Voltage Drop Calculations
- Thread starter 6506gary
- Start date
- Status
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
It appears in a Fine Print Note and in the Handbook. Both unenforceable, not Code.
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In general, the NEC only has non-enforceable Informational Notes on voltage drop. For example....
210.19(A)(1) IN4
215.2(A)(1) IN3
...and a few other places. The only place I know of required voltage drop calculations is for fire pumps and sensitive electrical equipment.
ramsy
Roger Ruhle dba NoFixNoPay
- Location
- LA basin, CA
- Occupation
- Service Electrician 2020 NEC
Voltage drop can be enforced if the architect/EE put it on the plans, regardless of building codes.
Also, some State's have adopted voltage drop informational notes at the state level. California was one of them, a few cycles ago, so any planning, and combination inspectors are now required to enforce voltage drop.
Also, some State's have adopted voltage drop informational notes at the state level. California was one of them, a few cycles ago, so any planning, and combination inspectors are now required to enforce voltage drop.
NewtonLaw
Senior Member
- Location
- Honesdale, PA USA
I see you have received the replies you need to find the "fpn" on voltage drop. Not sure what you are using for the voltage drop calculation but I attached an Excel spreadsheet I put together to determine single phase voltage drops that you may find useful. Select the wire size, run length and conduit type or open air. Then set the load impedance to get to the expected current load and power factor you expect. The voltage drop will be in percent and actual volts dropped. As a comparison I also use the NEC approximation calculation using the Z equivalent factor.
Hope this is helpful for you.
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
The Energy Code adopted in your jurisdiction likely has an enforceable voltage drop section
See about halfway down this article. Although the article is old, the section still is in there.
http://www.ecmag.com/section/your-business/energy-codes
See about halfway down this article. Although the article is old, the section still is in there.
http://www.ecmag.com/section/your-business/energy-codes
drktmplr12
Senior Member
- Location
- South Florida
- Occupation
- Electrical Engineer
Florida building code enforces voltage drop
florida-sparkey
Senior Member
- Location
- Pinellas Park, Florida
- Occupation
- Master Electrician
As far as I have seen here in Florida, most prints I handle state that they have considered voltage drop. When I do a simple sketch draw for submittal of a long circuit, I do the calc and put on there just for the record. In either case, I have not seen it enforced or calc tested by any AHJ past permitting.
Julius Right
Senior Member
- Occupation
- Electrical Engineer Power Station Physical Design Retired
No standard will impose the voltage limits. For instance:
American National Standard for Electric Power Systems and Equipment—Voltage Ratings (60 Hertz) ANSI C84.1-2006
The purposes of this standard are to:
(7) Provide a guide, with respect to choice of voltages, for new power system undertakings and for changes in older ones.
The standard recommends:
When voltages occur outside the limits of Range B, prompt corrective action shall be taken. See:
Table 1 – Standard nominal system voltages and voltage ranges (Preferred system voltages in bold-face type).
I think if you are at not less than Range B with your service -or utilization- voltage you are o.k.
American National Standard for Electric Power Systems and Equipment—Voltage Ratings (60 Hertz) ANSI C84.1-2006
The purposes of this standard are to:
(7) Provide a guide, with respect to choice of voltages, for new power system undertakings and for changes in older ones.
The standard recommends:
When voltages occur outside the limits of Range B, prompt corrective action shall be taken. See:
Table 1 – Standard nominal system voltages and voltage ranges (Preferred system voltages in bold-face type).
I think if you are at not less than Range B with your service -or utilization- voltage you are o.k.
drktmplr12
Senior Member
- Location
- South Florida
- Occupation
- Electrical Engineer
The inspector should be able to cite the reference document and paragraph that requires you to demonstrate compliance.
Where is the project located? Check your state's building code energy conservation section as suggested by Ron. Voltage drop considerations are due to increased energy consumption (I2R heat loss) that increased amperage resulting from fixed loads operating a lower voltages will cause. The building codes could care less if the equipment works or not. There is an exception for feeder and branch circuits dedicated to emergency circuits.
We have had permitting reviews that request clarification on voltage drops before, but they don't actually check the calculations. We actually put a value on the drawings for significant loads. That being said, they are looking at it, depending on which municipality you are working with. The lazy way to do it is to put a note saying voltage drops have been considered according to the standard. Many AHJ's will consider this adequate since they can point to it if there is indeed an issue and the EE will end up taking responsibility for the oversight if they didn't actually do the calculation
For reference:
Florida Building Code, 5th Edition (2014), Energy Conservation
C405.7.3 Voltage drop.
C405.7.3.1 - Feeders and customer owned service conductors.
Feeder and customer owned service conductors shall be sized for a maximum voltage drop of 2 percent at design load.
C405.7.3.2 Branch circuits.
Branch circuit conductors shall be sized for a maximum voltage drop of 3 percent at design load.
Here is a official FBC response to a question regarding voltage drop.
TLDR;
Question:Can EE's design construction projects to allow feeders more than 2% VD as long as feeder + branch VD does not exceed 5%?
Answer: No.
Where is the project located? Check your state's building code energy conservation section as suggested by Ron. Voltage drop considerations are due to increased energy consumption (I2R heat loss) that increased amperage resulting from fixed loads operating a lower voltages will cause. The building codes could care less if the equipment works or not. There is an exception for feeder and branch circuits dedicated to emergency circuits.
We have had permitting reviews that request clarification on voltage drops before, but they don't actually check the calculations. We actually put a value on the drawings for significant loads. That being said, they are looking at it, depending on which municipality you are working with. The lazy way to do it is to put a note saying voltage drops have been considered according to the standard. Many AHJ's will consider this adequate since they can point to it if there is indeed an issue and the EE will end up taking responsibility for the oversight if they didn't actually do the calculation
For reference:
Florida Building Code, 5th Edition (2014), Energy Conservation
C405.7.3 Voltage drop.
C405.7.3.1 - Feeders and customer owned service conductors.
Feeder and customer owned service conductors shall be sized for a maximum voltage drop of 2 percent at design load.
C405.7.3.2 Branch circuits.
Branch circuit conductors shall be sized for a maximum voltage drop of 3 percent at design load.
Here is a official FBC response to a question regarding voltage drop.
TLDR;
Question:Can EE's design construction projects to allow feeders more than 2% VD as long as feeder + branch VD does not exceed 5%?
Answer: No.
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