VE considerations for new Courthouse.

[PuertoRicoMEP]

Hi, I have been working with an earlie design (Design/development phase) for a new Courthouse and the engineers suggested some VE Items. The problems is that I am not sure of what he or she really wants. Here are the VE items.

1. Specify R-134 chiller in lieu of R-123 chillers.
~~The design has 2-250Ton water cooled chillers. The narrative suggest the usage of centrifugal chillers. In my understanding I should use screw chillers in order to change my gas to R-134. No taking in considaration other future costs, does the present cost of a screw chiller will be lower than a centrifugal chiller?

2.Provide outdoor air varaible volume intake fan system in lieu of outdoor air preconditioning unit.
~~The design has an OA AHU of 10KCFM. They want to replace the preconditioning unit with an AVV(air varaible volume)intake fan. Does this will affect the performance of my AHU's? Do I have to change the capacity of the unit that is connected to this OAAHU?

3.Use draw-out type breakers vs. insulated case power breakers in main distribution switchboards.
Like I said at the beginning, I am working with DD drawings, therefore I do not have a complete breakdown of the different power distribution equipment. The building will have an estimated load of 4Kamp@277/480V service. It will have Switchboard,Switchgears as the MDPE 's(main distributions panels). What will be the difference of an average percentage in cost between a draw-out type and an insulated case power breakers type braekers?

4. Add UV filter on AHU's.
What is the difference in cost and use between an UV filter and a HEPA filter?
.

 

[quark]

1. There are centrifugals for R134a but they run at higher pressres than that of R123. You can have better capacity control with centrifugals particularly if you have VFD and antisurge controls. Screw chillers are relatively cheaper.

2. If you are not pretreating the outside air then you have to do it in your AHUs and it is one and same either way. Moreover, variable volume outside system is not an alternative for outside air preconditioning system. It may be that you have to equip your outside air preconditioning system with variable volume system.

3. Not an expert on this. Electric Power Engineering is the right place to ask.

4. It may be a UV bank. HEPA filters can stop bacteria to some extent from entering into the area but you have to use disinfectants to kill them later. UV light kills bacteria but it can't take care of particulate matter where as HEPA filters do this effectively. Cost difference is irrelevant.

Regards,