Backflow preventer

[dpoppeli]

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?

 

[tombmech]

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.

 

[CarolinaPE]

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.

 

[tombmech]

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.)

 

[PEDARRIN2]

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.