vav systems and a bad design

[rhino12811]

i currently am working in a building that was built in 1986 and im quite sure that the hvacr system at that point worked great as it was,like all other systems, specifically designed for this building. the problem or CALLENGE i am confronted with is that as in other buildings when a new tennent comes into an office building thier needs of space use usually differs from the last tennent . hence there is the need for a build out. this not usually being a problem except in this case i have an etire first floor that had previously been all open to itself. the system is using pneumatic t-stats to control p.e. switches for my duct heaters in my vav's. all pretty much straight foreward. but unfortuanatly the only thing that seemed to be overlooked or more reasonably said, bypassed, was 1.the relocation of the t-stats (im sorry i, neglected to tell you that the area in discussion now has closed offices, hallways and still some open space, aproximatly 1/5 of what used to be all open space.) 2. moveing of any supply or return lines. all in all its not what youd like to see. my question is, have any of our fine fellow members ever run into this type of snafu and if not mayby someone could give me thier opinion about what they would do. and before i post this i am going to answer some obvios questions first. 1. i was not part of the build out. i only inherited it. 2. an obvious solution would be to relocate the t-stats myself and add additional ones branched into another, 3. call outside help in and get it done right quickly but at a huge cost. And finally let me say this, im not opposed to outside help and time is money and to satisfy our customers (tennents) is or should be first and foremost, unfortuanatly we recently lost our biggest tennent, who occupied the 3rd and 4th floors, therefore hireing outside help is not one of my options due to money constraints. and finally, yes last but not least QUITTING THIS JOB AND GOING SOMEWHERE ELSE IS NOT AN OPTION. YOU KNOW HOW IT IS, WE MUST OVERCOME AND CONQUER!!! so any suggestions or opinions would be apreciated!!!! THANKS EVERYONE.

 

[lilliput1]

The ductwork & thermostat must be zoned for each tenant & for perimeter or interior zone. The corresponding heating & cooling load of each zone should be calculated. Verify that there is adequate air/capacity for cooling & for heating. Make sure return air from zones can get back to the AC unit. Provide required minimum OA for ventilation at eac AC unit.

 

[imok2]

rhino12811
You seem to be making more out of this then it really is.
If you were designing a new VAV system for this floor, where would you start?

1 It was an open room with a required CFM to handle the heat load so if you can determine what that was you know what you can start with.
2. Make an overlay of the new floor layout and as lilliput said... determine what each heat load will be for each office and open area.
3. then you will know how many boxes you will need to have or remove, sizes, locations and thermostats to install for good control
4. Break it down in small steps

 

[rhino12811]

point well taken. i apreciate your help guys, thank you.

 

[paulkeating]

What bothers me is how you managed to lease out space to a tenant and have him belive that the a/c system could do more than it actaully could handle!!! Either the tenant was duped by you or he's trying to dupe you!!

I agree that you must treat it like a new project, come up with a fresh design (and try to end up with much the same main ductwork layout as you have existing) and then overlay your NEW design onto your EXISTING layout, look for what doesn't match, then start seeing what you can do to massage the NEW design back towards the EXISTING. When you can't massage it any further, well the remaining differences are what (a) you must pay to get done, or (b) the limitations your new tenants must accept. Maybe the tenant lease contains a clause that defines exactly what it was he bought in terms of a/c capacity and flexibility, so is there a chance he (the tenant) wil have to pay for the work?

And another thing - I was concerned about ypour remark re return air pathways being "obstructed" etc - how does that affect your smoke hazard management? Here is Australia that's a big problem with fit-outs where the building manager was too easy on the tenant and DIDN'T DO HIS JOB PROPERLY, only for the building manager to find that the smoke system fails it's annual re-testing .... and the building then faces a 14-day "fix it or we shut you down" notice ....