3.7.6.4 Furnace

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What 90.1 PRM Section(s) are relevant to this issue?
3.7.6.4 Furnace Heating Efficiency

Explanation of issue:
Since the time the NACM was initially passed to PNNL for PRMRM development, the 
equation for furnace AFUE -> Et was consolidated to the following:

Et = 0.005163 x AFUE + 0.4033

See GC issue 232 for background. The rationale for the change was the lack of 
information to support multiple equations. Is this change also acceptable for 
90.1?

Proposed resolution:
Revise PRMRM to be consistent with the NACM

Original issue reported on code.google.com by da...@360-analytics.com on 20 Oct 2014 at 6:38

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The rational in issue 232 is stated as lack of property in SDD to store whether 
system type is split or packaged. However, I do see that property in CBECC-Com, 
is there any other restriction as well?

Issue 232 mentions heat pumps as well, we modified NACM requirements with 90.1 
2013 specifications, so I guess we're ok where heat pumps are concerned.
Correct?

Original comment by supriya....@pnnl.gov on 20 Oct 2014 at 10:23

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Yes, we did eventually add a property to differentiate AirSystem sub-categories 
(AirSys:SubType), but currently this property is only used for checking minimum 
split-system condensing unit requirements.

We can implement the rule as described, but given that the regressions are 
dated (developed in the early 90s), and that efficiency requirements are 
largely the same for packaged and split systems, the added complexity didn't 
seem warranted.  Let me know what you'd like to do, just thought I'd highlight 
this in case you wanted to align with the NACM whereever possible.

Yes, we are OK on HPs.  I haven't done a review to see if the NACM air-source 
CAP-FT curves reflect meeting the COP17 performance requirements; I will add 
this to my internal tracking list.

Original comment by da...@360-analytics.com on 20 Oct 2014 at 11:15

• Changed state: Discussion

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We're ok with using the equation -
Et = 0.005163 x AFUE + 0.4033 for both packaged and split furnaces

We have tried to align with NACM wherever possible, unless 90.1 has some 
explicitly defined varying requirement, so this works fine

Original comment by supriya....@pnnl.gov on 20 Oct 2014 at 11:21

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I apologize, I overlooked subsequent issue 562 that finalized the AFUE -> Et 
for the NACM. This slightly tweaked equation results in 80% efficiency @ 
AFUE-78.

( 0.0051427 * AFUE  ) + 0.3989

Is this acceptable?

Original comment by da...@360-analytics.com on 9 Dec 2014 at 10:20

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David- The issue fell through the cracks. Yes- this is acceptable.
The revisions have been made to the PRM RM

Original comment by supriya....@pnnl.gov on 17 Jan 2015 at 12:14