air conditioning and open freezers

[friocold2008]

Good eveving people. I would like to tell you about a problem I´m having, hoping you could help me out with it.
There is this small frozen food store (about 100 sq meters) which sells lamb, ham, turkey, salmon, meat cuts, octopus, squid, etc. All of these products are located in open aisle type freezers. There is an air conditioning system which is suppose to provide cooling. The problem is that whenever the air conditiong system is operating, the cooled a/c air plus the cold coming out of the freezers create uncomfortable temperature for both the employees and the buyers: between 18 and 19 deg. C. On the other hand, if the a/c system is turned off, ambient temperature get better, but I´ve noticed that excesive amount of frost accumulates in the evaporator coils of the refrigeration equipment, I guess due to the lack of humidity control, otherwise supplied by the a/c system.
Is there any way to obtain humidity control from the air conditioning system without overcooling the store?
I´m no expert on a/c and would like to get some advice from any of you.
Regards.

[fowlie]

i am not clued up much on ac but iam sure they can reduce the humidity when you lower the speed of the fans allowing the cassettes to condensate more moisture on the coils,maybe you should repost this into the a/c forum as they guys would know for sure

[friocold2008]

Thank you very much fowlie. I`ll do as you say and post this in the a/c forum.

[Thermatech]

Are you able to take humidity measurments in the store with the ac cooling for one day & then on another day with ac off ?
What type of refrigeration units & ac system is installed in the store ?

Here in the UK I have on been on trouble shooting site visits to this type of store & found that the display cabinets have integral condensing units.
In this case the ac is installed because the intergral condensers are heating up the store.
but
This also makes the cooling load very high sensible heat load & so the ac is running in very low humidity conditions.
The return air sensor location & ac supply air flow needs to be carefully considered as heat from the integral condensers can short circuit into the ac unit return air flow & force the ac to continually cool when most of the store is already cold enough. In this case the ac can overshoot the set temperature.

[750 Valve]

reheat is probably the best way, remove the required moisture via refrigeration and then reheat back to desired supply air condition

[joe magee]

I'll assume you mean tubs or single deck freezers. Is it possible the registers are blowing air towards the cases and disrupting the air curtain? If that happens Your moisture laden floor air will infiltrate the case causing that frost buildup. I'm thinking Panama is very humid and just dropping the temp might not remove the moisture without some type of aux heat possible a furnace in the duct. Good luck

[sajigeorge]

you can control the humidity buy the air conditioner with maintaining temperature if you have heating sours (electric or furnace> by installing humidistat to maintaining the humidity, and you have to rewire the ac unit with heat and cool thermostat and humidistat.
good luck
saji,