Water Source heat pump

mlac · 06-29-09, 02:02 PM

I have been pondering the idea if a air source heat pump could be converted to a water source heat pump easily by removing the existing coils off the outside unit. build another set of coils using 3/8" copper tubing inside 1/2 or 5/8 copper tubing and bend this tubing to fit as much as possible in place of the old coil. tie the 3/8 tubing back into the freon side of the unit and tie the 1/2 or 5/8 tubing into a water source to cool and heat the freon instead of air. The water would be coming from a 35 gallon a minute free flowing well which would not require a pump and is 67 degrees year around (totally free water source) My thinking is if this is possible the 67 degree water would be a lot more efficient than 100 degree air in the summer and 30's air in the winter as the source to cool and heat freon. In my experience with heat pumps they work well in moderate temp ranges 40-85. below 40 the heat strips does most of the work and above 85 the unit runs to long. Years ago I seen a small window ac unit set up this way and it cooled a 1000' square foot camp. The out put temp was right at freezing.

Any Suggestions, Ideas from you guys?

AC_Hacker · 08-15-09, 05:53 PM

Give it a try...

I've heard from boat people that the rule of thumb to sub water cool for air cool is that an inch of water cooled tube equals 50 inches of air cooled tubing. I'd do more research before I started cutting, but it's something to think about.

Keep in mind that if the water tube gets to or below 32 it will freeze & burst.

Good luck and keep us posted.

Regards,

AC_Hacker

mlac · 08-16-09, 09:08 AM

Hey: AC
Thanks for the reply. wow 1" verus 50" thats a lot. So all I would have to do is get a good measurement on how much air coil I have in the unit and figure the min. I would need. I think I still would put the max amount I could in the unit. I dont think I could put to much. the lowest it could go is 67 degrees. It is hard to research information, Information is hard to find. I am having problems finding an ac guy to help do the work if the modifications was made charge the unit, by pass fan etc. They want to sell me a water source geo system. The problem with buying a new system is my well is low pressure high volume I would have to use pump to get pressure for a new system and that defeats the purpose to run a pump. I have also though about getting some large truck radiators and running the water thu them to cool the air off before it hits the air coils. Not sure how many it would take to get the temp that low. Im thinking a lot. I would want to move the outside unit to the other end of the house to make water piping easier. as far as freezing, I could let the water flow thu the unit all the time beings its free, so freezing shouldnt be a concern

AC_Hacker · 08-16-09, 03:27 PM

Sounds like you are trying to design your own refrigerant-to-water heat exchanger. It can be done. The design you are considering is called 'tube in tube' or 'tube in shell' heat exchanger. These heat exchangers have the advantage that they don't plug up so easily. Their disadvantage is that they occupy more space than some other designs, like the 'brazed plate' or 'flat plate' exchangers, which are more efficient but more likely to plug up in an application like yours.

If you are going to start with a air source heat pump, find out the BTU capacity of the exchanger you will be replacing, and build one with the same capacity. You'd be smart to find out what the dimensions of a commercially made equivalent tube in tube exchanger is and build one of the same size or somewhat larger.

I'm working on a similar project and have posted loads of info that might be very helpful to you in your project. Here's the link:

http://ecorenovator.org/forum/projec....html#post2631

If there's anything I can do to help, please ask.

Best of luck,

-AC_Hacker

mlac · 08-19-09, 09:19 AM

Yes im wanting to modify my air source heat pump and make it an open loop water source heat pump. I have a free water source and a pond to discharge into. I need a heat exchanger that is not easy to plug or is easy to access and do-it-yourself clean. the water supply is high in sulfur and iron (hard water). i am thinking that the defost system would need to be unhooked. the water suppy would be running 24/7 so i dont think it would freeze also the outside fan wiring would have to modified to made the unit the fan was running when it came on.

I have a 3 1/2 ton Tappan Heat pump
Cooling Btuh 40,000
SEER 10
Nominal CFM 1500

I have seen a small window ac unit converted by replacing the outside coils with a homemaded tube to tube coil using same type of water. It was amazing, the output temp was right at freezing temp. this tiny window unit cooled a 1000 square foot camp.

AC_Hacker · 08-20-09, 11:12 AM

Have you considered using a pipe loop in the pond? This would allow you to use a clean, sealed water-loop to your heat pump, no cleaning hassle. The pipe loop in the pond would be sunk to the bottom of the pond, and basically forgotten.

Regards,

-AC_Hacker

mlac · 08-20-09, 10:17 PM

Yes I have considered it, I dont think it would be better than straight out of the free flowing well. The pond is only about 5 feel deep and ponds has silk build up on there bottoms. I dont think I would get as good of heat exchange from the pond as I would from the well water. Plus people fishing would be catching the tubbing all the time. Im not sure what kinda exchanger the factory geo water source heat pump has, as far as plugging. I dont think there would be a problem using the well water using a tube to tube or tube in shell with removable clean out cover. I was thinking alone the line of building one like this Sentry Equip | Tube-in-Tube Heat Exchanger

AC_Hacker · 08-23-09, 09:50 AM

mlac,

Looks good. Here's one I'm making:

It has 1/4" tube inside 1/2" tube outside.

Both soft copper. I straightened them out pretty much and inserted the smaller inside the larger, then used a conduit bender to bend them both together.

Still need to braze up the end pieces.

I sort of cooled (no pun intended) to this particular heat exchanger project when I realized that a brazed plate exchanger was cheaper, smaller and more efficient. For my purposes, brazed plate will work great. For your proposed well water use, brazed plate would foul quickly.

If I were you, I'd just buy a twenty foot coil of soft copper tube, put it in a sheetrock mud bucket, run refrigerant through the coil and water through the bucket and call it good.

Another thought, you could feed the pre-heated mud bucket water into your water heater and save a bit-O-money in the process.

Best Regards,

-AC_Hacker

Daox · 08-23-09, 10:32 AM

Could you provide a picture or link to an example of a brazed plate exchanger?

AC_Hacker · 08-26-09, 03:36 AM

Here you go...

Regards,

AC_Hacker

06-29-09, 02:02 PM	#1
mlac Lurking Renovator Join Date: Jun 2009 Location: South Mississippi Posts: 5 Thanks: 0 Thanked 0 Times in 0 Posts	Water Source heat pump I have been pondering the idea if a air source heat pump could be converted to a water source heat pump easily by removing the existing coils off the outside unit. build another set of coils using 3/8" copper tubing inside 1/2 or 5/8 copper tubing and bend this tubing to fit as much as possible in place of the old coil. tie the 3/8 tubing back into the freon side of the unit and tie the 1/2 or 5/8 tubing into a water source to cool and heat the freon instead of air. The water would be coming from a 35 gallon a minute free flowing well which would not require a pump and is 67 degrees year around (totally free water source) My thinking is if this is possible the 67 degree water would be a lot more efficient than 100 degree air in the summer and 30's air in the winter as the source to cool and heat freon. In my experience with heat pumps they work well in moderate temp ranges 40-85. below 40 the heat strips does most of the work and above 85 the unit runs to long. Years ago I seen a small window ac unit set up this way and it cooled a 1000' square foot camp. The out put temp was right at freezing. Any Suggestions, Ideas from you guys? Last edited by mlac; 07-01-09 at 08:01 AM..

08-15-09, 05:53 PM	#2
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	Go for it... Give it a try... I've heard from boat people that the rule of thumb to sub water cool for air cool is that an inch of water cooled tube equals 50 inches of air cooled tubing. I'd do more research before I started cutting, but it's something to think about. Keep in mind that if the water tube gets to or below 32 it will freeze & burst. Good luck and keep us posted. Regards, AC_Hacker

08-20-09, 11:12 AM	#6
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	Use the pond... Have you considered using a pipe loop in the pond? This would allow you to use a clean, sealed water-loop to your heat pump, no cleaning hassle. The pipe loop in the pond would be sunk to the bottom of the pond, and basically forgotten. Regards, -AC_Hacker

08-23-09, 09:50 AM	#8
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	Looks Good... mlac, Looks good. Here's one I'm making: It has 1/4" tube inside 1/2" tube outside. Both soft copper. I straightened them out pretty much and inserted the smaller inside the larger, then used a conduit bender to bend them both together. Still need to braze up the end pieces. I sort of cooled (no pun intended) to this particular heat exchanger project when I realized that a brazed plate exchanger was cheaper, smaller and more efficient. For my purposes, brazed plate will work great. For your proposed well water use, brazed plate would foul quickly. If I were you, I'd just buy a twenty foot coil of soft copper tube, put it in a sheetrock mud bucket, run refrigerant through the coil and water through the bucket and call it good. Another thought, you could feed the pre-heated mud bucket water into your water heater and save a bit-O-money in the process. Best Regards, -AC_Hacker Attached Thumbnails

08-26-09, 03:36 AM	#10
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	Here you go... Regards, AC_Hacker Attached Thumbnails

08-16-09, 09:08 AM	#3
mlac Lurking Renovator Join Date: Jun 2009 Location: South Mississippi Posts: 5 Thanks: 0 Thanked 0 Times in 0 Posts	Hey: AC Thanks for the reply. wow 1" verus 50" thats a lot. So all I would have to do is get a good measurement on how much air coil I have in the unit and figure the min. I would need. I think I still would put the max amount I could in the unit. I dont think I could put to much. the lowest it could go is 67 degrees. It is hard to research information, Information is hard to find. I am having problems finding an ac guy to help do the work if the modifications was made charge the unit, by pass fan etc. They want to sell me a water source geo system. The problem with buying a new system is my well is low pressure high volume I would have to use pump to get pressure for a new system and that defeats the purpose to run a pump. I have also though about getting some large truck radiators and running the water thu them to cool the air off before it hits the air coils. Not sure how many it would take to get the temp that low. Im thinking a lot. I would want to move the outside unit to the other end of the house to make water piping easier. as far as freezing, I could let the water flow thu the unit all the time beings its free, so freezing shouldnt be a concern

08-16-09, 03:27 PM	#4
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	Sounds like you are trying to design your own refrigerant-to-water heat exchanger. It can be done. The design you are considering is called 'tube in tube' or 'tube in shell' heat exchanger. These heat exchangers have the advantage that they don't plug up so easily. Their disadvantage is that they occupy more space than some other designs, like the 'brazed plate' or 'flat plate' exchangers, which are more efficient but more likely to plug up in an application like yours. If you are going to start with a air source heat pump, find out the BTU capacity of the exchanger you will be replacing, and build one with the same capacity. You'd be smart to find out what the dimensions of a commercially made equivalent tube in tube exchanger is and build one of the same size or somewhat larger. I'm working on a similar project and have posted loads of info that might be very helpful to you in your project. Here's the link: http://ecorenovator.org/forum/projec....html#post2631 If there's anything I can do to help, please ask. Best of luck, -AC_Hacker

08-19-09, 09:19 AM	#5
mlac Lurking Renovator Join Date: Jun 2009 Location: South Mississippi Posts: 5 Thanks: 0 Thanked 0 Times in 0 Posts	Yes im wanting to modify my air source heat pump and make it an open loop water source heat pump. I have a free water source and a pond to discharge into. I need a heat exchanger that is not easy to plug or is easy to access and do-it-yourself clean. the water supply is high in sulfur and iron (hard water). i am thinking that the defost system would need to be unhooked. the water suppy would be running 24/7 so i dont think it would freeze also the outside fan wiring would have to modified to made the unit the fan was running when it came on. I have a 3 1/2 ton Tappan Heat pump Cooling Btuh 40,000 SEER 10 Nominal CFM 1500 I have seen a small window ac unit converted by replacing the outside coils with a homemaded tube to tube coil using same type of water. It was amazing, the output temp was right at freezing temp. this tiny window unit cooled a 1000 square foot camp.

08-20-09, 10:17 PM	#7
mlac Lurking Renovator Join Date: Jun 2009 Location: South Mississippi Posts: 5 Thanks: 0 Thanked 0 Times in 0 Posts	Yes I have considered it, I dont think it would be better than straight out of the free flowing well. The pond is only about 5 feel deep and ponds has silk build up on there bottoms. I dont think I would get as good of heat exchange from the pond as I would from the well water. Plus people fishing would be catching the tubbing all the time. Im not sure what kinda exchanger the factory geo water source heat pump has, as far as plugging. I dont think there would be a problem using the well water using a tube to tube or tube in shell with removable clean out cover. I was thinking alone the line of building one like this Sentry Equip \| Tube-in-Tube Heat Exchanger

08-23-09, 10:32 AM	#9
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Could you provide a picture or link to an example of a brazed plate exchanger?

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