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Re: [EnergyPlus_Support] Simultaneous heating and cooling in RTU




Hi,
You can set your heating coil to the same temperature output as your cooling coil and then let the reheat deal with the rest, you will still get simultaneous heating and cooling but it will be at the reheat now so only for some zones.�
The second thing you can do is to use a multizone set point. This allows you to set two temperatures a lower and a higher temperature on each coil. The coils will adjust to what is requested by the zones. There are two types you can set it by one zone which controls everything or you can set it on an average return temperature. Take a look at the setpoint mangers these are the controls that you need there names are fairly self explanatory the input output reference will fill in any gaps.
I hope this helps
Annie

Sent from my iPhone
On Jun 9, 2014, at 4:03 PM, "Julien Marrec <mailto:julien.marrec@xxxxxxxxx>julien.marrec@xxxxxxxxx [EnergyPlus_Support]" <<mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

> �
> Hi everyone,
> 
> I've inherited an E+ energy model, and I'm experiencing a problem of simultaneous heating and cooling in a rooftop unit.
> 
> The RTU has: mixing box > cooling coil > heating coil > supply fan.
> 
> It then serves multiple VAV boxes with reheat (no cooling coil).
> 
> I'm trying to set a discharge temperature of 55°F when in cooling mode and 75°F when in heating mode. The spaces served have a Tstat of 77°F in cooling mode and 65°F in heating mode.
> 
> Currently, I'm seeing that, at all times (winter or summer), the mixed air is trying to meet 55°F (due to SetpointManager:MixedAir), if above it is cooled to 55°F and then reheated to 75°F.
> 
> I clearly have a controls problem.
> 
> Right now, there are two SetpointManager:Scheduled for the RTU: one is controlling the temperature after the cooling coil (setpoint of 55°F), and the other is controlling the temperature after the heating coil (setpoint of 75°F).
> I also have two setpointmanager:Mixed air: one on cooling for the mixed air and one of heating for the supply temperature.
> 
> SetpointManager:Scheduled,
> ��� RTU 1 Cooling Supply Air Temp Manager,� !- Name
> ��� Temperature,������������ !- Control Variable
> ��� Always 13.89C or 57F,��� !- Schedule Name
> ��� RTU 1 Supply Fan Outlet; !- Setpoint Node or NodeList Name
> 
> SetpointManager:Scheduled,
> ��� RTU 1 Heating Supply Air Temp Manager,� !- Name
> ��� Temperature,������������ !- Control Variable
> ��� Always 24.72C or 76.5F,� !- Schedule Name
> ��� RTU 1 Supply Path Inlet; !- Setpoint Node or NodeList Name
> ���
> ���
> SetpointManager:MixedAir,
> ��� RTU 1 Cooling Coil Air Temp Manager,� !- Name
> ��� Temperature,������������ !- Control Variable
> ��� RTU 1 Supply Fan Outlet, !- Reference Setpoint Node Name
> ��� RTU 1 Heating Coil Outlet,� !- Fan Inlet Node Name
> ��� RTU 1 Supply Fan Outlet, !- Fan Outlet Node Name
> ��� RTU 1 Mixed Air Nodes;�� !- Setpoint Node or NodeList Name
> 
> (RTU 1 Mixed Air Nodes = RTU 1 Cooling Coil Outlet + RTU 1 Mixed Air Outlet)
> 
> SetpointManager:MixedAir,
> ��� RTU 1 Heating Coil Air Temp Manager,� !- Name
> ��� Temperature,������������ !- Control Variable
> ��� RTU 1 Supply Path Inlet, !- Reference Setpoint Node Name
> ��� RTU 1 Heating Coil Outlet,� !- Fan Inlet Node Name
> ��� RTU 1 Supply Fan Outlet, !- Fan Outlet Node Name
> ��� RTU 1 Heating Coil Outlet;� !- Setpoint Node or NodeList Name
> 
> 
> I'm wondering how I can properly set my controls to make sure I don't have simultaneous heating and cooling. I've thought about simply switching the coils, so that the heating coil is put before the cooling one, but there must be another way (and it would still try to meet 55°F in winter mode for the mixed air).
> 
> I must admit that I'm lost between all the setpointmanagers, availabilitymanagers, etc, so any help will be greatly appreciated.
> 
> Thanks,
Julien
> --
> Julien Marrec, EBCP, BPI MFBA
> Energy And Sustainability Engineer
> T: +33 6 95 14 42 13
> 
> LinkedIn (en) : <http://www.linkedin.com/in/julienmarrec>www.linkedin.com/in/julienmarrec



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 Posted by: annie <anniemarston@xxxxxxxxxxx>

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