CEE 243 Q9–Radiant SlabCEE 243 Q9 Radiant Slab Ricardo MaduroWhere is the Radiant Slab: Common Area/Entrance/Café Seating Area :Rdi Sl bRadiant SlabSummary TablePeriod: Apr 1 2009 –Apr 25 2009 ‐ During this period the booster pump was always offThese are On/Off Points or 0‐100% points. That is what causes the phigh variance coefficient. Functional Requirements: –The system should not turn on when OAT > 78F. ‐SlabSetpoints(71F and 66F) are measured as the aver age betweenSlabSetpoints(71F and 66F) are measured as the average between SpaceTemp and SlabTemp. To achieve these set‐points the valve should open/close in 10%, 5%, or 1% increments. Response: –When OAT >78F heater valve was never open = OK.‐ The heater valve did not open/close in the described increments. Response: –Theaverage between SlabTemp and SpaceTemp was never below to the set‐points of 71F and 66F. Still, the slab provided heating to the spaceNOTE: This average is the average of 6temperaturesthe space. NOTE: This average is the average of 6 temperatures. ‐Was the SpaceTemp OK?Response: –The SpaceTemp was OK most of the time, and also when the OAT was >78F (closed heater valve). ‐Some nights, when OAT<55, SpaceTemp drops under ~67FBehavior ‐‐ What allows the radiant slab to have a positive impact in the space’s temperature is the good correlation between OAT and the SupplyTemp (vs. th l i/li) d th lthe valve opening/closing) and thermal mass.‐ There seems to be no recirculation (?, lost energy) .‐ Would be good to have a sensor that measured flow.Radiant Slab Updated Datapoints: The SupplyTemp is increasing thus the system is heating at night (and the building is probably being flushed!), and the SpaceTemp is OK = Error! ‐Did this behavior improve?<Night period: 5:30 pm to 12:30 am><‐Night period: 5:30 pm to 12:30 am ‐>Radiant Slab Updated Datapoints: Position just changed from 5% to 100% and has some random points. Recommendations to the Building Owner•The system seems to be responding well to the OATSlabOffSetPoint•The system seems to be responding well to the OAT SlabOffSetPointso leave behavior the same.• The valve open/close system does not behave as expected (10%,5%, or 1% increments) it just turns on/off or just varies between 5% and 100%. Investigate what is the valve position responding to (could start by checking response to setpoints).•The Sequence of Operations document does not describe whenThe Sequence of Operations document does not describe when recirculation shall be used. This should be revised because there seems to be opportunity for it. Start by checking if the recirculation valve/pumpis ever opening and what is causing it to openvalve/pump is ever opening and what is causing it to open.• Check points that all sensors that describe electric load are accounted for, and are calibrated.Recommendations to Owner: Electric Load –The calculated electricity is consistently lower than data from Cardinal CoGen. The trends are similar except for a few glitches.similar except for a few glitches. Electricity Consumption - kWDuring this period the system seems to have stopped recording new measurements. Something 450.0Calculated Electricity Electricity Datagcaused it to record a constant value.300.0350.0400.0W)150 0200.0250.0Energy (kW0050.0100.0150.00.00 20000 40000 60000 80000 100000 120000 140000 160000Time (mins)Simulated vs. MeasuredThe simulation is following schedule that does not correspond to reality. Simulated vs. MeasuredDifference is notDifference is not always large, but inputs to this simulation should b idOpposite trends.be revised. Simulated vs. MeasuredIs this being simulated at all? The simulation did record something so maybe a schedule was notschedule was not defined?Simulated vs. MeasuredThe simulation result is close to double the actual data. This difference in water supply temper ature creates a significant impact on energy costs between model and reality. (Does the model use the supply temper ature for all other systems in this loop?)other systems in this loop?)Simulated vs. Measured – WAO! (?) • Architectural elements to model: Basic BIM Guide for a Radiant Slab:– The slab itself and its massing.– The slab’s insulation from the soil–the walls and windows of the room with their insulation.•HVAC Systems to model:Pumps valves that control flow the pipes•HVAC Systems to model: Pumps, valves that control flow, the pipes (the spacing between them, the length embedded in the slab, and their capacity to transfer heat), and some control system (i.e.: a thermostat). – Energy+ can be used to model radiant slabs.http //gundog lbl gov/dirpubs/epl cool pdf–http://gundog.lbl.gov/dirpubs/epl_cool.pdf5 Rules: 1)Define and communicate set‐points and explain the basis for them (i.e.: where do the 78,71, and 66F set‐points come from?) 2) Define and communicate traceable paths/responses that the system should follow. 3) Define desired goals/outcome and systematically compare them to the set‐pointsto correct problemsthe setpointsto correct problems. 4) Anticipate counterproductive interactions and correct them first (i.e.: Hti t iht h tti b tit)Heating at night when temperature is above set‐point). 5) Do not disregard information that seems to be correct, find out if the system is meeting its goal as you expect it to.