Baseboard/Fin Tube Coil Loads

6 posts / 0 new
Last post

Dear eQuest users,

I'm a novice eQuest user who is looking for some help regarding a project. I've used these forums to help gain knowledge of the program and how to make sense of it for my own work; however, the learning curve has been steep.

I developed a model for an existing building in conjunction with an onsite energy audit. In addition to completing an energy analysis and simulation, we are required to develop peak hourly heating and cooling loads for potential design of a GSHP system. The building uses 5 AHUs each with chilled water coils for cooling and hot water coils for heating. Additionally, there are fin tube radiators around most of the perimeter of the building. My goal is to disaggregate the ventilation portion of the peak heating load from the baseboard portion of the peak heating load. My research online and combing of forums indicates that disaggregating ventilation loads using eQuest is not a simple process. My initial thought was that if I can determine my hourly baseboard heating loads, I can estimate that the ventilation load accounts for the rest of the building's hourly heating load. However, after running an hourly simulation, I noticed that the heating coil load on the CIRCULATION-LOOPs that serve the fin-tube radiators show 0s from 1 AM - 6 AM. To verify this, I added "Zones" into my hourly simulation and noticed the same issue-0 "Baseboard heat output to zone (Btu/hr)" during hours from 1 AM - 6 AM.

On the Air-Side, the baseboards are controlled via "Outdoor Reset", and I verified that the reset schedule at the system level wouldn't preclude the baseboards from running during those hours. On the Water-Side, I verified that the boiler is in operation during those hours via a boiler schedule and that the actual HW loop serving the baseboards is in operation during those hours via a baseboard loop schedule as well. Based on the OA temp and the zone temperature (which is below the heating throttling range), the fin tube radiators should be operating per the model (and that's also how they operate the building in real life, as well).

I've seen the folks on this board provide some excellent advice and insight to other posters, so I hope you can do the same for me here! I'd appreciate if anyone can provide some insight as to why they think the fin tube radiators are showing 0 between 1 AM and 6 AM but seem to operate fine during the rest of the day. If you have any questions about the model or need more information, I am more than happy to oblige.

Scott Burger BEAP | Energy Engineer | scott.burger at
855 Route 146, Suite 210, Clifton Park, NY | 12065 | USA
T. +1 518 250 7261 | F. 518 371 2757

Connect with us! | LinkedIn | Twitter | Facebook | Connect App

[cid:image001.jpg at 01D5F84A.E2C29910]

[cid:image002.jpg at 01D5F84A.E2C29910]

Be green, leave it on the screen.

This email and any files transmitted with it are the property of Arcadis and its affiliates. All rights, including without limitation copyright, are reserved. This email contains information that may be confidential and may also be privileged. It is for the exclusive use of the intended recipient(s). If you are not an intended recipient, please note that any form of distribution, copying or use of this communication or the information in it is strictly prohibited and may be unlawful. If you have received this communication in error, please return it to the sender and then delete the email and destroy any copies of it. While reasonable precautions have been taken to ensure that no software or viruses are present in our emails, we cannot guarantee that this email or any attachment is virus free or has not been intercepted or changed. Any opinions or other information in this email that do not relate to the official business of Arcadis are neither given nor endorsed by it.

Burger, Scott's picture
Joined: 2020-04-06
Reputation: 0

Hi Scott,

A couple of quick observations:

- While "OA Reset" is the default control mode for baseboard heating, I'd suggest that "Thermostatic" is more representative unless you specifically have a reason for applying a schedule to your baseboard heating. That change may resolve your issue.

- Baseboard heating is applied first before zonal heating - so size your baseboard heating carefully

- Baseboard heating is not autosized unless you are using DOE-2.3 so you will have to explicitly determine the baseboard heating capacities in the zones.

Beyond that you may wish to share the .inp and .pd2


Brian Fountain
d 416 572 8501 m 416 562 6831

Brian Fountain's picture
Joined: 2019-05-02
Reputation: 0

Hi Brian,

I appreciate the quick response and your initial insights.

1. I tried adjusting the control method to "Thermostatic", but unfortunately that did not alleviate my issue. I previously defined baseboard heating capacities manually per zone, but I'll have to be cognizant of those capacities if I leave it as Thermostatic. In your opinion, why do you indicate that Thermostatic is more representative that OA Reset?
2. Oddly, changing the baseboard heating source to electric and returning the baseboard loop source to default (aka removing it's attachment to the HW loop), now shows baseboard loads all throughout the day. That indicates to me that there is an issue on the Water-Side that is preventing the baseboards at the zone level from operating between 1 AM and 6 AM. Any thoughts on typical water-side issues that would lead to this discrepancy (ie. loop/boiler schedules, baseboards attached to primary vs. secondary HW loops, etc.)? Since the baseboards show loads from 7 AM and on, my gut tells me that it indicates more of a scheduling issue than anything else, but frankly I'm baffled as to how the schedules are precluding those hours based on what I see.

Scott Burger BEAP | Energy Engineer | scott.burger at
Arcadis | Arcadis of New York., Inc.
855 Route 146, Suite 210, Clifton Park, NY | 12065 | USA
T. +1 518 250 7261 | F. 518 371 2757

Connect with us! | LinkedIn | Twitter | Facebook | Connect App

[cid:image001.jpg at 01D5F857.D998F160]

[cid:image002.jpg at 01D5F857.D998F160]

Be green, leave it on the screen.

Burger, Scott's picture
Joined: 2020-04-06
Reputation: 0

I'm might not phrase that the Thermostatic option is more "representative," but perhaps this more commonly reflects new construction/design, in some regions/localities. Fundamentally, Thermostatic means that the application/delivery of baseboard heat is dependent on a thermostat somewhere within the zone. In real world terms this may be an independent thermostat on the wall, or else tied to a thermostat also signaling with a fan-driven heating source. I might say this behavior of tying local heat deliver to local conditions is perhaps more intuitive, and therefore more likely "representative" of what many modelers would want to see if they had no designed system/sequence to reference. OA Reset however isn't really uncommon, and I would say is typically the most accurate option for existing/aged perimeter heating systems I'm typically modeling from around the midwest (USA). OA Reset allows you to, with a schedule, either define a hard "snap" of heating availability based on an outdoor temperature threshold, schedule that availability based on the calendar/season, and/or allow for a linear application of heat between a range of temperatures. A common inference is that there is NO thermostat in the zone limiting or causing the application of heat, so inherently you have more potential to introduce unmet hours as zones on the same heating loop have unique special snowflake needs hour over hour... however this is reality for many buildings. Baseboard heating loop/operation instead determined/scheduled by manual operation or within a BAS.

By observing no change in the outcome after switching to thermostatic, you've verified the issue isn't rooted in your scheduling efforts so I'd switch back for now. I would intutivelly look next to other inputs that could lock out operations of the baseboards - namely operations for the associated boiler(s) / loop(s) which could have stuff like snap schedules or other inputs preventing the delivery of heat to the baseboards... but it appears you may have already done that.

For clarity, I think you might have developed a more difficult set of questions for yourself by asserting "Ventilation Loads + Baseboard Heat Delivery = 100% of all heating." This would infer that your central heating coils have zero potential contributions anytime the OA dampers are shut... i.e. Return Air is always a comfortable 70 degrees. There are likely some skin loads and infiltration loads that the perimeter baseboards are not directly handling. If your ultimate goal is to isolate your ventilation heating loads, you might more simply make a copy of your model (after resolving the baseboard heat delivery situation and any other edits you want to make), then zero out all ventilation delivery in the copy (remove zonal OA inputs and set the AHU's to a fixed fraction of zero). Simulate and now you have all "non-ventilation loads" to compare / difference against your normal model's heating loads.

There are probably better ways, and I know eQuest 3.65 (in doe2.3 mode) has some new/enhanced systems load reporting I haven't fully explored, but that's an approach I've used in past years for similar ends.


[cid:image001.jpg at 01D5F91B.C92DE8C0]
Nick Caton, P.E., BEMP
Senior Energy Engineer
Energy and Sustainability Services
Energy Performance Contracting

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

[cid:image005.png at 01D5F885.DB42BAE0]

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

To clarify what you might see in the building - obviously a thermostat that controls a radiator could be a match for "thermostatic" control - if these controls are known to be used and operable condition.

There is also a common control valve mounted directly on the supply to the radiator, two frequently observed models are made by Danfoss and Honeywell, which has numbers 1-10 and a user could dial more or less heat output - although not literally tied to a temperature could also be modeled as thermostatic if the users are changing the dials as a feedback on temperature and if the controls are operable.

During a building walkthrough you may observe operable windows to be open, hot room temperatures, or other issues even where these control devices are present which might encourage you to model as OA Reset (or not reset as the case may be, but scheduled for plant availability or "snap" on and off with OAT).

Where this approach may introduce simultaneous heating and cooling it may not be as simple as adding the loads from zone and system together in order to size a new integrated system - it would be best to run a forward-looking load calculation, influenced by information that you observed.


David S. Eldridge, Jr., P.E., BEMP, BEAP, HBDP, GGA

Direct: (847) 316-9224 | Mobile: (773) 490-5038

Grumman/Butkus Associates | 820 Davis Street, Suite 300 | Evanston, IL 60201
Energy Efficiency Consultants and Sustainable Design Engineers | Blog | Facebook | Twitter

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

Since the initial question included ? a model for an existing building in conjunction with an onsite energy audit. In addition to completing an energy analysis and simulation, we are required to develop peak hourly heating and cooling loads for potential design of a GSHP system. The building uses 5 AHUs each with chilled water coils for cooling and hot water coils for heating. Additionally, there are fin tube radiators around most of the perimeter of the building. My goal is to disaggregate the ventilation portion of the peak heating load from the baseboard portion of the peak heating load?

I?d say, absolutely model baseboards as thermostatic for this effort of sizing ?peak ? loads for a potential GSHP system.? IF in fact the baseboards will even be kept. At the least they will need to be replaced with Euro-style radiators which can heat with lower-temperature HW and those new ones will certainly have thermostats per zone if someone is going to all this trouble to install loop fields or wells or whatever for this electrification effort.
You can segment out the load on the AHUs and the perimeter loop from system, zone or loop reports. If the AHU operation includes recirculated air, those AHU loads will not ONLY be ?ventilation loads? but they will be the entire AHU loads.

And that?s IF the GSHP system is even going to be a ground loop serving HW/CHW WWHP system, retaining all this existing stuff. Or is the goal to replace the existing HVAC with some DOAS units, and provide DX GSHPs at the zones so baseboard heat isn?t even needed? The ?ventilation load? in that case would come from the loads on the new model?s DOAS, which would likely include energy recovery and only OA. As you?ve gathered, there is no direct output of ?ventilation loads? in eQUEST?s system reports. Best I can figure is to run a model with design OA and no OA and calc the difference.

As far as modeling the existing building, if the model using ?thermostatic? baseboards vastly underpredicts the gas or oil use, then changing the baseboard control to OA-reset might represent the system better, but as noted on the thread, those inputs require a lot of prep work to correctly represent operation and capacity. There are many ways older HW loops and buildings can waste heating energy. Many HW loops are under some form of what I call manu-matic controls. For instance the HW temperatures are probably automatically controlled to a setpoint or reset schedule, but that setpoint may be manually adjusted seasonally by an operator, and usually a HW loop will be turned off for some ?summer? period. So inputting all the schedules associated with these modes is why accurately modeling actual existing HVAC control for calibration and savings calculation can be very time-consuming.

Note the control of the airflows and SATs from the ?5 AHUs? needs to be reasonable for your baseboard loads to be reasonable, even with thermostatic control. If separate zone terminal unit reheat is not modeled, the output of the baseboards will include heat to offset the cooling effect of SAT. (And actually, I recall a footnote somewhere in the eQ documentation, that even if reheat coils are input, the thermostatic zone BBs are always modeled as outputting heat up to the limit of their capacity, before the zone reheat kicks on. So that baseboard load will be greater than the perimeter envelope load. ) It was never noted if these AHUs were VAV, or CV, and how the airflow and OA is controlled. And you are right, the baseboards should not be off during the night unless some schedule is turning off the loop or pumps, or the reset schedule itself is doing it.

Good Luck! Hope that didn?t ramble on for too long.
P.S. it would be good to discuss expected design conditions with whoever is asking for you to ?develop peak heating and cooling loads? for some new HVAC equipment. Design engineers have a pretty structured way they do design loads, which differs from using TMY data and typical schedule sets in BEM. Their methods can be mimicked by inputting design days, or maybe they understand and prefer outputs from the actual year simulation. Back in my earlier modeling days, I recall a few uncomfortable situations when design engineers waited for simulation outputs to inform their design, and then basically tossed them out and went on to hurry up and do the loads for sizing themselves.

Porter, Fred's picture
Joined: 2015-02-03
Reputation: 0