We are working on the LEED certification for a hospital building with 10 floors height. In ASHRAE Standard 90.1-2007 Section 8.4 the voltage drop limits are 2% for feeders and 3% for branch circuits. In normal conditions the normal network transformers are feeding the loads and the voltage drop limits are met, while in up-normal conditions local generators are feeding the loads through a long feeder (100 meters) and the voltage drop in this case will be difficult to be met. Our question is: do we have to meet the voltage drop limits for the up-normal (emergency) conditions as well as the normal conditions? Noting that in order to meet the LEED requirements we need to double the feeder size and accordingly double the cost. Also note that the overall 5% voltage drop are met in the normal and up-normal conditions.

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Rudolph Carneiro

HVAC consultant

Optimized Systems

LEEDuser Basic Member

19 thumbs up

Mon, 09/09/2013 - 01:40

5% total drop is fine according to GBCI. LEED interpretation ID #10218 confirms it. There is an earlier ruling stating that 2% for feeders must be met but in a response I received from GBCI, the more recent ruling is what counts. I sent an ASHRAE interpretation request about a month ago just for fun. No response from ASHRAE yet.

Jean Marais

b.i.g. Bechtold DesignBuilder Expert

LEEDuser Basic Member

581 thumbs up

Mon, 09/09/2013 - 05:55

Very interesting...keep us posted. As to Mr Helmy's problem, my opinion is that unless "emergency" operation is part of the yearly routine running of the building, that it is not required, as it does not effect the annual energy consumption of the building. However, if you mean systems that cover peak energy consumption periods, then yes, the standard applies.

Rudolph Carneiro

HVAC consultant

Optimized Systems

LEEDuser Basic Member

19 thumbs up

Tue, 11/05/2013 - 16:00

Got a response from ASHRAE. It's posted on their website. ASHRAE says that the 2% and 3% requirements cannot be exceeded individually. I just sent GBCI the ASHRAE ruling to see if they change their position on voltage drop. Funny stuff. https://www.ashrae.org/standards-research--technology/standards-interpretations/interpretation-for-standard-90-1-2007. It's Interpretation 90.1-2007-23 – October 18, 2013 at the bottom of the page. It's on the second page, Interpretation number 5.

Ali Helmy

Electrical Engineer

DAR Al-Handasah

LEEDuser Basic Member

0 thumbs up

Sun, 01/12/2014 - 08:41

I sent an unofficial interpretation request to ASHRAE to ask about the above issue and they replied as follows: No, the requirements in 90.1-2007 are specific as to the 2% and 3% limits and do not make any allowances for emergency circuits. However, the 90.1-2010 version of the standard offers an exemption for emergency circuits that was put in to address these types of issues. You may be able to apply this more recent provision in the 2010 version if the local building authority will accept a more recent version of the standard as more progressive and applicable. therefore is it possible to apply a more recent version (2010 version) of a standard mentioned in LEED v2009 although the mentioned version is the 2007 one? While note that the project is registered as LEED v2009 project

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Mon, 01/13/2014 - 13:50

You are allowed to use any addenda to 90.1-2007. Not sure if that change was in an addenda but many of the changes to 90.1 in 2010 came from the addenda. If the change was not in an addenda but it provides clarity where it did not exist before you could also probably use it.

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ASHRAE 90.1-2007 - Section 8.4 - Voltage drop

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