Warehouse bathroom cooling

[mech5]

I have a situation where I have to provide cooling to a bathroom group that is located within a non-cooled warehouse. The heat load on the room will be satisfied with a residential grade packaged wall AC unit. Now, by code I have to provide 200-300 cfm of exhaust. My question is what is the best way to handle this situation?

Are any of these solutions valid? Are they feasible?

1. Run the fan constantly and size the unit for the heat load in the space plus the ventilation infiltration load introduced by the fan? Won't I overcool the space during the shoulder months? Where will the extra air come from? Do I need to provide an intake grille somewhere?

2. Run the exhaust fan only when the bathroom is being used and size the wall unit for only the heat load in the space and not the ventilation infiltration load?

Any help would be appreciated.
Thanks

 

[DrRTU]

The best way to handle the situation is to not provide cooling. Most codes prohibit recirculation, so your window unit will not work. A small spot cooler will work if you take the warehouse for the return but a smart inspector will want to check the dilution. At 200 – 300 cfm the washroom is very small. Just kill it with transfer air and exhaust to the outside.

 

[jterrell22]

Just finished a project like this. We had to cool a restroom area in a large unconditioned warehouse. We went with something similar to your second option above. We used a mini-split to condition the space. We put the bathroom exhaust on a delayed timer to allow the fan to run after the bathroom was unoccupied. You may want to look into an ERV/HERV in your case. It will reduce the ventilation load, and may adequately provide the exhaust you need as well.

 

[mech5]

Thanks for the responses. I think that I will probably just size the wall unit for the heat load in the space without any OA. I can interlock the exhaust fan with the lights, so that it will only run when occupied. If it happens to get warm in there, it will only be for a little while. People don't usially "hang out" in there for very long anyway.
My only concern now is the negative pressure in the space created during exhaust fan operation. Does anyone think this will be a problem and cause the door to stay slightly cracked open?
Thanks again.

 

[Drazen]

cooling bathroom contradicts with all I know about comfort.

the example given by jterrell, that applies to restroom area cannot be applied to bathroom in my opinion.

first of all, how do you find target design temperature for bathroom? you cannot apply anything that applies to general rooms, as wet body has very different comfort feeling.

second, it is almost impossible to have such strict control of air supply temperature, especially at part-loads, which will avoid not only discomfort, but even serious health problems. you simply cannot release 16 degree Celsius air in area where someone is bathing. you should specify minimum supply temperature to be about 24-25 degrees Celsius or even more, which could be really senseless, as you cannot recirculate air, you would have enormously large supply air volume needs, and even if that would be demand of very rich client, you would not be able to properly distribute such large quantities of air in small space.

 

[jterrell22]

I wouldn't worry about the negative pressure too much (it's a good thing in a bathroom). Most bathroom doors utilize a closer, and the resistance from the closer should provide enough force to counter act the pressure. The easiest way to overcome this would be to swing the door out if possible.

 

[RossABQ]

Drazen, you are assuming there is a shower in the facility; we don't know if that is the case, and based on the quoted ventilation rate, I'd guess it is really a "restroom" with lavatories and toilets only.

No mention of heating requirements? Will radiant electric units be provided?

 

[Drazen]

ross,

engineer's code of practice is very important part of engineer's performance, and if we do not stick to it, we will waste lot of time for nothing.

in this instance, if something is stated as bathing area, it must contain either shower or bathtub, otherwise it is simply not bathing area and than it can be some completely different story.

 

[317069]

Drazen
I agree with you, but I have one point regarding to health issue you mentioned.
in a regular house equipped with heating/cooling system, bathrrom has an air outlet provide both heating and cooling, what about this point

 

[RossABQ]

In the US, restrooms/toilet rooms are colloquilly called "bathrooms". It does not mean there are showers in the room, but the OP needs to clarify this point. As you note it changes a number of things.

 

[mech5]

There are no showers. There is just 2 water closets, 2 urinals, and 2 lavatories.

 

[sprinkler1000]

Based on the size and type of the bathroom I agree with posts that call for no cooling or heating. Work on the insulation to make temperatures on the summer season not very uncomfortable.

 

[jkauwale]

Is moisture a concern in your area?

As previously mentioned the bathroom will be negatively pressurized, which indicates that the makeup air will be unconditioned air. I ask if moisture is a concern, because when the unconditioned air enters the space and hits surfaces that have been cooled by the air conditioning unit, then condensation may occur. If condensation occurs, then mold may also become an issue.


Justin K, P.E.

http://www.engproguides.com

 

[mech5]

Yea, moisture is a very big issue. The building is located on a coastal region. I guess the best solution is to get rid of the wall ac unit and keep the exhaust fan. Probably call for a grill on the door.

 

[mech5]

I was looking at the code and it says that recirculation of air from these spaces is prohibited and all supply air must be exhausted. If I have a wall ac unit supplying AND returning 275 plus an exhaust fan, then not all of the air supplied will be exhausted. So therefore, the system goes against code.?? Is that right?

 

[RossABQ]

It says recirculation of air FROM these spaces TO other spaces is prohibited; recirculation within the space should not be a problem. But unless the expected warehouse temps are >85, just move air thru the room to outdoors. If heating is required to keep it above 55 - 60, use electric radiant.