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5.7.6 AFUE and HSPF conversions #232

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
What NACM Section(s) are relevant to this issue?
5.7.6.4 Furnace Fuel Heating Efficiency
5.7.6.5 Electric Heat Pump Heating efficiency 

Explanation of issue:
The AHUE and HSPF conversions are dependent on whether the system is a 
SinglePackage or Split system type. Based on my brief research, the efficiency 
requirements of HVAC equipment is now the same regardless if the system type is 
Split or Packaged.  There is currently no property in the SDD that is used to 
distinguish between split or packaged.  I can add one, but it appears that 
these are the only two ACM descriptors that are dependent on this definition, 
and if the appliance efficiency requirements are now the same, I wonder if 
these separate equations are still relevant.

Proposed resolution:
Revise the ACM to remove dependence of conversions on split vs packaged.  It is 
not difficult to add the necessary SDD property, but this is one more piece of 
information that the user has to define though it no longer seems that relevant 
(it would only be used in the ruleset for these conversions).  If the 
performance of modern split/packaged equipment really is that different, than 
it is fine to leave as is and I will add the property.

Please provide any additional information below.

Original issue reported on code.google.com by da...@360-analytics.com on 24 May 2013 at 3:35

GoogleCodeExporter commented 9 years ago 
Resolution:

Use "Single Package" conversion curve in all cases. This curve is more 
conservative (lower thermal eff prediction) than the split system curve for 
high AFUE. For moderate (75-85) AFUE curves are nearly the same. See 
attachment.  Note: I don't know the source of the current curves, and don't 
have the time to develope new ones.

Original comment by JohnJArent on 28 May 2013 at 9:53

Attachments:

GoogleCodeExporter commented 9 years ago 
Works for me.  Will the HSPF to COP conversion also be reduced to only use the 
"Single Package" curve as well.

Original comment by da...@360-analytics.com on 28 May 2013 at 11:22

GoogleCodeExporter commented 9 years ago 
John,
Still see separate curves for single package and split heat pumps (5.7.6.5).  
Can you confirm that only the Single Package curve will be used for all systems 
as well?

Original comment by da...@360-analytics.com on 24 Sep 2013 at 9:54

GoogleCodeExporter commented 9 years ago 
Making this change for the upcoming release v3.0.  I am removing the separate 
conversion equation for split system heat pumps from HSPF to COP, to simplify 
the ACM.

Original comment by JohnJArent on 19 Nov 2013 at 9:46

GoogleCodeExporter commented 9 years ago 
See attached file with changes

Original comment by JohnJArent on 22 Nov 2013 at 12:00

Attachments:

GoogleCodeExporter commented 9 years ago 
A few remaining issues with heat pumps (sorry, missed these the first time 
around):

- I believe the denominator of equation 39 should subtract the fan heat from 
the input power.
- We have the same (current) limitation of generating curves from COP rating 
point data as we do SEER/EER data, per the green text in Electric Heat Pump 
Heating Capacity Adjustment Curve(s). So, for the Dec release, we 
a) need a set of predefined curves as you provided for SEER/EER
b) omit from ACM now, and add in later when CBECC supports it

Either way, CBECC, per current priority list, we won't be supporting 
user-defined curves for the Dec release.

Original comment by da...@360-analytics.com on 23 Nov 2013 at 1:45

GoogleCodeExporter commented 9 years ago 
I'll check on eqn 39. For the performance curve, I suggest we just use a fixed 
curve for the ACM and CBECC.  For converting from HSPF to COP when COP is not 
available for small heat pumps, I recommend the following equation and language 
below.

Electric Heat Pump Heating Efficiency

Input Restrictions:
As designed
If the equipment does not contain a COP rating, but only contains a heating 
seasonal performance factor (HSPF) rating, the COP at rated conditions used in 
the energy simulation shall be determined by the following formula:

COP = 0.624 x HSPF – 0.026 x HSPF2

Original comment by JohnJArent on 25 Nov 2013 at 11:20

GoogleCodeExporter commented 9 years ago 
Where is this new equation for HSPF to COP coming from?  I just updated the 
rules with the resolution proposed in comment #5.

For confirmation post final language for the following descriptors when 
available.
Electric Heat Pump Heating Efficiency
Electric Heat Pump Heating Capacity Adjustment Curve(s)

Original comment by da...@360-analytics.com on 25 Nov 2013 at 11:38

GoogleCodeExporter commented 9 years ago 
Actually, my mistake - the conversion from HSPF to COP used in the ACM as 
posted in comment #5 is fine. (I had found another, more recent conversion 
documemted, but I don't think it is worth changing this without an engineering 
review of it.)

Original comment by JohnJArent on 27 Nov 2013 at 1:38

GoogleCodeExporter commented 9 years ago 
For this issue, I am resolving it by removing the user-defined performance data 
option for small heat pumps. The users will be required to use the applicable 
performance curves for the air-source heat pump or water-source heat pump, as 
appropriate.  See attachment.

Seran, note that this is a slight simplification of the previous ACM language. 
However, we don't have a fully developed performance specification for small 
heat pumps, in the same manner that I helped develop for the 2005 Title 24 
Standards for packaged DX units with gas furnaces, and I don't think these are 
that common in California nonresidential buildings.  Also, I think the 
performance curves at low temperatures become less important when the auxiliary 
heating is often activated.

Changing status to FIXED - if anyone has objections to this change, please let 
me know and we can reopen the issue for further review.

Original comment by JohnJArent on 27 Nov 2013 at 7:36

Attachments:

GoogleCodeExporter commented 9 years ago 
Thanks for the update John.  There is still one remaining issue, I believe the 
denominator of equation 39 should subtract the fan heat from the input power, 
not add it.

Original comment by da...@360-analytics.com on 27 Nov 2013 at 9:13

GoogleCodeExporter commented 9 years ago 
You're right - good catch. See equation in attached.

Original comment by JohnJArent on 7 Feb 2014 at 8:09

Attachments:

GoogleCodeExporter commented 9 years ago 
Rule update to reflect #12 committed to svn/branches/Dave140110_Rules, r1508

Original comment by da...@360-analytics.com on 15 Feb 2014 at 8:34