Here’s how the manual explains heat mode, in summation: Water from the earth loop moves thru coax tubing where the water heats R-410A which turns it into a gas. The gaseous refrigerant gets compressed in a compressor and turns into an even hotter gas which then gets pumped to the radiator to heat up the returning cool air, creating warm air to be pushed to the rest of the house.
What i don’t understand is the cooling mode. I’m going put word for word what the manual states.
I don’t understand why the R-410A needs to be used as a heat transfer at all. If the earth loop water is around 54 degrees F, which apparently is hot enough to turn R-410A into a gas, doesn’t that mean the R-410A is cold enough by itself that it doesn’t need to be heat transferred or compressed and can just be pumped thru the radiator? How hot is the return air during summertime (live in Maryland) that it can make such cold R-410A heat up so much that it needs its heat transferred back to the earth loop?
Another follow up question: When the refrigerant runs thru the compressor it heats up again, but as it travels thru the coax tubing, the refrigerant turns from a super hot gas into a cool liquid. How is that even possible when the heat cycle uses the same method to turn the cold refrigerant into a gas? It’s using the same method to get 2 different states of matter, or am i not understanding that part at all?
This is just a heat pump with a huge heatsink at 54 °F.
In Heating mode, heat is extracted from the ground and pumped into the house. It’s more efficient than an standard heat pump, because the ground is much warmer in the winter than the air would be. In Cooling mode, heat is pumped from the house into the ground. Once again, it’s more efficient, because the ground is much cooler than the summertime air.
You might want to look this Wikipedia entry on heat pumps to get a better understanding of what is going on.
It uses the same method, but the difference is that the flow of refrigerant is reversed in heating. (vs cooling)
The result of this is that in the winter you’re extracting heat from the earth and discharging it into your home; and in the summer you’re extracting heat from your home and discharging it into the earth.
The flow of water (actually, methanol or glycol…) remains the same. The flow of refrigerant is what determines what type of heat transfer you’re doing; heating or cooling.
I read that in the manual, but something just isn’t clicking in my head. Even if the process is reversed, the refrigerant is still getting compressed to 165 degrees F and then cooled by the earth loop water (our’s uses distilled water and glycol, btw). But when it is getting cooled in the coax, it’s still warm enough to be a gas… does that “expansion valve” turn it into liquid again to start the loop?
How can such a high temp (165F) be used in cooling regardless of the direction of flow?
I’m usually so mechanically inclined that this is mental anguish.
I have a Waterfurnace; been installed almost one year now. I can’t recommend it highly enough (uh, meaning I do recommend it highly)!
So in cooling mode, what they’re saying is, you have a liquid. You depressurize it and let it turn into a gas. This sucks heat of the air. Now you’ve got this hot, compressed fluid, which you pump through the cold ground. It gets cool by transferring this heat into the ground. It really works just the same as your standard central air conditioning, except the hot fluid is cooled off by indirect contact with the earth instead of air being forced by a fan to carry off the heat. Much, much more efficient.
In heating mode, of course, you have a cold fluid going through warmer ground. It becomes less dense (maybe gaseous, but I don’t know that). Now when it gets to compressor, it’s squeezed hard, and so it gives off heat, which is then used to heat your home. Of course once the liquid has given off its heat, it’s cold again, and can go get more heat from the ground.
If you’re considering a Waterfurnace, you can’t go wrong. It’s cheap to operate, the carbon offsets are huge vs. natural gas, and it’s a heck of a lot more comfortable than my old natural gas system (less cyclic, more constant).
I don’t know how to explain this succinctly----and the fact is that it takes people who do this for a living years to fully grasp—but it essentially boils down to 2 things:
1) The nature of heat transfer, and;
2) The nature of Pressure/ Temperature relationships.
As to the first item, (1) the greatest transfer of heat takes place when an element is “changing states.” A BTU is defined as “the amount of heat required to raise the temperature of one pound of liquid water by one degree.” So…it would take 1 BTU to raise----for example----- 1 pound of water from 211F degrees to 212F degrees.
Here’s what you need to understand about heating/cooling: When you want to change “state”-----in this example from water to steam ----the BTU requirements skyrocket. So…while it only took 1 BTU to go from 211F water to 212F water, it takes 965 BTUs to go from 212F water to 212F steam.
Similarly, it takes a 144 BTUs to change 32F ice to 32F water (once again 1 pound; about a pint) and yet only 1 BTU to go then from 32F water to 33F water!
So you can see the Holy Grail for gaining the maximum transfer of heat (and that’s whether you’re endeavoring to “accept” the heat or “reject” the heat) is when a change of state takes place.
So…if I simply eliminated the R410a and used water I would simply accept or reject BTUs at 1 BTU per pound of water; a mighty inefficient way to transfer heat…unless…I could “change the state” of water as part of this process. The problem is, of course, the maximum transfer of heat using water happens when we change from water to steam (at 212F at atmospheric pressure) or when when changing water to ice. (32F at atmospheric pressure) So water while is amazingly stable it requires to wide a range of temperature to be practical.
Which brings us to the solution. (Item 2) What we need is a compound that is extremely stable like water but has a lower boiling/evaporating or condensing point. That’s where the pressure/temperature relationship comes into play. As an example, we like to say that water boils at 212F and that’s only partially true. Water boils at 212F at atmospheric pressure. In Denver----5000 ft above sea level---- there is lower atmospheric pressure. As a result, water will boil there closer to 203F.
So this pressure temperature relationship exists everywhere in nature, but we never think about it. What Freon does is offer us a compound that will boil at temperature substantially lower than water (212F) So…Freon will “boil” or “evaporate” around 70F. So when we run Freon through your A/C coil and warm 75F return air from your furnace flows across your coil ir begins to “boil” or “evaporate” and that “change of state” provides the greatest acceptance or rejection of BTUs.
Remember the example above about turning 212 water to 212 steam or 32 ice to 32 water; the greatest transfer of heat takes place when there is a change of state. Here’s another example: Soldiers in Saudia Arabia take a canteen, fill it full of warm water and then wrap the outside of the canteen with gauze. They drench the gauze with water and then set it on on 120F tarmac. As the wet (water) gauze changes state (evaporates) it removes heat/BTUs (read: heat transfer) from the water in the canteen. The result: cool water in the canteen. The “evaporation” process (read: change of state) “transferred” heat from the water to the environment.
What R22/R410a does is give us a stable compound that will “boil” or “evaporate” (which is going from a liquid to a gas, and attain maximum heat transfer while doing it) and then “condense” (go back from a gas to a liquid and attain maximum heat transfer while doing it) repeatedly.
Now we’ve talked briefly about water. These refrigerants will boil or condense at vastly different temperatures and temperatures than water. So, your A/C system is finely tuned to run at specific temperature and pressures based on the characteristics of those compounds.
As an example, R22 (Freon) will boil at 70F roughly at 70 Psi (roughly). R410a is a different compound and it too will boil around 70F roughly. But it requires 150Psi to boil at that temperature. The whole “pressure temperature” relationship is a difficult one to understand, but the water example is a good one to start at. It will boil at 212 in Dayton, OH and 203 in Denver, CO. That is an example of a P/T relationship. Your A/C system is an engineered/designed pressurized environment. It is designed at specific pressures that correspond to the boiling or condensing characteristics of the refrigerant being used.
I don’t know if that is useful or not. But this can get complicated.