Dear All,
I have following doubts, I would be very grateful for your valuable time,
1. We have modeled a boiler with 82% *combustion efficiency* in eQUEST with
HIR = 1.219 which is just the inverse of boiler efficiency . But from LEED
reviewer, we got comment saying that, HIR of 1.219 is equivalent to 77%
efficiency. Could you please let us know, how to convert combustion
efficiency to HIR
2. We have two buildings, one is Main Office building (7 day week, 8hr
running and Air-Conditioned, Main Office building has 5 to 7% of total two
building areas) and the other is Factory+Office building (7 day week,
Factory is 24 hr running and Air-Conditioned with 100% of occupancy,
lighting and equipment on all the time. While the Factory's Office is 24hr
running and Air-Conditioned with 50% of occupancy, lighting and equipment
on all the time) which are connected by enclosed bridge (air conditioned).
These buildings are modeled together in eQUEST and it comes to be System 7
(Boiler for heating) as per Table G 3.1.1. After reading it for many number
of times and to confirm my understanding of the section, doubts are as
follows on ASHRAE Appendix G Section G3.1.1
- What should be the system type for Main Office building
(Conditioned area is around 45000 Sq ft)? and let me know the exception of
G3.1.1 if any gets applied
- What should be the system type for factory's Ground
Floor Office building? (Area is around 150000 Sq ft) and Does the exception
"Schedules that differ by 40 *equivalent *full load hours" gets applied?
since the diversity is 50% for factory's office, if this exception is not
applicable, let me know how the equivalent full load hours need to be
calculated )
- What should be the system type for Factory's First
Floor office building? (This floor is total office, and ground floor
factory area is of double height from ground)
- Does the exceptions of Section G 3.1.1 applies at
building level or at each system level? Exception "b" says both the things,
so there is confusion
- Does the term "Peak thermal loads" in exception "b"
consider the load added due to outside air as well?
Let me know, if you need any further clarification to resolve my doubts.
Thanks,
Vamshi.
Hi Vamshi,
Just wondering, you say two buildings? Was there any MPR issue raised
within PIf1 in the review about having only one building per LEED submittal?
Ramya
Regarding boiler HIR input vs. efficiency... Your reviewer's commentary isn't clear by your description, but you might find the attached recent discussion informative regarding thermal vs. combustion efficiencies.
The issue of whether it's appropriate to model boiler thermal efficiency (inclusive of flue/jacket losses), and if so exactly how, is to my best understanding a bit of a toss-up right now for 90.1/LEED. The attached discussion thread takes the issue to the sidewalk's end however, so I hope you can use this to figure out where your reviewer is coming from and how to respond in turn.
~Nick
[cid:489575314 at 22072009-0ABB]
NICK CATON, P.E.
I don't know if this helps, but from the perspective of eQuest/DOE-2, the HIR is the ratio of the fuel heat input to the boiler to the heating capacity at full load. I.e. all DOE-2 cares about is how much fuel to assign each unit of heat produced for the building. If you know what the fuel input and the heating capacity at full load are you may be able to bypass the thorny nature of the combustion efficiency vs. thermal efficiency question?
Cheers,
Dan
?
Daniel Knapp, PhD, P Phys, LEED? AP O+M
Hi Daniel!
The wrench in the spokes is that 90.1 prescribes a combustion efficiency (less flue/jacket losses), without providing any further guidance for how to arrive at an overall thermal efficiency for modeling purposes.
It isn't a problem isolated to eQuest/DOE2, but put another way 90.1/LEED only provide part of what we need to define baseline HIR inputs for a comparison to real-world equipment and losses. A full discussion is within the attached thread if you're interested =).
This of course might have nothing to do with Vamshi's reviewer's commentary - I don't think that issue has been made clear just yet...
~Nick
NICK CATON, P.E.
Dear All,
Thank you very much for your time. It was very useful information and good
learning for me. I would be following the conservative approach as
suggested by Nick for boiler HIR modeling.
I also would be requiring your esteemed assistance on the Query No. 2.
Which is the major issue for the LEED Reviewer.
As queried by Ms. Ramya Shivkumar, there is no MPR issue and the reviewer
does not have any problem of modeling two building together. The issue is
about which system needs to be modeled and interpretation of section G
3.1.1 as queried in my previous mail.
Thanks,
Vamshi.
Dear All,
Could any help me out with the issue. Is it like, this site is only meant
for doubts related to eQUEST? (I asked the related doubt 2 months back
also, but could not get any answer. On the same we got the LEED reviewer
comment). If so, requested to suggest me the sites where I can ask the
doubts related to ASHRAE.
Your valuable time is appreciated.
Thanks,
Vamshi.
You can check http://www.leeduser.com
Hope it helps you!
Personally I would have made the same conversion from efficiency to HIR.
I'm not aware of a conversion that will take an efficiency of 77% and
get you an HIR of 1.21.
I think the best course of action would be to contact the review team
directly. They are fairly responsive to questions, and it helps avoid
the guessing game.
I think your other option would be to writeup your confusion while
addressing the comments. You could explain the potential impact on the
model with the two values. It is unlikely the reviewer would deny the
whole credit if they don't like the input, they may just adjust your
results.
This is the kind of grey area that you can waste hours and hours and not
really accomplish anything.
- Steve
I agree with Steve - if you need more direct guidance or clarification than you've already seen here, you're best advised to contact your project's reviewer for clarification directly through the available channels.
This [Equest-users] is a great forum for discussion of all-things energy modeling, not exclusive to equest alone. The nuances of LEED and 90.1. The responses you've seen so far are telling however: Your reviewer's comment (as shared), is not clear, and the subject matter (90.1 baseline efficiencies of large boilers) is known to be a definite grey area, as has been brought up already.
The best we can do as a body of fellow energy modelers is share our collective experience and information we've come up with on the matter. It's ultimately your choice to make to decide how to use this information and what actions to take.
Rest assured, unclear review commentary is not an unheard-of experience. My commentary responses have in the past included corrections and clarifications to best present my understanding of an issue for my reviewer's benefit as well, though it may be less work to at least try reaching out to the review team directly, schedule allowing.
Best of luck, and let us know how it turns out!
~Nick
[cid:489575314 at 22072009-0ABB]
NICK CATON, P.E.
I wanted to just add one more point to this whole discussion. We should certainly try to understand both the intent and application of code and the LEED guidelines and how best to do that using the software available. That being said, overly scrutinizing an efficiency number to the + 1% can give a false sense of preciseness. Think about what the uncertainty is in some of the most basic parameters that go into the model. Such as the occupancy, lighting and equipment use, how the control systems react, infiltration rates, and a number of other things.
Yes, for LEED many of these are controlled for between the two cases, but some are not, and it also does not stop most clients from asking for what we think their savings is going to be in absolute terms. I don't want to dissuade anyone from trying to figure out these issues, ultimately we need to find ways to get results to approach reality in all cases, but I don't want anyone to get lost in the details when there are often much bigger question marks.
Brendan Hall, PE, LEED AP BD+C