Benjamin's profile - activity

1) You want to use the PIU system if you have fan-powered boxes in your VAV system. You need to be able to capture the fan energy used by those boxes, and this is the only system that can capture that fan power. This will not resolve your unmet hours, but this is the correct system for modeling FPBs.

2) A throttling range of 2F is very tight, particularly with a VAV system. You may want to read the help files in eQuest in regards to throttling ranges for VAV boxes - 4F is very acceptable, even 6F would probably pass muster (as indicated by the eQuest help files). All of our eQuest models use a throttling range of 4F.

3) Unconditioned zones next to conditioned ones absolutely can have an impact. If this is what was happening, the zones next to the unconditioned spaces would have the underheated hours - is this the case?

Baseboards should be, in almost all cases, specified as Thermostatic. This means that the baseboard will max out it's capacity before calling for heat from the main system. Presumably, if baseboards are installed, you'd want these to do the majority of the heating in each space. You should also be specifying a capacity (or -1 for no capacity) - if you don't put a value in, the baseboard will autosize and may give you heating where you don't want it. Check your SV-A report to see what baseboards you are getting.

With that said, it seems counter-intuitive that you would have both heating installed in the VAV boxes, and also have baseboards installed as well.

In general, I'd look at how you've specified your heating & cooling at the system and zone levels. It definitely sounds like a controls issue, if you've got multiple zones simultaneously heating and cooling. It'd be easier to provide more focused answers if you can post a link to your actual model...

As David said, it sounds like you are trying to use the .skp file, which is unnecessary for anything related to OpenStudio. The only file you should be working with is the .osm file, and you should be using the OpenStudio Open and OpenStudio Save, rather than the sketchup version of open and save.

This may sound trite, but it's not intended as such: what makes building materials "european?" You may want to clarify your question a little more.

Most software can simulate thermal comfort. I believe that they all refer to ASHRAE-55 standards for determining comfort within each space - EnergyPlus certainly does, and eQuest I'm pretty sure does as well. If you are not familiar with the ASHRAE-55 standard, that would be a good place to start as far as how thermal comfort is determined.

eQuest, EnergyPlus, OpenStudio and DesignBuilder interface) can all certainly meet your needs, and all will use weather files as appropriate for your region. You classify your space types as you desire - in your case, assigning stalls for sales cooking, and corridor space - including the effects of internal loads like lighting and equipment on the space.

They may increase simulation time slightly - I doubt it does have much impact, but I think it's more simply a case of housekeeping for clarity in your model. If you have a ton of schedules that aren't being used it can create clutter and confusion, particularly if someone other than you is looking at your model.

Tropo I just retagged your question to include the modeling software you are using.

Just use Dropbox or something similar and share the link.

Don't really have an answer for you, but in OpenStudio (a GUI for E+) you can control the number of timesteps per hour... OS defaults to 6 per hour. This would seem to suggest that you can changes the number of timesteps per hour without an error.

You'll need to purchase Sketchup to use OS, yes. Every version of sketchup I've used had an 8 hour free trial, then you had to purchase to keep using.

Stephanie, if you want to send your .osm file to me at benjamin.ratcliffe.work@gmail.com I can have a look at it, but I make no promises. There are better OS experts on this site than I :)

Make sure you have set the program to Do System Sizing Calculation as shown in the image above. This setting should be on if you are autosizing VRF. You should also turn on the Zone Sizing & Plant Sizing if you are autosizing everything.

The file is using version 1.4.0, if anyone has that on their computers - I am not able to open this file using version 1.6.0

Utility rates can currently only be added through a measure (such as the Xcel Energy Measure ) which sets up the EnergyPlus objects for you.

You can modify this measure to suit your own needs and match your own jurisdiction, but you'll have to directly manipulate the Tariff objects in EnergyPlus to get what you need. This page contains examples of various Tariff objects as they appear directly in EnergyPlus

This link has a comparison spreadsheet between the two proposed models, eQuest versus E+ (click on the Graphs tab to view the comparisons between the various end uses). I can explain away the differences in everything except fan energy and cooling (where the largest variances exist).

I'm actually inclined to favour the E+ results over the eQuest results in this case.

One issue that may or may not impact your decision - OS version 1.6 Sketchup plugin only works with 2015, and not previous versions. If you move to OS version 1.6 but don't have Sketchup 2015, this may cause you problems when you try to open the model for editing in Sketchup.

Perhaps some of the OS team here can work around this issue?

In Canada the MNECB has receptacle power densities by space type.

I certainly will post an update when the models are finalized. We are still trying to nail down the proposed in eQuest, because eQuest simply wasn't built to model this kind of building and the systems that are being installed.

I have a couple of comparison spreadsheets for both the proposed and reference buildings to compare between eQuest and E+ that I will post up when I get a chance, just to maybe stimulate the discussion.

The Sketchup Plugin for 1.6.0 only works with Sketchup 2015.

I suspect that perhaps you are using a version of Sketchup from before 2015, which is likely the source of your problem. This would be why your version of Sketchup is loading an older version of the OpenStudio plugin.

We're working on a small residence for a private school, and used eQuest for an initial model, with the intent to use OpenStudio for the final model submission in a few months. We have not submitted a model using OpenStudio before (and I'm really the only who has done any E+ work at our company).

The building has a number of features in it (VRF, DOAS, indirect water heating, external enclosure for VRF compressors) which aren't well modeled in eQuest, and required a number of workarounds which to me seem at best, grossly inaccurate.

My question is how much variance should be expected between the two models? Does anyone have experience with comparing the two engines and have an idea about where differences should be expected?

Currently, the lighting, equipment, and DHW are fairly well in line, with some variances due to how the buildings were specified within each software. These are fairly easily explainable. Where the problems are arising are with the fan and pump energy, as well as heating and cooling energy.

Any insights anyone has with comparing these two software packages would be very helpful.

This is definitely the side I favour. I think the programming community is much larger and more established, and it makes sense to have resources where the answers are immediately available with little clutter.

But our community is much smaller, and having an unfriendly, impersonal place may drive people to look elsewhere, if they think everyone here is unfriendly.

This is a duplicate question, is it not? https://unmethours.com/question/2344/...

HI Matt - I retagged this with EnergyPlus, but if you are using an interface like OpenStudio or Design Builder can you please retag your question?

How can I see the .inp file? Would help to make a more informed answer :)

Glad you solved it, Jenny :) Like I said, it really depends on the building on what solution will solve the problem. Every building is unique, and eQuest in my experience is a peculiar program - the most unexpected thing can be the cause of the problem.

Try autosizing your system heating/cooling capacities as well, if you've input these values - leaving it blank will cause eQuest to autosize the values.

Other reports which may or may not be helpful in diagnosing the problem: SS-P (System heating and cooling performance summaries), SV-A (system design parameters), SS-F (zone demand summary), PS-C (plant equipment summary)

Without seeing the actual model it's hard to nail down a specific cause... If you are willing, post the .inp and .pd2 files and I can try to have a look at it over the weekend, or perhaps others here can help you as well.

IMO this is exactly where energy modeling shines, to answer questions like this, and I would absolutely use an energy model in this situation.

Using a piece of software like eQuest and the Design Development wizard, you can quickly investigate a number of different system types. You won't be able to examine more exotic systems like VRF or other complex designs that don't fit into eQuest's neat little packages, but at least you can check out the majority of the standard system types out there, as well as investigating various ECM's that may wish to implement. A skilled eQuest user could bang out wizard models in a couple of hours, or maybe half a day. A master of EnergyPlus could likely do the same, but my own (somewhat limited) experience suggests that E+ requires a little more finesse and detailed inputs, which you wouldn't have at this stage of the process.

You could also examine a free piece of software like RETScreen - http://www.retscreen.net/ - which will let you try out various pieces of equipment.

In this case, you aren't generating the model for a client, but to help your design process and give more informed answers to the client. Without a model, you'd have to fall back on rules of thumb, and as you stated in your question, there are so many complexities involved in a design that rules of thumb will probably just get you into trouble later on.

First, read through this thread:

https://unmethours.com/question/359/w...

Although many suggestions are for EnergyPlus/OpenStudio, the same techniques will apply to eQuest.

There are many possible solutions. Examine your SS-R report, and find which zones are having issue - it may all be in one zone which can help to focus your efforts.

First, I'd look at your Throttling Range (at the zone level) - it defaults to 2F, which is a fairly tight range. Try 4F or even 6F, and see how much of an impact it has. This is particularly relevent for VAV systems.

Try autosizing the airflow/heat capacities, and see what eQuest thinks the capacities should be.

If you are using Floor Multipliers, heating and cooling capacities need to be entered at the zone level rather than the system level. In this case, it would show up in the SS-R report with the Mid level zones having the underheated/cooled hours, but the Bottom and Top floors are fine.

Also check your outdoor air rates - are you bringing in too much outdoor air? This would cause the systems to have to work harder to condition the air.

At the end of the day, if it is just one or two zones, you can add an electric resistance baseboard to cover the unmet capacity and reduce the hours to an acceptable range. This would be the very last resort though...

Starting with 1.5.4 OS uses EnergyPlus 8.2. This is more of a developer version, and unless you are comfortable with perhaps some bugs, I'd stick with the major versions (1.5.0). Version 1.6.0 should be coming very soon which will be compatible with 8.2.

With 1.5.0, you'll need to have EnergyPlus 8.1

I'm not certain you can do it with Ideal Air Loads, but with an actual HVAC system you can certainly make the systems available only for the night hours by creating an Availability Schedule, then run your simulation over the period of months you are interested.

I believe OS only has the Adiabatic Pipe implemented.

Is there anything different about a biomass boiler than a regular boiler, other than the fuel source?

This is a very peculiar behaviour in this model.

After looking at the .inp, I couldn't see anything immediately that was the cause.

I noticed that the model with daylighting had significantly higher autosized system cooling capacities than the model with no daylighting. This was on all floors, not just the floor with daylighting. You may want to try specifying the cooling capacity of each system in the daylighting model, with the autosized capacities from the non-daylighting model.

It could also be related to the windows - many of the windows on the third floor are specified using the "Simplified" specification method. I don't fully understand why, but I've been told that eQuest doesn't properly handle the angle of incidence of solar radiation to the window when they are "Simplified", and so it may not be giving you the correct solar gains in those third floor spaces. What this means is that when you turn on the daylighting calculation, it may be giving you too much solar gains in those spaces when it does the daylight calculation, resulting in higher cooling loads. You might try a window from the glass library and see if that makes a difference.

One other comment, Ashok, that isn't related to this problem, but I wanted to let you know - when you use the VRF curves provided by Daikin and import them into the eQuest, one of the heating curves doesn't import properly - the line is too long and eQuest truncates the exponent.

The curve "VRV Heating EIR-F-EWB/ODB AC" imports with coefficient number 4 as 7.145853, but it should be 0.07145853 in the model. Again, not a problem for you since you aren't using that particular curve, but could be a problem down the line. :)

You've also got no OA objects specified for those two thermal zones... did you add some in, as well as People objects to breath the outdoor air?

maximum outdoor air flow rate (10.0000) < minimum outdoor air flow rate (11.0000)
* ~~~ * To set the minimum outside air flow rate use the "Design (minimum) outdoor air flow rate" field in the Sizing:System object

Bolded line appears to be your error. Your maximum OA flow is specified to be lower than the minimum specified OA flow.