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No heat from water to air loop in OpenStudio

asked 2016-04-20 06:07:15 -0600

Urado gravatar image

updated 2016-04-20 09:24:40 -0600

Starting from the OS template 'Packaged Rooftop VAV with Reheat', I tried to change the terminal for VAV NoReheat. I have no errors, but there is no heating in my zone.

To illustrate:

  • This case works fine (some unmet hours but no problem with the simulation):


  • But this case doesn't work:


I don't think there is any problem with the object AirTerminal:SingleDuct:VAV:NoReheat, as it works fine with other cases such as:


What I have tested: different setpoint manager, supply air temperature, variable or constant fan/terminal, hardsized some parameters... In all cases the result is the same: no heating !

For all my tests, the common point when the problem occurs is the presence of a 'Coil:Heating:Water' and a AirTerminal:SingleDuct:VAV:NoReheat. So I think the problem is between the water and air loop. The E+ Output:DebuggingData also shows some strange behavior. For example the node between the air terminal and the thermal zone in the air loop shows: 'Fluid Type: Water'. It seems it lacks a heat exchanger (water to air) but I can't simply add a Fluid-toFluid HX in my air loop...

Someone has an idea to fix it ?

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do you check the connection of heating coil ? Does it connect to a hot water loop ?

BL gravatar image BL  ( 2016-04-20 07:43:16 -0600 )edit

@Bo_Lin if the heating coil wasn't connected the sim would fail and it clearly shows the perpendicular nodes from the connected water loop.

MatthewSteen gravatar image MatthewSteen  ( 2016-04-20 07:50:23 -0600 )edit

Yes Indeed. The case with a Coil:Heating:Water and an AirTerminal:Reheat works fine. The problem only appears when I use an AirTerminal:NoReheat instead.

Urado gravatar image Urado  ( 2016-04-20 07:55:11 -0600 )edit

"The case with a Coil:Heating:Water and an AirTerminal:Reheat works fine" is the reheat hot water?

Julien Marrec gravatar image Julien Marrec  ( 2016-04-20 09:22:29 -0600 )edit

@Julien Marrec Yes, HotWater Reheat, linked to the hot water loop.

Urado gravatar image Urado  ( 2016-04-20 09:46:12 -0600 )edit

1 Answer

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answered 2016-04-21 03:28:18 -0600

Urado gravatar image

updated 2016-04-21 10:05:08 -0600

As @Julien Marrec said in comment, we need an AirTerminal:SingleDuct:VAV:HeatAndCool:NoReheat in this case.

The explanation is given in the documentation for AirTerminal:SingleDuct:VAV:HeatAndCool:NoReheat:

The difference between the two is in heating mode. For the Single Duct VAV NoReheat terminal unit, the air flow rate is reduced to the minimum value (max air flow rate x zone minimum air flow fraction) when zone heating is required. For the AirTerminal:SingleDuct:VAV:HeatAndCool:NoReheat terminal unit, the air flow rate in heating mode is increased to meet higher zone heating loads (similar to what is done in cooling mode).

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Asked: 2016-04-20 06:07:15 -0600

Seen: 384 times

Last updated: Apr 21 '16