Leed EA cr1 plug load

[DrRTU]

I am working on a project that requires 5 watts/ft2 for the plug load. When I run the Appendix G simulation, it pops up with 67% misc power. This unregulated load in the baseline and proposed is screwing with the potential saving on the building. Appendix G states I need to have a minimum of 25%. This high percentage of misc. power makes an excellent system difficult to shown a good percent improvement. This is a typical office building. I normally see building of this type running 2.5 to 3watts/ft for plug load. When I lower the plug load to 2.5 watts/ft2 in baseline and proposed (same schedules) it returns with 2 points. Have others tried to do an exceptional calculation?

 

[AbbyNormal]

not familair with the LEED calcs Dr but wondering on how you arrive at 5W per square foot in the first place

from an NEC point of view you are supposed to add 180VA per duplex receptacle

NEC will make an office building carry at least 1 VA per square foot for recpes but this can be skinny

As well the NEC allows a load reduction for receptacles. Now you are probably familiar with this already but to re-hash- basically on the elctrical laod you calculate which is very conservative you carry the plugs at 180 VA, but you only count the first 10000 VA like this and you derate the remainder in half.

So for example if you had 50,000 sqaure feet of office and supposedly 50,000 x 5 = 250000 va for receptacles. you would count the first 10000 at 100% and derate the remainder to 50% so it would be 10000 + 240000/2 =130000 VA or 130000/50000=2.6 VA per sq ft



Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[AbbyNormal]

the NEC makes you calculate loads very conservative, if I tell the power company the building has a 1000 kVA load, they will probably install a transformer sized about 60 to 70% of that load-- based on standard sizes they had in inventory I would seriously doubt they would install anything larger than 750

I have run a lot of load tests on existing buildings, they come in quite low compared to the official calc

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[DrRTU]

The 5 watts/ft2 was from the developer. In this case, bigger is not better.

 

[AbbyNormal]

be easy to control RH with 5W a sq f0t equipment load

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[DrRTU]

Actually, the spec. calls for RH at 52% max. and if the sensible load runs way less than the 5 watts/sqft. then my VAV RTUs will run unloaded and I will be oversized.

 

[AbbyNormal]

good thing the building is only on paper at this point in time

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[AbbyNormal]

Equipment and lights at 5W a sqaure foot still sounds excessive

Maybe those daylighting Btu's will help

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[RossABQ]

Are these offices with computers? Figure 100 sf per office, 200 W per computer, maybe less with LCD monitors. Lights at 1.5 W/sf, not hard to get up to 5 when you add in the copiers, printers, tasklighting, etc.

 

[AbbyNormal]

5W a square foot and you wonder why there is problems with part load dehumidification

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[DrRTU]

The Building will have a maximum of 5.0 w/ft2 plug load and lighting at 1.0 w/ft2. I am going to use 2.5 w/ft2 as the plug load in both the baseline and proposed simulations. I believe this is a reasonable design assumption. At 2.5 w/ft2 the plug load is running about 40% of cost. I have selected my fan for the full 5.0 w/ft2 so my simulation of the actual is correct. In other LEEDs building I have run, I saw plug loads running .75 to 2.5 w/ft2. for typical office spaces.

The exact wording of the LEED v2.2 is "The default process energy cost is 25% of the total energy cost for the Baseline building. For buildings where the process energy cost is less than 25% of the baseline building energy cost, the LEED submittal must include supporting documentation substantiating that process energy inputs are appropriate. For EA Credit 1, process loads shall be identical for both the Baseline building performance rating and for the Proposed building performance rating. However, project teams may follow the Exceptional Calculation Method (ASHRAE 90.1-2004 G2.5) to document measures that reduce process loads. Documentation of process load energy savings shall include a list of the assumptions made for both the base and proposed design, and theoretical or empirical information supporting these assumptions. "

LEED is very clear if you are light on process loads but if you are heavy on plug loads then it's a guess.