Either will work just fine.
To understand this, start with a typical central air conditioner—the ones with a condenser in the back yard. A/C is all about moving heat from one place to another.
So…in a central system the coil in your furnace “accepts” or “picks up” heat and it is carried outside where it is “rejected” or “expelled” in to the environment through the outside coil (condenser) . Voila! You simply moved heat from one place to another.
The advantage to the condenser outside is that the ait going “in” the condenser and the air coming “out” both come from outside. So…there is no “net effect” to the pressure in your home.
Even a window unit has some louvers on the side of the cabinet that allow the air in the condenser and the air out both come from outside. So…once again…no effect on the pressure in your home.
In a portable unit however…the air coming out of that hose going to the outside came from inside your house. The problem is that your home is now under negative pressure. The link that was provided was only partially accurate----sure your portable unit will now get air [essentially] from the other rooms…but…those other rooms cannot remain negative either. So…ultimately all of the air that is exhausted has to “made up”, and that means that all air that is exhausted has the same amount coming in from outside—every crack and every time you open a door.
Air flow is measured in “CFM” so if that portable A/C has a 100 CFM fan for the exhaust than 100 CFM is coming into the home from other sources to keep the house “neutral” to the environment. Nature wants it that way.
A 2 pipe system does nothing more than providing a means of make up air. If that exhaust fan is moving 100 CFM than the second pipe is bringing in 100 CFM from the outside just like the cracks in the door and windows were in the one pipe system. In fact, it is the same air, you’re simply getting it from a direct, managed source. Its still outside air, and will still need to be cooled.
I see little advantage to a 2 pipe system.
Correction:
After re-reading that link------and if I understand it completely------
If the 2 pipe system is “sealed” in that the air brought in is piped to the condenser and the condenser only, (and sent right back out) than I see the 2 pipe system is preferable.
IOW, if the 2 pipe system has a “dedicated” air flow for the condenser----so the the air “in” the condenser and the air “out” is the same air------- without mixing it with “room” air----that the 2 pipe system is better. Much better, IMV.
Get a 2 hose! We put a 1 hose portable A/C unit in an old motor home and put one hole in the side wall in the bath to run the exhaust hose. I cooled fine in the Texas summer heat but the front of the motor home got hotter!
We figured out that if the unit was pumping the heated air out of the single hose, the air in the motor home was being replaced via leaks under the dash so the front of the motor home was being fed with 100 + degree hot air from outside!
We replaced the unit with a 2 hose unit (yes, cut a second hole) and the 2 hose unit, of the same BTU, would cool the entire motor home.
We also put a small hole in the floor to install a drain hose rather than have it re-evaporated into the air.
Since then we put a 2 hose unit in our home master bedroom because we wanted the room cooler for sleeping without cooling the entire house. We didn’t use a drain hose on this one and let it evaporate the water back into the air.
We recommended this to some friends that also put one in the master bedroom because the neighborhood association would not allow a window A/C unit.
Do you have any estimates on the electricity savings? How big is your bedroom vs the rest of the house? I’ve considered doing this in my house, but I’m not sure of how much it will really save.
The first time this thread came up, it seemed obvious that a two-hose set-up would be more efficient.
After reading this a second time, it seems that, to a first approximation, one hose or two would be be just as efficient. With two hoses, you’re bringing in 90 degree air through one hose, heating it to, say, 150, and expelling it through the other hose. With a single hose, you’re bringing in 90 degree air through cracks in the house, heating air to 150, and expelling it.
The air being heated to 150 in the two-hose case is starting at 90, while in the one-hose case, it’s starting at 70, so there would be an efficiency gain there, offsetting the efficiency loss of having the outside air leak into the house.
Can someone provide some simulated numbers that show where the efficiency gain of a two-hose set-up comes from? Would I see an efficiency gain if I had a tube to directly bring in outside air to burn in my furnace.
This is a separate issue from whether your house will be more comfortable, since away from the AC, the rooms will be warmer due to the outside air.
I propose that the only meaningful measure of efficiency is one based on the cooling comfort in the house. Most air conditioners do not consume their own cloud of cold air. Comparing one that does by using the metrics developed for ones that don’t is kind of like touting the great fuel efficiency of a trailer.
Unless, of course, you’re a zombie and don’t mind the heat.
Not quite. In a one pipe system you are bringing in 90 degree air cooling it to 50 degrees then using it to cool the condenser. Because the compressor is not 100% efficient you are using more energy to cool the air than the air will pick up going across the condenser. On a two pipe system there is never the wasted work.
Say what? It’s the two-pipe system that has the 90 degree outside air coming directly to the AC. The one pipe system has 70 degree house air coming to the AC.
Regardless, can you show with numbers where the difference in efficiency is coming from?
It is wasted energy to cool air to use as condenser air.
Place a move and cool in a space and run it without bring in outside air and the space temperature will increase. I seen that happen in a closed server room.
For every BTU of heat removed room air more than one BTU of energy will be consumed.
I have a 10,000 BTU window air conditioner in my family room with a lot of windows. On 95 degree day it can maintain room temperature in the 74 to 76 degree range. A 10,000 single pipe move and cool would begin to loose temperature around 87 degrees.
Yes, I know that. Everyone in this thread already knows that. I’m asking about the relative efficiency of one-hose versus two-hose AC. Nothing in this post addresses that. If you don’t know the answer, that’s OK, but please let someone else who does answer the question.
Sorry I read your post ass prove it with the numbers. Sorry but I do not have access to the numbers at thiss time.
Sorry to bring this thread back up, but I ran across a video that now completely explains why a 2 hose system COOLS better, in what I think is a superior way over what has been voiced here, though I do understand what the 2 hose guys are saying. No A/C is completely efficient of course, so I doubt than any numbers you come up with would prove the matter either way, but if the two hose system did not have an energy advantage, it surely cools faster, and would shut off way before the one hose would. Watch the elaborate video on this issue…
By the way, the only reason the air in the room is cooler than outside, is that you already did work (used power) to cool that air. The cooler air is not free, so to speak, and you are using it. Hot air outside is cheaper air. Watch the video. So, it is possible that the one hose could actually work in a single room/area, at the expense of other connected areas, but overall energy use is surely higher.
And the two hose can surely paas more air over the coils, which is an advantage over using cooler air. The amount of heat the air carries away is all that matters, not how cold the air is. Running a fan is cheaper than cooling air, surely.
But I am concerned that the 2 hose system is bringing possibly dirty, moist air or air containing insects, into the unit, inside the house. Hmmm.
Could they have found a presenter with a more boring voice? I dropped off halfway through.
And the air outside can be simply too hot ! You need the air con when its really really hot.
Its far better to have to cool a bit of warm air from elsewhere in the house
than to try to pump heat into the very hot outside air …
The device loses efficiency when heat flows back from the very hot side (the pump and the tubes) to the room …
A two hose system brings air inform the outside across the condenser coils and then back out side. The dirty moist air should not stay inside the house. Unless the system has leaks.
May I respectfully thank all those who have in good faith submitted comments on this topic. I have tried both a one exhaust pipe and a two pipe unit in my bedroom in a house where the outdoor temperature can be from 80 to 90 deg F. In the one pipe portable air conditioner installation, the negative pressure in the bedroom caused the bedroom door to open if left unlatched, or the negative pressure in the bedroom made the bedroom door difficult to close. This indicated to me that air was being drawn into the bedroom from the rest of the house. Other posters have clearly made this point.
It should be noted that a window air conditioner does not have this problem because the condenser and evaporator air flows are totally independent, and the air flow is driven by two fans on a common shaft.
Since I have horizontal sliding windows that make a vertical window unit almost impossible to use, and I do not like pulling hot unfiltered air into the rest of the house, I chose to purchase a two pipe unit from Sears two or three years ago. It has 2 fans on one shaft that attempt to make the unit work like a window unit. There is forced air past the condenser, not convection flow. Much to my surprise there is still a negative pressure in the bedroom. It seemed that I have to use almost the same amount of extra force to close the bedroom door in both cases to overcome the negative pressure. Since I had no easy way of measuring the differential with respect to the rest of the house for either unit, I kept the 2 pipe unit. I have not been able to find data on the cfm for the exhaust pipe of either style unit. At the time of adding this comment I have not seen any advertisement for 2 pipe units. I assume the problem is partially it is awkward to install 2 separate pipes, and by my experience the 2 pipe system has not been properly developed to eliminate the negative room pressure.
I wish that I could have provided some clear data to promote the 2 pipe unit as the only way to go, but my experience in room pressure and the market of the 1 pipe portable only may make the decision very simple. Efficiency of use of electrical power will not likely be a prime consideration for a portable air conditioner. It would be better to use a window unit or some other form that involves separate locations for the evaporate rand condenser.
For the spell checkers “evaporator and”