Modeling a VRF System
Posted: Mon Dec 19, 2016 8:59 pm
Alright this is probably something super simple that I am missing, but I have used the VRF modeling walkthrough from IES and am not getting the results that I believe I should be. Basically I have a 'sample' building to try and get this right with 2 zones: one zone has 0 people and one has 500. This is pretty extreme but I want to make sure there are times where one zone has a large cooling load and one has a heating load.
So I have a generic heat source feeding a heating coil in each zone, and a simple chilled water loop feeding a cooling coil in each zone. The heating coil parameter 'Max. heat recovery with HX (%) is set to 100, so my understanding is that it should use all heat being removed from the other zone. The cooling source is a part-load chiller and is correctly referencing the heating source under the 'Condenser heat recovery recipient' parameter.
Now I am struggling to post a picture of my results, though I am sure there has to be a way but here is a breakdown of what I am seeing midday on April 7: heating coil load = 282 kbtu/h, cooling coil load = 173 kbtu/h, recovered chiller heat = 33 kbtu/h, and the heat pump load = 249 kbtu/h.
Is there any reason why my recovered chiller heat is not 173 kbtu/h? The heat pump is utilizing the recovered heat correctly so I am assuming that is set up the right way, but why is my recovered chiller heat so low (the max. heat recovery is definitely set to 100)? Are there other parameters that may contribute to this?
Any and all help is very appreciated, I have about 6 jobs interested in VRF but are hesitant due to the higher initial cost of the system. I would love if all 6 of them went VRF, but I am wanting to provide some good data showing the benefits of these systems first.
Thank you,
Tyler
So I have a generic heat source feeding a heating coil in each zone, and a simple chilled water loop feeding a cooling coil in each zone. The heating coil parameter 'Max. heat recovery with HX (%) is set to 100, so my understanding is that it should use all heat being removed from the other zone. The cooling source is a part-load chiller and is correctly referencing the heating source under the 'Condenser heat recovery recipient' parameter.
Now I am struggling to post a picture of my results, though I am sure there has to be a way but here is a breakdown of what I am seeing midday on April 7: heating coil load = 282 kbtu/h, cooling coil load = 173 kbtu/h, recovered chiller heat = 33 kbtu/h, and the heat pump load = 249 kbtu/h.
Is there any reason why my recovered chiller heat is not 173 kbtu/h? The heat pump is utilizing the recovered heat correctly so I am assuming that is set up the right way, but why is my recovered chiller heat so low (the max. heat recovery is definitely set to 100)? Are there other parameters that may contribute to this?
Any and all help is very appreciated, I have about 6 jobs interested in VRF but are hesitant due to the higher initial cost of the system. I would love if all 6 of them went VRF, but I am wanting to provide some good data showing the benefits of these systems first.
Thank you,
Tyler