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u4ia2000
31-10-2009, 08:04 PM
With oil prices going up and up and an eye on the future I'm thinking greener these days out of necessity. I was looking at solar panels but they are really expensive and I don't have 2000 sq.ft. of southern facing roof so the next best thing and most economical would be to cut consumption. I have a fairly new well insulated home so can't do much there. Hence, I'm looking at "Water source heat pump A/C and water heating" since most of the consumption falls in these two categories anyway. But, all the A/C installers want to sell a whole new A/C system at a much increased cost I might add.

My question is couldn't one (after consulting an refrigeration specialist) buy a water to refrigerant heat exchanger and install it just after the air cooling coils in an already new A/C heat pump unit? It seems to me that would bring the refrigerant temp. down and be just as efficient as the water source units. I realize it would have to be installed by a specialist so one didn't freeze anything up but couldn't that be done? By the way I have 3 water wells on my property already.
J Daniel :confused:

cadillackid
01-11-2009, 03:47 PM
seems that would be a waste.. using a condensor fan and such and then running the refrigerant through a water / refrigerant heat exchanger... more than likely even if installed by a specialist it would still void your warranty out on the unit that is meant to be a refirgerant to air heat exchanger..

I am all for improvising ,designing, and building.. but you want to get the right components together esp if this is an energy saving measure...

are you looking to use your existing system but just add a heat exchanger? or are you replacing you existing system?

being in florida I would look at some variable speed equipment maybe even inverters as they tend to have better energy management than a standard single stage..
-Christopher

taz24
01-11-2009, 05:47 PM
With oil prices going up and up and an eye on the future I'm thinking greener these days out of necessity. I was looking at solar panels but they are really expensive and I don't have 2000 sq.ft. of southern facing roof so the next best thing and most economical would be to cut consumption. I have a fairly new well insulated home so can't do much there. Hence, I'm looking at "Water source heat pump A/C and water heating" since most of the consumption falls in these two categories anyway. But, all the A/C installers want to sell a whole new A/C system at a much increased cost I might add.

My question is couldn't one (after consulting an refrigeration specialist) buy a water to refrigerant heat exchanger and install it just after the air cooling coils in an already new A/C heat pump unit? It seems to me that would bring the refrigerant temp. down and be just as efficient as the water source units. I realize it would have to be installed by a specialist so one didn't freeze anything up but couldn't that be done? By the way I have 3 water wells on my property already.
J Daniel :confused:


I may have read your post wrong but you are missing out part of the heat pump system.

You need 2 water heat exchanges for a water to water heatpump.

If you are doing water to air I see your point, I think.

Yes you can do what you ask, you would need to look into it in detail but in principle it could be done.

taz

Gary
01-11-2009, 06:20 PM
I have read the original post several times and have no idea what you are describing or proposing. The only way it would make sense to me is to make a series of assumptions about what it is that you want to do... and I hate making assumptions.

u4ia2000
01-11-2009, 08:24 PM
seems that would be a waste.. using a condensor fan and such and then running the refrigerant through a water / refrigerant heat exchanger... more than likely even if installed by a specialist it would still void your warranty out on the unit that is meant to be a refirgerant to air heat exchanger..

I am all for improvising ,designing, and building.. but you want to get the right components together esp if this is an energy saving measure...

are you looking to use your existing system but just add a heat exchanger? or are you replacing you existing system?

being in florida I would look at some variable speed equipment maybe even inverters as they tend to have better energy management than a standard single stage..
-Christopher

Okay yes, I didn't give a detailed description. But, the idea is to take a 2.5 ton Trane heat pump (out of warrantee I think) and leaving the entire air system intact and initially cooling the refrig. extracting out 2.5 tons of heat. Then at the exit of the cooling coils placing a water to refrig. heat exchanger to extract and additional 1 to 2 tons of heat. That should make the exit air temperature of the unit say 50 degrees instead of the 70 degrees it is now, roughly speaking. Thereby, reducing the run time of the unit considerably. If one designs measures to keep the evaporator coils from freezing (in cooler weather) and safety features to keep the exchanger from freezing in case of unforeseen shutdown it should work-- unless there is something I don't-- that's plenty and that's why I'm here. I was a Jet Propulsion Systems tech. for the AF for 20 years so what do I know?

And, thanks, for your input so far. I'm thinking of a "Brazed Flat Plate" exchanger.

Gary
01-11-2009, 10:24 PM
So... you are starting with an air to air heat pump, which is going to be left intact, as is.

Next, you are going to do something with presumably the air flowing into or out of either the indoor coil or the outdoor coil or maybe both.

And you are going to do something or other with a brazed plate heat exhanger, that involves dropping the temperature of who knows what from 70 degrees (F/C?) to 50 degrees (F/C?) in order to accomplish whatever it is that you want to do.

And none of this has anything to do with water source heat pumps.

Does that sound about right?

Brian_UK
01-11-2009, 11:06 PM
Yep, I think you've got it one Gary, or is it seven; I'm getting confused.


I was a Jet Propulsion Systems tech. for the AF for 20 years so what do I know?To be honest, we're not sure. ;)


I don't see how adding an extra evaporator to an already superheated refrigerant is going to make an effective heat pump. Still, I'm willing to learn.

Gary
02-11-2009, 06:04 PM
It is not my intention to insult the OP. He no doubt has a clear picture in his mind of what he wants to do and how he wants to do it. But we cannot read his mind.

He must provide us with a clear and accurate description or we cannot help him.

u4ia2000
02-11-2009, 07:48 PM
So... you are starting with an air to air heat pump, which is going to be left intact, as is.

Next, you are going to do something with presumably the air flowing into or out of either the indoor coil or the outdoor coil or maybe both.

And you are going to do something or other with a brazed plate heat exhanger, that involves dropping the temperature of who knows what from 70 degrees (F/C?) to 50 degrees (F/C?) in order to accomplish whatever it is that you want to do.

And none of this has anything to do with water source heat pumps.

Does that sound about right?

I fear trying to explain will only confuse you further. But, to answer your questions and some others here the idea is to further cool the outside refrigerant (not air) BEFORE it goes into the (inside) evaporator with a "water to refrigerant" heat exchanger. And, yes that would involve draining the refrigerant, cutting the refrigerant line where it comes out of the outside A/C unit, connecting the refrigerant line to the "exchanger refrigerant fitting", then connecting the "outlet heat exchanger fitting" to the refrigerant line to continuing inside the home to the evaporator unit. Hopefully, reducing the inside air duct temperature from roughly 70F to 50F, Does that help?

u4ia2000
02-11-2009, 08:06 PM
Yep, I think you've got it one Gary, or is it seven; I'm getting confused.

To be honest, we're not sure. ;)


I don't see how adding an extra evaporator to an already superheated refrigerant is going to make an effective heat pump. Still, I'm willing to learn.

we're?
It's NOT an evaporator it's a heat exchanger and the refrigerant continues through it at the same system pressure and is cooled further by water. Which is 20 times more efficient at exchanging heat as air.:D

Gary
02-11-2009, 08:27 PM
Okay... now we are getting somewhere. :)

The smaller line between the indoor and outdoor coil is called the liquid line. In cooling the liquid line with water you are further subcooling the liquid, so let's call the refrigerant/water heat exchanger a subcooler.

A subcooler will indeed increase the efficiency of the system and is a worthwhile thing if the cost of pumping the water is less than the energy savings provided by the subcooler.

In cooling mode, typically the air exiting the indoor coil will be about 20F less than the temperature of the air entering the coil. If the room temp is 75F, then the indoor coil leaving air temp will be about 55F. A subcooler will reduce this leaving air temperature somewhat, depending upon how much heat is tranferred to the water, but the reduction is going to be far less than the 20F reduction that you are estimating. At best it will drop the leaving air temperature a few degrees.

Typically the temperature of the liquid as it leaves the outdoor coil will be a few degrees above the outdoor temperature and the subcooler can reduce this to a few degrees above the water temperature.

At the same time the water temperature will be raised, at best, to about the same as outdoor temperature.

A subcooler can be a good thing, but don't expect miracles.

u4ia2000
02-11-2009, 09:53 PM
Okay... now we are getting somewhere. :)

The smaller line between the indoor and outdoor coil is called the liquid line. In cooling the liquid line with water you are further subcooling the liquid, so let's call the refrigerant/water heat exchanger a subcooler.

A subcooler will indeed increase the efficiency of the system and is a worthwhile thing if the cost of pumping the water is less than the energy savings provided by the subcooler.

In cooling mode, typically the air exiting the indoor coil will be about 20F less than the temperature of the air entering the coil. If the room temp is 75F, then the indoor coil leaving air temp will be about 55F. A subcooler will reduce this leaving air temperature somewhat, depending upon how much heat is tranferred to the water, but the reduction is going to be far less than the 20F reduction that you are estimating. At best it will drop the leaving air temperature a few degrees.

Typically the temperature of the liquid as it leaves the outdoor coil will be a few degrees above the outdoor temperature and the subcooler can reduce this to a few degrees above the water temperature.

At the same time the water temperature will be raised, at best, to about the same as outdoor temperature.

A subcooler can be a good thing, but don't expect miracles.

Yes, we are getting some where-- thanks.

Let's put some numbers to this. In Florida the heaviest A/C load is in hot weather say 90F. The ground water temperature is pretty constant in winter and summer at 70F. So, correct me if I'm wrong but that means under this condition the liquid line (92F)would be further reduced by about 20F. And, as I'm sure you know only a few degrees difference can make a big difference in A/C cost. Also, in winter it would be reversed, right? (40F to 70F) Furthermore, this is opposed to spending at least $2500 at ton for a new "Water Source A/C" unit which takes one 10 years to recoup the cost.

Downside, if it's not done right the maintenance will probably eat me alive.

Gary
02-11-2009, 10:35 PM
On the contrary, in heating mode the liquid flow is reversed with the liquid coming from the indoor coil, it's temperature being a few degrees above indoor temperature. At best, the liquid temperature would be maintained as it enters the outdoor metering device and hence the outdoor coil.

Again, don't expect a big difference.

Gary
02-11-2009, 10:40 PM
Don't confuse a subcooler with a water source heat pump. The water source heat pump has a large heat exchanger which completely replaces the outdoor coil. It is an entirely different animal from a relatively small add-on subcooler.

u4ia2000
03-11-2009, 12:58 PM
On the contrary, in heating mode the liquid flow is reversed with the liquid coming from the indoor coil, it's temperature being a few degrees above indoor temperature. At best, the liquid temperature would be maintained as it enters the outdoor metering device and hence the outdoor coil.

Again, don't expect a big difference.

Thank you, again for your reply.
And, sorry for the basic knowledge layman's questions that may require answers beyond the scope of this forum. I realize I should ferret out the answers someplace else but where's a better place to go than the pros-- I really appreciate your knowledge.

Just how does that work-- I suppose you are saying the A/C outside still runs taking heat out of the cold outside air (down to 40F, that is) and then pumps it inside as a hot liquid where it dumps it's heat then comes back outside "at near inside air temp.", is decompressed/expanded/cooled and goes through the air coils to pickup more heat.

So, now I suppose the (previously summer) liquid line becomes a gas/vapor line and it's temperature at the exit of the coils is a few degrees above the outside air. Then would go through the "subcooler" to pickup more heat from the 70F water. Or, do I have this wrong?

I guess my question is why the small gain you are attributing? Is it because of the size the subcooler would have to be to make a big difference? And, by the way what is an OP?

u4ia2000
03-11-2009, 02:25 PM
Don't confuse a subcooler with a water source heat pump. The water source heat pump has a large heat exchanger which completely replaces the outdoor coil. It is an entirely different animal from a relatively small add-on subcooler.

Sorry, didn't read this post until I answered your last one.
So then, how big to be a few degrees above or below the ground water temperature? I'm thinking since water is 20 times more efficient than air at transferring heat around 2 X 4 ft. brazed flat plate or would that cost about a million dollars. I looked at the specs. on a 12'' X 13" but that only brought the refrig. temp. down a few degrees but it only increased the water temp. a few degrees also.

cadillackid
03-11-2009, 02:34 PM
theoretically in summer mode the larhge line is the suction line and the small line is the liquid line... if your expansion device is indoors at the inlet of the indoor coil.. (and I hope its a thermal expansion valve and not a piston).. then in winter the large line is the hot gas line... the indoor coil is your condensor.. and the small line going back to outside is your evaporator inlet.. if you run that through the subcooler.. in summer it will further cool the refrigerant that goes to the indoor coil... in winter it will be the PRIMARY heat exchanger whereas the outdoor main coil will be your subcooler...
so you have to watch for a couple things..

1] in winter you are going to add heat to that refrigerant and cause it to evaporate in the subcooler.. if you dont move enough water across it you run the potential of freezing up your water lines...

2] in cold weather you run the potential of actually warming your refrigerant in the "subcooler" to above outside temperature... then running it through the main coil would cool it back down.. so you might want to consider some type of outdoor fan control circuit so that if your refrigerant coming out of the water exchanger is warmer than the outside temp in heat mode you dont run the outdoor fan...


Next, you are only getting 70 degree vent temperatures on your system now? something seems wrong with that..
1] if you stick a thermometer in the air plenum just before the coil... and then again i the air plenum just afyer the coil.. then check the difference... it should be between 16-20 degrees F depending on humidity load..

if you are not getting that then a couople things could be wrong..

a) are you pushing more than the rated CFM of air for the indoor coil over it?

b) is the humidity INSIDE the house incredibly high? its a good idea to take wet bulb and dry bulb temperatures when testing....

an OP is te "original poster" - the one who started this topic on the board.
-Christopher

Gary
03-11-2009, 03:40 PM
This will help bring you up to speed:

http://www.refrigeration-engineer.com/forums/showthread.php?t=19701

fixit
03-11-2009, 04:39 PM
Hello U4

The water source heat pump has a large heat exchanger which completely replaces the outdoor coil.

Well why not change your outdoor coil with a brazed plate heat exchanger this would involve the same effort as putting in a subcooler heat exchanger.

Regards

u4ia2000
03-11-2009, 10:47 PM
Hello U4

The water source heat pump has a large heat exchanger which completely replaces the outdoor coil.

Well why not change your outdoor coil with a brazed plate heat exchanger this would involve the same effort as putting in a subcooler heat exchanger.

Regards

Smaller water exchanger and it just seemed a waste to bypass all those new looking, beautiful air coils. And, two heat exchangers are better that one, right? But, after reading Cadillackid's post above maybe I should consider what you suggest-- for simplicity of design. Also, is an air system really designed to handle a water exchanger? To answer my own question, no, or a subcooler eather-- differant type of refrig. or does that matter?

Can you or anyone give a rough estimate of the size of a flat plate exchanger for 2.5 tons?
I did some numbers and came up with about 1.148 sq. ft. to lower the refrig. temp. about 20F but that's probably way off. That was assuming 160F refrig. and 70F water at 6 GPM. I don't know what the refrig. temp. runs or how much flow there is.

mad fridgie
03-11-2009, 11:10 PM
I see it this way, your primary use is cooling (air cond)? You want to reduce power. You have some water available. You are unlikely to have the skills and tools to complete this project your self.
Simple solution, use your water to cool the air entering the condensor.
Use a simple irrigation demister. Costs you very little, with hugh savings. may have to look at TEV orifice size. (do not know much about how US systems are made and controlled) Simply by dropping your discharge by 1C (1 and bit F) you drop pwer consumbtion by 3.5%, should be able to get close to wet bulb. (do not know Florida, apart from big crocs and aligators, and disney and last of all Gary)

cadillackid
04-11-2009, 01:26 PM
in most parts of florida in the summer time the dewpoint is in the low to mid 70s F all summer long... misting a condensor is somethiong ive done in ohio before.. and it worked... till the nozzles kept clogging up from the well water and I also noticed the affects of constant moisture on the outdoor cabinet...

I think at some point here you will get into more $$ than it would take to put in a multi-stage variable speed system..

however like the OP I would somehow want to use the water... could always take that water and pre-cool the INDOOR AIR with it as well... if the ground water is 55-60 degrees and the indoor air is 75-80 degrees theres some potential for an INDOOR air to water heat exchanger....
-Christopher

fixit
05-11-2009, 08:33 PM
Hello
all those new looking, beautiful air coils.? In summer is your well source water supply temperature 21C

Is this a new system,and what gas is in the system

fixit
06-11-2009, 07:05 PM
Hello
What gas is in the system,
Your well water supply is 21c ?

Gary
06-11-2009, 07:51 PM
Smaller water exchanger and it just seemed a waste to bypass all those new looking, beautiful air coils. And, two heat exchangers are better that one, right?

Well... maybe. If those beautiful air coils get rid of all the heat then what are you going to warm your water with?

So let's consider another alternative. Instead of putting the small BPHE in the liquid line after the air condenser, let's move it to the discharge line before the air condenser... and let's call this a de-superheater.

The discharge line is the line between the compressor and the condenser, so we are grabbing the heat before it gets to the air coil. This being a heat pump we place the BPHE between the compressor and the 4-way reversing valve so that we can de-superheat in both cooling and heating modes.

Realistically, we can get about 10-20% of the heat output, i.e. 10-20% of 2 1/2 tons... and we can preheat your domestic water from 70F to about 120-130F (at best)... your domestic water heater does the rest.

cadillackid
06-11-2009, 08:47 PM
wouldnt you also want to put a fan cycler on the outside unit as well? seems that way when the water heat exchanger does the job by itself - no need for the outdoor fan to be on and waste energy
-Christopher

Gary
06-11-2009, 08:56 PM
wouldnt you also want to put a fan cycler on the outside unit as well? seems that way when the water heat exchanger does the job by itself - no need for the outdoor fan to be on and waste energy
-Christopher

Absolutely... but being a heat pump it probably already has fan control.

Gary
06-11-2009, 09:17 PM
And again... we don't want to confuse this with a full blown water source heat pump which is far more complex, does a lot more, saves a lot more energy... and costs a lot more.

desA
07-11-2009, 02:32 AM
Realistically, we can get about 10-20% of the heat output, i.e. 10-20% of 2 1/2 tons... and we can preheat your domestic water from 70F (21.1'C) to about 120-130F (48.9-54.4'C) (at best)... your domestic water heater does the rest.

I've taken the liberty of adding in the SI temp equivalents.

I'd say that this is about the strength of it in terms of desuperheater capability.

Practically, though, 50-55'C water is adequate for most domestic applications. Going above that brings in a number of other issues (limitations) in terms of the hot-water storage vessel.

An example - stainless steel, under pressure, at temps greater than 55'C, for long periods of time, in the presence of chlorinated water, can rupture... :eek:

u4ia2000
07-11-2009, 08:10 PM
And again... we don't want to confuse this with a full blown water source heat pump which is far more complex, does a lot more, saves a lot more energy... and costs a lot more.

Most likely a good idea but 10 to 20% isn't good enough for me-- you have convinced me. I'm putting out for bids on a new "Water Source Heat Pump" system to Carrier and Hydron Module. What others do you recommend? Or, can't you recommend on here? Most likely if we did come up with a good hybrid system here I couldn't find a local A/C tech. with enough savy to install it properly. I've got some CD's maturing in January and with interest rates so low I can get a 6 to 10% return on my investment by investing in my own electric bill. As Ben Franklin said, "A penny saved is a penny earned".
And, thanks, I really appreciate your input.:confused:

cadillackid
09-11-2009, 02:02 PM
also dont forget since you are in the USA that you should check into a system that meets the efficiency standards for the Obama Energy Tax credit.. you get up to 30% or $1500.00 (whichever is smaller) in Tax CREDIT on your new system.... I believe water sourced heat pumps are included in this... make sure your company of choice is aware of what systems qualify and which ones dont... thats a nice little dent in the cost of a new system..
-Christopher

u4ia2000
10-11-2009, 08:48 PM
So let's consider another alternative. Instead of putting the small BPHE in the liquid line after the air condenser, let's move it to the discharge line before the air condenser... and let's call this a de-superheater.

The discharge line is the line between the compressor and the condenser, so we are grabbing the heat before it gets to the air coil. This being a heat pump we place the BPHE between the compressor and the 4-way reversing valve so that we can de-superheat in both cooling and heating modes.

Realistically, we can get about 10-20% of the heat output, i.e. 10-20% of 2 1/2 tons... and we can preheat your domestic water from 70F to about 120-130F (at best)... your domestic water heater does the rest.

I've done some research since my last post and come across a place that manufactures pretty much what Gary mentioned all made up in a package ready to install at ;I can't post links so remove the Spaces and Xs from; XwXwXw DOT doucetteindustries DOT com FORWARDSLASH products_vented_res DOT XhXtXm :confused:
This unit installs between the compressor and the 4way valve and taps off hot water. It claims to increase efficiency 10% but if it were supplied with ground water instead of return hot water it might go to 20% or higher.

Gary
10-11-2009, 09:16 PM
I've done some research since my last post and come across a place that manufactures pretty much what Gary mentioned all made up in a package ready to install at ;I can't post links so remove the Spaces and Xs from; XwXwXw DOT doucetteindustries DOT com FORWARDSLASH products_vented_res DOT XhXtXm :confused:
This unit installs between the compressor and the 4way valve and taps off hot water. It claims to increase efficiency 10% but if it were supplied with ground water instead of return hot water it might go to 20% or higher.

www.doucetteindustries.com/products_vented_res.htm