Hi all - thanks in advance for reading... To say this has been a saga would be an understatement...
We have two 3 ton Bosch Geothermal units installed in our new construction sprayfoam insulated home almost exactly 12 months ago. Shortly after that time, I noticed that humidity seemed high, so our installer recommended activating the "Dehumidification" setting on our Honeywell Prestige HD 2.0 T-stats. Downstairs went from the 50% range to 42-44% almost immediately, and it has remained there since. Upstairs didn't perform as well, but we soon switched into heat mode, and the problem went away...
Fast forward to this spring... Humidity downstairs stayed fine, but upstairs was regularly above 60%, and we've had dozens of visits from our installer, and now several from Bosch, after I contacted them via Twitter. Bosch has been EXTREMELY responsive, but we're all a bit at a loss still, though it seems we're headed in the right direction. Here's what we've done (not necc in order)...
1. Put the fan speed on slow. No help.
2. Forced stage 1 for 60 minutes, and then eventually even disconnected stage 2 activation. No help.
3. We changed the drainage trap on the air handler to prevent airflow from sucking in water. No help.
4. We re-leveled the air handler to be sure there was no overflow... No help.
5. We adjusted the back loop re-circulation circuit to be higher and lower pressures... No help. (This is a loop form the main output back to the return to prevent overpressurization if only one small zone is calling).
6. We tried a variety of dehumidification settings on the T-Stats, though there is no dehumidifier on the system, so this just runs the temp down a bit intermittently. Didn't do anything upstairs, though it does seem to help downstairs...for some reason. Last night, for example, the humidity down there got to 48% for the first time ever, after I turned off the dehumidification setting for 5 days... I was about to be happy about how it wasn't needed, and then turning it back on fixed the issue.
7. Opened all three upstairs zones to be 20% open even when not calling, to improve circulation. Not much help.
8.Replaced a temp control valve that was faulty. No effect on humidity, but cooling was faster.
9. The copper line-set was undersized for the run, so it was changed. After doing that and charging the compressor and water loop within half a hair of perfect, the BTU calculations went far beyond ideal... Humidity went down a little, but not consistently.
10. I put a hygrometer in the upstairs master, and monitored it. I finally got a standalone dehumidifier, which got us to around 56% on a good day. Better than 65%. Still not ideal.
11. Most recently, we tested the humidity in the attic, and it was 62%. So, we added a return in the attic, which is totally sealed with foam (open cell under the roof, closed in the walls). The attic already had a register, but no return. We also made the register larger. At the same time, we moved the dehumidifier into the attic, and have it on a continuous drain into the air handler drain line...
THIS DID THE MOST so far. As of now, we can regularly get down to 50%, but still occasionally get up to 58% like we did last night...and therein lies the mystery. Last night, our bedroom got up to 58%, which was easy to notice because I woke up sweaty for the first time since step 11.
I went into the attic, and all was well. No leaks, no sweating, and the dehumidifier was running. Temp was 70, and humidity was 42%!
So, my question is...WHAT GIVES?!
Does the attic just still need to dry out?
ONE variable from last night that really got me thinking is that we just got a puppy, and she sleeps in our mudroom, which has an exhaust fan. I turned it on overnight to give some white noise - not a permanent plan, but we wanted to see if it would cut down on whining. Well, with that on, the downstairs humidity went to 48% for the first time since we moved in...
Well, that got me thinking. We also have a bathroom upstairs with a kitty litter box in it, and we run that fan (110CFM Panasonic - fairly silent) ALWAYS.
So, we passed our blow-test with flying colors, and we have replacement air with powered baffles for our 1200CFM vent hood...
So...is it possible that running our vent fans (appropriately sized, as opposed to contractor grade) is pulling humidity/outside air BACKWARDS through the other vent fans in the house? This am I turned off the fan in the cat room, and the humidity is 51% as I remotely monitor from work while typing this... We'll see if it gets lower.
I am kicking myself that I didn't think of that earlier, since I knew that our 1200CFM hood needed replacement air for risk of backdrafting out pilot lights, but never considered a 110CFM fan to be worthy of consideration... Anyway, if anyone has any thoughts, I'd appreciate it.
For reference, we are in Atlanta, and it's been hot with 75-90% humidity over the majority of this period, with rare exceptions... We have two 3 ton units, and the upstairs is a split. The upstairs in minimally oversized, but several opinions have agreed that the sizing is appropriate.
One other item - the Bosch reps think that the open cell foam in the attic could be wet from prolonged humidity and may just need time to dry out, but if the attic humidity is already at 42% is that still a consideration? Dicuss...
Thank you in advance. I'll send my wife's amazing baked goods from our DCS setup (that got me into this forum in the first place) to anyone who solves the mystery.
sktn77a
sktn77a
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