Humidity Control

[weeliang82]

What is the most suitable air conditioning system for a humidity controlled environment?

For example, in hospitals or pharmacies where humidity must be kept low all the time to keep the medicines and drugs in good condition...

In my opinion, the best system for humidity control is using VRF systems, comparing to normal air cooled split unit. Pls correct me if wrong...

P/s: In terms of Digital Scroll & Inverter Scroll, which technology is better in controlling the humidity of room?

[tmm]

Weeliang82, in general terms any air-conditioning unit will remove moisture [condensate] as part of the cooling process. To acheive this within tight limits, as might be required by the storage of drugs, I would look more carefully at the conditions which you expect to operate within.
Remember to extract moisture you must reduce the coil temperature below the 'dew point temperature'. In sustained operation [de-humidification system] the reduced coil temperature will result in the formation of ice [If you look at the average a/c controller it normally only goes as low as 18C for just this reason] which in typical VRF systems would result in a fault code [the production of ice on the suction outlet is sensed by the thermister producting the same effect as a shortage of charge].
The ice will be sensed [de-ice stat] and this will prompt a hot-gas 'defrost' to clear the coil prior to return to normal operation.
So you need to consider your local conditions and those which you wish to produce and hold before adopting any air-conditioning system.
If you post your anticipated RH Values it would be helpful.

tmm

[El Padre]

"Close control" systems address this particular need, a full function close control unit will include a humidifier, de-humidifier etc.

Try a search on close control systems.

Cheers

[Brian_UK]

As previously said, you need a dedicated system if you require full humidity control.

VRF/VRV system are comfort cooling only as are individual split systems.

[weeliang82]

Thanks to all for the prompt reply..

However, the question that my client ask me is that what are the air conditioning systems that are most suitable for humidity control. I assume that he was comparing between chiller, VRF and normal air cooled split units...

So, between the three, what are the best systems that can achieved the best result in humidity control...

In Malaysia, the Relative Humidity is around 70%

What is the target RH value in clinics/medical center?

P/s: Sorry if i'm asking noob question, as I'm quite new to the industry...

[tmm]

Weeliang82, If we can accept that the chiller is operating at 6/12 C Flow/Return & that your DX [ BE that VRF or Split System operates on or about 0C] then these would be the better option since they are significantly lower than the dew point and so will extract more mositure.

50% RH would normally be considered as acceptable for medicines.

tmm

[Emmett]

As El Padre and Brian already stated you need to use a dedicated system in which you will cool and dry the air as much as is possible and then re-heat and add humidity as required to meet your specification. At least this is how we do it for our labs which require precise temperature and humidity control.

[Brian_UK]

You need to start from the unit that is going to maintain your room conditions and then select the cooling source to suit it. Not the other way around.