RE: [EnergyPlus_Support] Air Exhaust from zones problem

There are so many ways to do it with the different managers and schedules. In the template example:

Sizing:System,
VAV Sys 1, !- name of an AirLoopHVAC object
sensible, !- type of load to size on
autosize, !- Design (minimum) outside air volumetric flow rate {m3/s}
0.3, !- minimum system air flow ratio
4.5, !- Preheat design temperature {C}
.008, !- Preheat design humidity ratio {kg-H2O/kg-air}
11.0, !- Precool design temperature {C}
.008, !- Precool design humidity ratio {kg-H2O/kg-air}
12.8, !- Central cooling design supply air temperature {C}
16.7, !- Central heating design supply air temperature {C}
noncoincident, !- Sizing Option
no, !- Cooling 100% Outside Air
no, !- Heating 100% Outside Air
.........
more fields.
================

I have not tried the above method. I have used the one below..

HVACTemplate:Zone:Unitary,
SPACE1-1, !- Zone Name
Furnace DX 1-1, !- Air Handling System Name
All Zones, !- Thermostat Name
autosize, !- Zone Supply Air Max Flow Rate {m3/s}
1.1, !- Zone Supply Air Sizing Factor
Flow/Person, !- Zone Outdoor air MethodFlow Type
0.00944, !- Zone Outdoor air Flow Rate per Person {m3/s}
0.0 !- Zone Outdoor air Flow per Zone Area {m3/s-m2}
0.0 !- Zone Outdoor air Flow per Zone {m3/s}
, !- Zone Supply Plenum Name
, !- Zone Return Plenum Name
None, !- Baseboard Heating Type
, !- Baseboard Heating Availability Schedule
0.0;

A4, \field Outdoor Air Method
\type choice
\key Flow/Person
\key Flow/Zone
\key Flow/Area
\key Sum
\key Maximum
\default Flow/Person

If you use the Sum or Maximum, the OA flow rate can be set to a higher value than the fan flow value. A normal HVAC system seldom operates at 100% fresh OA rate.

After the sizing run, enter the fan flow rate value for the OA inlet flow rate. If the fan is off, there is no air to the zone. 100% fresh air to the zone will also require the fan to be on all the time.

Autosize would generate a flow rate for the Zone, this number should be compared with the OA and fan flow rate, to verify that it is 100% fresh air.

Dr. Li

To: energyplus_support@yahoogroups.com
From: pedro_peixeiro@hotmail.com
Date: Mon, 7 Jun 2010 07:35:58 +0000
Subject: RE: [EnergyPlus_Support] Air Exhaust from zones problem

I think I see your point. Setting up those schedules as 1 guarantees only that Outdoor Air Flow values defined in the Sizing:Zone object are met. Is this right?

What would be the procedure to set up the OA flow rate as the same as the fan rate? i'm using a Fan:ConstantVolume.

To: energyplus_support@yahoogroups.com
From: yli006@hotmail.com
Date: Sat, 5 Jun 2010 14:07:56 -0400
Subject: RE: [EnergyPlus_Support] Air Exhaust from zones problem

The discussion started with:

"The system i'm trying to simulate is working with 100% outside air, and thus i need all zone air to be exhausted outside, with no return. "

My suggestion or respond to that was that the Fan flow rate should be taken into account in order to achieve this condition. If the OA flow rate is less than the Fan flow rate, part of the return air will be sent to the mixed node of the OA mixer box. I cautioned that the 100% OA with multiplier = 1 does not always mean 100% OA fresh air intake to a zone.
=============================
The follwing is   for Linda:

In fact the OA mixer box should be configured the same way as the plant loop, with the environment as a large air tank. The zone is a small air tank, or a small air tank with holes inside the large air tank.

The OA intake node air is mixed with part of the returned air from the Zone to form the mixed air output to the HVAC equipment branch.

The zone return air is split into the relief node air, and the by-passed returned air.

For the CBVAV model, the by pass damper can be a branch at the zone splitter and mixer.

This OA mixer and splitter pair configuration matches that of a similar plant water loop, when pump rate is higher than the demand rate..

In this way, the air loop and the water loop have the similar topology.
================
For the Zone node, one pair of the zone nodes is used to complete the leak-less primary air loop or AFN ducts. The second pair is for infiltration and ventilation.

The environment is a large air reservoir or tank. It feeds the HVAC loop via the stream intake and relief nodes of the OA box. By-pass branches are used to meet the zone and loop air adjustments, similar to the arangement for the water plant.
=====================
In the water plant loop no one will ask for 100% fresh water, except when the tank is also providing the domestic water usage, with cold water to the tap. The plant operates with zero fresh water input, because there is no leak. There is a safety valve hidden as the maximum plant temperature setting.

=========================
Pedro also had the following in his mail:

Severe ** Demand Side Outlet Node Name (Return Air Path or ZoneHVAC:EquipmentConnections) not valid = ZONE EQ1 OUTLET NODE
~~~   ** Occurs in AirLoopHVAC = UTANN

For this type of error which also appeared in my IDF, I am checking my IDF against a schematic diagram. In my case, (Mr. Ooi's ORICA project) I could make this error message disappear, but the SVG diagram was still not complete. Mr. Ooi submitted a ticket and obtained a reply from

> 'Richard Raustad
>
> EnergyPlus Support'
>
> Ticket Details
> ===================
> Ticket ID: 2504
> Department: General
> Priority: Medium
> Status: Open
>
His IDF now has no warning or error and the SVG diagram is correctly displayed.   Therefore, I do not have a unsolved problem myself in using EPlus.

Dr. Li

To: energyplus_support@yahoogroups.com
From: yli006@hotmail.com
Date: Sat, 5 Jun 2010 08:04:43 -0400
Subject: RE: [EnergyPlus_Support] Air Exhaust from zones problem

Eplus document is correct. It is the usage of these field that may not be approproate for the situation. All I am pointing out to the reader is that if you want the OA input to be same as the Fan flow rate, setting the schedule multiplier value to one will not given you what you intended to have.

"This statement is not correct, because by setting the multiplier to 1 does not define the quantity of flow. 1 of zero is still zero."

If you disagree, it is yours to do so. I was just clearifying my thought on this matter.

If both the above schedules are given values of 1.0, the system works at 100% outdoor air, (maximum OA flow rate, which may be smaller than the fan flow rate. Return air is still mixed at the mixed node.)
so in a system if 100% outdoor air is required regardless of any other condition, these fields are helpful."

Yes the multipliers are useful to reduce the OA flow rate.

My original e-mail defined what I assume is the 100% fresh OA intake. It is not the full or maximum OA intake by itself.

In face 'autosizing' is also helping to increase the confusion.

Dr. Li

To: energyplus_support@yahoogroups.com
From: pedro_peixeiro@hotmail.com
Date: Fri, 4 Jun 2010 22:22:15 +0000
Subject: RE: [EnergyPlus_Support] Air Exhaust from zones problem

If its not correct, than its a discussion that someone with your experience should have with someone from the E+ team, so people like me that are on a learning stage dont get wrong information. Input/output reference pdf, page 1566, or searching by the pdf page, 1605:

"Field: Minimum Fraction of Outdoor Air Schedule Name
This is an optional field with the schedule values in decimal fractions (0.0-1.0). This field
enables the user to limit the minimum amount of outdoor air permissible and thus also helps
in getting at least the minimum amount of air in.

Field: Maximum Fraction of Outdoor Air Schedule Name
This is an optional field with the schedule values in decimal fractions (0.0-1.0). This field
enables the user to limit the maximum of amount of outdoor air permissible and thus also
limits the permissible maximum outdoor air into the system.

If both the above schedules are given values of 1.0, the system works at 100% outdoor air,
so in a system if 100% outdoor air is required regardless of any other condition, these fields
are helpful."

This is directly taken form the pdf. I'm not making things up, i'm just reading the manuals. Clearing out this matter would be usefull, so i can know what to count on. thank you.

To: energyplus_support@yahoogroups.com
From: yli006@hotmail.com
Date: Fri, 4 Jun 2010 10:28:15 -0400
Subject: RE: [EnergyPlus_Support] Air Exhaust from zones problem

"If both the above schedules are given values of 1.0, the system works at 100% outdoor air"

This statement is not correct, because by setting the multiplier to 1 does not define the quantity of flow. 1 of zero is still zero.

My argument was that the intake air must all flow through the fan and the zone and then exhaust to satisfy the 100% fresh air condition.

Therefore, you make the OA intake rate,(volume) the same as the fan rate. If the fan is not supplied with the air quantity you want, then what is the 100% you are referring to.

Any volume of air that is not supplied by the OA inlet is made up by return air or other means, so that the OA mixer node will satisfy the fan flow requirement, and the 100% fresh air condition is not met.

This argument is not system dependent, excep the Fan. If there is no fan, no wind there is no fresh air..

Dr. Li

To: energyplus_support@yahoogroups.com
From: pedro_peixeiro@hotmail.com
Date: Fri, 4 Jun 2010 07:41:17 +0000
Subject: RE: [EnergyPlus_Support] Air Exhaust from zones problem

It makes sense what you say. But there is a way to make sure you have 100% fresh air, like Mario said. I checked the Input/output reference, and it does say the following (relative to Controller:OutdoorAir, Field: Maximum/Minimum Fraction of Outdoor Air Schedule):

"If both the above schedules are given values of 1.0, the system works at 100% outdoor air"

For now, i'm just trying to make a simple system working by the most standard way possible, so I can get myself a systematic procedure that assures me adaptability to various situations, so I'll try not to forget the previous point.

Anyway, my problem still persists. I added the OutdoorAir:Mixer and the Controller:OutdoorAir but the program still gives me the same error:

Severe ** Demand Side Outlet Node Name (Return Air Path or ZoneHVAC:EquipmentConnections) not valid = ZONE EQ1 OUTLET NODE
~~~ ** Occurs in AirLoopHVAC = UTANN

This node is defined as the outlet node of the AirLoopHVAC:ZoneMixer and the Demand Side Outlet Node in AirLoopHVAC.

Still need some tips-and-tricks to solve this one. thanks!

Pedro P.

To: energyplus_support@yahoogroups.com
From: yli006@hotmail.com
Date: Wed, 2 Jun 2010 13:13:37 -0400
Subject: RE: [EnergyPlus_Support] Air Exhaust from zones problem

I have seen many people wanted to use 100% outside air and does not know what to do.

If your OA intake volume rate is the same as the fan capacity and the zone air flow rate, the return air is automatically relieved, 100%.

If you do not connect the return air node of the zone to the OA mixer, the zone air is also 100% exhausted to the outside environment.

Am I right?

Dr. Li

To: EnergyPlus_Support@yahoogroups.com
From: pedro_peixeiro@hotmail.com
Date: Tue, 1 Jun 2010 08:43:12 +0000
Subject: [EnergyPlus_Support] Air Exhaust from zones problem

hello everyone.

i'm doing my first attempts on HVAC simulation, and i've hit my first wall. The system i'm trying to simulate is working with 100% outside air, and thus i need all zone air to be exhausted outside, with no return. My first idea was to use a AirLoopHVAC:ZoneMizer object to bundle all the air from the zones, and use the Outlet Node Name defined here as the Demand Side Outlet Node Name in the AirLoopHVAC object. But it seems E+ doesnt like my ideia, i'm getting a severe error saying the node name in the AirLoopHVAC object is not valid. If someone could point me out a hint or two on how to do this, or at least reference me an example file that uses a similar system, i would be very gratefull. thank you for your time!

Pedro.

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