Older home with no AC plenum…replace our entire AC system as suggested?

We have an older home that has a large living-area/fireplace room; the AC unit sits over it in the attic. Earlier this year, in that room, we noticed a crack beginning to form in the ceiling sheet rock, forming a fairly straight line toward the fireplace. When we called someone over to repair it, he went into the attic to investigate and found that the ductwork coming from the AC was likely to be causing the problem: the ceiling insulation beneath the plenum (or what he thought was the plenum at the time) was wet. He figured that the duct insulation was no longer preventing condensation from forming, and the resulting water was causing the ceiling crack…we would have to get that issue repaired before fixing the ceiling.

Last Friday we called an AC tech to look at the situation. He showed me that instead of a plenum, we actually have a large, square portion of duct, less than a foot long, emerging from our AC coil to form a “T-junction” with the main duct line running to the rest of the house. The tech explained that such duct-line arrangements were originally designed for heating only…when AC was first brought into our home, it was simply connected to this arrangement, likely because current methods weren’t in use at the time. He explained that this arrangement isn’t what is done nowadays: a real plenum would use static pressure to help improve the cool-air flow to the rest of the house. Because the T-junction isn’t helping to move cold air as quickly, it lingers in the junction, and so it increases the chance that condensation will form.

The tech said that he didn’t know anyone who would re-insulate and re-vapor-barrier the existing setup, since that arrangement isn’t done nowadays. However, according to his measurements, the area where our heater, AC coil, and T-junction are in the attic is too small to simply install a proper plenum and redo/reinsulate our duct lines. He said we need to buy a new heater, which will be smaller and more efficient…that will give them room to put a new coil next to it and finally, insert the plenum where it belongs…then run new ducts throughout the whole house. Because we have an older AC system, that would mean we will also need to purchase a new outside condenser as well (to match the new coil and its new refrigerant-type). All of this is to the tune of almost $11,000.

Both my wife and a friend of mine suspect that we are being sold a “Cadillac” solution. I plan on getting a second opinion anyway, but I’d love to hear some input from any other knowledgeable HVAC folks who could tell me if someone is trying to hose us. Thanks!

Emerson Liebert Air Conditioner Fan Runs Abnormal

We have 2 Emerson Liebert air conditioners inside a datacenter. Issue is not a home issue but devices are all same and I supposed finding some expert here. Here is the thing:

This 2 devices are designed to work together, communicating via network cables over ethernet switch. Both has Hiross compressors, one has an additional unit named Siemens Poly Cool Superheat (I am not sure but it might be something like Variable Frequency Drives). Our mechanic said its compressor is also different than other’s.

This device was broken for over a year. We have had a mechanic fixed the device today. Everything seemed normal while the mechanic was at ours. Later, I have noticed something weird. Condenser’s fan runs at a very high rpm than interrupts in 2 or 3 seconds. Then, just it is almost stopped, runs again at a high rpm. It continues like so. Even room temperature was over than set value, it runs like so.

Is there anyone knows about Hiross or Siemens Poly Cool module or Emerson Liebert air conditioners?

Leacky AC Evaporator

We just moved into our new place. So many new things need to learn. Just like the problematic AC. My apologizes if I do not know the correct terminology for some of the parts. I will try my best though.

The air handler with evaporator was installed in a closet on the 2nd floor. The evaporator is at the bottom in the air handler unit. And there is a big hole on the floor plywood right underneath the air handler to let the return air come in.

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So the problem we have is that if we run the A/C for about 1.5 to 2 hours, we can see water drips to the ceiling of the first floor. And there is a water mark on the ceiling. So I just drilled a hole and let the water run down to avoid further damage. And I also took a picture through the hole to see what is going on(the filter has been removed). I saw condensate forming on the bottom of the drain pan. I’m not sure if the coil sweating.

enter image description here

What I’ve found/tested are:

  • The main drain pan seems working okay. I can see it catches water and
    let it go away through the pipe to the drain-line. But the pan is
    dirty. And it seems not overflowed.
  • Looks like there is no backup drain pan so the condensate drops
    directly on the ceiling.
  • The filter is a washable filter and has been cleaned.
  • Tried to put a dehumidifier in the closed but didn’t help too much.

I’m not sure what I can do next to fix this problem permanently. I thought I should install a secondary pan and clean the coil regularly. Am I on the right path? If you get an idea, please let me know.


Can gas return back into a sparkling beverage on cooldown?

We all know that if a sparkling beverage (let’s say, CocaCola) spends some time outside of the fridge and gets warm, the gas comes out of the liquid, rises the inner pressure and makes the bottle walls more tight and the cap to curve outwards. Also, drinking this does not seem very tasty. My question is this: if I cool down the bottle again, will the gas be re-absorbed by the liquid and will the drink restore its qualities?

Edit: sorry, could not add tags like gas or liquid since they do not exist yet :D , and I do not have enough reputation.

How do I fix my humidity problem in my home?

I have an older home. Last year I didn’t have this problem but this winter, to save money I keep my temperature a lot lower. I’m seeing a lot of condensation on the windows and now on my livingroom wall, water running down and mold forming. It also smells like mold in my home. Will purchasing a good dehumidifier help? I am also thinking of adjusting the humidifier on my furnace? Another issue may be that my bathroom doesn’t have an exhaust fan but I can’t afford to have one put in. I need the best, cheapest solution.

Will a cloud form in a depressurized room?

If a room is depressurized will a visible cloud or mist form?

I would expect it would, but when I apply a vacuum to a flask I see no cloud form inside the flask. Would a room behave differently than the flask?

I am more interested in the case of sudden evacuation than a gradual depressurization.

How to prevent condensation inside the camera when taking pictures in a cold place?

Suppose you keep your camera at, say, 20 degrees C at a relative humidity of 60%. This means that the air inside the camera will have the same humidity at the same temperature, the relative humidity will increase if the camera cools down. Then you go outside for several hours where it is -20 C, put your camera on a tripod. After some time the camera will cool down and you will get condensation inside the camera.

The only thing I can think of is to go outside with the camera a day or so earlier, remove the lens and let it sit there for a while, making sure no dirt or snow enters the camera. Then you put the lens back on and put the camera in an airtight bag filled with the outside air. You only get the camera out of the bag the next day when taking pictures outside. However, removing the lens while outside seems to me like a dangerous thing to do, you are bound to get dust inside the camera…

Difference between adsorption and condensation

So I just stumbled across the Wikipedia article on adsorption – and I asked myself, if there is a difference between (physical) adsorption and condensation on a surface?
When I look at the water drops on a cold bottle of your favourite beverage, I think this is covered by what I know about adsorption. Or is this kind of condensation just one of many adsorption reactions?

Any help is appreciated :)

What could cause moisture on my bonus room floor?

Last week during a cold snap with high winds. I discovered moisture along the floor on one side of my bonus room, above the attached garage. Their was enough moisture that the baseboard molding buckled and pulled away from the wall. This occurred on the western facing wall. All other walls / floors were fine with no visible moisture.

I opened up the attic hatch to this area and saw plenty of insulation. Bats in the wall and blown in for the floor area.

I can’t figure out what would be causing this, as the house is 2 months old.

Any ideas?

Is it risky to change lenses in the cold?

I am generally a lazy person, so I am extremely averse to changing lenses on my camera in the cold. I am concerned about my fingers getting cold, but here I read that condensation is extremely dangerous for my camera in cold weather conditions. I understand that condensation occurs when I take my camera from cold air into a warm house, and moisture collects on the lenses. This moisture can harm the interior of the camera, as water does harm to electronics. Besides, water drops can freeze if I leave the warm building for the outside again, so a common advice is to pack the camera into an air-proof bag.

Now, if I am shooting outside, is the camera interior air-proof? Is the air inside the lens and near the sensor warm? Is it dangerous to open the compartment and change lenses outside? How am I supposed to change lens when shooting outside in winter?

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