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Take a look at this forum response. I had a similar question and they said we needed to combine the systems and zones into 1.
Thanks for the input. I will model this as a separate system/zone, I will specify that this system gets outside air from the true system that the room is served by, and I will break off a portion of the true system’s design fan power and CFM and distribute it to the separate system representing the duct heater.
I don’t believe there are any energy code mandated requirements for the shared floor/ceiling in this scenario. The energy code only mandates requirements for raised floors that separate conditioned and unconditioned space, which is not the case here. This is likely why when you test different insulation values, it makes no difference. There is no requirement for insulation here based on energy code. However, it is likely a good idea to have some for sound mitigation.
Since there is no requirement, you do not have to input this surface in the lower unit’s energy model. As far as I’m aware, putting this in as an interior surface on the lower floor will actually add additional floor area to the unit, which is incorrect. There is no way to model a ceiling only, it must only be modeled as an interior surface ceiling/floor on the unit above only. Check your lower unit’s model floor area on the CF-1R and see if it is double counting the area because of the way you’ve input the ceiling in the model.
For your ductless system, make sure to select the system element, distribution tab, and specify the heating distribution and cooling distribution. This is where you specify your system is ductless, not by selecting the system type at the system input. See attached image for reference.
Thanks Robert and Pat!
I have not heard of the limits given by utilities on size. I would also be interested in finding out about this if that is the case.
The requirements in Part 6 are in 150.1(c)14.
Assuming that the lower story is one of the residences and the upper story is the other residence, I believe the correct thing to do would be to include an interior surface with type floor on the upper story model and mark it as being adjacent to another dwelling unit. In the lower story model, this room would not have a roof or other interior surface representing the ceiling.
Being that split-system heat pump water heaters are a more rare type of system, I would question what the software’s input for “Residential heat pump water heater location” is actually asking for/assuming. It is likely treating the heat pump water heater as a combined system and therefore assuming the compressor and storage tank are installed in the same location that you input into the software (which is not the case for the split-system heat pump). I don’t know if the software has a way to account for this. Would anyone from EnergySoft be able to comment on this?
Since this error comes straight from the CEC’s calculation engine, I would recommend that you reach out the CBECC res and try and describe what is going on and the error you are receiving. If you get an answer, I’m sure everyone would appreciate it if you shared it here.
Here is the email for the CBECC res support team.March 19, 2020 at 11:13 am in reply to: ERROR: Object reference not set to an instance of an object #5722
Couple of things you could try.
First rule out any glitches in the model/software (unlikely this is the problem, but worth ruling out)
- Save and close the software (not just the model but the entire program). Reopen and see if the issue persists.
- Restart your computer and see if the issue persists.
- If you can, see if the issue persists on someone else’s computer (you could attached the model and I could test it out)
Troubleshoot your model
It sounds like your model has/had some elements that referenced other elements of the model. It is possible that these “other elements” were deleted.
For example, maybe an interior wall was set adjacent to a space, but then that space got deleted. Another example might be a system that had been specified to receive outside air from another system, but then the other system was deleted. This may be the case if you were using an ERV or supply fans to provide outside air to the space conditioning systems. There may be other cases like this that I am not aware of involving other elements like overhangs, sidefins, etc. The point is that when you delete something that is referenced, sometimes the reference will remain, but the reference will point to nothing (since the object has been deleted) causing an error in the program.
Hope this helps.
I’m not 100% sure how to model every detail, but hope to point you in the right direction. Open energy pro 8 and from the menu select the help dropdown and select contents. Then type “Hydronic”. Click on the “Hydronic Systems” topic.
It sounds like you are modeling a “combined hydronic space and water heating system”, so I’d recommend reading that section and following their directions as best you can.
I have found that referring to the 2019 Residential Compliance Manual sections that they reference is also helpful. It looks like they reference sections 4.7.1 and 4.7.2 which also may have helpful info worth checking out. That document is free and can be downloaded from the CEC’s website here:
I believe the water heater will have to be approved in the CEC’s appliance database. You will need to search the database and find the water heater you plan to use. There are two ways to search the database at the paths below. Note that regarding the filters, less is more when searching the database. I often use only 1 filter then export the data to excel and search from excel, rather than clicking through the result pages on the website.
See attached image for the epro help menu.
See attached image illustrating how to view the CBECC log file. In my experience, the CBECC log file isn’t the most helpful with troubleshooting errors.
Based on your error, it sounds like you have modeled overhangs or sidefins. Doing this requires you to input the location of window and door elements within each wall. The error indicates that one or more of your window/door elements have been specified in the same location on the wall, i.e. they “overlap”.
I would recommend clicking through each of your wall elements in which there is a door or a window and verify the wall widths and wall heights are accurate. I would then click through the windows and doors in each wall and verify the widths, heights, and X and Y position on wall are accurate. If you do this, you will likely find that one or more of the window/door elements are overlapping on your walls.
I have found it helpful to do a little sketch drawing for each wall, in which the wall is drawn based on the width and height input into the model and then the windows and doors are drawn onto the wall based on the specified width, height and X and Y position or each window and door in the model.
Also, I have been told that modeling sidefins and overhangs is optional. We typically avoid doing it because it complicates the model so much. We will only model them if needed for compliance. I have rarely needed to include them to get a model to comply.
Also note that in heating climates, sidefins and overhangs typically hurt you on compliance.
If the two systems are completely different this is what I assume we should do. I’m not too sure how to combine the efficiencies
- Heating Capacities – Add them together
- Heating Efficiency – take the average of the two (maybe take a weighted average based on capacity?)
- Cooling Capacity – Add them together
- Cooling Efficiency – take the average of the two (maybe take a weighted average based on capacity?)
- CFM – add them together
- horsepower or fan watts – add them together
Can you verify if these assumptions are correct and if any aren’t provide corrections?December 10, 2019 at 10:52 am in reply to: Including common spaces/hallways in Residential Performance Compliance #5500
The language of section 126.96.36.199 is a bit ambiguous to me, as it says “Corridors and other common areas within conditioned space must be provided a ventilation rate of 0.06 cfm/sqft”. If this only applied to spaces that were conditioned, I would expect it to say something more like “Conditioned corridors and other conditioned areas within conditioned space must be provided…”.
Since it doesn’t say this, it seems like the requirement is to ventilate corridors and other common areas if they are contained within a building with other surrounding conditioned spaces, regardless of whether those corridors or common areas are conditioned or not. For example, the unconditioned common hallways within a multi-family building would still be surrounded by, or “within”, the conditioned residential spaces, so the corridors would fall under this ventilation requirement. In this case these unconditioned corridors would still need 0.06 cfm/sqft of ventilation air, right?
Additionally, I don’t think the paragraph, “Corridors and other common areas within conditioned space..” is intended for the corridors contained within the dwelling units, because the dwelling units themselves have their own ventilation requirements outlined in the section above 188.8.131.52 equation 4-9 or table 4-17. So it must be intended for corridors outside the dwelling units.
So it seems like both conditioned and unconditioned hallways (and other common areas) shared between dwelling units in a multi-family building would still need to meet this 0.06cfm/sqft ventilation requirement. Thoughts?
Thanks for your reply. I also found these examples from page 4-127 of the 2016 Nonresidential compliance manual and this seems to relate to my question. This was in the section regarding space-conditioning system alterations.
It seems that you are correct and that it isn’t as simple as installing new VAV boxes, we must also check the existing VAV system and make adjustments to ventilation as needed.
The energy code ace website has a training section where it shows various classes you can register for for free. Here is a link to the website.
Once there, on the right side of the page there is a filter section. If you filter by Topic and select Energy pro under the modeling section you will find various upcoming courses.