Water softner for HVAC

[Manu68]

Hello Experts,

I was looking for the details for the water quality for humidification system in AHU of HVAC system.
Can you please provide the permissible limits of the TDS (Total dissolved salts).

I found that most of the softners handle the Calcium and Magnesium salt in the TDS. However they do not reduce the Clhoride salts.
I am under the impression that Calcium and Magnesium salts are the ones to be addressed and not Clhoride.
Since Clhorides are more towards the Potable water for the drinking purpose. I heard from suppliers that for Chloride removal we need Reverse osmosis and not just water softner. Is that true?

Are there any experience yu could kindly share. What is the recommendation from ASHRAE.

Thanks in advance.

Best regards,
Manu

 

[PEDARRIN2]

You would likely have to follow manufacturer's guidelines for maximum TDS

Ionic softeners exchange sodium for the calcium and magnesium. They do not lower the TDS, merely change the constituents.

If the humidifier "boils" the water, there will be issues of precipitating whatever dissolved solids are in the water. We typically design a reverse osmosis system with softening upstream. This will remove ~95% of all the ionic components. If the source water is domestic, you will have to use some carbon adsorption upstream to take out the chlorine (no chlorides) which will degrade the reverse osmosis membranes.

If the humidifier atomizes the water by forming very small droplets, you can probably get away with just a softener. We have specified the TAC type "softener" by Watts (One Flow) for these applications with fairly good success. That way you do not have the brine to deal with.