No heating load to systems

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Hi all,

I thought I was wrapping up my baseline model and then for some reason I
discovered that the only heating energy being used is going through the zone
baseboards. When I take out the baseboards, the results show a big fat ZERO
for any space heating energy the DOE2 error shows below. How can the design
loads not get passed to the system. The baseline systems are VAV with
reheat, but for some reason there is no heat or reheat unless I specify
pre-heat (which there is none) or baseboards... any ideas are
appreciated--because I thought I was closer to finished with this model
until this issue popped up.

***ERROR***********************************************************************

Loop: Hot Water Loop has zero design flow.

Check input for consistency, or specify design loads.

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600

Pasha:

Have you specified your Reheat-Delta-T for your zone VAV boxes? Send the .INP and .PD2 if you require further help.

John R. Aulbach, PE, CEM

John Aulbach's picture
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Joined: 2011-09-30
Reputation: 1

Thanks John--I hadn't input the reheat delta t, thinking that it was one of
those "blank" default auto-calc things.... so by inputting a 30 deg delta,
that took away the error in the bdl file, but the results are still not
showing any space heating consumption and yet somehow I have 0.0 hours out
of throttling range---I thought this had to be too good to be true.

I've attached the current .pd2 & .inp files I am running. If you do have
time to take a quick peak at my inputs...this baseline file is based on
Appendix G compliance. please note my system names do not match the system
selection I have for baseline case.

Thanks for your time and attention to give me a hand.

Pasha

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600

You might need to add a hot water loop pump instead of just relying on a
boiler pump. See if that affects your heating energy consumption.

Also, your zones don't appear to have any thermostat schedules
configured.

James Hansen, PE, LEED AP

James Hansen's picture
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Joined: 2011-09-30
Reputation: 200

Thanks James. I do have an additional HW loop pump...but I will take a
look at the thermostat schedule stuff.

Pasha

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600

Pasha,

I suspect this might be because there is no space heating schedule.

HEAT-TEMP-SCH

Takes the U-name of a schedule of TYPE = TEMPERATURE that gives the
heating setpoint of the zone thermostat. If not specified, the program
will assume that the zone has no zone-activated heating control. If
omitted, no heating in zone. For constant volume DDS, MZS, and PMZS
systems this schedule provides the value of the lower end of the
heating/cooling throttling range; the COOL-TEMP-SCH provides the value
of the upper limit of the range

If you assign a heating schedule to the spaces you will get your space
heating loads.

I would have thought that you wouldn't have much of a cooling load
either because you don't have that defined either.

Vikram Sami, LEED AP

Vikram Sami's picture
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Joined: 2011-09-30
Reputation: 0

Hi Vik--Yes, per James suggestion I have added both these schedules and am
now seeing better results without errors--so I am backing up with both my
model files to make these adjustments.

I guess I took for granted that all "default" input boxes even when they are
left blank still defaulted to a baseline input...

Thank you to all of you for taking time out of your busy project schedules
to give me some support---it's not soo lonely in this simulation world.

Cheers,
Pasha

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600

Pasha,
I tried running your model as-is, and came up with a bunch of warnings
re low preheat/heating capacities. I added preheat
along with some humidity control for all the zones, and got the attached
output.
Maybe the program was just not doing the heating voluntarily, and had to
be forced to.
Hope this helps,
Umesh

Umesh Atre's picture
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Joined: 2011-09-30
Reputation: 0

Hi Umesh,

thanks for your attention to my issue. Unfortunately because this is a
baseline case I can only put in pre-heat if my proposed design has it, and
my case does not. What I thought was interesting in my case was that the
preheat & baseboard inputs were showing heating energy consumption, but the
AHU & HW coil was not showing any heating energy---I have know learned that
because I didn't have the T-stat schedule input this was not offering the
"call for heating" that the AHU was looking for.

At some point when I switched my project from Wizard to DDedit mode (&
changed my HVAC system type from chosen in the Wiz) so I went through the
input spreadsheet and "reset" the inputs back to default since I had changed
from an initial FC system selected in the wizard. I didn't realize that by
"re-setting" the t-stat schedules they didn't default to a common schedule,
they just defaulted to nothing---so nothing was what I got.

this is a great simulation community and resource where we can all support
and help each other learn and learn from others' trials & troubles. keep
the communication flowing...

Pasha

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600