Forzen Coil

[ChipFuller]

On our plant, we have a bay with an air handler plus unit heaters. This past winter the coil on the air handler froze. The reason is because it’s modulated steam going into the coil with the main condensate return being 42” above the return on the coil. Because of this situation, there is not enough steam pressure to lift the condensate. This causes the condensate to flood the coil then freeze.

One option was to raise the air handler so the condensate gravity flows into the main condensate return. I can’t do that because of the height issues.

Here’s my question I was wondering if I installed an orifice union around the modulating valve and replace the F&T trap with an inverted bucket trap if this would provide enough lift to prevent the flood coil. My other thought was to install an automatic pump trap to lift the condensate or an Armstrong Posi-Pressure System. Has anyone installed an Armstrong Posi-Pressure Systems before? Any thoughts or comments would be appreciated.

 

[imok2]

Go here:

http://www.google.com/search?q=lift+fittings&sitesearch=

http://www.shipcopumps.com

Click on "single step lift"
This fitting is good for a maximum of 5 feet

 

[SAK9]

Also check if you have got a "vacuum breaker" installed at the coil inlet.

 

[steamguy1958]

One option on this application is to install a "safety drainer" arrangement. This arrangement incorporates a second trap into the system. This trap is installed by adding a tee in the vertical drop between the coil discharge and the primary trap and piping over to a second F&T which discharges to a drain located at a point that is below the AHU's level. The idea is that in any instance where the your control valve modulates back to the point where there is no longer adequate differential for drainage through the primary trap, condensate will back up to the tee and then go to drain through the safety drainer as opposed to backing up into the coil. This piping practice is outlined in Armstrong's bulletin N101 Steam Conservation Guidelines. As mentioned before, incorporating a vacuum breaker into the system is a very necessary component for this arrangement to work properly.

If a drain is not available, a second option would be to use a product that acts as a standard F&T trap when differential is present and acts as a steam motive pump in the absence of differential. Sarco is the only manufacturer that comes to mind. This would be found on their website and is marketed as the APT series trap.

I hope this information helps!

Danny Morrison, Owner
Industrial Products Group, LLC