For the guys that *think* moisture can't migrate into an air conditioning system unless the system operates under a vacuum.
Do you think an induced draft furnace 'with a cracked heat exchanger' can introduce CO in your airstream?
As per your thinking, the supply ducting is under positive pressure, the heat exchangers are under a slight vacuum. It should be transferring indoor air to the exhaust airstream. So how the hell does CO enter into the indoor airstream?
Please explain why one is different than the other.
Real simple, furnaces only have a Delta P of an inch or 2 of WATER COLUMN, not over 50 POUNDS PER SQUARE INCH(LPCO setting) or higher.
FWIW, the furnaces I have found with compromised HX, have symptoms of blown out pilots, tripped roll out switches, and carboned up fire boxes, not CO in the airstream.
Like I said in the other thread... SHOW ME where moisture at ambient pressure can get into a refrigerant system that has a minimum SP of 50PSI, with just a very small leak(a couple of ounces per year)...
The pressure is *still* higher. So the end result is the same no matter how you slice it.
So, are you saying it isn't happening?
The 50 PSI is irrelevent, venturi effect doesn't care what pressure you're dealing with. The POE oil is going to suck up the moisture like a sponge.
The air and moisture still has to get *INSIDE* of the refrigerant system against the pressure inside of the system.
Yup, I have used one, I have used eductors in several other applications, for moving liquids and vapors *OUT* of a space, as they are designed for high volume from a high pressure area to a low pressure area, not the other way around. You could use venturi effect to move air and moisture out of the system with the refrigerant as the high pressure source, but to use venturi effect to get air and moisture to flow against high pressure refrigerant to get inside of the system... that dog don't hunt.
If the static pressure less than atmospheric pressure, then moisture can ingress into the system. Unfortunately it isn't less than atmospheric, otherwise refrigerant wouldn' be escaping. In the sludge sucker analogy, notice that nitrogen is not spewing out of the inlet hose. All gasses have a dispersion rate into other gasses for which formulae can be found, but in most cases that rate is very slow, much slower than the flow rate of refrigerant in the outward direction.
There may be something happening at the edges of the hole, but it doesn't cause reverse flow of moisture into the system, it only causes the air around the refrigerant leak to be pulled along with it in the outward direction.
Low and medium temp apps are a different story. They typically run suction pressures near or even below atmospheric. If evap pressure is above atmospheric by only a few psi, with very little pressure differential between the refrigerant in the evap and the atmosphere, then the speed of the escaping gas stream might well be slower than the dispersion rate of moisture into the stream. I don't know what the dispersion rate is, but I do know there is one, so at some point moisture can enter the system, even if system pressure is above atmospheric. But I suspect it can't be very much above atmospheric.
In systems that use rubber lined hoses to transport refrigerant, moisture ingression can occur at much higher system pressures. But there is a difference between ingression through a relatively dense solid than ingression through a gaping hole. In the case of air permeating rubber there are intermolecular forces helping it along. The rubber acts more or less like a dessicant, actaully drawing the moisture in toward the inner surface where it can be knocked loose by the passing refrigerant.
I searched the web for info on this topic and I couldn't find any literature specifically adressing this question, period. I can only assume that no serious researchers considered it an open question.
When the fan isn't running, the pressure inside the exchanger is higher, therefore CO will communicate with the heated air. Otherwise, there would have to a venturi effect at the site of the hole or crack caused by the air movement. If not, the CO will not exit at the crack or hole if the pressure on the other side of it is higher. Also, remember the increased pressure caused by the blower fan can cause air to infiltrate the heat exchanger through the crack or hole, causing the heat exchanger to effectively "overflow", and therby cause spillage. That's why an obvious place to check a home for CO is in furnace room. Not the only place, BTW.
Great post. I have to side with Bob l, Noone and you on this one. The amount of ingression or diffusion is microscopic with out the pressure differential being higher outside the system. The venturi effect could cause some migration at pressures with small Delta's. If there is a filter dryer on the system any of that would be contained there. Seems very insignificant to me. As Bob said, educate me, I don't like being wrong or spreading miss-information.
Joseph
p.s. Next to Paul, KJ is "one" of the few senior posters left on this newsgroup.
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