltage Drop Distance
Actually there isn't, but there is a FPN stating a recommended voltage drop of 3% or 5%. Take a look at 210.19(A)(1) FPN No. 4. FPN's are not enforceable.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Voltage Drop Distance
Do you know the actual load that this receptacle will be called upon to carry? For example, if you can justify saying that the load is limited to 14 amps, then you could use a #6.
My calculation tells me that a #4 will get you a 3% VD. But the transformer at the other end is probably your best bet.
Do you know the actual load that this receptacle will be called upon to carry? For example, if you can justify saying that the load is limited to 14 amps, then you could use a #6.
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