PagoMitch
Mechanical
- Sep 18, 2003
- 66
Hopefully someone from a tropical area can help here; have a real goofy problem.
Currently doing some work in a hospital in the tropics. Chilled water supply temps are 42F, return is 57F. Needed the large delta t in order to use existing piping and still meet load requirements of 480 tons now, 720 tons when all areas are conditioned.
The problem is condensation. Using 3 layers of 1" thick Armaflex/Rubatex cellular foam product, with the smooth-skin vapor barrier, the system works most of the time in the un-air conditioned corridors. However, the piping passes through several "fales", or large open seating areas with openable windows. This added load makes the supply line insulation condense - not a lot, but enough to keep buckets in the corridor under the drips.
They now want to provide air conditioning to another building, which will require a 6" supply/return lines to run under a breezeway type cover about 70 feet. This will subject the piping to the full outside air design conditions of 90F at 90%RH; this yields a dewpoint of about 87F.
Unfortunately I cannot just add more insulation. The concrete structure that supports the piping will not accommodate piping any larger. I've talked to some of the engineering staff at hospital facilities in Honolulu, and they get by with 2" of insulation; it's just a lot more humid here. The only solutions I can come up with is:
1. Using a pair of 4" chws pipes and increase the insulation to 4", or
2. Install some anti-freeze type heaters on the last layer of insulation, and then cover with aluminum weather cover. The heaters could be controlled by dewpoint sensors, similar to chilled beam condensate controllers.
Both of these solutions seem...nuts to me. Unless someone has any recommendations for other insulation? We actually tried 3" fiberglass with vapor barrier. But it did not work as well as the Rubatex, and worked WORSE when abused and crushed; condensation would form and saturate 40' lengths of insulation, making a mess to clean up.
Currently doing some work in a hospital in the tropics. Chilled water supply temps are 42F, return is 57F. Needed the large delta t in order to use existing piping and still meet load requirements of 480 tons now, 720 tons when all areas are conditioned.
The problem is condensation. Using 3 layers of 1" thick Armaflex/Rubatex cellular foam product, with the smooth-skin vapor barrier, the system works most of the time in the un-air conditioned corridors. However, the piping passes through several "fales", or large open seating areas with openable windows. This added load makes the supply line insulation condense - not a lot, but enough to keep buckets in the corridor under the drips.
They now want to provide air conditioning to another building, which will require a 6" supply/return lines to run under a breezeway type cover about 70 feet. This will subject the piping to the full outside air design conditions of 90F at 90%RH; this yields a dewpoint of about 87F.
Unfortunately I cannot just add more insulation. The concrete structure that supports the piping will not accommodate piping any larger. I've talked to some of the engineering staff at hospital facilities in Honolulu, and they get by with 2" of insulation; it's just a lot more humid here. The only solutions I can come up with is:
1. Using a pair of 4" chws pipes and increase the insulation to 4", or
2. Install some anti-freeze type heaters on the last layer of insulation, and then cover with aluminum weather cover. The heaters could be controlled by dewpoint sensors, similar to chilled beam condensate controllers.
Both of these solutions seem...nuts to me. Unless someone has any recommendations for other insulation? We actually tried 3" fiberglass with vapor barrier. But it did not work as well as the Rubatex, and worked WORSE when abused and crushed; condensation would form and saturate 40' lengths of insulation, making a mess to clean up.