[Bldg-sim] NECB - MURB Reference Heating Type
David Eldridge
DEldridge at grummanbutkus.com
Mon Feb 18 13:34:20 PST 2019
One of the interesting aspects of this is the link to unitary products for instance would include certifications for water-cooled equipment consistent with a WLHP system as you mentioned Aaron – if the code just said “unitary” it would be clear - it’s only that the Table 8 reference uses the word “air-cooled” instead of applying to all unitary equipment so that a WLHP system seems to be left out of the matrix.
1) Central CHW & HW w/ FCU – use identical
2) Air-cooled unitary – use identical
3) PTHP – use identical
4) Other – use through-the-wall baseline
It’s strange to me that the WLHP option which I’d consider to be “in the middle” of the options above as sort of an option 1.5 is excluded and then you are left in “through-the-wall unit purgatory” where the baseline system is partially defined. i.e. if the fully applied system with boilers, chillers, and FCU is on one edge of the range and PTHP are on the other end of the range, why wouldn’t WLHP fit in there?
That said, it seems to be how it reads. So to your question, you mentioned 8.4.4.9.4 and that your sample compliance building used air-to-air heat pumps with electric resistance heat, which makes sense that a TTW unit in practice is going to be heat pump and/or electric resistance heat. A furnace option would not be part of a TTW unit either. If the baseline is supposed to make sense that is – I think an argument could be made that on an annual basis the WLHP system takes primary heat from the boiler more than the compressors for cold climates, but I’m not an expert in NECB so you’d be best positioned to comment there whether it calls for a hybrid system or not.
It would be pretty contrived to have a baseline that used an air-to-air heat pump as primary and then had auxiliary hot water – in practice any building that went to the trouble to add the hot water system’s cost would tend to use it as the primary system. The combo that makes practical sense is for the auxiliary heat to be electric resistance.
David
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From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Aaron Smith via Bldg-sim
Sent: Monday, February 18, 2019 10:44 AM
To: 'Chris Hadlock' <cjhadlock at gmail.com>
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] NECB - MURB Reference Heating Type
Hi Chris,
Thanks for your response. It would make sense if the Reference Building were also a WLHP but based on AHRI definitions I think a WHLP is pretty clearly not:
a. an “air-cooled unitary<http://www.ahrinet.org/Certification/AHRI-Certification-Programs/Unitary-Air-Conditioner-Equipment>” product,
b. a packaged terminal air conditioner<http://www.ahrinet.org/Certification/AHRI-Certification-Programs/Packaged-Terminal-Air-Conditioners> or heat pump<http://www.ahrinet.org/Certification/AHRI-Certification-Programs/Packaged-Terminal-Heat-Pumps>, or
c. a fan coil.
A WLHP is water-cooled unitary product.
If they simply said “unitary” or “air-cooled or water-cooled unitary” then it would makes sense to me that you model an identical system but they specifically state “air-cooled unitary”.
Aaron
Aaron Smith, P.Eng
Principal, Mechanical Engineer
LEED® AP BD+C, BEMP, BEAP, CGD
M&R Engineering Ltd.
From: Chris Hadlock [mailto:cjhadlock at gmail.com]
Sent: February-18-19 11:27 AM
To: Aaron Smith <asmith at mreng.ca<mailto:asmith at mreng.ca>>
Cc: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: Re: [Bldg-sim] NECB - MURB Reference Heating Type
Hi Aaron,
The way I would interpret it is the Reference system will be identical to your Proposed system (i.e. WLHP connected to fossil fuel boiler). If you had a air-source, water-source (i.e. river, lake) or ground-source, then you would have to worry about auxiliary heating (per Section 8.4.4.13.2). The "through-the-wall" system only applies in the otherwise case (i.e. when your system is not one of the ones listed).
This is my interpretation - I'd be interested to hear others.
Chris
On Sun, Feb 17, 2019 at 10:10 PM Aaron Smith via Bldg-sim <bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>> wrote:
Hello,
I’ve got a question about the NECB Reference Building heating system type for Multi-Unit Residential Buildings. Specifically what should it be when you have water-loop heat pumps connected to a fossil fuel boiler?
Table 8.4.4.7.-A of the 2015 NECB states that Reference Building HVAC systems for Multi-Unit Residential areas are:
“Where the proposed building or space is heated as well as being cooled with an air-cooled unitary, packaged terminal or room air conditioner (or heat pumps), or fan coils, the reference building or space's HVAC system shall be modeled as being identical to that of the proposed building or space; otherwise, the reference building or space shall use through-the-wall systems.”
I’d consider water-loop heat pumps to be in the “through-the-wall systems” category so the cooling would be air-cooled DX. It doesn’t describe the heating source for “through-the-wall systems” but 8.4.4.9.4 says that the energy type of the reference building’s heating system shall be identical to the energy type of the proposed building’s heating system. The code considers heat pump to be an energy type so I think it should be an air-source heat pump. I’m just not sure about the auxiliary heat – electric resistance or hot water?
I tried running this in CAN-QUEST but got some errors. When I run a 4-storey office building with WLHP, the reference building is coming out as air-source heat pump with electric resistance heat so I’m leaning toward using that. I can see there being an argument for hot water auxiliary heat though based on the proposed building having a fuel-fired boiler (to avoid fuel switching).
Thanks,
Aaron
Aaron Smith, P.Eng
Principal, Mechanical Engineer
LEED® AP BD+C, BEMP, BEAP, CGD
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