View Full Version : Ceiling မ်ား တြင္ မႈိ စြဲကပ္ျခင္း

10-17-2012, 10:55 AM
MEF မွ အကို အမ မ်ား ခင္ဗ်ာ

ကၽြန္ေတာ္တို ့ ACMV service contract ရထားတဲ့ project တစ္ခု က ceiling ေတြမွာ မႈိစြဲသကဲ့သို႕ အကြက္မ်ား ျဖစ္ေနပါတယ္။ ဒါေၾကာင့္ RH% ကို မည္မွ် ထားရွိသင့္ေၾကာင္း အၾကံေပးေစလို ပါတယ္၊Air Supply ကိုေတာ့ FCU (Chill water type ) ပဲ သံုးပါတယ္။ တခု ရွိတာက chill water return side မွာရွိတဲ့ motorize valve က fully open/ close ျဖစ္ေနပါတယ္။ 30', 45' ေလာက္ ကို ၾကာၾကာထားလို ့မရ ပါဘူး။ Air flow ကို တိုး ေလွ်ာ့ လုပ္ျပန္ ေတာ့လည္း 1hr/ 2hr ေလာက္ပဲ RH% ကို ထိန္းထားႏုိင္တယ္။ Temperature 22'C ျဖစ္ျပီး RH ကို ၅၀ ~ ၆၀ေလာက္ရွိခ်င္ပါတယ္။ မႈိစြဲတာ က FCU တပ္ထားတဲ့ rooms ေတြသာ ျဖစ္ျပီး AHU သံုးတဲ့ Corridor ကေတာ့ ဘာမွ မျဖစ္ပါဘူး။ AHU ကေတာ့ ၂၄နာရီ run ပါတယ္။ FCU ကေတာ့ လိုအပ္မွသာဖြင့္ေလ့ရွိပါတယ္(about 10hrs per day)။ ဒါေပမယ့္ ကၽြန္ေတာ္တို ့ FCU ကို continuously running လုပ္ျပီး စစ္ေဆးၾကည့္တဲ့ အခါ မွာလည္း RH% မျငိမ္တာကိုေတြ ့ရွိရပါတယ္။ Motorize Valve နဲ ့ သက္ဆိုင္ပါသလား။ Motorize valve လဲလွယ္ရမယ္ဆိုရင္ FCU တစ္ခုစီအတြက္ Motorize vale ၁၉ ခုေလာက္္လဲလွယ္ရမွာမို ့ RH% stable ျဖစ္ေစရန္ မည္သို ့ ေဆာင္ရြက္သင့္ေၾကာင္း အၾကံျပဳေစလိုပါတယ္ ခင္ဗ်ား။
Note .. Air flow is 2400CMH for 1 room and each room have 4 diffuser (600CMH), Positive pressure room. 90% Return Air use. FCU in/ out water pressure 70 / 68 psi , water Temperature 9 / 14'C .
Differential pressure of Room and corridor is 3~4Pa.


10-19-2012, 02:14 PM
Can you check this FCU's flow rate(L/s)!!!
Balancing valve opening is based on this flow rate.Once during T&C period do some body taking water balancing n air balancing???
But,you can ask supplier(eg.Daikin/Trane....)giving your FCU's model number and they will shortly answer to you that(how many turns need to open this Balancing Valve)
My thinking is if valve opening is more than necessary,outlet air temp. become less and RH% coming high.
Note-Just discussion.

10-23-2012, 08:23 PM
"My thinking is if valve opening is more than necessary,outlet air temp. become less and RH% coming high." Absolutely Right Brother.
Now we find source of problem that is cooling load.These rooms are now using for equipment store, meeting room , pantry room ..etc. Therefore cooling load is not stable.So, FCU control the balancing valve according to the temperature.But designation of air flow is stable. These condition is easy to reach the dew point temperature. Therefore we reduce the air flow from each diffuser. According to our experiment , condition is stable and RH% range is below 70%. Nevertheless we need to discuss with consultant who is calculating the cooling load before T&C period.

11-12-2012, 08:05 PM
May I ask some for understanding,
1- what did u mean 90% of RA?
2- Outside Air supply to all FCU?
3- Is it ceilng return or ducted?
4- Rigid or felxiible connection to SAD to Grilles?
Just guessed that wasn't related to chilled water flow & balancing valve nor actuator valve.

11-15-2012, 04:24 PM
Dear brother,
Warmly welcome your question .I would like to reply answer.

1. 90% RA means we use 90% of return air from the room and 10% of fresh air from fresh air duct.
2.We use 10% fresh air from FAD to each FCU.
3.All of FCU are duct type design.
4.We use flexible duct to SAD to diffuser but we use flexible duct is little bit larger than normal to prevent friction losses.
Your sentence "Just guessed that wasn't related to chilled water flow & balancing valve nor actuator valve." is acceptable answer. But we found problem is cooling load . According to consultant calculating , we provided cooling capacity. But cooling capacity is larger than actual.That's why mould can grow on ceiling that we think. The otherwise we can only suggest to customer if the room didn't use for something else , must be close FCU. This is our concept. If you have any idea please let me know.
Kindly regards