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Does ideal loads consider light/equiment heat gains

asked 2018-07-16 08:37:26 -0500

MA_Meilleur gravatar image

updated 2018-07-16 11:02:45 -0500

I have an openstudio V2.5.1 large office model in cold climate (heating degree days around 4000) on district heating and district cooling with almost no unmet hours. EUI 124 kwh/m2 ; TEDI 51 kwht/m2

By putting ideal loads on for all thermal zones, my heating consumption almost doubles. EUI 171 kwh/m2 ; TEDI 97 kwht/m2

What could explain this considering that my heating equipment has the same efficiency (100%) ?

Maybe if the heat gains form lights, equipment, fans, pumps are not considered in the thermal balance it would make sense, but the documentation I red didn't gave me a clear answer on this hypothesis.

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How did you set up the ideal loads objects? Did you include outdoor air ventilation, and are your HVAC system schedules matched? What zone systems did you use for the district cooling and heating case?

mdahlhausen gravatar image mdahlhausen  ( 2018-07-16 11:34:37 -0500 )edit

@MA_Meilleur, could you tell me how you calculated TEDI in openstudio?

yashar gravatar image yashar  ( 2020-07-24 19:04:00 -0500 )edit

I had a similar thing happen to me, in a unique situation where some of my zones have very very high peak internal gains. I was comparing an Ideal Air Loads system type to a water source heat pump system. TEDI and CEDI were both very different between the two cases, and after some investigation it was clear the IAL was not accounting for the peak loads properly. As far as I could tell all inputs were the same between the two options that might impact this (counting for ventilation, use of economizers, heat recovery, etc). I never could figure out why the IAL wasn't performing.

Abarker gravatar image Abarker  ( 2020-07-28 09:31:04 -0500 )edit

@Abarker Hi, is there any difference between TEDI and heating load? In fact, by definition, TEDI is the annual heating delivered to the building for space conditioning and conditioning of ventilation air which is similar to Heating load definition. In the openstudio end use table, I can find a row related to Heating composed of Electricity and natural gas (GJ). Could we use these values to calculate TEDI? (electricity +Natural gas/floor area.year). or I need to consider other values?

yashar gravatar image yashar  ( 2020-07-28 17:31:38 -0500 )edit

@yashar it might depend on how TEDI is specifically defined for the standard your looking at, but generally your description seems right to me. I'm not familiar with Open Studio tables, but if you have access to the .html output file Energy Plus creates, TEDI can usually be found in the Energy Meters section by looking at the annual GJ values for both HeatingCoils:EnergyTransfer and Baseboards;EnergyTransfer (if any). These should sum up to reflect annual heating delivered from all heating coils and baseboards, of any type.

Abarker gravatar image Abarker  ( 2020-07-28 20:54:05 -0500 )edit

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answered 2020-07-29 02:03:49 -0500

yashar gravatar image

@Abarker Thank you very much for you response. The result that I was talking about was the energy plus HTML.output. As you know, there is End Uses table in energy plus report that you can find all of the energy that is used for heating, cooling, interior lighting, exterior lighting and so on. I attached an example in order to show my method and know your idea about it. C:\fakepath\Untitled23.png

I know my question is so basic because I just started working with Energy plus and openstudio, but I would appreciate it if it is possible for you to show me the Energy Meters sections and related column and row for calculating of TEDI.

I am looking forward to hearing from you.

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Asked: 2018-07-16 08:37:26 -0500

Seen: 272 times

Last updated: Jul 29 '20