{"action":"created","issue":{"url":"https://api.github.com/repos/NREL/EnergyPlus/issues/4973","labels_url":"https://api.github.com/repos/NREL/EnergyPlus/issues/4973/labels{/name}","comments_url":"https://api.github.com/repos/NREL/EnergyPlus/issues/4973/comments","events_url":"https://api.github.com/repos/NREL/EnergyPlus/issues/4973/events","html_url":"https://github.com/NREL/EnergyPlus/issues/4973","id":89141866,"number":4973,"title":"DX heating coil defrost operation causes increase in coil COP","user":{"login":"ejhw","id":1276021,"avatar_url":"https://avatars.githubusercontent.com/u/1276021?v=3","gravatar_id":"","url":"https://api.github.com/users/ejhw","html_url":"https://github.com/ejhw","followers_url":"https://api.github.com/users/ejhw/followers","following_url":"https://api.github.com/users/ejhw/following{/other_user}","gists_url":"https://api.github.com/users/ejhw/gists{/gist_id}","starred_url":"https://api.github.com/users/ejhw/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/ejhw/subscriptions","organizations_url":"https://api.github.com/users/ejhw/orgs","repos_url":"https://api.github.com/users/ejhw/repos","events_url":"https://api.github.com/users/ejhw/events{/privacy}","received_events_url":"https://api.github.com/users/ejhw/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/NREL/EnergyPlus/labels/Defect","name":"Defect","color":"e11d21"},{"url":"https://api.github.com/repos/NREL/EnergyPlus/labels/EnergyPlus","name":"EnergyPlus","color":"c7def8"},{"url":"https://api.github.com/repos/NREL/EnergyPlus/labels/Priority","name":"Priority","color":"e11d21"},{"url":"https://api.github.com/repos/NREL/EnergyPlus/labels/S2%20-%20Medium","name":"S2 - Medium","color":"fbca04"}],"state":"open","locked":false,"assignee":{"login":"nmerket","id":5325034,"avatar_url":"https://avatars.githubusercontent.com/u/5325034?v=3","gravatar_id":"","url":"https://api.github.com/users/nmerket","html_url":"https://github.com/nmerket","followers_url":"https://api.github.com/users/nmerket/followers","following_url":"https://api.github.com/users/nmerket/following{/other_user}","gists_url":"https://api.github.com/users/nmerket/gists{/gist_id}","starred_url":"https://api.github.com/users/nmerket/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/nmerket/subscriptions","organizations_url":"https://api.github.com/users/nmerket/orgs","repos_url":"https://api.github.com/users/nmerket/repos","events_url":"https://api.github.com/users/nmerket/events{/privacy}","received_events_url":"https://api.github.com/users/nmerket/received_events","type":"User","site_admin":false},"milestone":null,"comments":3,"created_at":"2015-06-17T22:24:05Z","updated_at":"2015-07-07T21:22:06Z","closed_at":null,"body":"I have noticed that DX heating coil defrost operation causes an unexpected increase in coil COP (applies to both SingleSpeed and MultiSpeed coils; not tested for VariableSpeed). The following plots are from testing a MultiSpeed coil with identical performance curves for the two speeds and no part load cycling losses.\r\n\r\nThis issue is best seen by plotting hourly coil COP (calculated as `Heating Coil Total Heating Energy` / `Heating Coil Electric Energy`) against the outdoor drybulb temperature. There is an increase in COP of ~0.5 for temperatures below 0ºC, when defrost operates. Compare this to the COP values resulting from the EIR vs. T curve output (shown in blue). I can't think of any reason why defrost operation should increase the coil COP. \r\n![screen shot 2015-06-17 at 4 06 28 pm](https://cloud.githubusercontent.com/assets/1276021/8219925/e37ef0a6-150a-11e5-8bb2-cd449c76e27c.png)\r\n\r\nThe same effect can be seen when looking at a time-series plot:\r\n![screen shot 2015-06-17 at 4 06 40 pm](https://cloud.githubusercontent.com/assets/1276021/8219926/e65fa090-150a-11e5-9e30-5ce6ac0d44ae.png)\r\n![screen shot 2015-06-17 at 4 06 46 pm](https://cloud.githubusercontent.com/assets/1276021/8219927/e8331ad2-150a-11e5-8b51-b0171f7f77be.png)\r\n\r\nThe above results are using `Resistive` defrost with `Timed` control, but I see the same effect for `ReverseCycle` defrost and using `OnDemand` control. I confirmed that changing the maximum defrost temperature changes the temperature below which this increase in COP occurs.\r\n\r\nidf and associated files to be uploaded by @nmerket."},"comment":{"url":"https://api.github.com/repos/NREL/EnergyPlus/issues/comments/119346153","html_url":"https://github.com/NREL/EnergyPlus/issues/4973#issuecomment-119346153","issue_url":"https://api.github.com/repos/NREL/EnergyPlus/issues/4973","id":119346153,"user":{"login":"nmerket","id":5325034,"avatar_url":"https://avatars.githubusercontent.com/u/5325034?v=3","gravatar_id":"","url":"https://api.github.com/users/nmerket","html_url":"https://github.com/nmerket","followers_url":"https://api.github.com/users/nmerket/followers","following_url":"https://api.github.com/users/nmerket/following{/other_user}","gists_url":"https://api.github.com/users/nmerket/gists{/gist_id}","starred_url":"https://api.github.com/users/nmerket/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/nmerket/subscriptions","organizations_url":"https://api.github.com/users/nmerket/orgs","repos_url":"https://api.github.com/users/nmerket/repos","events_url":"https://api.github.com/users/nmerket/events{/privacy}","received_events_url":"https://api.github.com/users/nmerket/received_events","type":"User","site_admin":false},"created_at":"2015-07-07T21:22:06Z","updated_at":"2015-07-07T21:22:06Z","body":"I think the problem is happening somewhere in [here](https://github.com/NREL/EnergyPlus/blob/develop/src/EnergyPlus/DXCoils.cc#L10640-L10668). (Note so I can find it later.)"}}