Reheat/preheat/heating help

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I have a constant volume VAV system with a preheat coil, no heating coil,
and reheat box at the terminal. The preheat is steam and the reheat is hot
water. I am looking for verification on the way i set this up in the
model. I set the heating capacity to 0 on the system level and entered in a
preheat coil under the preheat/baseboard tab. Also under the preheat tab, i
entered my capacity and leaving air temp (50deg). On the coil cap/control
tab i have entered my zone entering max supply temp = 87 deg, thats the temp
i want the reheats to go up to. Then under each separate VAV zone, i
entered the reheat capacity under the Maximum Heating Rate.

Let me know if i confused anyone or need to send pictures or files.

--
Rob Hudson

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Has anybody done a VRF system in eQuest? Or know of any resources that would detail how to do this?

I want to make sure I am not rebuilding the wheel here.

Phylroy Lopez B.Eng LEED A.P.

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Can't be done explicitly in eQuest. I searched the
www.onebuilding.orgarchives for VRV and VRF to see what past
discussions and advice has been
put out there. At this point this is the best suggestion I can give. I'm
trying to model one now for a LEED project--not a smooth process.

pasha

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I believe that the best way to model a VRF system in eQUEST is to create an air to air heat pump system. You can create custom performance curves so the model does not penalize you as much when the temperature decreases. You will not be utilizing VRFs energy sharing capabilities but you should be close depending on the building's diversity.

Good luck,

Otto

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Here's some guidance that's out there.

Carol

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There are two methods listed in the Energy Trust guidelines. Has anyone
tried both modeling methods?

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Austin, where can I find a copy of the "Energy Trust guidelines" I tried Google, but I can only find the Oregon State Energy Trust web site, not the guidelines. Could you please add a link to your post, or point me in the right direction.

Thanks
Eddie Corwin, Energy & Sustainability Engineer

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Eddie,
This was posted to the list recently.
I think this is what you are looking for.

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It's the Energy Trust of Oregon. I don't know how they will help you except
point you to the pdf I sent you all ready. See above. Good Luck.

Carol

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Thanks for the responses people, I'll try them out.

Phylroy Lopez B.Eng LEED A.P.

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Pasha,

Here is the info you needed for your VRV project. I'll send it via this
email as others may need similar data:

I have included some input data below for the units you requested. I have
given you the data in EIR form as that is what gets put into Equest and I
figured it would save a step.

Here is the data I would enter for the systems:

*Outside Units*

PURY-P234TGMU-A

Cooling EIR: .315 Heating EIR: .294

PURY-P72TGMU-A

Cooling EIR: .307 Heating EIR: .271

PURY-P144TGMU-A

Cooling EIR: .336 Heating EIR: .291

PURY-P108TGMU-A

Cooling EIR: .307 Heating EIR: .282

*Inside Units*

PKFY-08 - .14watts/cfm

PKY-12 - .08watts/cfm

PKY-15 - .08watts/cfm

PKY-024 - .06 watts/cfm

PKY-30 - .07 watts/cfm

Let me know if this works for you or if you need additional info,

Cheers,

Carol

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Carol, this is awesome--thanks for your assistance as always and I'll check
back with you and all to let you know how it worked out for my project.

thanks again,
Pasha :)

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
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Hi all,

It's my pleasure to share information. I might be able to get some curve fit
info, too, but you will need to absolutely know what you are doing to
implement it. It is for when you are calling VRF/VRVs air source heat pumps.
NOT FOR WATER SOURCE. I will forward when I get it. You will use it only if
you are able to do so with skill!

Peace out,
Carol

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For curve fit info, I have always used the manufacturer's performance data sheets and picked several points off of the charts and then generated a curve using that information. I'm not sure how "typical" the curves are between one manufacturer and another, or between one model and another for that matter.

I have not seen any curves anywhere on the internet for VRF/VRV equipment. I've generated them myself every time. That said, this is what I have come up with on my past projects:

Cooling EIR=f(EWB,ODB)=
a=-3.86460948
b=.13359652
c=-.00097171
d=-.02367110
e=.00010817
f=.00022779

Cooling CAP=f(EWB,ODB)=
a=-5.1623230
b=.14462045
c=-.00076546
d=.01399993
e=-.00000870
f=-.00021874

Heating EIR=f(EDB,OAT)=
a=-.06203419
b=.02622044
c=-.00012317
d=.04781748
e=-.00021321
f=-.00057526

Heating CAP=f(EDB,OAT)=
a=.76658428
b=.00072927
c=-.00001362
d=.03394593
e=-.00012465
f=-.00031964

These curves were for a Daikin VRV-III system that was NON-heat-recovery and between 10-14 tons in capacity.

I would not recommend using these curves on Mitsubishi, Sanyo, etc., just by virtue of the fact that they all do it a little bit differently. My assumption is that they are at least similar.

I won't pretend like I know how to model the energy-recovery versions of any of these products.

Hopefully this helps you guys get on the right track. I felt terrible reading the VRV posts coming across the listserv all week and saying nothing about them, so here is my contribution, albeit limited.

Happy Friday

Gary Schrader

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