Fitness Center Dehumidification

[rmusa]

Fitness center:

10000 sf total space 7000sf fitness area
Two 10 ton RTU, One 5 ton RTU
RTU’s oginally designed for a standard Retail space -
10000 CFM supply air total, 2500 CFM OA total
7 ft windows

Condensation on glass on very cold days (25 degf or less)
No baseboard heat

What is most economical solution to eliminate condensation? Space does not feel so humid, just condensation dripping from
duct/glass/window mullions.

 

[pocketengineer]

Have you analyzed why condensation occurs?

 

[Rehacayli]

there can be a lot of reasons for this..
if it is like this on all seasons(if it would be from outside I'd expect this on summer on north hemisphere), than it is from the humans. what is the room temperature setpoint and what temperature does the RTU's blow in? maybe you are blowing in too cold air to the windows.
you said that there is condensation on the ducts, are the ducts insulated?

generally when you have condensation, the first reaction should be eliminating the humidity in the room. you can use dehumidifier in the room on the main branch, it is not so cheap but a good way to go. but if it is from the temperature than there can be a lot of solutions.

if you can measure the temperature and %RH of the room and the RTU blowing, we might have a better idea.

 

[willard3]

Do a careful heat gain/loss and include the latent load from people.

Units designed for retail spaces usually have 2-row coils that don't deal with humidity control, the thing you want.

 

[dbill74]

Could use more information.
New/old problem?
When was the space converted to fitness center?
condensing in morning/evening only?
Is the condensation seasonal? I.E. summer / winter only?
What part of the country is this located in?
Where changes made to RTU / Exhaust systems when space was converted to fitness center?
Are there showers? Is the condensation near the showers?

Point of these questions is; you need to first determine the cause of the condensation, then you can develop a solution to the problem.

My guess is the RTU's need to be replaced. Or add a DOAS.
I've designed box retail centers in the past and typical design is to use a basic packaged Dx RTU. Which works well for typical retail center where you will have 15-20% OA. Unfortunately, these typical packaged RTUs don't do well with removing humidity when OA gets to 25-30%. Also, as Willard mentioned, "dehumidification" may not be available.
Good bet would be that that RTU's were re-balanced during the retrofit to a fitness center to accommodate the increased amount of OA that would be required.

Condensation on duct suggests RTU SA temp was reset to below 55 deg F or is malfunctioning to produce SA at less than 55 deg F. When this happens, even insulated duct can sweat. I've seen this, had a sensor on an AHU go bad once and AHU started overcooling the air, SAT was close to 50 deg F and insulated duct started sweating. We replaced the sensor and things went back to normal.

Add to that you probably have an owner who is trying to "pre-cool" the space by setting thermostat's in the 68-70 deg range. The result is abnormally moist air hitting cold surfaces and condensing.