A/C only system(s) for restaurant dining room


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Old 01-23-19, 08:22 AM
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A/C only system(s) for restaurant dining room

I'm on Roatan Island in the Caribbean where it's hot and extremely humid year round. I'm working up plans for an 80 seat restaurant dining room.

Electricity is nearing US$0.40/kWh with frequent outages. I'm contemplating multiple small split systems evenly distributed around the perimeter as they are the most energy efficient and I can turn some of them off when occupancy is low. My concern is units directed into a common space will fight each other to control the temperature as each unit has its own thermostat. Is this a reasonable concern?

Electricity is US equivalent 120/240. Three phase power is not an option as it's unreliable; I'm an EE.

I'm looking for suggestions on how to approach the problem of cooling the space including using dehumidifiers in addition to A/C only inverter based units. During rainy season, cooling requirements are low but mold control is an issue.

The folks that maintain A/C and refrigeration equipment on the island are not trained professionals, so I can't/won't ask them for an opinion.

We ship product out of Miami, so recommendations for what units to purchase are also appreciated.

Thank You
 
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Old 01-24-19, 04:40 AM
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Air-conditioning needs in a restaurant are not that simple.
You will have a kitchen where you will need to have a continuous air change which will use an exhaust fan and air make up unit to to replace exhausted air.

It is normal to have an air-conditioning unit in the make up air to make the kitchen space reasonably comfortable.
Apart from this you will have air-conditioning in the dining space for clients and servers.


Mini split units would work and be relatively inexpensive but you need to be aware of the need to frequently clean the evaporator coils and fan when installed in a restaurant.
If there was a separation and door between the cooking and dining area you could reduce regular cleaning but mini-split units are not that easy to dismantle.


If you do use mini-split units it would work well to get a system that can have multiple evaporator coils connected to a singe outdoor unit.
Control between the individual evaporators would be averaged between one thermostat or individually cycled if you have multiple thermostats.
 
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Old 01-24-19, 05:24 AM
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GregH:
The plan is to have the kitchen behind 2 sets of swinging doors to minimize any environmental contamination to the dining room. I'm considering a push pull system of typical kitchen exhaust fan plus another fan located on the outside wall of an adjacent storage area to push outside air into the storage area to slow the air and muffle the sound. A perforated & filtered wall element pushes that air into the kitchen as make up air. I'm looking for an ever so slight negative pressure in the kitchen to help contain contamination.

With the high electrical costs here, no one puts A/C into the kitchen area. Believe it or not, I get a chill when the temp gets below 80 degrees after being on the island for over a decade. Kitchen staff are acclimated to the temps they typically see all over the island.

My concern is for the dining room where the body heat load varies between 0 and 90 people considering patrons and staff. Again, electrical costs are a primary consideration and is why I'm looking at maybe 10 one ton mini split units because as units get larger, they also get less efficient. I could add more units if required via experience.

My experience with a high efficiency Friedrich inverter test unit shows the need to clean the compressor about once a month. The air handler screen never looks dirty, but I wash it anyway and can then see a tiny dust buildup. It's the compressor I'm concerned with as the aluminum fins are packed so tight that no tool can be used to probe if there's dirt in there. Given its construction, there's no way to shoot water from the inside outwards to push out dirt the way it came in.
 

Last edited by GregH; 01-25-19 at 04:15 AM. Reason: Reformat unintentional link
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Old 01-24-19, 08:51 AM
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On a split unit..... the compressor is outside in the condenser.
Inside you have the filter and the evaporator coil that needs cleaning.

A condenser shouldn't need a monthly cleaning unless it's sitting on dirt.

As Greg mentioned... look into units that run several evaporators on one condenser.
That would have to be more efficient than multiple condensers.
 
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Old 01-24-19, 08:56 AM
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You need to look at VRF Will cool the restaurant, Kitchen and bring in the fresh air. plus remove the humidity in lower load times.
 
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Old 01-24-19, 09:26 AM
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Every time I check the outside unit the fins are covered in cobwebs, dirt dust, etc and the unit is 8' off the ground mounted on an outside concrete wall. I even put a rain & sun shield over the unit so noon sun wouldn't hit it. We've got a dirt road 20' from the building and the cars kick up a dust cloud that, I believe, finds the unit.

The inside has a pretty fine mesh screen covering the coils, and it's never dirty to the eye. It's only when I wash it that I can see a minor change in color.

@airman.1994
I had to look up VRF. From what I read, it's what I understand as inverter technology. Correct me if I'm wrong or missing something. The Friedrich unit I have is inverter based and does a good job. I chose it because it had the highest efficiency rating at the time. I'll check out units with multiple air handlers per compressor to see if they are as efficient via specs. Given that electricity is 3 times the typical US rate, it's the operating costs I want to reduce. I also want multiple units in case one has an issue that takes it out of service. Here, it can take a week for someone to show up to fix it. It's called 'island time'.
 
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Old 01-25-19, 04:25 AM
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It is not more efficient to use 10 one ton units than say 3 - 3 ton units.
3 systems with 2 evaporators each would be a better choice.


It is not necessary to use seamless pipe insulation.
The split needed to install insulation over already installed pipe can either be glued or taped with an appropriate product to seal it.
Armaflex branded insulation for example has compatible glue and flexible paint for its product.
 
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Old 01-25-19, 04:52 AM
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Yesterday, I searched for units with multiple air handlers. They were all SEER rated lower, some much lower, than the smallest single air handler units available. If SEER isn't a reliable measure of efficiency, what is?

My reference to non split insulation was for cases where the plumbing lines were just a few feet long, making it reasonable to use short sections of non split insulation which is much less expensive and requires less work to install as there's no glue or tape required.
 
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Old 01-25-19, 08:15 PM
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The seer rating of an airconditioner means nothing if the unit is not applied correctly.
If over/under sized or as you propose with too many stages that inefficiency will far outweigh any savings the seer rating would offer.
Three sytems with the thermostats placed strategically is the way to go in your situation..

Also, if you set those thermostats a degree or so apart from each other you will get good cycling of the units which would be more beneficial than worrying about seer ratings.
 

Last edited by GregH; 01-26-19 at 04:46 AM. Reason: Typo
 

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