×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Small Chill Water System

Small Chill Water System

Small Chill Water System

(OP)
I am trying to put together a small chiller system for an existing in-row cooling unit in a server room. [u]We are keeping the in-row cooler[/u]. Is it acceptable to purchase a 3 ton residential type condensing unit and then match it with an indoor refrigerant to water brazed plate heat exchanger with all the necessary pressure, temperature, flow and refrigerant controls.

I understand that I will have to include some kind of low ambient control on the condensing unit.

I am also installing a buffer tank and small expansion tank on the chillwater side.

There are complete systems available - both glycol and split - but they are cost prohibitive.

Any tips would be appreciated.

RE: Small Chill Water System

I'm a little surprised all that equipment is that much less cost than a 3-ton in-row Liebert split system. Is low ambient control on a residential type unit going to be good enough where you are? Where I am, that wouldn't work, we need control down to -20F.

RE: Small Chill Water System

(OP)
We presently have an APC In Row chilled water unit that is supplied from our main building chiller system. Works great until the power goes down. The building chiller is not on our generator circuit. I am going to keep the APC unit and supply chill water from a different source that is supplied from our generator circuit.

I'm going to 0F for low ambient. Indiana. We've been using our building chiller all winter anyway - that can't be good.

I haven't paid enough attention to low ambient until I started to research this project. I've been quoted refrigeration units to cope with the low ambient.

RE: Small Chill Water System

Two challenges with running a resi/light commercial condenser in low ambient conditions: oil return and head pressure control. Fan cycling wears the condenser fan motors out more quickly. There are single phase controls that can turn the condenser fan into a variable speed, responding to condenser pressure or temperature. Hot gas bypass would be an additional low ambient aspect on top of controlling the condenser fan; using that depends on how steady the heat load is in the conditioned space, and whether or not you can maintain at least 100-105°F condensing temperature in the condenser during your coldest weather.

There's also a device on the market called a Rawal valve that is supposed to offer some form of condenser capacity control as well. I haven't really studied how that device works but I know it's been around awhile. Could be similar to a "headmaster" control used in commercial refrigeration.

RE: Small Chill Water System

Also, have you thought about not completely unplugging from the chilled water supply of the building's central plant? In other words, if your little 3 ton resi condenser craps out, would you have the ability to switch over to building chilled water to tide you over until the three tonner is repaired?

RE: Small Chill Water System

You might be better off starting with a walk-in cooler condenser unit. Likely already has provisions to work in low ambient.

RE: Small Chill Water System

(OP)
Thanks everyone.

We will keep the in row unit connected to the building chill water system. We'll just open the isolation valves if needed.

I do have a vendor that can put together a standard residential condensing unit with low ambient control(s). I am already seriously considering a walk in cooler type unit. It has the head pressure control that has been referred to.

RE: Small Chill Water System

Why don't you buy a small chiller rather than trying to make one out of parts? Trane CGA/VGA, York YLCA...

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources