×
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

Backflow preventer

Backflow preventer

Backflow preventer

(OP)
A small constant-temperature room air-conditioner condenser unit will usually be cooled with about 5 gpm chilled water.  I am providing domestic-water backup connection which would be higher flow due to higher temp.  I know I need backflow preventer.  Question is will double check valve be sufficient or is reduced pressure type needed?  Rephrased, would a refrigerant leak into domestic water be considered a health hazard taking into account refrigerant type/pressure/quantity?

RE: Backflow preventer

Probably, but I think your concern is focused on the wrong thing: the chemical treatment in the chilled water would be the primary concern.

Water makeup to chilled water or condenser water systems are always supplied from a backflow prevented source - a reduced pressure, double check type - it doesn't sound like this application is much different.

RE: Backflow preventer

Is it a dual cool unit (chilled water & refrigerant)?  For a room a/c (aka "window unit") I have not seen one on chilled water much less dual cool.  How would you cross contaminate a refrigerant line with a water line?  If you have  a manufactuer and model number or spec "cut sheet" I could take a look at it for you.

RE: Backflow preventer

I think he described a water-cooled condenser using chilled water, and then potable water as a backup.  That's a common method for water-cooled equipment.  Cooling tower water is not always available, or the chilled water source may be air-cooled, anyway.  In the old days, it would've been cooled with potable water and just dumped - but we don't do that anymore.  (Although I still find ones that were installed that way.)

RE: Backflow preventer

I did a project for a MRI room where the condenser had a potable water backup.  We had to supply a 1.25" domestic water line with a reduced pressure zone backflow preventor and a floor drain under a raised floor.  So they are still out there.

I always spec a similar piece of equipment when I supply water to a piece of HVAC equipment unless the equipment has an integral air gap, then I just supply the water.

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