[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [EnergyPlus_Support] Radiant Floor vs Forced Air





Although the zone criteria for oda is the same in both models, check the supplied air from the DOAS is far less than the non-100%ODA system. You may have a cold zone that e+ AHU is doing it's best to heat with ODA. (especially, but not exclusively if you are supplying a human 18-23 degC air temp)

As for radiant systems, the number 1 thing to track is surface temp. For the heated floor, 28 C is good...40 is bad.

Lastly, consider dropping the room air thermostat heating temperature by 1-2 degC, due to the raised operative temperature.


Am 11.12.2017 1:10 vorm. schrieb "Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>:
 

Dear Forum,

I'm comparing performance of a forced air heating system against a heated floor for a 100K ft2 (~10K m2) warehouse ... and I've never evaluated a heated floor energy model so I am not quite sure how it "thinks". 
  • I have confirmed that geometry, materials, setpoints and schedules are identical.
  • The forced air system uses a gas-fired 92% efficient heating coil and a fixed minimum outdoor airflow for ventilation.
  • The heated floor uses a gas-fired 94% efficient boiler, and also has a DOAS that introduces the identical outdoor airflow of UNheated air into the zone.
  • The heated floor system has 2" (~50mm) EPS insulation under a concrete slab, while the forced air system has no underfloor insulation
  • It seems that the heating energy for both systems should be moderately close - same minimum outdoor airflow, same zone heating load, very similar heating efficiency ... but my results are 240% MORE natural gas energy for the heated floor.
  • Unmet load hours are ~300 for both models
  • Both systems provide no heat in the summer months
I've compared IDFs and see no errors, yet the gas difference makes no sense to me - so I must be missing something. Can you offer any suggestions?

p.s., IDFs attached in case anyone has time to review them, but I'm mostly wondering if there's something about how the heated floor works which is substantially different than forced air and requires, for example, a different control scheme.

--

James V Dirkes II, CEO / President
The Building Performance Team Inc.
1631 Acacia Dr, Grand Rapids, MI 49504

(alphabet soup of efforts for greater understanding: PE, BEMP, BCxP, LEED AP)

Direct / Mobile: 616.450.8653
jim@xxxxxxxxxxxxxxxxxxxxxxxxxxm

Website l  LinkedIn

Coffee conversation: Caring about truth means that we will look for evidence that disproves our proposition with the same diligence that we look for evidence that supports it.





__._,_.___

Posted by: Jean Marais <jeannieboef@xxxxxxxxx>


EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx

The EnergyPlus web site is found at:
http://www.energyplus.net/

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are currently allowed but be mindful that not everyone has a high speed connection.  Limit attachments to small files.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the &quot;search&quot; button.




Visit Your Group
Yahoo! Groups
PrivacyUnsubscribeTerms of Use

__,_._,___