oa from system

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Hello,

I have a SZRH system which should provide outside air to the FC system.
The air it provides should always be 68 F. What temperatures shall I put
for cooling design and heating design / thermostat setpoint T. I put min
supply temp and max supply temp to 68 F and the other design
temperatures to 53/90F cause I do not have a thermostat there ( the air
is always provided with 68 F). Then I specified the OA constant to 4000
cfm and determined the min outside air ratio =1. Is there sth wrong with
my temperature settings as I do not get any coil loads for the system
(SS-J report)? When I set all temperatures to 68 F the ventilation air I
require is too huge. Do I have to put the min OA ratio to 1, 0 or shall
I leave it blank for the FC system? I mean is it enough to put OA from
system SZRH? Cause someone told me I have to put it to 0 as I do not
have any outside air put I do it is from the system. I am confused.

Thanks for your help.

Verena

Verena Kindl2's picture
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Try a system type of IU, with the induction ratio matching that of the FCs. The main system then needs to be set to 100% OA with constant cool and heat control set to 68F. You will have to fake in extra fan power to match that of the FCs. Hope this helps.

Josh

Joshua D. Wolfe's picture
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Thanks Josh, but I already tried to model a IU unit but i have a different temperature range of the coils for the main AHU (90/50?C) and the coils of the FC (45/36?C) and I can not assign to different loops to the IU. So I am still trying.

________________________________

Von: Joshua Wolfe [mailto:jwolfe at geo-marine.com]
Gesendet: Dienstag, 1. September 2009 14:11
An: Verena Kindl; equest-users at lists.onebuilding.org
Betreff: RE: oa from system

Try a system type of IU, with the induction ratio matching that of the FCs. The main system then needs to be set to 100% OA with constant cool and heat control set to 68F. You will have to fake in extra fan power to match that of the FCs. Hope this helps.

Josh

Verena Kindl2's picture
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Thanks for the great help. But how do I specify the constant cool and heat control to 68 F? I can not find where I can specify the temperature for the system unit only the zone entering supply temp (see figure) but this is the temperature after the Fan coils ?

Thanks Verena

________________________________

Von: Bishop, Bill [mailto:wbishop at pathfinder-ea.com]
Gesendet: Dienstag, 1. September 2009 14:49
An: Verena Kindl; equest-users at lists.onebuilding.org
Betreff: RE: [Equest-users] oa from system

Verena,

You should be able to assign different loops to the system-level and zone-level coils:

Regards,

William Bishop, EIT, LEED? AP

Verena Kindl2's picture
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Hi,

as i now can define two different loops to my IU system is there a way to specify two different hot water coil delta T for the loops cause I can enter only one hot water coil delta T ? That is why I wanted to assign two different loops cause they have different delta T. And is there a way to assign a two different chilled water loops as well?

Thanks

Verena

________________________________

Von: Bishop, Bill [mailto:wbishop at pathfinder-ea.com]
Gesendet: Dienstag, 1. September 2009 14:49
An: Verena Kindl; equest-users at lists.onebuilding.org
Betreff: RE: [Equest-users] oa from system

Verena,

You should be able to assign different loops to the system-level and zone-level coils:

Regards,

William Bishop, EIT, LEED? AP

Verena Kindl2's picture
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Hi equester,

i was checking my results fort he chilled water loop. I entered a delta
T of 11,8 F and a capacity of 21 MBTU/ h and in the PV-A report I find
also 21 MBTU/h and a flow of 3556.5 gpm (593 lb/s). I checked the delta
T using the formula Q=m*c*delta T

Delta T = Q/(m*c)

Delta T = 21*e6 Btu/h / (593 lb/s*3600s/h* 1 Btu/lbF ) = 9,8 F

The mass flow is too high and the delta T too low but i have not
specified a massflow for the loop so it was up to equest sizing the
massflow. Do you get appropriate massflows ? I tried it with other delta
T but the temperature difference is always too low and the massflow to
high. Sizing option is primary. Any idea? Have a nice weekend.

Verena Kindl2's picture
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Try Q=500*gpm*dT

Charles Land's picture
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Did u have jokes for breakfast ?

________________________________

Von: Charles Land [mailto:cland at geo-marine.com]
Gesendet: Freitag, 4. September 2009 19:00
An: Verena Kindl; equest-users at lists.onebuilding.org
Betreff: Re: [Equest-users] capacity check

Try Q=500*gpm*dT

Verena Kindl2's picture
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I am so sorry i thought you were making fun of me. But actually the
units conversion tricked me. I am so sorry.

________________________________

Von: Charles Land [mailto:cland at geo-marine.com]
Gesendet: Freitag, 4. September 2009 19:00
An: Verena Kindl; equest-users at lists.onebuilding.org
Betreff: RE: capacity check

Try Q=500*gpm*dT

Verena Kindl2's picture
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Good morning,

i have a question regarding the floor multiplier. I use one system per
floor and I multiply the middle floor times 50. In my reports I can see
it creates a system for all the 50 floors not a system for every floor.
So in case I use one system per floor I cant use the floor multiplier ?

Regarding the outside air from system. I want that the air inside my
office zones (perimeter) goes to the corridor (core). Is this
automatically the case or do I have to specify that UVT gets OA from
system. Cause I am afraid that by outside air it means outside air that
the system gets and not the already heated inside air in my zone. I want
to have the already heated air in the corridor. Shall I put then min OA
ratio = 0 ?

Thanks a lot

Verena Kindl2's picture
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Hi all,

I have an induction unit for the whole building, supplying 204000 cfm
outside air to the building. So I specify the supply flow of the system
(204000 cfm) and set the min outside air ratio =1. In the SV-A report it
shows on the system level 0 outside air and therefore no cooling/heating
capacity and for the zone it shows about 800-1100 cfm outside air. Only
if I do not specify the supply flow on the system level then I also get
an outside air ratio of 1 for the system level. Why is it not possible
to tell equest that the 204000 cfm it supplies is only outside air. I
have not specified an economizer so it should be outside air all the
time ??

Have a nice weekend.

Verena Kindl2's picture
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Hi Verena,

Check your zone level OA values. If you want to specify 100% OA at the
system level you have to clear the zone level inputs as they will
override the system level OA inputs.

Regards,

Jordan Bouchard, LEED(r) AP

Bouchard, Jordan's picture
Joined: 2011-09-30
Reputation: 0

Thank you, but i already thought about that and i have nothing specified
there. But now I tried to specify the flow to each zone instead of doing
it for the whole system and then the outdoor air ratio is calculated
correctly. Of course I considered the induction ratio so I specified for
each zone 1962 cfm supply flow (induction ratio of 2) then I get an
outdoor air ratio of 1 and 918 cfm OA per zone. Do you think I can do
that? It is strange so as the other way should work as well.

________________________________

Von: Bouchard, Jordan [mailto:Jordan.Bouchard at stantec.com]
Gesendet: Freitag, 11. September 2009 15:08
An: Verena Kindl; equest-users at lists.onebuilding.org
Betreff: RE: [Equest-users] outside air ratio

Hi Verena,

Check your zone level OA values. If you want to specify 100% OA at the
system level you have to clear the zone level inputs as they will
override the system level OA inputs.

Regards,

Jordan Bouchard, LEED(r) AP

Verena Kindl2's picture
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I have also noticed that you have to be careful about how you specify OA
for induction systems. If I enter zone-level OA cfm and also enter
system-level SUPPLY-FLOW, I end up with NO outside air even though the
MIN-OUTSIDE-AIR is set to 1.00. The problem goes away if I enter a
system MIN-AIR-SCH (whether or not I have the SUPPLY-FLOW entered) or if
I leave the SUPPLY-FLOW blank (default).

To get a better idea of what the OA is actually doing, I create an
Hourly Report Block and select the following options under the "HVAC
System" variable type:
"Ratio of outside air to total supply air"
"Total system supply air flow rate"

There are a ton of other variables available in the hourly reports that
you can use to troubleshoot your models.

Regards,

William Bishop, EIT, LEED(r) AP

Bishop, Bill2's picture
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Be careful when entering the outside air CFM via a percentage of the
system because for LEED the outside air must be the same for the
baseline and the proposed model. If the baseline model requires more
supply air than the proposed model the outside airflows will be
different between the two models.

Otto

I have also noticed that you have to be careful about how you specify OA
for induction systems. If I enter zone-level OA cfm and also enter
system-level SUPPLY-FLOW, I end up with NO outside air even though the
MIN-OUTSIDE-AIR is set to 1.00. The problem goes away if I enter a
system MIN-AIR-SCH (whether or not I have the SUPPLY-FLOW entered) or if
I leave the SUPPLY-FLOW blank (default).

To get a better idea of what the OA is actually doing, I create an
Hourly Report Block and select the following options under the "HVAC
System" variable type:

"Ratio of outside air to total supply air"

"Total system supply air flow rate"

There are a ton of other variables available in the hourly reports that
you can use to troubleshoot your models.

Regards,

William Bishop, EIT, LEED(r) AP

Otto Schwieterman's picture
Joined: 2011-09-30
Reputation: 0

Hello all,

I specified for my IU system the design temperatures at 75/72 F and the
thermostat setting points to the same range 75/72 F ( cooling/ heating
). I supply the air with 68 F and the FC in the zone should do the rest.
For the first glance I let equest autosize the circulation loops. So I
expected that the space temperatures are always between 72-75 F ( as
the fans are running 24 h ). But this is not the case, it is mostly
according to the SS-O report between 65-70 F. I created also an hourly
report to monitor the zone temperature but there I can see the same
result ( obviously it should be the same as space=zone ). The cold and
hot air flows are also zero does it affect my result ? I was thinking it
is maybe the temperature I supply the zone with (68 F) and not the
actual zone temperature but then it should be always 68 F. Any idea ?

Hope u had a good week start.

Regards

Verena

Verena Kindl2's picture
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Sorry to bother you again, but i am still trying to fix my problem (to
achieve a room temperature of 72-75 F with an IU unit). I think my
mistake is that I put the zone entering and hot deck max leaving
temperatures both to 68 F and therefore I can not get 72 F room
temperature even so I specify the design temperatures to 72/75 F.

Which one is the main air handling unit coil and which belongs to the
fan coil unit? I tried :

Main AHU coil ?

FC max leaving temp?

But then I get a warning:

Shall I ignore the warning as the room temperatures are fine or do I
have to edit something else?

________________________________

Von: Verena Kindl
Gesendet: Montag, 14. September 2009 13:21
An: 'equest-users at lists.onebuilding.org'
Betreff: zone temperature

Hello all,

I specified for my IU system the design temperatures at 75/72 F and the
thermostat setting points to the same range 75/72 F ( cooling/ heating
). I supply the air with 68 F and the FC in the zone should do the rest.
For the first glance I let equest autosize the circulation loops. So I
expected that the space temperatures are always between 72-75 F ( as
the fans are running 24 h ). But this is not the case, it is mostly
according to the SS-O report between 65-70 F. I created also an hourly
report to monitor the zone temperature but there I can see the same
result ( obviously it should be the same as space=zone ). The cold and
hot air flows are also zero does it affect my result ? I was thinking it
is maybe the temperature I supply the zone with (68 F) and not the
actual zone temperature but then it should be always 68 F. Any idea ?

Hope u had a good week start.

Regards

Verena

Verena Kindl2's picture
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Good morning,

could anybody please send me an instruction how to set up the
temperatures for a IU system ? I put

And my space temperatures are . My results look like:

I put min supply to 68 F ??

It is driving me crazy and i am getting a bit desperate. I am sure I am
doing a stupid mistake.

Cu later

Verena

Verena Kindl2's picture
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Hi all,

I try to model a supply flow with a constant temperature of 68 F in VAV
system. I set cool control constant and all the hot/cold min/max
temperatures in the VAV system to 68 F. But unfortunately now the
cooling coil air temperature is always 68 F and the heating coil air
temperature is similar to the air entering temperature (48 F in the
winter). It seems to me like equest is cooling and heating with the
cooling coil which is not possible? Any ideas how to provide the
constant temperature supply flow??

Thanks a lot.

Verena Kindl2's picture
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Good morning,

does anybody know where i can find the sample runs, the doe 2 help is
referring to ? And do you know why in the VAV system the cooling coil is
hotter than the heating coil in case I enable the main heating coil ?

Thanks for your help

Verena Kindl2's picture
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