baseboards activating when zone is already above heat setpoint?

9 posts / 0 new
Last post

Hi all,

I hope you're able to see the image below. If not, I uploaded it here: https://imgur.com/a/WpQ8FSR It shows eQuest 'hourly results', specifically it shows a warm day in the year, July 3rd, for a model I'm looking at.

In my model, from 1pm-4pm on July 3rd, the heating setpoint is 71 ?F (grey column), cooling setpoint is 76 ?F (blue). Outdoor temp is ~84 ?F (orange), zone temps are ~75-77 ?F. The question is, why are my baseboards (yellow column) activating and heating the zone? The temp in the zone is above the heating setpoint, so the baseboards should not be turning on.

The baseboards are set to 'thermostatic' control. I've been unable to set baseboard schedule (see 2nd screenshot below - if anyone has a suggestion for this problem, I'd love to hear it). But regardless of the schedule, if the zone heat setpoint is 71 ?F, and zone temp is above 74 ?F, why are baseboards turning on?

Cheers,
Matthew

Matthew Yarmon's picture
Offline
Joined: 2020-08-21
Reputation: 0

The zone temp is after the net effect of the systems so it may be in range because the baseboards ran - is there an airside system that could have overcooled?

DSE Mobile
773.490.5038

David Eldridge's picture
Offline
Joined: 2012-05-08
Reputation: 1

Hi Matthew!

A couple thoughts:

* Baseboard operations can be specified at both ZONE and SYSTEM levels. I?m not entirely sure (intuition alone) which takes precedent if you have both. You may want to review what is entered at the SYSTEM level under the heating tabs? that could explain the delivery of heat at a time when the zonal temp conditions do not warrant the baseboard?s operation.
* Regardless, applying a schedule to the baseboards (and/or baseboard loop, if you have that set up as a distinct loop in the hydronic tab) can probably override this behavior by making the baseboards only available when seasonally appropriate (by calendar) and/or by utilizing an OADB snap temperature threshold to limit baseboard heating availability.
* An error popping up in application of a schedule is possibly what it?s saying on the tin: the schedule may simply an incompatible type (the only valid option for BASEBOARD-SCH is RESET-RATIO)? but sometimes the eQuest interface is just behaving badly. If you?re uncertain the schedule (annual/week/day schedules inclusive) are of an appropriate/compatible type, then I?d advise starting from scratch by first loading in a compatible library schedule, and adjusting from there. If you are confident the schedule is of the correct type, then I might try ?forcing? this assignment by saving a separate copy of your project, closing eQuest, adding the appropriate assignment to 1 zone via the INP file in a text editor of your choosing, then opening that modified project to see if it ?sticks.? If so, then you may likely be able to proceed with assigning that schedule to the remaining zones as appropriate.
* Might be worth noting, if you want to control baseboard heating availability at the circulation loop level, you?ll have a couple few more viable options in terms of schedule type.

I hope this is helpful!

~Nick

[cid:image006.jpg at 01D67C6E.61F63320]
Nick Caton, P.E., BEMP
Senior Energy Engineer
Energy and Sustainability Services
Energy Performance Contracting
D
M
E

913 . 564 . 6361
785 . 410 . 3317
nicholas.caton at se.com
15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219

[cid:image003.png at 01D67C6D.8E983EB0]

Nicholas Caton2's picture
Offline
Joined: 2019-03-25
Reputation: 0

I suggest removing the baseboard schedule. It is supposed to be used only
when baseboard output is controlled based on outdoor temperature,
independent of zone temperature. So leave the baseboard schedule as
"undefined" and set the zone control to "thermostatic". Does that work?

-Erik

*Erik Kolderup, PE, LEED AP*
erik at kolderupconsulting.com | 415.531.5198 | www.kolderupconsulting.com

On Thu, Aug 27, 2020 at 10:34 AM Nicholas Caton via Equest-users <

Erik Kolderup's picture
Offline
Joined: 2011-09-30
Reputation: 0

Ah ? fair point Erik!

The RESET-RATIO schedule type is intended to allow for a scaling of the baseboard output in relation to OADB, and that certainly could a degree of functionality you don?t truly need. If you do need (only) seasonal ON/OFF availability control, that?s probably more simply/intuitively accomplished with a schedule on a baseboard loop, oftentimes.

That said, I?ve perhaps ?misappropriated? the RESET-RATIO scheduling option, above and beyond its intended functionality, to solve the simulation of a variety of baseboard operational situations. You can for example:

* Set up a RESET-RATIO DAY schedule to scale its output between a factor of 0.0 and 0.0 (not a typo) to effectively make the baseboard unavailable for a certain portion of the year, then use a ?normal? day schedule scaling up to 1.0, for the times it?s supposed to be active.
* Set a minimum turndown of something like 0.2 or 0.5 to explore and simulate the reality of stuck/leaky valves that result in the introduction of heat independent of ZONE comfort needs (sometimes generating unmet hours and/or simultaneous heating/cooling).
* Tightening the temperature thresholds on a DAY schedule (i.e. 55.0 Low and 55.1 High) can effect a binary ?ON/OFF? availability, similar to SNAP scheduling. This is sometimes a more appropriate reality for baseboard thermostatic valves than a gradual introduction of HW flow over a range of temps.
* You can if needed layer any of this with parallel scheduling on the baseboard loop to capture independent boiler scheduling and/or circulation loop valve controls.
* It?s appropriate to note ? this flexibility/granularity of baseboard operational behavior can sometimes toe or cross the line of ?more than the modeler can know/measure.? Keep that perspective in mind to temper your presented findings and personal expectations, as you leverage these techniques to explore building system behavior and energy savings opportunities.

So granted, a RESET-RATIO schedule may end up being a case of hammering a nail with a wrench in some contexts? but it?s a relatively flexible tool to get the job done for a variety of real-world circumstances. This might also be the case of ?when all you have/know is a hammer, then every problem looks like a nail.?

~Nick

[cid:image002.jpg at 01D67C79.62603E90]
Nick Caton, P.E., BEMP
Senior Energy Engineer
Energy and Sustainability Services
Energy Performance Contracting
D
M
E

913 . 564 . 6361
785 . 410 . 3317
nicholas.caton at se.com
15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219

[cid:image003.png at 01D67C73.2BBBA790]

Nicholas Caton2's picture
Offline
Joined: 2019-03-25
Reputation: 0

Hi Nick,

Huge thanks, you've pretty much solved my problem. I didn't know that "RESET-RATIO" was the only schedule type allowable for baseboards.

I've got it set up now as a reset ratio schedule, and as you can see, the baseboards are off when outdoor dry-bulb is above 65 ?F. I'll fine-tune the actual temperatures based on what I need, but for now this does help. I changed the baseboard control type from 'thermostatic' to 'outdoor reset' as well in the spreadsheet. I'm also going to look into using the other method you suggested, updating the circulation loop details.

Screenshots below for those interested:

Greatly appreciate your help!
Matthew

Matthew Yarmon's picture
Offline
Joined: 2020-08-21
Reputation: 0

The group has been very helpful today regarding the baseboard heating issue I had. I have a few more basic questions I've been itching to ask:

(1) If I place a new shell directly above an existing shell, how to I tell eQuest that the existing shell's roof is no longer exposed to the outdoors? I'm wondering how to do this in both Wizard mode and Detailed mode. (A work-around I've come up with is to set the existing shell's roof to an impossibly high R value.)

(2) I have two shells in eQuest, separated by an unknown distance. I'd like to measure the distance between the shells so I can position them as needed. Is there a way to measure this? I would then go into the shell and adjust its position on Screen 1 in the Wizard ("Specify Exact Site Coordinates"). (Or I could adjust in Detailed mode, although I haven't adjusted shell position in Detailed mode up to this point.)

(3) In Detailed Design wizard mode, how do I add exhaust fans (or can exhaust fans only be added in detailed mode)? I only see an option for supply fans. I know how to add them in Detailed mode, but not Wizard mode.

Thanks again,

Matthew

Matthew Yarmon's picture
Offline
Joined: 2020-08-21
Reputation: 0

Happy to be of assistance - I hope you'll stay engaged with the list and perhaps join us in helping others as you build your skillset/expertise (best way to learn is through teaching)!

(1) If I place a new shell directly above an existing shell, how to I tell eQuest that the existing shell's roof is no longer exposed to the outdoors? I'm wondering how to do this in both Wizard mode and Detailed mode. (A work-around I've come up with is to set the existing shell's roof to an impossibly high R value.)
In wizards, where you have a dropdown to assign a roof construction, there's an option to say "No exterior exposure (adiabatic)." This is the most direct way to handle this from the wizards, and will result in an adiabatic surface being generated (similar to what happens when you have two shells side by side with overlapping exterior perimeters).
In detailed mode, you can improve on that outcome by changing the interior surface generated this way into a heat-transferring surface (Assigning a construction), for which you'll need to assign a NEXT-TO space (typically from the floor above). This is however often a lot of work for very little if any meaningful effect. It may be helpful to first consider whether and where you anticipate a significant state of temperature differences for which intra-zonal heat transfer is something you want to quantify/incorporate.
In detailed mode, to swing in a simpler direction, you can simply delete any exterior (roof) surfaces that were generated by accident. This could leave a visible "hole" in your model (aesthetic hit?), but in terms of function you aren't losing anything relative to assigning an adiabatic surface, other than the thermal mass of that construction.
For cases with partially exposed roofs (where the 2nd floor doesn't totally cover the 1st floor shell, leaving some actual roof area), I often end up employing a combination of these techniques to ensure I have the right amount of exposed roof construction, but no other exterior surfaces "sandwiched" between shells.

(2) I have two shells in eQuest, separated by an unknown distance. I'd like to measure the distance between the shells so I can position them as needed. Is there a way to measure this? I would then go into the shell and adjust its position on Screen 1 in the Wizard ("Specify Exact Site Coordinates"). (Or I could adjust in Detailed mode, although I haven't adjusted shell position in Detailed mode up to this point.)
My first response, only appropriate to me and others who typically develop their floor plans in CAD first... is to simply scale off the differences within your CAD platform of choice.
Assuming you don't have that effort in place, this is achievable in Wizards / Detailed, but I think easiest in Wizards, if you have the option:

1. I would personally advise, for sanity reasons, starting by ensuring all shells are positioned using exact site coordinates, with X & Y = 0. This will ensure all shell geometries share a common X/Y coordinate-system. I kind of wish this was the default behavior for the wizards, as I consider it a best practice that will help beginners avoid/simplify a series of potential pitfalls in shell positioning. Allow Z coordinate to vary for different shell elevations.

[cid:image002.png at 01D67D21.03706A60]

[cid:image008.png at 01D67D21.03706A60]

1. For the shell you want to shift: Navigate to the 2nd shell wizard screen, and enter the "custom" option for defining zone/perimeter inputs. Note that you can use the "Background" dropdown to select the another shell of interest and it'll pop up for reference.
2. Use the selection tool to select (activate/highlight) a reference vertex of interest. In this example I've selected the right-most vertex of the triangle-shaped shell. This will highlight the vertex coordinates in the list on the left (X = 223.6, Y = 0.00). Jot that info down (or take a screenshot - this works too).

[cid:image010.png at 01D67D2B.A1E4F210]

1. Before leaving this view - identify where you want your selected vertex (right-most on the triangle) to move/land. I'm going to shift this triangle shell such that the selected vertex is "on top of" the right-most vertex of my diamond shell.

[cid:image011.png at 01D67D2B.A1E4F210]

1. Now we just need to figure out the X/Y coordinates for the landing spot. Open up the same custom zoning input window for the other shell, highlight the "landing spot" vertex, and note the coordinates again (234, 132):
[cid:image006.png at 01D67D2A.91F8D2F0]

1. Now we know enough to triangulate the distance (A2 + B2 = C2) between the two points if all you need is distance. To complete the action of shifting the shell:
* In wizards: Break my rule of always using 0 for exact site coordinates of the shell (first screen of input), and enter the relative corrections necessary for each axis
* In detailed: You can do the same shift by double-clicking the shell to be moved in the component tree, then editing the X/Y coordinates there accordingly.
(3) In Detailed Design wizard mode, how do I add exhaust fans (or can exhaust fans only be added in detailed mode)? I only see an option for supply fans. I know how to add them in Detailed mode, but not Wizard mode.
DD Wizard screen 14 --> Zone Details... --> Exhaust Fans. You'll probably want to first tweak the zone groupings first to effect something like a "restroom block" to ensure the input exhaust is only applied where it's actually happening.
You should find any CFM input here replicated/distributed in detailed mode under the HVAC tab, zone inputs, Outside Air & Exhaust for the dropdown.
[cid:image007.png at 01D67D2B.5E717D50]
(note these sum to 250 CFM, per the preceding wizard input - exhaust is distributed in proportion to each zone's area in the group)
[cid:image013.png at 01D67D2B.A1E4F210]

[cid:image015.jpg at 01D67D2B.A1E4F210]
Nick Caton, P.E., BEMP
Senior Energy Engineer
Energy and Sustainability Services
Energy Performance Contracting
D
M
E

913 . 564 . 6361
785 . 410 . 3317
nicholas.caton at se.com
15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219

[cid:image003.png at 01D67D1E.46263BD0]

Nicholas Caton2's picture
Offline
Joined: 2019-03-25
Reputation: 0

Hi Nick

I could probably post this to the group but it's a simple question: can the DOE 2.3 DOAS feature be added in Wizard mode, or only in Detailed mode?

And is it folly to try to convert a DOE 2.2 model to DOE 2.3 to add DOAS?

Cheers,

Matthew

Matthew Yarmon's picture
Offline
Joined: 2020-08-21
Reputation: 0