Question-and-Answer Resource for the Building Energy Modeling Community
| 2019-12-12 08:51:17 -0500 | received badge | ● Popular Question (source) |
| 2017-04-03 06:40:58 -0500 | commented answer | Water Heating Equipment Performance Requirements per ASHRAE 90.1-2007 Thank you for your reply! So you are saying that EF is just for determining the skin loss and the water heater eff. is still 100% for electric heaters right? (which makes sense of course). I thought that EF according Table 7.8 is heater efficiency adjusted by the tank volume. So once again: it doesn't matter what simulation engine is used, however the water heater eff. in baseline case is 100% (in case of electric water heater) and skin loss is determined by EF. Please confirm if it is true. I need to know it once and for all. Thank you very much. |
| 2017-03-31 09:16:55 -0500 | asked a question | Water Heating Equipment Performance Requirements per ASHRAE 90.1-2007 Hi all, can someone help me please to determine the correct EF (energy factor) for baseline electric water heater according to ASHRAE 90.1-2007 per Table 7.8? The design case water heaters parameters are as follows: V = 2 x 1000 L = 2000 L (528,4 gal US) Electric Input = 2 x 4,5 kW = 9 kW According to these parameters the equation in my opinion should be "0,93 - (minus) 0,00132 * V", because the electric input is less than 12 kW and overall storage volume is more than 20 gallons: 0,93 - 0,00132 * 528,4 = 0,232 EF = 23,2% Please let me someone know if it is correct calculation. Obviously it is very bad efficiency and LEED reviewer insist that it should be corrected and rewised in energy model. But I don't know how it should be corrected, because it's just simple math. Maybe I'm wrong in the equation, or should be used another equation? Thanks in advance for any advices and suggestions. Martin |
| 2016-09-15 10:12:01 -0500 | commented answer | Baseline AHU system level sizing - LAT Thank you! I appreciate your help. |
| 2016-09-15 09:36:17 -0500 | commented answer | Baseline AHU system level sizing - LAT Thank you very much! This is what I needed to know. Just for sure: Am I right with the reheat coil reset = 72F to 92F? I hope so... |
| 2016-09-14 06:07:50 -0500 | asked a question | Baseline AHU system level sizing - LAT Hi everyone! Can somobedy explain me please how should be AHU heating coil leaving air temepratures correctly set? Especially for system 5-7 there is packaged VAV with reheat and I wonder what temeperatures should be used for AHU heating coil and zone heating coil (reheat coil). I would say that reheat coil should be set with supply-air-to-room-air temperature difference of 20°F because of design airflow rates, so if room heating setpoint is for instance 72°F then reheat coil is set at 92°F. But my question is what about AHU heating coil? Should it be set the same as reheat coil? Or quite opposite = at 52°F and it would be something like preheat coil? Is it prescribed somewhere in App.G? Thanks for any advice in advance! Martin |
| 2016-04-27 08:37:12 -0500 | received badge | ● Scholar (source) |
| 2016-04-27 08:37:08 -0500 | commented answer | Baseline system parameters with DES heating in LEED? Alright then Damien, thank you very much for your help! |
| 2016-04-26 10:20:38 -0500 | commented answer | Baseline system parameters with DES heating in LEED? Yes, you are absolutely right that supply temp. resets have not almost any impact on the results... OK, so you are saying to follow App. G (temp resets, pump power) and heating source with 100% efficiency, right? The efficiency, I would say, is because G3.1.1.1 Purchased Heat where is stated "...on-site boilers shall not be modeled in the Baseline". I understand it correctly? And thank you Damien for your previous replies... |
| 2016-04-22 16:01:22 -0500 | commented answer | Baseline system parameters with DES heating in LEED? Thank you very much for your reply. I appreciate that! Yes, I noticed in the revised section 1.4 spreadsheet in helpful notes that Option 1 should be modeled something like that. But when I selected within "General HVAC" how the DES was modeled, helpful notes in "Water-side HVAC Details" has changed only when "ASHRAE 90.1-2007 Appendix G without addenda" was thicked and no change when DES v2 Option 1 selected. And it confused me. Have you noticed that in the 1.4 spreadsheet? |
| 2016-04-22 10:04:18 -0500 | received badge | ● Student (source) |
| 2016-04-22 08:39:05 -0500 | asked a question | Baseline system parameters with DES heating in LEED? Hi everyone! I would like to ask you for some help or guidance with DES heating modellling in baseline building especially with setting up a system parameters like energy efficiency, temeprature resets ect. This is my first LEED-2009 CS project with DES heating and I'm already a little bit confused how to model it correctly. We chose an Option 1 (the building stand-alone scenario) and from what I have read in DES v2 Guidance it is not clear to me if the baseline heating source has to be modelled with exactly the same energy efficiency, the same temeprature resets and pump power like in Proposed building or it should follow the Appendix G with minimum efficiency requirements and resets stated in sections 6 to 9 of the ASHRAE 90.1 standard. To be more precise, is the Baseline heating source modelled exactly as the Proposed heating source with Option1 or not? Thank you very much in advance for any help. I need it so much because now I'm not able to complete the simulation... Martin |
