Comfort Cooling, but 50%-70% limitation

[Makeit go Right]

I have an application where a large printer needs cooling, and the room conditions wanted are:

Drybulb……….20 – 25 degrees C
Humidity……..50% - 70%

My (simple) plan would be to install a cassette, with the possible add-on of a small humidifier unit plugged into a power socket with a humidistat, to guard against the humidity dropping below 50%. Maybe set it at 55%RH.

I am trying to avoid a close-control system unless really necessary as the price spirals, as does the client, and he will start looking elsewhere.

On the other hand, this “simple” solution may not be a real solution at all, and wind up a mess for me as the installer – what do you think, anyone?

[Brian_UK]

It could work but a couple of things to contemplate...

What sort of printing takes place? some print actions produce an awful amount of paper dust and similar which can clog up filters and evaporators really quickly.

What type of humidifier are you going to use? A steam generator can work but if it is a small unit what are the expected cylinder replacement costs going to be and how often?

Also will the 'small' unit be able to provide the duty during the winter period?

WIll you have to provide a ducted fan driven system to deliver the humid air into the space?

Overall, yes it could work; I've seen it done before if things are sized correctly and sufficient attention is given to filter cleans etc.

[sihombing]

dear Makeit go Right,
can you please give the dimension of your printing room? How much the cooling capacity you need for that room and also the relative humidity (outdoor)?

rgds,
sihombing

[Andy W]

I have experienced the exact same scenario quite a few times, what I did was:

Give the customer a quote to install a close control system which as you know costs lots but is absolutely guaranteed to do the job and watch the customer faint, alternatively explain that a basic no thrills air con system will control the temperature just fine and humidity for most part of the year but occassionally the humidity may rise and if it becomes a problem a small humidifier could be installed and at the stage the sizing of a humidifier could be calculated more accurately.

It is all down to cost at the end of the day, give the customer both options he will go for the cheapest and it gives you a little protection as you have forewarned him.

[Mickvee]

I would also check the if any chemicals vapours are around as I have seen at printer where the evaportor coils have been corroded by the printing chemicals vapours.

[NoNickName]

We have experience with such jobs. We did a/c for a company in nottingham which prints gas invoices and envelopes.
Close control is the way to go, possibly with washable filters. The paper dust is really an issue.
Some companies require explosion proof equipment when the airborne dust is thick.

[frank]

You've also got to make sure that you don't direct the airflow over the presses as this tends to dry out the ink :eek: - they are very sensitive bits of kit :(

[Darshi]

I think this job can be done without refrigeration and heating.

Indoor air Quality can also be improved considerably by using 100 fresh air.
Create ambient building connectivity and your client will bless you forever because he saves Pounds every hour.

Use an air to air heat exchangers to bring out door cold air in summer and add humidity if required.
In winter the machine heat could be recovered by the same exchanger.
If you can provide design parameters,i will be glad to help you design a most energy efficient comfort cooling system for this application.The Air to Air Heat exchangers are available in England and are available ex-stock

[Peter_1]

Darshi, they want 20-25°C, what will you do when it's outside 30°C when there's heat production inside and you use 100 % fresh-air????
Won't work.

What I should do, install an indoor unit 1 size larger then the outdoor unit.
I think the client made that spec because it was written somewhere on a manual but printers these day can work under large variations of temperatures and humidty.

[Darshi]

Peter,
If the temperature goes to 30 deg C the Rh will come down below 50% and if that is so,we can perhaps use indirect/direct evaporative combination.

The air quantity required may be almost double or even more but it may still save the refrigeration energy costs.
No doubt ,the system can work only if the ambient DB-WB =>10 or in other words the ambient RH at 30 deg C is < 30% or lower. As I said earlier,it will depend on the ambient conditions.What is the summer design data for this location?