Hi, Toby
Sorry that if I make you sound stupid. When a question is asked in the forum, usually only get a portion what was intended to ask.
At first, you seems to be confused by the number of components in the HVAC system, that was the reason why I said that the normal procedure is to cool the air to get the humidity ratio you need for the 25°C 55% RH, and then let the room air heat it back up. If the duct temperature is too low, a heating coil at the AHU can be used to add more heat, so that the result air temperature in the room is 25°C. Because the humidity ratio is adjusted, therefore the RH value will hold.
The humidistat tells the system how much moisture is pressent or needed in the room. When this is set in the EPlus system object, the supply air is adjusted to the required temperature. I called it the dewpoint as it is close to that.
When the outdoor air is dry, aspecially in Winter, humidifier is needed to add moisture into the indoor air stream. This is also included in the EPlus object. Both dehumidification and humidification requires extra energy.
Your first or second question seems to want to know what is the added load for 1 to 8 person under the controlled environment. Because it is already the controlled environment, the added load is the people load itself. Therefore, the activity schelule and occupency, etc. determines the annual load and not the weateher file any more. That was what I wanted to point out. Because half the year, the load saves the heating load, and the other half year adds to the cooling load, the net may be very small.
The IdealLoadsAirSystem is one which provides heeting and cooling directly into a zone without using any equpment. It is easy to use, but difficult to understand how it is done. If you have any more question on EPlus please do not hesitate to ask.
I am now 81 years old and retired, and I enjoy helping users to understand how the EPlus should be used.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: tobycheung00@xxxxxxxxxxx
Date: Fri, 14 Sep 2012 02:18:32 +0000
Subject: [EnergyPlus_Support] Re: Simplest way to control RH in a zone
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
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Sorry that if I make you sound stupid. When a question is asked in the forum, usually only get a portion what was intended to ask.
At first, you seems to be confused by the number of components in the HVAC system, that was the reason why I said that the normal procedure is to cool the air to get the humidity ratio you need for the 25°C 55% RH, and then let the room air heat it back up. If the duct temperature is too low, a heating coil at the AHU can be used to add more heat, so that the result air temperature in the room is 25°C. Because the humidity ratio is adjusted, therefore the RH value will hold.
The humidistat tells the system how much moisture is pressent or needed in the room. When this is set in the EPlus system object, the supply air is adjusted to the required temperature. I called it the dewpoint as it is close to that.
When the outdoor air is dry, aspecially in Winter, humidifier is needed to add moisture into the indoor air stream. This is also included in the EPlus object. Both dehumidification and humidification requires extra energy.
Your first or second question seems to want to know what is the added load for 1 to 8 person under the controlled environment. Because it is already the controlled environment, the added load is the people load itself. Therefore, the activity schelule and occupency, etc. determines the annual load and not the weateher file any more. That was what I wanted to point out. Because half the year, the load saves the heating load, and the other half year adds to the cooling load, the net may be very small.
The IdealLoadsAirSystem is one which provides heeting and cooling directly into a zone without using any equpment. It is easy to use, but difficult to understand how it is done. If you have any more question on EPlus please do not hesitate to ask.
I am now 81 years old and retired, and I enjoy helping users to understand how the EPlus should be used.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: tobycheung00@xxxxxxxxxxx
Date: Fri, 14 Sep 2012 02:18:32 +0000
Subject: [EnergyPlus_Support] Re: Simplest way to control RH in a zone
Hi Dr. Li,
Thanks for your reply.
I know the method I am using sound stupid.
What I am really doing is to find out the hourly ventilation load only in specific indoor conditions (Temp and RH) with fixed occupant activity level say 120W per person.
I agree with you the outdoor air condition is dominant over the occupant factor. Therefore I assume and fix the ventilation rate with 10L/s/p in the percieved zone and aim to find out the amount of hourly vent load form varying outdoor to fixed indoor conditions. Somehow it is meaningless to find up to 8 person in this calculation, coz it just depends on the amount of vent flow, while sweating of occupants is neglected for sedentary activities.
By the way, I have tried your suggestion. The RH seems cannot reach target setpoint in some hours within a year, especially for the cold days with low temp and RH at outdoor. Anyway, your comments are useful for me to fine tune my excerise. Thanks you so much.
Toby Cheung
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
>
>
> Hi, Toby I do not know why you wanted to do this exercise. If you can cool and control the single room to 25°C you should already have a cooling system of some sort. Calculate what is the dew point temperature for 55% RH at 25°C. A humidistat in a xone will do this calculation. Cool the circulating air to that temperature, all the excess moisture would be condensed out at the cooling coil. If the zone do not have sufficient heat to warm the air up to 25°C, add a reheat heater. All these are in the EPlus HVACsystem.
> For a single room a window unit would do the trick. If you want to control the temperature and humidity exactly, you may need a system desinged for a clean room or an operating theatre of a hospital.
> It is ridiculous trying to do this for 1-8 person for a whole year. Pardon me for saying so. You do not know how much a person would sweat. The person does not sweat the whole day. For the whole year, there are Winter and Summer. When a person is working out in a gym, the maximum activity level is about 400 watt. Not all the sweat is evaporated and condensed again by the HVAC. If this person works out 4 hours a day all the year around, Winter months does not count, as he will be helping to heat the zone. For Sumer time, 183 x 4 x 0.200 kwh would be the total energy added to the system. If the person is not working out in a gym, the amount would reduce to 1/4. Do you know that the moisture from the outdoor air may be a lot more than that from the person. So your question on ventilation load also does not make sense. Dr. Li
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: tobycheung00@...
> Date: Thu, 13 Sep 2012 12:22:43 +0000
> Subject: [EnergyPlus_Support] Re: Simplest way to control RH in a zone
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> Thanks for your reply.
>
>
>
> Yes, I have found this object.
>
> Yet, it seems work with a serious of components (such as heating coil, humidifier, in/out nodem ... etc.) which I am not very familiar with.
>
>
>
> And I have tried the example files which related to RH control.
>
> It seems include alot .... and not easy to understand by myself.
>
>
>
> Well, if I just want a zone with temp=25oC and RH=55% for all hours within a year. Which kinds of components do I need to concern with ? Just very simple setup and any types of AC system is ok for me ~~ Many thanks.
>
>
>
> Toby Cheung
>
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Vaibhav Jain <vaibhav.energyarchitect@> wrote:
>
> >
>
> > Have you checked, ZoneControl:Humidistat object? You will understand its
>
> > functioning from IO reference.
>
> >
>
> > Vaibhav Jain
>
> > www.vaibhavjain.co
>
> >
>
> >
>
> >
>
> >
>
> > On 13 September 2012 13:30, tobycheung00 <tobycheung00@> wrote:
>
> >
>
> > > **
>
> > >
>
> > >
>
> > > Dear All,
>
> > >
>
> > > Can anyone please suggest me the simplest (use minimum connected
>
> > > equipment) way to control the relative humidity in a zone ?
>
> > >
>
> > > My condition is easy. I want to control the temperature and the relative
>
> > > humidity in a zone, and finally want to find out the hourly ventilation
>
> > > load of increasing number of occupant(1~8) within a year, according to
>
> > > hourly outdoor conditions change.
>
> > >
>
> > > Its easy to control the zone temperature and yield the ideal zone load.
>
> > > Yet adding humidity control seems a lot more complicated...
>
> > >
>
> > > Could you please suggest which components must be added in order to
>
> > > facilitate the Humidity control. Many thanks.
>
> > >
>
> > > Toby Cheung
>
> > >
>
> > >
>
> > >
>
> >
>
Thanks for your reply.
I know the method I am using sound stupid.
What I am really doing is to find out the hourly ventilation load only in specific indoor conditions (Temp and RH) with fixed occupant activity level say 120W per person.
I agree with you the outdoor air condition is dominant over the occupant factor. Therefore I assume and fix the ventilation rate with 10L/s/p in the percieved zone and aim to find out the amount of hourly vent load form varying outdoor to fixed indoor conditions. Somehow it is meaningless to find up to 8 person in this calculation, coz it just depends on the amount of vent flow, while sweating of occupants is neglected for sedentary activities.
By the way, I have tried your suggestion. The RH seems cannot reach target setpoint in some hours within a year, especially for the cold days with low temp and RH at outdoor. Anyway, your comments are useful for me to fine tune my excerise. Thanks you so much.
Toby Cheung
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
>
>
> Hi, Toby I do not know why you wanted to do this exercise. If you can cool and control the single room to 25°C you should already have a cooling system of some sort. Calculate what is the dew point temperature for 55% RH at 25°C. A humidistat in a xone will do this calculation. Cool the circulating air to that temperature, all the excess moisture would be condensed out at the cooling coil. If the zone do not have sufficient heat to warm the air up to 25°C, add a reheat heater. All these are in the EPlus HVACsystem.
> For a single room a window unit would do the trick. If you want to control the temperature and humidity exactly, you may need a system desinged for a clean room or an operating theatre of a hospital.
> It is ridiculous trying to do this for 1-8 person for a whole year. Pardon me for saying so. You do not know how much a person would sweat. The person does not sweat the whole day. For the whole year, there are Winter and Summer. When a person is working out in a gym, the maximum activity level is about 400 watt. Not all the sweat is evaporated and condensed again by the HVAC. If this person works out 4 hours a day all the year around, Winter months does not count, as he will be helping to heat the zone. For Sumer time, 183 x 4 x 0.200 kwh would be the total energy added to the system. If the person is not working out in a gym, the amount would reduce to 1/4. Do you know that the moisture from the outdoor air may be a lot more than that from the person. So your question on ventilation load also does not make sense. Dr. Li
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: tobycheung00@...
> Date: Thu, 13 Sep 2012 12:22:43 +0000
> Subject: [EnergyPlus_Support] Re: Simplest way to control RH in a zone
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> Thanks for your reply.
>
>
>
> Yes, I have found this object.
>
> Yet, it seems work with a serious of components (such as heating coil, humidifier, in/out nodem ... etc.) which I am not very familiar with.
>
>
>
> And I have tried the example files which related to RH control.
>
> It seems include alot .... and not easy to understand by myself.
>
>
>
> Well, if I just want a zone with temp=25oC and RH=55% for all hours within a year. Which kinds of components do I need to concern with ? Just very simple setup and any types of AC system is ok for me ~~ Many thanks.
>
>
>
> Toby Cheung
>
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Vaibhav Jain <vaibhav.energyarchitect@> wrote:
>
> >
>
> > Have you checked, ZoneControl:Humidistat object? You will understand its
>
> > functioning from IO reference.
>
> >
>
> > Vaibhav Jain
>
> > www.vaibhavjain.co
>
> >
>
> >
>
> >
>
> >
>
> > On 13 September 2012 13:30, tobycheung00 <tobycheung00@> wrote:
>
> >
>
> > > **
>
> > >
>
> > >
>
> > > Dear All,
>
> > >
>
> > > Can anyone please suggest me the simplest (use minimum connected
>
> > > equipment) way to control the relative humidity in a zone ?
>
> > >
>
> > > My condition is easy. I want to control the temperature and the relative
>
> > > humidity in a zone, and finally want to find out the hourly ventilation
>
> > > load of increasing number of occupant(1~8) within a year, according to
>
> > > hourly outdoor conditions change.
>
> > >
>
> > > Its easy to control the zone temperature and yield the ideal zone load.
>
> > > Yet adding humidity control seems a lot more complicated...
>
> > >
>
> > > Could you please suggest which components must be added in order to
>
> > > facilitate the Humidity control. Many thanks.
>
> > >
>
> > > Toby Cheung
>
> > >
>
> > >
>
> > >
>
> >
>
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
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