Unexplained Water Temperature Out of Range Warnings in EnergyPlus

asked 2015-06-04 13:43:46 -0600

mleach
556 ●5

updated 2015-08-11 18:23:57 -0600

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I have a model with three plant loops: one for space heating, one for space cooling, and one for domestic hot water. I'm getting large numbers of the following warnings:

* Warning * GetSpecificHeatGlycol: Temperature is out of range (too high) for fluid [WATER] specific heat *
* ~~~ * ..Called From:PlantLoopSolver::UpdateAnyLoopDemandAlterations,Temperature=[5024.90], supplied data range=[0.00,125.00]
* ~~~ * Environment=RUN PERIOD 1, at Simulation time=01/01 21:15 - 21:30
* Warning * GetSpecificHeatGlycol: Temperature is out of range (too low) for fluid [WATER] specific heat supplied values *
* ~~~ * ..Called From:PlantLoopSolver::UpdateAnyLoopDemandAlterations,Temperature=[-43.64], supplied data range=[0.00,125.00]
* ~~~ * Environment=RUN PERIOD 1, at Simulation time=01/02 14:00 - 14:15

I've seen similar warnings before and they usually indicate that plant loop temperatures are outside of intended range. I looked at detailed timestep data for each plant loop, however, and I don't see any indication that my loops are not controlling properly. If my plant loop supply side inlet and outlet temperatures look normal, what else could be causing these warnings?

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1

Might be worth reporting out ALL the node temps and flow rates for each plant loop. Maybe you're hitting these temps in one of the bypass branches when there is really low flow or something.

aparker ( 2015-06-10 10:30:46 -0600 )edit

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answered 2015-08-12 15:22:26 -0600

kwalkerman
1482 ●8 ●9

I have had similar warnings in loops where low flows are mismatched to equipment capacity - for example, if there is low flow through a chiller, the chiller may cycle on to meet the loop setpoint and over-cool the fluid. When this happens, sometimes the model also runs slowly, as the iteration bounces back and forth between turning the equipment on and off. Check temperatures at a number of nodes on the loop, as well as flow through these loops.

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answered 2016-09-03 16:49:10 -0600

Alex Vlachokostas

928 ●4 ●15

updated 2016-09-03 22:49:07 -0600

@mleah I had the same error. Oddly enough, I did not have any glycol fluid type in my system. Although it might seem unrelated... what fixed the problem in my model was correcting the fileds at the WaterHeater:Mixed object. My model had a Solar Tank Storage and a Instantaneous/Tankless system. Both are modeled as WaterHeater:Mixed objects but for the Solar Tank Storage system the !- Heater Maximum Capacity {W} field should be 0 and for the Instantaneous/Tankless system the !- Heater Maximum Capacity {W} field should be 845000. There is a similar question on unmet hours here

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@Alex Vlachokostas to clarify, the GetSpecificHeatGlycol algorithm in EnergyPlus is called to check the fluid properties for ANY plant loop where a liquid circulates -- even if that loop doesn't contain glycol. You can read more about this in my answer to this post.