How effective is one SantaFe Ultra 205 dehumidifier in provided the required dehumidification
and OUTSIDE AIR for a 15,000 Sq Ft DAY CARE CENTER ?
IMC 403.3.1.1
___ Summary: 10 CFM / person + 0.18 CFM/ Sq Foot
____ = 10 * 25 + 0.12 * 1000 = 250 + 180 = 430 CFM per 1,000 Sq Foot Day Care Area [ < 5 year olds ]
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Post # 8
" ... It's a 15,000 Square Foot single-story, Day Care Center.
It is wood frame with an unconditioned attic.
We have 8 RTU's on the roof. ... "
We are looking at installing multiple dehumidifiers, not just one. I didn't provide all details in my original post to keep is brief and concise. Here's the background on why we are even looking at this if your are interested:
Building was built in two phases -- Phase 1, 10K square feet was finished in 2019, Phase 2, 5k square feet was finished in 2022. We are in Zone 4. We have been having excessive humidity in the building every July-Sept.
2019 - We brought it to the GC and HVAC installers attention, HVAC installer said the building just needed to dry out and it would not be an issue after that.
2020 - We wait a year, the next summer it is still super humid (consistently mid 60's into 70's, sometimes into 80s). GC and HVAC installer troubleshoot the system, try a few different things like adjusting OA and fan speed, but it doesn't noticeably change. Phase 2 was already in the planning stage and the mechanical engineer (different from HVAC installer) recommended we install RTU's with gas re-heat in the Phase 2 area, saying that would address the humidity.
2021 - Phase 2 is completed in late 2021
2022 - Summer comes and humidity is still an issue, despite adding the re-heat RTUs. We have third party HVAC designer come in and inspect the system. They recommended a TAB done since none was ever done for the system. TAB was completed in late 2022.
2023 - Summer comes and humidity is, again, still and issue. GC has engineer come out to look at everything, he says everything is working as designed and he has no explanation for humidity. HVAC contractor tries a few more tweaks.
2024 - Summer comes and still humid. GC has a third party engineer look over the plans to get opinion on system sizing, according to GC, thir-party engineer says it looks reasonable. GC and HVAC installer propose installing dehumidification system, but stated that they do not think the HVAC system is the source of the humidity and that it has to be coming from some other source. HVAC contractor wants to install a single Quest 876 in our resource room. My concnerns with this are:
1) This will take up significant space in that room
2) Very expensive, given it's not addressing the cause of the humidity, just the symptom of the issue
3) I'm not convinced a single unit in that room will adequately serve the whole building from that location. (Dehumidfier will have an open return side and the supply will be ducted to the 4 rtu's in Phase 1.)
Given the above, I asked about installing multiple units like the Santa Fe unit in the attic, but the HVAC contractor said that would be significantly more expensive and was skeptical that they would work properly if installed in the attic. We do not have excess space to put these units inside the building.
So that's where I am today.
Notes / Specs
Phase 1
RTU 1 - Trane YSC092 - 7.5 Ton | 2800 CFM | 700 OA
RTU 2 - Trane YSC092 - 7.5 Ton | 2700 CFM | 750 OA
RTU 3 - Trane YSC092 - 7.5 Ton | 2700 CFM | 750 OA
RTU 4 - Trane YSC102 - 8.5 Ton | 3100 CFM | 800 OA
MUA 1 - CaptiveAire - 1600 CFM (kitchen)
Commercial kitchen hood - specs unknown
Exhuast fan for bathrooms
Phase 2
RTU 5 - Lennox KGB048S - 4 Ton | 1500 CFM | 500 OA (min?)
RTU 6 - Lennox KGB036S - 3 Ton | 1100 CFM | 250 OA (min?)
RTU 7 - Lennox KGB048S - 4 Ton | 1600 CFM | 475 OA (min?)
RTU 8 - Lennox KGB036S - 3 Ton | 1100 CFM | 400 OA (min?)
** I believe these 4 RTU's also have CO sensors to control OA
