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Industrial HVAC question
Posted on 4/19/26 at 9:21 am
Posted on 4/19/26 at 9:21 am
Our office has a humidity issue. I asked an HVAC company to come give me an estimate on what it would take to cut the humidity down a bit. They proceed to tell me that the space above my office ceiling is the "return air" and that in order to fix this, they'd have to have dedicated ducts dropped down into each room to act as return air for each space and try to draw the humidity out that way.
My question is could a crawl space dehumidifier either in the office or above the ceiling help me control some of the humidity levels? Dry air attracts moist air, so, party of me thinks it's better than nothing.
The estimate was high, so want to try another alternative before doing that.
My question is could a crawl space dehumidifier either in the office or above the ceiling help me control some of the humidity levels? Dry air attracts moist air, so, party of me thinks it's better than nothing.
The estimate was high, so want to try another alternative before doing that.
5
Posted on 4/19/26 at 10:09 am to TaderSalad
A multi-speed blower may help. Passing the air thru the coils slower allows greater dehumidifying. Takes moisture out before reaching low set temp.
Posted on 4/19/26 at 10:51 am to TaderSalad
My heart is hurt baw.
More information about what type of system you have would be helpful. First solution to try is to raise your temp a few degrees. The colder the air is the more humidity it will carry. Is this a whole building issue or isolated to a few offices?
Does your system used chilled water or is it strictly refrigerant based?
Make sure your supply ducts are insulated properly. Warm air in your plenum space will cause condensation on your ducts if they aren't properly insulated.
Your vendor is correct. Adding dehumidification equipment on a system not originally designed for it is hella expensive.
More information about what type of system you have would be helpful. First solution to try is to raise your temp a few degrees. The colder the air is the more humidity it will carry. Is this a whole building issue or isolated to a few offices?
Does your system used chilled water or is it strictly refrigerant based?
Make sure your supply ducts are insulated properly. Warm air in your plenum space will cause condensation on your ducts if they aren't properly insulated.
Your vendor is correct. Adding dehumidification equipment on a system not originally designed for it is hella expensive.
Posted on 4/19/26 at 10:53 am to TaderSalad
What kind of office are you talking? I have a 2.5 ton residential unit in my 2000 sq ft office. So that's a lot different than if you are running a 10,000+ sq ft multi story.
Have you tried using a standard residential plug in dehumidifier? If you can get it to drain to an open drain, they can help a ton. Its by no means a long term solution, but if it helps you short term it will help determine your long term solutions.
Have you measured your actual humidity?
Many HVAC units you can turn the fan speed down, the modern units for residential come usually with the highest fan speed because that is the most energy efficient. But turning the fan speed down makes the unit wrong longer and allow more time to remove humidity.
Have you tried using a standard residential plug in dehumidifier? If you can get it to drain to an open drain, they can help a ton. Its by no means a long term solution, but if it helps you short term it will help determine your long term solutions.
Have you measured your actual humidity?
Many HVAC units you can turn the fan speed down, the modern units for residential come usually with the highest fan speed because that is the most energy efficient. But turning the fan speed down makes the unit wrong longer and allow more time to remove humidity.
Posted on 4/19/26 at 6:12 pm to TaderSalad
Cavity above the ceiling as return air is very common in an office building. Your humidity is high because you are getting humid outside air perhaps more than what the system is designed for. And yes dehumidifiers on that kind of system are pricey
Dedicated return air ducts would help
Dedicated return air ducts would help
Posted on 4/19/26 at 7:07 pm to TaderSalad
Providing my company was called we would check:
How the building works, doors opening/closing. Is it near open water. Is the building old/loose.
Coils, make sure their clean.
Refrigerant charge, subcooling/superheat are within manufacturers specs.
**** Static pressure of the return and supply ducts. Are they within the manufacturers specs.
Fan speed is it set properly. Example: new customer's AHU was factory set for 6 tons of airflow. They send everyone one of them out set this way IDK why. This unit was a 3 ton.
Check to see if unit has outside air ducted in, it's code here. Close them when no one is looking!
Does AHU have ecm motor? Is the module failed "on," won't turn off? <-- We recently went to a two story home that had engineers, big HVAC companies blah, blah. Entire upstairs had mold remediation done to no avail. Years of frustration for the client. We found the failed X13 motor stuck in the on position. They think I'm a genius. My post history says otherwise.
Find an HVAC company that will go through the system. Then tell you what they know and not what they think.
At the very minimum I would make sure the indoor Blower is cycling on/off, then test static pressure of the ducts. Duct work is rarely sized properly.
Good luck.
How the building works, doors opening/closing. Is it near open water. Is the building old/loose.
Coils, make sure their clean.
Refrigerant charge, subcooling/superheat are within manufacturers specs.
**** Static pressure of the return and supply ducts. Are they within the manufacturers specs.
Fan speed is it set properly. Example: new customer's AHU was factory set for 6 tons of airflow. They send everyone one of them out set this way IDK why. This unit was a 3 ton.
Check to see if unit has outside air ducted in, it's code here. Close them when no one is looking!
Does AHU have ecm motor? Is the module failed "on," won't turn off? <-- We recently went to a two story home that had engineers, big HVAC companies blah, blah. Entire upstairs had mold remediation done to no avail. Years of frustration for the client. We found the failed X13 motor stuck in the on position. They think I'm a genius. My post history says otherwise.
Find an HVAC company that will go through the system. Then tell you what they know and not what they think.
At the very minimum I would make sure the indoor Blower is cycling on/off, then test static pressure of the ducts. Duct work is rarely sized properly.
Good luck.
Posted on 4/19/26 at 8:26 pm to wrongRob
We came across plenty of outside air dampers that either froze up or the actuators had failed and the buildings or individual floors would run more comfort calls than normal. I'm assuming big building-chilled water ahu's since you dropped industrial in there. I'd check this first because it's a maintenance issue and is the quickest and easies fix and your post leads me to believe you didn't always have this problem.
Posted on 4/19/26 at 9:09 pm to Wraytex
There's a whole bunch of people on here who know the ins and outs of commercial HVAC. It's funny reading all of it because most of it is what I was thinking. What about the VAV boxes? They're not putting reheat into the system Y'all guys are great.
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