Chilled Water System - Pay Back Period

[Buildtech2]

Hi Guys,

Can anybody tell me what would be the pay back period of a chilled water plant for residential blocks of capacity approximately 465 Tons. I need to give this information to one of my client as he need to make a decision between chilled water and DX system.

Thanks

 

[cdxx139]

Simple payback is determined by the difference of first cost of the two systems divided by the difference of operating costs of the two systems.

What are the components of each system? Is the chilled water system water cooled or air cooled?

knowledge is power

 

[Buildtech2]

Thanks for your response.

The chilled water system is air cooled.

 

[Buildtech2]

Further to my previous post, I would like to comment as follows.
The proposed two systems are:

1.DX split system

2. Air cooled chilled water system

 

[KiwiMace]

First cost, operation and maintenance are the main parts of the equation here, but payback period means money, so it depends on who is paying for what. They might be selling cooling to the residents at a fixed price, in which case it is important to produce the cooling as cheaply as they can. Small DX split systems may be sold with the apartments, handing off all future responsibility for the operation and maintenance costs, then code minimum will probably prevail.

You need to have a good handle on where the money is changing hands to make this calc.

 

[cdxx139]

Youll find the kW/ton difference for air cooled vs DX to be not substantial enough to offset the increased cost, and your payback could be over 10 years. The benefit is in the intangibles like occupant comfort, not soemthing a developer is going to put to high on his priority list.

knowledge is power

 

[RobsVette]

Agreed with the above items. You might get a little bit of savings from economies of scale (since you would be doing all the cooling in one spot) however the traditional reasoning for using a central cooling plant in a building or campus is the be able to use a machine that can use an open cooling system (Condenser water system with cooling tower) that allows you to use a condensing temperature at the outdoor air wetbulb as opposed to the outdoor air dry bulb that can be attained using an air cooled machine. This reduces you condensing temp dramatically and as a results saves alot of energy (and space.)