Author Topic: Condensation on register  (Read 4663 times)
wattMaster
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Re: Condensation on register « Reply #15 on: June 18, 2016, 03:04:48 PM » Author: wattMaster
Measure the humidity in the room when the register is blocked and in various places inside the duct that comes to the register

When condensation is forming (at changes of air temperature) the moisture sensor may behave eratically - The water content in the air becomes non uniform, so what the sensor will show is a hit and miss
I can do that, except for inside the ducts which is nearly impossible at this time.
Can I just keep the sensor at the vent for a while to even out the reading?
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Re: Condensation on register « Reply #16 on: June 18, 2016, 03:17:26 PM » Author: Ash
Not sure about that.. There may be some effects like condensation on the sensor itself that can break anything

Poke the sensor deep into the duct on a long stick from the register. Dont hit walls as they are probably covered with dust, that we dont want on the sensor
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Re: Condensation on register « Reply #17 on: June 18, 2016, 04:42:10 PM » Author: wattMaster
Not sure about that.. There may be some effects like condensation on the sensor itself that can break anything

Poke the sensor deep into the duct on a long stick from the register. Dont hit walls as they are probably covered with dust, that we dont want on the sensor
My meter is an older version of this, where the humidity sensor is a white cylinder next to the thermistor, in the cavity.
I just can't stick that in the duct to measure it, as it is too big and we would have to remove the register, and it would be touching the edge always.
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Re: Condensation on register « Reply #18 on: June 18, 2016, 05:23:17 PM » Author: Ash
Why ? Prop it so it is in mid air
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Re: Condensation on register « Reply #19 on: June 18, 2016, 06:42:11 PM » Author: wattMaster
For reasons I can't explain right now, (And it would take a long time to explain) We can't mess around with the vent right now. I might eventually be able to measure it, but right now, we'll have to just think of other things. But I like your solutions.
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Medved
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Re: Condensation on register « Reply #20 on: June 19, 2016, 04:43:16 AM » Author: Medved
The air coming from the evaporator can not condense anything, even when it evaporated some of the droplets. It can not evaporate anything when it approaches the 100%RH (that is, when evaporation stops) and the condensation happens only when the temperature drops so, the water content exceeds 100%RH (thats the point, when the condensation happens).

So it is either water spitting from the evaporator (so clogged condensate drain; it really does not need that much air speed for that)
Or some other (still humid) air getting cooled on the refrigerated vent. But for that the room air has to come to contact with the cold part without mixing with the much dryer air coming from the AC (in absolute water content). And that I see as quite unlikely, when the "coldness" is supposed to be carried in just by the air from the AC evaporator. When the warm, moist air just mixes with the colder dry air, there is no reason for any condensation, because the water vapor gets "dissolved" into the dryer air...

So I really see the clogged condensate drain as more likely cause...

Regular moisture meters won't tell much, they need the temperature to stabilize before providing any usable readings.
Plus the normal room air may show way lower RH (I would guess something between 30..60%) than the AC output (typically around 90%), but still the AC output air contains way less water vapor. The difference is just in the temperature. So even when the hygrometer you are using is extremely fast response, it will show more the temperature changes (higher temperature means lower RH reading) than the real water content.

Because all humidity sensors I know physically respond mainly on the RH, the eventual absolute humidity figure the instrument displays is a result of calculation from the sensed RH and temperature. And for that to be accurate, both temperature, as well as humidity sensors have to be at exactly the same temperature. And that needs quite some settling time and homogeneous environment.
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Re: Condensation on register « Reply #21 on: June 19, 2016, 10:27:10 AM » Author: wattMaster
The air coming from the evaporator can not condense anything, even when it evaporated some of the droplets. It can not evaporate anything when it approaches the 100%RH (that is, when evaporation stops) and the condensation happens only when the temperature drops so, the water content exceeds 100%RH (thats the point, when the condensation happens).

So it is either water spitting from the evaporator (so clogged condensate drain; it really does not need that much air speed for that)
Or some other (still humid) air getting cooled on the refrigerated vent. But for that the room air has to come to contact with the cold part without mixing with the much dryer air coming from the AC (in absolute water content). And that I see as quite unlikely, when the "coldness" is supposed to be carried in just by the air from the AC evaporator. When the warm, moist air just mixes with the colder dry air, there is no reason for any condensation, because the water vapor gets "dissolved" into the dryer air...

So I really see the clogged condensate drain as more likely cause...

Regular moisture meters won't tell much, they need the temperature to stabilize before providing any usable readings.
Plus the normal room air may show way lower RH (I would guess something between 30..60%) than the AC output (typically around 90%), but still the AC output air contains way less water vapor. The difference is just in the temperature. So even when the hygrometer you are using is extremely fast response, it will show more the temperature changes (higher temperature means lower RH reading) than the real water content.

Because all humidity sensors I know physically respond mainly on the RH, the eventual absolute humidity figure the instrument displays is a result of calculation from the sensed RH and temperature. And for that to be accurate, both temperature, as well as humidity sensors have to be at exactly the same temperature. And that needs quite some settling time and homogeneous environment.
The one about humid, still air seems more likely because:
The air out of there is at a really low output, so it would not blow much air around.
The vent is at the top of the bathroom, where it is tilted, so all of the got air in there would go to that area, where the vent and condensation is.
The vent is small, and not all of the space is used for moving air.
The area where condensation forms is blocked from the cooled air that would blow it away, because of the low output and the direction of the louvers.
And the condensation area is in a spot where water from the evaporator could possible not get to, and if it did go to the vent, we would have seen it forming on the louvers, which is not the case.
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Re: Condensation on register « Reply #22 on: June 19, 2016, 08:09:56 PM » Author: icefoglights
So it must mean that the air surroundung the vent is too humid, but how do we fix that?

Move to Arizona?
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Re: Condensation on register « Reply #23 on: June 19, 2016, 08:21:16 PM » Author: wattMaster
So it must mean that the air surroundung the vent is too humid, but how do we fix that?

Move to Arizona?
Not an option.  ::)
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Re: Condensation on register « Reply #24 on: June 20, 2016, 11:21:33 AM » Author: Medved
You must have really high humidity there...
Normally with split AC installations (so when a separate heat exchanger is used in each room, so no air ducting or so) all the water condense on that exchanger, so it removes the humidity from that room, so prevents such unwanted condensations.

With a central exchanger and air ducting, the only option is to install a kind of air mixer: A device, which mixes the cold air from the duct with the warm air from the room, only then returns the mixed air back to the room. Then the eventual condensation happens inside of that mixer, where it is easier to handle than when the mixing happens only in the room itself...

Otherwise I see no other option...
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Re: Condensation on register « Reply #25 on: June 20, 2016, 11:29:32 AM » Author: wattMaster
You must have really high humidity there...
Normally with split AC installations (so when a separate heat exchanger is used in each room, so no air ducting or so) all the water condense on that exchanger, so it removes the humidity from that room, so prevents such unwanted condensations.

With a central exchanger and air ducting, the only option is to install a kind of air mixer: A device, which mixes the cold air from the duct with the warm air from the room, only then returns the mixed air back to the room. Then the eventual condensation happens inside of that mixer, where it is easier to handle than when the mixing happens only in the room itself...

Otherwise I see no other option...
With 1-2 of our ducts, (One right above the thermostat) they point straight at the inlet for the evaporator, so it's kind of already air mixing. I also noticed after we did our fix, the condensation on the vent is almost gone, but we will have to monitor it.
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