Water Heat Circulator

[Oscar_Lives]

"Unpressurized"??? Are you going to put it under a vacuum?

[nick pine]

No. The hot fins would be surrounded by a shallow vertical glycol tank at atmospheric pressure, 6' above a basement floor, with a fountain pump to move it up into the top of the vertical PVC pipe containing the pressurized copper pipes when the glycol reaches 110 F and a return from the lower part of the PVC pipe to the glycol tank. The glycol levels in the tank and the PVC pipe would be equal.

Nick

[sp_mclaugh]

What a surprise.

through

It's a hypothetical situation, brought up to show the BAD points of the system. Doing anything like that WOULD be stupid, which is what I suggested. Besides, like you said (I think it's the one intelligent comment you made), the pressure relief valve would kick in before this happened.

By the way, you seem to have this "obsession" with colleges. First of all, like I said, I only mentioned physics when you were bashing Nick because of it. Second, real colleges aren't f****ng ADVANCED PLUMBER / HVAC schools. No, they don't teach us the various trade school techniques that Paul Milligan has to go through in his everyday life. (to anyone else reading this: I don't mean to bash trade schools... just Paul)

I was talking about the pressure in the cold water pipes breaking the filler valve. No, I don't know ANYTHING about these, nor do I EVER plan on learning anything about them. All I know is that there are a variety of them, and that they must not cut off the water all that well, or else we wouldn't have anti-siphon technology on our toilets. The comment was made in passing, anyway; I don't care to argue about what pressure it would require to destroy the refill valve in a goddamn toilet.

It's not my idea, you dumb f*ck. While I was trying to POLITELY discuss the idea, I was CLEARLY not promoting it.

Yeah, saving energy is stupid. Blow me.

Like I said before, people smarter than you are installing these types of things in their homes already:

You dumb, dumb f*ck. I&#39;ve made it clear already, *I* am not TOUCH < watered-down regurgitation of what was already devoid of any intelligent content >

[nick pine]

You surely have a backflow preventer on the water supply pipe entering the house, and why would the water want to go back to the water company, given the much lower resistance of the path back through the water heater and the cold water pipe into the AC heat exchanger? You seem to have a big blind spot here.

No...

That&#39;s extremely unlikely. You might calculate the increase in pressure resulting from pumping 0.2 gpm back into the water heater with a reasonable pipe loop length before announcing that it would be significant or imagining that there&#39;s a one-way check valve in series with the water heater drain.

Many people with such a determination to be ignorant would also choose to be silent :-)

Nick

[nicksanspam]

There&#39;s no need to modify anything owned by the landlord if the laundry sink has a couple of taps with hose threads...

Nick

[nicksanspam]

[re a $98 window AC in the middle of an apartment with an unpressurized tank around the hot fins and a heat exchanger that warms pressurized water from a cold tap (with 1/3 the usual electrical energy) and pushes it back into the apartment&#39;s hot water supply tap...]

If your apartment needs AC from 4 PM till 2 AM and the 12 apartments use most of their hot water from 6-8 AM and 5-9 PM, you might push

0.2gpmx60x(2AM-9PM) = 60 gallons of 110 F water back into the water heater when nobody&#39;s using hot water...

An adaptive controller might learn from history by noticing that dumps were often required from 9 PM to 2 AM and overcooling the apartment (below the setpoint, but still within the comfort zone) from 5-9 PM...

Nick

[sp_mclaugh]

SUMMARY:

Right now, my problem has pretty much been solved by use of water-cooled ACs or water-cooling chiller-based ACs. But the thread is continuing mostly discussing ways to produce hot water while using air conditioning.

ORIGINAL PROBLEM:

Method to cool a room which doesn&#39;t have space for a window unit, and is not worth investing in any type of central unit. A 10,000 BTU portable AC has already been tried on a small room, and just doesn&#39;t work well.

SUGGESTED SOLUTIONS:

The very first idea was to use 60 degree cold water and pass it through a radiator / heat exchanger and a fan, and then just dumping the water down the drain. People do it all the time with lake or river water, but it was decided that at about 2 gallons per minute, it would be too wasteful to use with city water (even if I&#39;m not directly paying for it, it will be noticed by someone).

The next string of ideas was to use the cold water to cool the condenser coil of an AC. This progressed to then pumping the heated water INTO the hot water pipe - providing very cheap hot water. The only downside being that if hot water wasn&#39;t being used quickly enough, the cold water pipe would start getting hot, and the AC would suffer performance. A second means of cooling the AC would be needed.

This "second option" would be either just DUMPING the hot water, or using some type of heat exchanger outdoors. Either just running water tubing through a kiddie pool, or building a small "cooling tower".

Now, we started to diverge on opinions here. I didn&#39;t want to have plumbing running both to my water pipes AND to the outdoors. They would have to cross the entire length of my apartment to do so. Also, although I usually like the idea of being energy-efficient, I wouldn&#39;t PERSONALLY see much savings from pumping the hot water back. So I was in favor of using SOLEY a water-cooling circuit to cool the condenser of an AC.

I found these types of systems in marine AC&#39;s (ie Flagship Marine&#39;s self-contained ACs) and even some portable AC&#39;s (ie: King Kompac by Koldwave), so I&#39;m speaking to companies and deciding which one to get.

While doing this searching, I also found the REVERSE type of unit; also not terribly expensive: water chiller ACs. The condenser can be air-cooled or water-cooled, but the EVAPORATOR is submerged in water (I&#39;m assuming it&#39;s a titanium evaporator, but I haven&#39;t gotten an answer yet). The marine industry uses these a lot on medium-large boats.

That was one of the options being considered.

I don&#39;t know if there are any anti-backflow devices at the apartment level. I know the fire department started requiring anti-siphon devices so that they didn&#39;t suck things out of homes when using fire hoses. ie: if you were spraying pesticide through a water hose. But for apartments, I don&#39;t know what level that happens at: individual units, or the whole complex.

If there are no anti-backflow devices, just read Nick&#39;s earlier posts. As he said, it probably wouldn&#39;t require a very large pump to push water back into the hot water pipe. Like I said: something to consider when I move, maybe.

Maybe at an apartment or community level, it would work. I don&#39;t know, and it probably depends on the particular apartment complex or community.

That&#39;d be pretty much the same thing as using the hot water heater. I guess it would give me the option not to share the energy savings with anyone else. But the extra plumbing and huge tank would make me even less likely to do that.

----------------

Hopefully that summarizes everything pretty well. Nick, if you want to continue this thread in the direction you were leaning, feel free. Unless I decide to BUILD one of the two types of AC&#39;s I mentioned, I think I&#39;m all set.

[sp_mclaugh]

Nick,

I was referring to the hypothetical case of trying pushing water all the way to the street level (if it had nowhere else to go). Not talking about your idea in general. The way you described your idea, this case would never happen, because the water always has somewhere to go (even if that is just a loop). Sorry if that sounded like I meant something else.

Again, I was referring to the pressure relief valve kicking in before you started pumping water all the way down the street. Not something that ever would happen (or ever could happen, with anti-backflow devices).

I shouldn&#39;t have even mentioned that case, my bad.

[nicksanspam]

Something to do with your reading skills?

Yes.

The OP lives in an apartment (see "apartment" above.) He has incoming hot and cold water supply taps (see "tap" above.) He&#39;s considered pushing some pressurized cold water through a copper pipe in a heat exchanger and back into the hot water supply tap with a small pump. There is no mains pipe (see "mains pipe" above?)

I&#39;m afraid of it was said.

Untrue (some communities allow this for heat pumps), but who cares?

Good idea. We call those "apartment-sized water heaters."

Nick

It is not my function to be a flyswatter. -- Nietzsche

[News]

I find this thread disjointed. Does the OP want to use the cold water mains as a heat sink for an a/c? If so how do you get the cold water taken from the mains pipe back into the mains pipe? I must have missed that of it was said. No water company would allow you to do in reality. How about dumping any waste heat from an a/c into a thermal store cylinder, that either supplies a run cylinder or an on-demand water heater. When fully hot then the usual method of dumping heat would need to be used.

[nicksanspam]

The pressure relief valve might open if the sum of the pressure increases resulting from a) pushing 0.2 gpm of water out of the water heater tank into say, 100&#39; of 1/2" cold water pipe and back to your apartment plus b) expanding a tankful of water by heating it from 60 to 110 F exceeds the valve limit. The latter is doubtless accounted for by an expansion tank, if there&#39;s a backflow preventer at the street.

The Hazen-Williams equation says 100&#39; of 1/2" copper pipe with a 0.2 gpm flow has a 0.0004227x100x0.2^1.852x0.5^-4.871 = 0.063 psi pressure head, which is likely small compared to the T&P valve design margin. If not, it would likely pop every day, even without that miniscule overpressure.

Nick

[News]

I also find it mad.

They do? How odd. So if all the road had heat pumps hot water would come through the cold tap.

Well that&#39;s the way to go then. Simple. :-)

[CM]

The obvious problem is after pumping just a few gallons there would be hot water coming out the cold water tap. (Unless there was a constant use of hot water - not likely even in a big apartment building.) Worse is if the neigbors start getting hot water out of their cold water taps, or someone gets an extra-hot shower. Could result in a nasty lawsuit.

Not only that, but it could easily waste more heat than it saves, since cold water pipes are usually uninsulated, heat would escape from the now hot "cold" pipes and warm the space you are trying to cool.

There are proper ways to use waste heat from AC units to pre-heat water, but they must be properly designed and built. This "water tap" scheme simply isn&#39;t proper.

CM

[CM]

Normally, I would not recommend the portable units, as they are usually much more expensive, less efficient, and bulky, when compared to standard window mount or through-the-wall mount AC units. Their sole redeeming feature is ease of setup. In this case, the ease of setup becomes an overriding factor.

Where I live, hurricanes are not a problem, so I use a window unit (and it&#39;s almost time to install it again).

CM

[nicksanspam]

Rarely, IMO, with only 1 out of N apartments using this scheme, with an automatic adaptive controller and (rare) hot water dumper.

It&#39;s difficult to "waste more heat than it saves," since 100% of the AC heat is normally wasted. In this scheme, most of the heat would go down the drains, ideally after showers, dishwashing, and so on.

"Simply not proper"? :-) You sound like George Ghio...

Nick

[stretch]

In order to push water back into the water mains or the water heater will require a high head pump, that uses a lot of power, which would waste the energy you are trying to save.

The only way to do that with a low powered circulator is to draw water out of the cold water line and push it back into the hot water line. Thus the total amount of water in the loop remains constant. You would have to be sure there is no check valve in the existing water piping that would stop this from happening.

Because water is not compressible, if you used a high head pump, you would just pop the the water heater relief valve and waste the heat anyway. I have seen that done with water source heat pumps in emergencies. Would you like to have a $600.00 per month water and sewer bill?

Just a few things to consider.

Stretch

[nicksanspam]

I disagree.

Good idea.

Nick

[nicksanspam]

Preliminary results testing a Haier HWR05XC5 5K Btu/h AC ($98 from Wal-Mart, with a digital remote control), inside a room, measuring the cool output air temp with a Testo velocity stick, the central hot fin temp with a Raytek Mini-Temp IR thermometer, and the electrical power with a Kill-a-Watt meter:

hot cool power relative room time fin (F) air (F) (watts) COP temp RH notes

7:20 67.0 53.5 341 9.7/3.412 61.3 65% = 2.84 7:22 82.0 44.8 385 2.84x341/385 = 2.52 7:24 87.5 38.5 413 2.84x341/413 = 2.34 7:30 91.5 36.3 442 2.84x341/442 blocked some = 2.19 hot airflow 7:34 102.0 37.0 484 2.00 7:40 101.5 37.8 491 1.97 blocked more... 7:50 115.5 38.8 555 1.74 61.9 61%

Final hot fin temps:

116 118 123 111 115.5 118 113 121 118

The AC was sitting on top of a dry muck bucket, tipped backwards at 2 degrees, set to cool to 61 F at low speed. I didn't see any condensation during the test or at 10 AM. Page 9 of the AC manual says "Caution: the compressor of your air conditioner _will not_ work when the temperature goes below 65 F."

I didn't measure the cool airflow with the stick (altho it reads down to 1 lfm, digitally :-) The "relative COP" above is just a calc based on the nominal 9.7 SEER spec, derated with larger temp diffs and higher power consumption. It may be pessimistic, since the nameplate says 515 watts.

Preliminary conclusions:

It's hard to tell what the hot water temp might be from this test, since the fin temps vary a lot with position over the back face. The next step might be to make a bath for the hot fins and disconnect their fanblade.

It looks like a cool water bath might be helpful in wintertime to keep the COP up and avoid icing and allow disconnecting the fan motor. Steve Baer suggests cooling greywater this way, with normal summertime AC.

Nick

[sp_mclaugh]

As I mentioned to Nick in a private message, this use of the heat from the condenser coil is analagous to the use of a desuperheater on a large HVAC system. They are found often on geothermal (ie, ground/water loop, not air) heat pump systems. Probably because the clients buying those systems are interested in efficiency and energy savings. The desuperheater works by passing water over the refrigerant line (in a heat exchanger) right before it gets to the condenser. At this point, the refrigerant is a superheated vapor. The desuperheater is setup so that the refrigerant still remains a vapor, but is no longer superheated (its temperature drops to approximately the boiling temperature).

Nick's suggestion is basically the same idea, with a window-size AC, and a DIY standpoint. The condenser would basically be converted to a desuperheater by immersing it in water (or maybe glycol, depending on the setup).

Using ONLY the hot water loop to cool the refrigerant is equivalent to an HVAC system that doesn't even have a condenser, strictly speaking. The desuperheater would have to completely replace the condenser. That is really the basis of our previous arguement; whether it could dissipate enough heat without adding another cooling method. This depends on the usage of hot water. I think for a normal household, the answer is surely no; you would need to dissipate more heat. Maybe it would work for cooling 1 apartment where hot water is shared between 10 apartments. But even then, you'd need a very large hot water tank to "buffer" the periods of high and low water usage.

The "dumping hot water" method that was suggested is merely equivalent to cooling a condenser with tap water. The "long water hose in a pool" is equivalent to cooling a condenser with a closed loop of water. An obvious alternative is to seperate the desuperheater from the condenser (ie: braze on another condenser), and then air-cool the condenser. But this would require cutting the refrigerant lines, adds complication to a DIY project. Whether or not a second cooling method is used, the general idea of "cheap hot water" is good.

Like I said before, I'm now discussing this part of the thread only from a hypothetical standpoint.

[sp_mclaugh]

One more comment:

Even if the AC use of one apartment is equal to the hot water use of 10 apartments, and the water usage pattern is NOT a problem: this system would impose restrictions on either the type of refrigerant used, or the maximum temperature of the hot water. After all, the temperature of the condenser has to be LESS than the boiling point of the (pressurized) refrigerant.

In order to heat water AND run the AC at the same time, you're probably going to need 2 seperate condenser-type units. Either that or specialized refrigerants or optimized pressures. I don't have any tables of boiling points of various types of refrigerants at various pressures, so I can't comment any further.