Humidity causing algae and moss

[meab]

Hi All

Have a chilled water system for air-conditioning of hotel rooms, my problem is in the rooms we are so damp and having algae and moss forming and have to repaint on a very regular basis the normal humidity levels are approx 84% in the mornings and approx 64% in the evenings. Any ideas on how i can over come this

Thanks

[Gary]

In order to achieve ~50% RH, the temperature of the air leaving the coil needs to be 20F/11K lower than the temperature of the air entering the coil. You probably need to lower the water temp. The alternative is to slow the airflow through the coil.

[r.bartlett]

Your probably have oversized units which cool the rooms before removing sufficient humidity. Do the units have any for of heating..Silly question I know considering the location. I am free for site visits btw :-)

[Magoo]

Totally agree with Gary's comment, get the chilled water temperature down. The coil temperature needs to get below the air dew point to start removing moisture and lower the RH %. The chilled water loop temp should be in region of +6.0 'C entering cooling coil

[meab]

Thanks Guys: the temp of water currently about 10 degrees do not have heating option. will try and get the temp to about 6 degrees and see.

Thanks again

[r.bartlett]

What about blocking off half of the coil to reduce the capacity which will make the unit run sufficiently longer to remove the humidity..

[chillerman2006]

Hi Meab

one thing to look out for if the chiller is running on R407c, you can not drop the chilled water temp below 8c without risking freezeing the vessel, you can if you introduce glycol into the system but then you require more energy consumption to cool the same amount of water.

just be aware of R407c & its glide

R's chillerman

[Gary]

What about blocking off half of the coil to reduce the capacity which will make the unit run sufficiently longer to remove the humidity..

Two things need to happen:

a. The coil needs to be cold enough to remove the humidity.
b. The system needs to run long enough to remove the humidity.

If the coil is not cold enough, then it doesn't matter how long it runs. It can't get there.

[install monkey]

are the flow rates correct? ie as per comissioning sheets,filters clean, bathroom extract fans working? is there fresh air supply to the fan coil? if so warm the supply air to lower the humidity of the supply air( moisture content will be the same but rh will be lower)

[Gary]

are the flow rates correct? ie as per comissioning sheets,filters clean, bathroom extract fans working? is there fresh air supply to the fan coil? if so warm the supply air to lower the humidity of the supply air( moisture content will be the same but rh will be lower)

If the moisture content is the same, how does that help?

[r.bartlett]

Two things need to happen:

a. The coil needs to be cold enough to remove the humidity.
b. The system needs to run long enough to remove the humidity.

If the coil is not cold enough, then it doesn't matter how long it runs. It can't get there.

Indeed but chilled water at 10 C in a tropical climate I would expect it would already be on the wet bulb line without the need of reducing it further but i do not have a psy chart to hand

[install monkey]

warming air lowers the rh it still contains the same ammount of moisture in the air but warmer air can hold more moisture thus absorbing some of the damp windows/walls.
i asked about the ventilation as expelled co2 has a high moisture content,also using a shower without mechanical air extraction can send humidity levels through the roof

[r.bartlett]

warming air lowers the rh it still contains the same ammount of moisture in the air but warmer air can hold more moisture thus absorbing some of the damp windows/walls.
i asked about the ventilation as expelled co2 has a high moisture content,also using a shower without mechanical air extraction can send humidity levels through the roof

I've been on holiday there and the bedrooms I frequented in two different hotels felt cold and clammy..

[chillerman2006]

I've been on holiday there and the bedrooms I frequented in two different hotels felt cold and clammy..

That's how I describe my mrs mate :D

[install monkey]

did u nick the dehumidifiers and wee up the walls?:p

[Gary]

Indeed but chilled water at 10 C in a tropical climate I would expect it would already be on the wet bulb line without the need of reducing it further but i do not have a psy chart to hand

If the coil surface temp were 10C, it would indeed be cold enough to do the job... but perfect heat transfer seems unlikely. The coil surface temp is going to be substantially higher than the water temp.

[r.bartlett]

That's how I describe my mrs mate :D

she's fine with me and the lads down the fire station:D

[chillerman2006]

she's fine with me and the lads down the fire station:D

:D:D:D you fookher, litrally:D:D:D

[Gary]

warming air lowers the rh it still contains the same ammount of moisture in the air but warmer air can hold more moisture thus absorbing some of the damp windows/walls.


If you raise the temp, thus lowering the humidity, then drop the temp back down, thus raising it's humidity... what is gained?

[mad fridgie]

i would suggest that it is the use of the room more than problems with the AC, If it is hot and humid out side, you come in crank up the AC while you are there, bring the mass of the structure down in temp. When you leave the AC goes off, fresh air is introduced, condensation is formed. Everthing is damp.

[chillerman2006]

i would suggest that it is the use of the room more than problems with the AC, If it is hot and humid out side, you come in crank up the AC while you are there, bring the mass of the structure down in temp. When you leave the AC goes off, fresh air is introduced, condensation is formed. Everthing is damp.

Evening Mad

That makes good sense, I spent a couple of weeks working in scotland winter 2009, I was freezing, every morning I left for work I would leave the heating on to come back to a warm room & every night I got back, I found the heating had been turned off by hotel staff. checked for pir's so it must have been them

ps. I'm a southerner not one of these tough scotsman in kilts & tee-shirts all weathers

[Gary]

i would suggest that it is the use of the room more than problems with the AC, If it is hot and humid out side, you come in crank up the AC while you are there, bring the mass of the structure down in temp. When you leave the AC goes off, fresh air is introduced, condensation is formed. Everthing is damp.

That would fit into the not-running-long-enough-to-do-the-job category... and bringing in fresh air would no doubt make things worse.

I don't doubt that it's all of the above.

[benijoseph]

Mr meab,

R u happy with the cooling part if yes! change the wall paint with a gel based paint which have low
retention of humidity HAVE good sealing of the door ,keep it closed always .

rgds.

[chillerman2006]

Mr meab,

R u happy with the cooling part if yes! change the wall paint with a gel based paint which have low
retention of humidity HAVE good sealing of the door ,keep it closed always .

rgds.

Yeah thats sounds good :rolleyes:

It will be running down the walls and soaking into the bed ! (water bed anyone):D

Your not in the Trade of Hotel Refurbishments are you ?

Meab, just listen to all the good answers on how to lower RH

Dont mask a problem - Cure It

[benijoseph]

Mr.chill,
DON'T GET HOT, HOTEL REFURBISHMENTS ALSO IS A GOOD TRADE I DON'T MIND DOING IT FOR A GOOD CAUSE,
if meab is happy with the cooling then he can try! no AC can induce Rh into the room.
HUMIDITY HAVE TO COME FROM OUT SIDE ,with good cooling Rh of the room will never go up!
rgds,