I have a VAV with PFP system for basecase, and I need to know how to count for the zone fan power in table 1.4, knowing that I did enter each AHU's fan power from the Energy model to table 1.4, then got to find that the modeled peak fan power exceeds the allowed fan power of table 1.4.
I also had a reviewer comment stating that "it is unclear whether all of the exhaust fans listed on drawing have been modeled", while my other systems are exhaust fans for basement and smoking zones, so I need to know if I should insert each exhaust fan as a system to table 1.4, and if so can I insert it as system 9, or define a new entry "Vent Fans" for example, knowing that all exhaust is fully ducted.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
August 5, 2014 - 10:32 am
I am assuming you are referring to the newer Table 1.4 spreadsheets.
Table 1.4.7A will do the fan power calculations for each system. In order for them to be absolutely correct each individual system must be entered in a column. The zone fan power for the boxes is in addition to the calculated fan power. It is not entered in Table 1.4.7A. It is one of the statements within Table 1.4.6.
Do not enter them as a system in Table 1.4.7B. Exhaust fans for unconditioned spaces are process loads and get entered in Table 1.4.4. Exhaust fans associated with a system get entered in Table 1.4.7B under Exhaust Fan Power.
Omar Elrawy
Green Building Consultant | ResearcherGreenA Consultants
55 thumbs up
August 11, 2014 - 11:37 am
Yes I'am referring to the updated version of table 1.4. Thanks for making it very clear, now the exhaust fan is on a riser and connected to all floors, while the systems are one system/floor, can I attached the exhaust fan power to any of the systems and add a narrative.
Also can I do the same in table 1.4.7 A or not, knowing that these fans exhaust Toilets, Smoking zones, and copy Rooms.
As for Fan Energy it is clear that I do not need to enter the PFP fan power separately, but that check (statement) in table 1.4.6 doesn't give me more allowance although the PFP system consume more fan energy. My problem is that the basecase simulation results gives higher fan energy than table 1.4.7 allowed fan energy, so is there any advice how can I manage to comply?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
August 11, 2014 - 3:37 pm
It depends on how you model the exhaust system. You could model it separately and if you do this would be entered in Table 1.4.7B under one of the systems one the first "Other (Describe)" rows just below the System Fan Power. If you split up this system (cfm per floor applied to the exhaust fan HP) and model it within each system then it is just part of the Exhaust Fan Power in Table 1.4.7B.
Are you referring to the demand (kW) for the Baseline fans? It should be higher that the allowed fan power from Table 1.4.7A. In a constant volume system it should be equal to the total of the allowed fan power plus the fan power for the PFPs. The reviewer should be able to figure out this issue and not raise it during the review.
Omar Elrawy
Green Building Consultant | ResearcherGreenA Consultants
55 thumbs up
August 12, 2014 - 4:53 am
What about table 1.4.7A, can I insert the exhaust fans to it, in other words: am I allowed to model exhaust fans in basecase? knowing that these fans exhaust toilets, smoking zones, and copy rooms
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
August 12, 2014 - 9:21 am
The exhaust fans are already included in the G3.1.2.9 calculations for the Baseline. You do not model them in addition to the calculated baseline fan power.
Omar Elrawy
Green Building Consultant | ResearcherGreenA Consultants
55 thumbs up
August 13, 2014 - 5:07 am
I just need more clarification, does that mean that I don't insert the basecase exhaust rate (cfm) in these zones to the Basecase Energy Model?, nor the basecase exhaust kw/cfm to the Basecase Energy Model? and what about the Table 1.4.7A exhaust cell, should I leave it as zero?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
August 13, 2014 - 2:58 pm
You can assign all of the baseline fan power to the supply fan or you can proportion the baseline fan power between the other fans. If you do proportion them it is best to proportion them in a similar ratio to the proposed fans.
So you can leave the exhaust as zero or fill it in depending on how you have allocated the fan power in the baseline model.
All that really matter, since you are not actually designing the baseline system, is that the fan power is calculated and modeled correctly.
Omar Elrawy
Green Building Consultant | ResearcherGreenA Consultants
55 thumbs up
December 10, 2014 - 2:37 pm
Dear Marcus,
Referring to my original question I'am confused about something. The reviewer's comment was that: "The interior fan demand reported in Table EAp2-4 for the Baseline case exceeds the Baseline fan power allowance reported in the Supplemental Table 1.4".
Knowing that the values entered to Table EAp2-4 are enduse values generated by the simulation tool, Knowing that I changed Table 14 System from VAV with pfp to VAV with reheat to find that fan power allowance didn't decrease; meaning that the table isn't counting for the zones' PFP powers;
Should I supply a narrative explaining that the PFP fan powers did cause this increase, or there is a certain check that I'am missing?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
December 11, 2014 - 9:42 am
Sounds like you will be replying to the preliminary review comments.
With a VAV system the fan demand should be significantly less than the total fan power in Table 1.4.7A. I would try to figure out why this was not the case in your preliminary model. Without seeing the numbers in the context of your project it is difficult to say for sure if the PFP fans were the cause of the difference but I have my doubts and perhaps the reviewer does as well.
Ultimately it does not really matter why this was the case, since you changed the system what are your revised results showing? When you submit the final model I would make sure that the fan demand is less than the fan power. If it is not you will need to figure out why and explain it or fix it.
Omar Elrawy
Green Building Consultant | ResearcherGreenA Consultants
55 thumbs up
December 11, 2014 - 10:49 am
Marcus, thanks for your reply, I re-posted my questing thinking that my reply here won't reach you.
Yes I'am replying to the preliminary review comments, and I didn't change the system, i did this trial just to test the excel file (table 1.4.7A) response to system type.
However I think I found it now; your reply of " system the fan demand should be significantly less than the total fan power in Table 1.4.7A" made me go back to the energy model output, to notice that I'am using the "NonCoincident enduse KW" value from my simulation tool's output; while the "Coincident enduse KW" is about half the value. should I go on using the "Coincident KW" for all enduse values?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
December 11, 2014 - 10:54 am
The demand entered should be the peak demand for the year for that energy end use. Sounds like the coincident kW is the right one.
Omar Elrawy
Green Building Consultant | ResearcherGreenA Consultants
55 thumbs up
December 12, 2014 - 7:49 am
Thank you Marcus.