[Bldg-sim] NECB - MURB Reference Heating Type

Tue Feb 19 11:31:41 PST 2019

Hi Chris,

I don’t think a WLHP can really be a through-the-wall system – I believe that implies that the cooling is air-cooled DX.  Unless you were thinking the unit would reject heat outdoors in the summer and use the heating loop as a source of heat in the winter?  I don’t think that can be modeled though.

I think modeling a PTHP will satisfy both Table 8.4.4.7.-A, 8.4.4.9.4 and 8.4.4.9.5 if you say both Proposed and Reference cases have a “Heat Pump” energy type and ignore the fact that one happens to be WLHP and the other is ASHP.  I don’t think you consider a WLHP to have two energy types (electricity and natural gas) – it is one energy type (heat pump).  I think that is the closest you are going to get.  Refer to 8.4.4.20 where they say if your energy type for SWH is air-, water- or ground source heat pump, the energy type of the reference building’s service water heating system shall use an air-source heat pump.  I think that provides a pretty strong case for ASHP.  I think it should have electric auxiliary heat as well based on my findings from the office building test case in CAN-QUEST.

I appreciate the comments.

Regards,

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 3:06 PM
To: Aaron Smith <asmith at mreng.ca>
Subject: Re: [Bldg-sim] NECB - MURB Reference Heating Type

Hi Aaron,

I see your point and agree with you that it doesn't seem to fit any of the listed system types based on the AHRI definitions. So agreeing that it would be a "though-the-wall" system type. However I believe that we end up back with a water-loop heat pump based on the remaining NECB requirements.

For one, section 8.4.4.13.2) does not apply to water-loop HP's, and this is really the only section that talks about auxiliary heating. Conclusion: no auxiliary heating???

Furthermore, Section 8.4.4.9.5) seems to imply if the Proposed heating system has more than 1 energy type, than the Reference shall as well (and in the same proportion). It also says the operating schedule and priority of use shall also be the same. Not sure how the meet this requirement (i.e. heat pump and gas boiler operating in concert) without modeling a water-loop HP. 

So my interpretation is that the only way I see to meet all of these requirements is to model a water-loop heat pump. Otherwise I would say you'd be in violation of one or more of the requirements. And a WLHP can still be a through-the-wall system can it not?

Your thoughts?

Chris

On Mon, Feb 18, 2019 at 11:44 AM Aaron Smith <asmith at mreng.ca <mailto:asmith at mreng.ca> > wrote:

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 <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

     t: (902) 422-7393

     f: (902) 423-4945

     e:  <mailto:asmith at mreng.ca> asmith at mreng.ca

     www.mreng.ca <http://www.mreng.ca/>  

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