New Zealand DIY Water Source HP. - Page 3

jeff5may · 04-01-17, 09:10 AM

So can you please elaborate on the original build? From what I can gather, it looks to be an amazing success. A water-to-water heat pump has all kinds of challenges and losses on both sides of the system, so achieving high efficiency (as well as sustained continuous operation) is quite an achievement.

3.5 tons of heating (~40KBTU) for 3500 Watts input power puts it in the range of 4+ on COP. This equates to a heat pump unit that would cost at least $4000 US dollars to purchase, plus probably an equal amount in materials for the indoor and outdoor loops. Being a variable-speed unit, did it perform better at reduced capacity? What kind of pumping strategy (both water and compressor) did you figure out? This topic, as well as capacity control method, is a huge stumbling block for many members. As I'm sure you know, the process is much more complicated than just connecting part A to part B and C and so on until the whole thing just works.

Yes, it's disappointing that the underwater heat exchanger didn't last forever, but it looks to me like it could be repaired pretty easily. A new anchoring rig could be devised that would avoid the galvanic corrosion issue. Why are you considering rebuilding the whole system just because the one part sprung a leak? Is the tubing made of some unrepairable exotic alloy, or are there other issues present that make you want to abandon it?

I'm certain that other users (besides me) would be very interested in hearing about your adventure making this thing work. The overwhelming majority of people believe it is impossible to make something like your rig work, much less save any money on heating bills. I see pictures that prove it exists, but how could you have done this without a PhD in thermodynamics and an army of skilled tradesmen?

geoheatnz · 04-01-17, 01:32 PM

Hi all,
when i started my original project we had just built the house so budget was tight. I had collected various compressors and pumps controllers etc , i bought the evap and condenser from a local company but their capacity was lacking.

There was a 16k approach temp so at 5c water out i was evaporating at -11 , also on condenser the same thing , water out at 35c condensing temp 50c.
The compressor was a twin reciprocating piston unit , meant for commercial duty, so very noisy . Given the conditions that the evap and condenser presented to the comp it could not give the capacity needed to get the house warm. Just not enough guts in it!!

So pretty disapointed with the whole thing at this point , i really hadnt done my home work on the evap and condenser performance , they where the cheapest option at the point so i went with them.

I then discovered the multiple leaks on the stainless stream hx and that was final straw really. I pulled it from stream and into shed and cleaned up and easyflo silver brazed them , i removed cross braces and returned them to stream for rest of winter. The damage was done and pitting continued and i decided i needed to try something different.

geoheatnz · 04-01-17, 02:04 PM

I had a Daikin Ry125luy1 , which is a 12.5kw reverse cycle heatpump , i only had the out door unit and no matching indoor.

I removed all electronics and eev and replaced with a txv . There is a NZ company called Temperzone who build all sorts of a/c heatpumps , they use a simple 230v control board which includes protections for hp , lp , low reffrigerant charge , defrost and delay comp starts . It has 3 temp sensors and also a out door fan speed controller for a/c mode. for

I managed to come across two of these second hand and they work great. I had also 2 small plates that i paralled together and used as condenser , these were placed inside my plant room with piping running to the Daikin outdoor.
This setup worked well for the start of winter when no defrosts were happening. I only run the heatpump on night rate electric as it is less than half of day rate, i try to get all heating done in this period. When the temps get to 2c or so the unit is defrosting every 30 mins and house is noticeable cold on these mornings.

The comp in the daikin is a 5hp scroll , so i know that if i can give it the right conditions it can do the job , so i have pulled comp from the Daikin and am building water to water unit Mk2.

geoheatnz · 04-03-17, 01:02 AM

Ive attached a few photos , showing condenser with desuperheater mounted above , to allow any liquid to drain down to condenser. Condenser is a dual circuit , ive got a ball valve on one side to increase high pressure if needed.
Reciever will be under condenser and then to subcooler .

geoheatnz · 04-03-17, 01:06 AM

Sorry about photos , ill try to spin them 90.

pinballlooking · 04-03-17, 08:58 AM

Here they are.

jeff5may · 04-03-17, 12:13 PM

It's funny how financial burdens bring out the best in people. Many modern machines were invented by people building something themselves because they could not afford (or have the desire) to purchase a manufactured unit. Such is the road we travel: with experience comes skill and wisdom. It sounds like your unit did better than many others' first attempts.

I have some questions about your current project. Are your evaporator and condenser heat exchangers matched very closely? It looks as if you have a lot more desuperheater + condenser than evaporator surface area. Also, with such a small footprint and such short runs of refrigerant piping, you most likely don't need to worry about subcooling or an additional liquid receiver. That condenser looks like it could hold your entire system charge with ease.

geoheatnz · 04-04-17, 01:52 AM

Hi Jeff,
The condenser is physicaly twice the size of the evap , its a dual circuit plate and i have put a ball valve on one side to experiment with how system performs . These plates are just some items that ive come across but are pretty close to what i need.
I have an eev so running a low high side pressure shouldnt be a problem.

Ron342 · 04-04-17, 05:33 AM

Odd that the stainless stream hx tubes would be corroded by stainless cross braces in a fresh water stream?? Were they radically different types of stainless??
Congratulations on your bending, brazing, tubing attachments etc - makes me ashamed to look at my own!
I think you have some experience in this stuff, guy!

jeff5may · 04-04-17, 12:54 PM

That's what it looks like to me. Most of the commercial units put the oversized heat exchanger on the outdoor side. This has a few positive effects on the system.

First, the outdoor exchanger has less temperature swing on the refrigerant circuit than the indoor exchanger. With a refrigerant-to-water evaporator circuit, this means better superheat control and less oil foaming action inside the HX. The added mass and heat transfer surface area acts to buffer and absorb strange transient events that could cause problems with a smaller HX.

On the indoor side, you have a desuperheater coil, so it would absorb a decent portion of the heat. This would reduce the size of condenser HX you would need to take care of the rest of the latent heat transfer. A smaller exchanger indoors helps to get the system producing useful heat faster on every startup. Having too low high side pressure is actually a problem, as higher head pressure (to a certain extent) ensures that your refrigerant condenses faster and at higher heat flow. Especially with refrigerant-to-water, where the refrigerant may need to work extra hard to force a temperature rise in the water.

04-03-17, 01:02 AM	#24
geoheatnz Lurking Renovator Join Date: Jul 2011 Location: feilding , n.z Posts: 27 Thanks: 4 Thanked 8 Times in 5 Posts	Ive attached a few photos , showing condenser with desuperheater mounted above , to allow any liquid to drain down to condenser. Condenser is a dual circuit , ive got a ball valve on one side to increase high pressure if needed. Reciever will be under condenser and then to subcooler . Attached Thumbnails

04-03-17, 01:06 AM	#25
geoheatnz Lurking Renovator Join Date: Jul 2011 Location: feilding , n.z Posts: 27 Thanks: 4 Thanked 8 Times in 5 Posts	Sorry about photos , ill try to spin them 90. Last edited by pinballlooking; 04-03-17 at 08:56 AM..

04-03-17, 08:58 AM	#26
pinballlooking Super Moderator Join Date: Jun 2013 Location: SC Posts: 2,923 Thanks: 172 Thanked 564 Times in 463 Posts	Here they are. Attached Thumbnails __________________ Current project Aquaponics system , Passive Solar Greenhouse build To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. Solar Install 12.5 Kwh- To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. Mini Split installs - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. EV Chevy Volt - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

04-01-17, 09:10 AM	#21
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	So can you please elaborate on the original build? From what I can gather, it looks to be an amazing success. A water-to-water heat pump has all kinds of challenges and losses on both sides of the system, so achieving high efficiency (as well as sustained continuous operation) is quite an achievement. 3.5 tons of heating (~40KBTU) for 3500 Watts input power puts it in the range of 4+ on COP. This equates to a heat pump unit that would cost at least $4000 US dollars to purchase, plus probably an equal amount in materials for the indoor and outdoor loops. Being a variable-speed unit, did it perform better at reduced capacity? What kind of pumping strategy (both water and compressor) did you figure out? This topic, as well as capacity control method, is a huge stumbling block for many members. As I'm sure you know, the process is much more complicated than just connecting part A to part B and C and so on until the whole thing just works. Yes, it's disappointing that the underwater heat exchanger didn't last forever, but it looks to me like it could be repaired pretty easily. A new anchoring rig could be devised that would avoid the galvanic corrosion issue. Why are you considering rebuilding the whole system just because the one part sprung a leak? Is the tubing made of some unrepairable exotic alloy, or are there other issues present that make you want to abandon it? I'm certain that other users (besides me) would be very interested in hearing about your adventure making this thing work. The overwhelming majority of people believe it is impossible to make something like your rig work, much less save any money on heating bills. I see pictures that prove it exists, but how could you have done this without a PhD in thermodynamics and an army of skilled tradesmen?

04-01-17, 01:32 PM	#22
geoheatnz Lurking Renovator Join Date: Jul 2011 Location: feilding , n.z Posts: 27 Thanks: 4 Thanked 8 Times in 5 Posts	Hi all, when i started my original project we had just built the house so budget was tight. I had collected various compressors and pumps controllers etc , i bought the evap and condenser from a local company but their capacity was lacking. There was a 16k approach temp so at 5c water out i was evaporating at -11 , also on condenser the same thing , water out at 35c condensing temp 50c. The compressor was a twin reciprocating piston unit , meant for commercial duty, so very noisy . Given the conditions that the evap and condenser presented to the comp it could not give the capacity needed to get the house warm. Just not enough guts in it!! So pretty disapointed with the whole thing at this point , i really hadnt done my home work on the evap and condenser performance , they where the cheapest option at the point so i went with them. I then discovered the multiple leaks on the stainless stream hx and that was final straw really. I pulled it from stream and into shed and cleaned up and easyflo silver brazed them , i removed cross braces and returned them to stream for rest of winter. The damage was done and pitting continued and i decided i needed to try something different.

04-01-17, 02:04 PM	#23
geoheatnz Lurking Renovator Join Date: Jul 2011 Location: feilding , n.z Posts: 27 Thanks: 4 Thanked 8 Times in 5 Posts	I had a Daikin Ry125luy1 , which is a 12.5kw reverse cycle heatpump , i only had the out door unit and no matching indoor. I removed all electronics and eev and replaced with a txv . There is a NZ company called Temperzone who build all sorts of a/c heatpumps , they use a simple 230v control board which includes protections for hp , lp , low reffrigerant charge , defrost and delay comp starts . It has 3 temp sensors and also a out door fan speed controller for a/c mode. for I managed to come across two of these second hand and they work great. I had also 2 small plates that i paralled together and used as condenser , these were placed inside my plant room with piping running to the Daikin outdoor. This setup worked well for the start of winter when no defrosts were happening. I only run the heatpump on night rate electric as it is less than half of day rate, i try to get all heating done in this period. When the temps get to 2c or so the unit is defrosting every 30 mins and house is noticeable cold on these mornings. The comp in the daikin is a 5hp scroll , so i know that if i can give it the right conditions it can do the job , so i have pulled comp from the Daikin and am building water to water unit Mk2.

04-03-17, 12:13 PM	#27
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	It's funny how financial burdens bring out the best in people. Many modern machines were invented by people building something themselves because they could not afford (or have the desire) to purchase a manufactured unit. Such is the road we travel: with experience comes skill and wisdom. It sounds like your unit did better than many others' first attempts. I have some questions about your current project. Are your evaporator and condenser heat exchangers matched very closely? It looks as if you have a lot more desuperheater + condenser than evaporator surface area. Also, with such a small footprint and such short runs of refrigerant piping, you most likely don't need to worry about subcooling or an additional liquid receiver. That condenser looks like it could hold your entire system charge with ease.

04-04-17, 01:52 AM	#28
geoheatnz Lurking Renovator Join Date: Jul 2011 Location: feilding , n.z Posts: 27 Thanks: 4 Thanked 8 Times in 5 Posts	Hi Jeff, The condenser is physicaly twice the size of the evap , its a dual circuit plate and i have put a ball valve on one side to experiment with how system performs . These plates are just some items that ive come across but are pretty close to what i need. I have an eev so running a low high side pressure shouldnt be a problem.

04-04-17, 05:33 AM	#29
Ron342 Apprentice EcoRenovator Join Date: Feb 2010 Location: Maryland Posts: 120 Thanks: 26 Thanked 12 Times in 8 Posts	Odd that the stainless stream hx tubes would be corroded by stainless cross braces in a fresh water stream?? Were they radically different types of stainless?? Congratulations on your bending, brazing, tubing attachments etc - makes me ashamed to look at my own! I think you have some experience in this stuff, guy!

04-04-17, 12:54 PM	#30
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	That's what it looks like to me. Most of the commercial units put the oversized heat exchanger on the outdoor side. This has a few positive effects on the system. First, the outdoor exchanger has less temperature swing on the refrigerant circuit than the indoor exchanger. With a refrigerant-to-water evaporator circuit, this means better superheat control and less oil foaming action inside the HX. The added mass and heat transfer surface area acts to buffer and absorb strange transient events that could cause problems with a smaller HX. On the indoor side, you have a desuperheater coil, so it would absorb a decent portion of the heat. This would reduce the size of condenser HX you would need to take care of the rest of the latent heat transfer. A smaller exchanger indoors helps to get the system producing useful heat faster on every startup. Having too low high side pressure is actually a problem, as higher head pressure (to a certain extent) ensures that your refrigerant condenses faster and at higher heat flow. Especially with refrigerant-to-water, where the refrigerant may need to work extra hard to force a temperature rise in the water.