90.1-2010 Section 11, ECB, question on multiple heat sources

4 posts / 0 new
Last post

I am modeling a project that has air-to-water heat pumps as the main plant. There is a natural gas back-up boiler for those few hours in the year where it is too cold for the heat pumps to meet the heating load.

I am not sure how to interpret 11.3.2.(j).(2) - For systems with mixed fuel heating sources, the system or systems that use the secondary heating source type (the one with the smallest total installed output capacity for the spaces served by the system) shall be modeled identical in the building design and the primary heating source type shall be used in Figure 11.3.2 to determine the budget system type.

In this case, as the heating water loop serves all systems in the building - all systems receive heat from the secondary heating source type at some point in the year - the language of this clause leave me wondering what baseline system to use?

My interpretation is to use System 9 ignoring the back-up natural gas heat source?

Christopher R. Jones, P.Eng.
Technical Specialist
Sustainability & Energy

[cid:image001.png at 01D32AF1.7FBB69B0]
T +1 416-644-0252

2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4 Canada

wsp.com

Please consider the environment before printing...

Bldg simulation's picture
Offline
Joined: 2016-04-13
Reputation: 200

Hi Chris,

The way I would interpret 11.3.2.(j).2 is that the primary heating source should be selected from the map, and the secondary heating source should be modeled identical to the one in the proposed building. So, in system 9, instead of having the auxiliary heat as electric, it would be natural gas. Would be interested in hearing how others interpret this clause.

Regards,
Rahul

__________________________________________________
Rahul Athalye
Energy Research Engineer
Pacific Northwest National Laboratory
509-372-4297

Bldg simulation's picture
Offline
Joined: 2016-04-13
Reputation: 200

Thank you for your reply.

I neglected to describe the proposed system - an ERV DOAS with 4-pipe fan coils. The ERV has heating, cooling coils. The project is non-residential.

Christopher R. Jones, P.Eng.
Technical Specialist
Sustainability & Energy

[cid:image001.png at 01D32AF9.82579EC0]
T +1 416-644-0252

2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4 Canada

wsp.com

Please consider the environment before printing...

Bldg simulation's picture
Offline
Joined: 2016-04-13
Reputation: 200

Hi Christopher,

I would point you to Table 11.3.2A footnote g that refers to Electric heat pump and boiler systems. Based on the text there, I assume you would use System 6 for the budget baseline design, which is the same as your proposed system type. In your proposed, the heat pump is the primary heat source (provides the majority of the heating to the spaces), so you follow to System 6 and then map the boiler fuel source to match the proposed system. For example, NYSERDA's protocol references Chapter 11 System 6 specifically for water loop heat pumps with gas boiler backups when the rest of that program references Appendix G.

Thanks,

The Weidt Group?
[cid:image002.png at 01CEBDCD.F3DD6040]
Michael Shannon, EIT
5800 Baker Road
Minnetonka, MN 55345
T 952.938.1588 F 952.938.1836
michaels at twgi.com | www.twgi.com

The energy practice of EYP Inc.
Ranked #1 in Sustainability

Bldg simulation's picture
Offline
Joined: 2016-04-13
Reputation: 200