surface duct condensation

[alfredobertiz]

I have installed split ducted air handling unit DX type the ducting system was insulated with 1 inch thick rubber. My problem is, during extreme condition condinsation is present on the duct surface. How can i eliminate this condisation. At what outside condition and supply air duct temperature should the condensation remove. shall I replace 1 inch thick with 2 inhes thickness insulation. please help

[nike123]

Download this software (http://www.armacell.com/www/Armacell/INETArmWinASDownload.nsf/frmMail?OpenForm&Lang=UK) and make your own calculation.

[Abby Normal]

you can try more insulation

typically the surface of the insualtion will be a few degrees cooler than the ambient air

sometimes duct work is installed in vented attics, and in particular attics with a steep pitch

When it is hot and sunny out, the air in the attic gets superheated, 60C or more

the surface of the insulation in this case is very high as it will not be too much cooler than the super heated air.

Under less extreme situations, and especially with the steep roof, the hottest air can stratify up high, and the air surrounding the duct work is cooler. This could end up with the duct surface cool enough to sweat.

Where I am there are very high dewpoints 27 to 29C. When tropical systems come through, the dry bulb temperature is not much different than the dewpoint. It is overcast, raining heavily, so the attic air is not overly hot, and has an extreme dewpoint.

The surface of the insualtion will be a few degrees cooler than this surrounding air, and will sweat profusely. Sometimes all the insulation in the world does not help.

If this is an indoor sweating problem it should be solvable with more insualtion and DUCT SEALING. If these ducts are exposed to ambient air, you may be looking to minimize the problem

[nike123]

I have installed split ducted air handling unit DX type the ducting system was insulated with 1 inch thick rubber. My problem is, during extreme condition condinsation is present on the duct surface. How can i eliminate this condisation. At what outside condition and supply air duct temperature should the condensation remove. shall I replace 1 inch thick with 2 inhes thickness insulation. please help

You should use specialized insulation instead of rubber.
Rubber doesn't have properties for that purpose.
Check this specialized products (http://www.armacell.com/www/armacell/armacell.nsf/ansHTMLSeitenLookUp/USA-TI_Frame?OpenDocument) and calculate required thickness on this site (http://www.armacell.com/www/ArmWinAS/armwinb.nsf/webcalc?OpenForm&Seq=2&Country=UK&Language=English&a).

[icecube51]

if youre system is working correctly,the simplest solution could be a extra condensate tray underneed the duct,and connect the drain pipe whit the duct drain pipe.
if its on a attic,it will bother no one.

just a hint to keep it simpel,;)

Ice

[nevgee]

if youre system is working correctly,the simplest solution could be a extra condensate tray underneed the duct,and connect the drain pipe whit the duct drain pipe.
if its on a attic,it will bother no one.

just a hint to keep it simpel,;)

Ice

Drip tray under a duct to collect condensation :eek:....where's the drip in all of this?
Surely it would be good practise to provide proper insulation to avoid any condensation. A good insulating material. fibre glass, phenolic foam, expanded rubber etc and a good vapour barrier would prevent any condensation problems.

[icecube51]

Drip tray under a duct to collect condensation :eek:....where's the drip in all of this?

try and read between the lines, done it many times. everything is working normal till the gif a "spaghetti evening",and it starts to rain,just in the area of the duct.:o. come and fix this please...... put a extra tray underneath and "voila"...problem solved. and on very low budget to.:p try and give some estimate whit special insulation and see where it gets you.

Ice

[Peter_1]

...split ducted AHU... DX ....insulated with 1 inch thick rubber. Problem...extreme condition condinsation on the duct surface.
How can i eliminate this condisation. At what outside condition and supply air duct temperature should the condensation remove. shall I replace 1 inch thick with 2 inhes thickness insulation. please help

If you have condensation, then this is because your surface cools to dewpoint conditions of the surrounding air.
How to avoid: increase condensation temperature inside your ducts or decrease humidity around the outside of the ducts.
At what conditions will it disappear? At temperatures above your condensation temperatures which you can't predict without more specific information.
So increase thickness of the isolation or choose another and better isolation type then you have now.

[nike123]

or increase humidity around the outside of the ducts.

You surely mean decrease humidity instead of increase.;)

[Peter_1]

Oeps, edited

[vijay_study]

Hi,

While selecting insulation thickness select for condensation in lieu of heat loss if high humidity ambient is prevalent.

Following data shall be required before hand to select insulation material thickness
a) Supply air temperature inside duct
b) Ambient air temperature and relative humidity

Thanks

[Ke-Fibertec UK]

Using textile ducting when supplying the air below dewpoint, will still not result in surface condensation forming.
Textile ducts do not need to be insulated as the air passes through the material meaning the temperature on either side of the duct is the same.

[Brian_UK]

Using textile ducting when supplying the air below dewpoint, will still not result in surface condensation forming.
Textile ducts do not need to be insulated as the air passes through the material meaning the temperature on either side of the duct is the same.If you resist the 'salesman' instinct within you then might have read the thread properly and realise that your product is unsuitable for this application :(