What are the dis/advantages to the 2 systems if you were prescribing one to a 5 level (20,000SF/Floor) Building in Florida. Building Dimensions are 350' X 62' and a 75' Height. Mixed use ranging from medical office space to thermal spa on top level.
I am trying desparately to convince this owner to go ground mounted air cooled chiller system vs. this DX system which would operate on 6-7 zones per floor.
Can anyone give me a great argument and not the obvious one, why the hell wouldn't you. The pricing for the air cooled chiller system is to be in the range of 2.0 to 2.2 million design build. I can not put a number figure on this DX system which would be broken into multiple 10 ton units throughout.
thanks in advance to all the knowledgable souls on these page....
Any more information you can give? I feel like I'm missing something here, but in my point of view (and I'm not an expert)...
Having a central system (large ground DX chiller) allows you to build in diversity into the cooling system. You can accomodate for the diversity of uses in your building - with the correct design, it can accomodate for even the hottest/humidest days there, without having to tax the system.
As well, and I may be incorrect, but i believe that the efficiency of the central chiller system is higher than individual DX systems. Usually, smaller units (10 ton DX units) have a lower efficiency - typically, the larger the mechanical tonnage, the more efficient it is - and with a VFD, it will likely be more energy efficient with staging of compressors and such.
FUTURE: also having a slightly-oversized system, the flexibility is built in for future changes, especially with A: global warming and B: increased electrical/heat output of devices and/or programmatic changes, the cooling system will already be set in place and will not need a complete demo of the old small DX box on the roof. Also, in terms of maintenance, the ground chiller will be easier and cheaper to maintain then 10 boxes on the roof.
The downsides, however, are that the chiller will take up a chunk of realestate on the ground plane - which will likely need fencing of some sort, be noisier, and maybe an eyesore while the little DX units on the roof will be sight-unseen.
Let me know if I sound completely off-base...I'm an HVAC engineer turned architectural designer just in case ur wondering.
the air cooled chiller option would only take up a 20' X 30' space on the ground. Operating (2) units. Our goal is to utilize the roof as a sun deck as much as possible and a bunch of DX boxes really doesn't do it justice.
It will take several zones per floor to utilize a DX system and the thought of having 10 ton mechanical spaces all around the floorplan is not really appealing. The initial cost factor involved is coming to almost 2wice the cost when the two systems are compared(DX vs. air-cooled). This number is the obvious problem here.
Has anyone developed and designed a 5 level building using a DX system as described? and if so what are the downfalls. thanks for the repies...
a brief of prj.
Project Data:
1st Level - Diagnostic Imaging Center / 152occupany Auditorium
2nd Level - Technical Office Spaces
3rd Level - Lasik Eye Surgeon / Cosmetic Dentistry / Cosmetic Plastic Surgeon
4th Level - Alternative Office Space - Chiropractor / Physical Therapist / Etc.
5ht Level - Thermal Spa and Gym Area
approx. 20,000SF per level ~ 100,000SF
Post Tension Flooring - Precast Concrete Panel Exterior
In my neck of the woods, clients love cheap stuff (lowest initial cost) and I see the "let's just do a gazillion DX units" approach being used a lot around here. The tenants are usually metered directly for electricity, so higher utility costs don't matter to the owner. Residential A/C contractors can build the system, since it's just a bunch of smaller systems. Also, any one-man AC company (again, the cheapest) can service the system.
You are correct that your floor plans will probably suffer from the enormous number of A/C closets required and there will be a field of D/X units somewhere. Maintenance will not be fun as all these inside and outside units malfunction and die at different times, but your client may or may not care.
The best argument may be that not doing the D/X thing will save floor space and create more leasable area. I also wonder if having a half-assed mechanical system lowers the resale value of the building. Again, I'm not sure people care about that.
Jul 15, 19 11:09 am ·
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HVAC: DX System vs. Air Cooled Chiller
What are the dis/advantages to the 2 systems if you were prescribing one to a 5 level (20,000SF/Floor) Building in Florida. Building Dimensions are 350' X 62' and a 75' Height. Mixed use ranging from medical office space to thermal spa on top level.
I am trying desparately to convince this owner to go ground mounted air cooled chiller system vs. this DX system which would operate on 6-7 zones per floor.
Can anyone give me a great argument and not the obvious one, why the hell wouldn't you. The pricing for the air cooled chiller system is to be in the range of 2.0 to 2.2 million design build. I can not put a number figure on this DX system which would be broken into multiple 10 ton units throughout.
thanks in advance to all the knowledgable souls on these page....
todd
Any more information you can give? I feel like I'm missing something here, but in my point of view (and I'm not an expert)...
Having a central system (large ground DX chiller) allows you to build in diversity into the cooling system. You can accomodate for the diversity of uses in your building - with the correct design, it can accomodate for even the hottest/humidest days there, without having to tax the system.
As well, and I may be incorrect, but i believe that the efficiency of the central chiller system is higher than individual DX systems. Usually, smaller units (10 ton DX units) have a lower efficiency - typically, the larger the mechanical tonnage, the more efficient it is - and with a VFD, it will likely be more energy efficient with staging of compressors and such.
FUTURE: also having a slightly-oversized system, the flexibility is built in for future changes, especially with A: global warming and B: increased electrical/heat output of devices and/or programmatic changes, the cooling system will already be set in place and will not need a complete demo of the old small DX box on the roof. Also, in terms of maintenance, the ground chiller will be easier and cheaper to maintain then 10 boxes on the roof.
The downsides, however, are that the chiller will take up a chunk of realestate on the ground plane - which will likely need fencing of some sort, be noisier, and maybe an eyesore while the little DX units on the roof will be sight-unseen.
Let me know if I sound completely off-base...I'm an HVAC engineer turned architectural designer just in case ur wondering.
the air cooled chiller option would only take up a 20' X 30' space on the ground. Operating (2) units. Our goal is to utilize the roof as a sun deck as much as possible and a bunch of DX boxes really doesn't do it justice.
It will take several zones per floor to utilize a DX system and the thought of having 10 ton mechanical spaces all around the floorplan is not really appealing. The initial cost factor involved is coming to almost 2wice the cost when the two systems are compared(DX vs. air-cooled). This number is the obvious problem here.
Has anyone developed and designed a 5 level building using a DX system as described? and if so what are the downfalls. thanks for the repies...
a brief of prj.
Project Data:
1st Level - Diagnostic Imaging Center / 152occupany Auditorium
2nd Level - Technical Office Spaces
3rd Level - Lasik Eye Surgeon / Cosmetic Dentistry / Cosmetic Plastic Surgeon
4th Level - Alternative Office Space - Chiropractor / Physical Therapist / Etc.
5ht Level - Thermal Spa and Gym Area
approx. 20,000SF per level ~ 100,000SF
Post Tension Flooring - Precast Concrete Panel Exterior
In my neck of the woods, clients love cheap stuff (lowest initial cost) and I see the "let's just do a gazillion DX units" approach being used a lot around here. The tenants are usually metered directly for electricity, so higher utility costs don't matter to the owner. Residential A/C contractors can build the system, since it's just a bunch of smaller systems. Also, any one-man AC company (again, the cheapest) can service the system.
You are correct that your floor plans will probably suffer from the enormous number of A/C closets required and there will be a field of D/X units somewhere. Maintenance will not be fun as all these inside and outside units malfunction and die at different times, but your client may or may not care.
The best argument may be that not doing the D/X thing will save floor space and create more leasable area. I also wonder if having a half-assed mechanical system lowers the resale value of the building. Again, I'm not sure people care about that.
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