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Define machines which produce heat

asked 2015-01-16 08:55:40 -0500

Marcelba gravatar image

updated 2015-07-26 19:05:46 -0500

Hello i defined a few machines which produce heat, which is given into the zone. Therefore i Defined the Field. Fraction Lost with 0.5 so half of the energy will be give to the room. I expected that i will than have lesser gas consumption for the zone, but the opposites happens. When i place more and more electric equipment into the zone, the Gas Consumption increase

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when i increase the Desing Level from my electric equipment form for example 200 to 8000 that i need more gas for heating than before. i have fraction at 0.5 so half of the heat from my machines goes into the room the rest i used for mechanical work

Marcelba gravatar image Marcelba  ( 2015-01-16 10:02:54 -0500 )edit

This is the reverse of what one would expect. We will need more info about the model, including the type of hvac system, to figure out why. Probably easiest if you post your idf file.

MJWitte gravatar image MJWitte  ( 2015-01-16 15:57:42 -0500 )edit

it is a HVAC Systm with Cooling with electricity and heating with gas. When i put i machines the cooling in summer increases but in the winter time i have got a higher gas Consumption when i put in machines. so the influence of the machines in summer is right and seemed logic to me, but not in the winter. i ve go 23 degrees air temperatured defined for the zones.

which part of the idf file do u need?

Marcelba gravatar image Marcelba  ( 2015-01-22 04:33:06 -0500 )edit

@Marcelba First, try to diagnose it yourself. Add some hourly output:variables that show what is happening in the zone heat balance, internal gains, and the hvac system. If you still have questions, then we need to see the complete idf file. And specify what epw file you are running with. If you prefer not to post that publicly, then you can send it to the EnergyPlus helpdesk at

MJWitte gravatar image MJWitte  ( 2015-01-22 08:51:02 -0500 )edit

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answered 2015-01-16 09:22:02 -0500

keb gravatar image

updated 2015-01-16 09:38:42 -0500

By default the Fraction Lost is 0 which indicates all the equipment power is given off in the zone, so increasing it to .5 would indeed increase your gas consumption since the .5 means that half the energy is 'lost' or converted.
See E+ documentation here for clarification.

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With fraction Lost=1 i have 857 Gas and cooling in July 1101 with fraction Lost=0.5 i have Gas 1620 and Cooling in July 60 so with 0.5 some of the heat from the machines is used to warm up the room, which makes sense. But actually i should need more cooling in the summer with fraction 0.5, but here its the other way round?!

Marcelba gravatar image Marcelba  ( 2015-01-16 09:54:53 -0500 )edit

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Asked: 2015-01-16 08:55:40 -0500

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Last updated: Jan 16 '15