Another hot water tank heat pump - Page 4

AC_Hacker · 10-14-13, 12:04 AM

Quote:

Originally Posted by NiHaoMike

He wasn't using the compression fitting to seal in refrigerant. He used it to seal the water so it doesn't leak from around the tubes.

Look again.

-AC

jeff5may · 10-14-13, 07:03 AM

Can't really tell from the photos. The tubing isn't discolored at the fittings, though. Either the tubing is solid through the tank fittings (i'm assuming) and compression fittings hold in water, or there is a break in the piping at each fitting (I'm hoping not) and the compression fittings hold in refrigerant and water. Only HV23t knows for sure.

Whether or not it was done that way this time, this is far too common an amateur mistake! High pressure lines like refrigerant and hydraulic lines do not act like a garden hose! You can't just use a barb fitting or a zip tie on them, they must have high pressure fittings and be crimped, flared or brazed/welded together. Pipe fittings won't work either, they must not have tapered threads. Teflon tape or pipe dope cannot hold back the pressure forever, either.

Quick-disconnect type fittings may or may not develop leaks right away, but if the connections are vibrated or moved, it can be assumed with certainty that they will eventually leak (this happens commonly in cars: brake and a/c lines and fittings are replaced during routine maintenance as cheap insurance against repeated failure).

As with any homemade design, you are better off over-building your contraption the first time through to eliminate Murphy's Law from having its way with your creation. If you err in your judgement, it will be revealed to you sooner or later. Trial and error is how many machines are perfected after the architects are done dreaming. Real-world results always beat blueprints and simulations.

randen · 10-25-13, 07:11 PM

Well so far so good. I wound a tighter more neat cork-screw type HX. The copper cork-screw was wound into the threaded bung hole. It proved to be a little on the difficult side but the end product was good. It is a neatly placed HX in the bottom of the tank where it will perform the best. It required an extra manipulation through the top threaded holes to keep the coil from walking up the inside of the tank. With a flashlight in one hole steel rod in another and an eye looking down the third I managed to keep it where it needed to be. Tomorrow we'll braze up the Hacked air-conditioner fill the tank with water and see how it will function.

Randen

AC_Hacker · 10-26-13, 12:27 AM

Quote:

Originally Posted by randen

...I wound a tighter more neat cork-screw type HX...

Interesting new approach!

-AC

jeff5may · 10-26-13, 07:39 AM

AHA! So that's how you get a golf ball through a garden hose!

Seriously though, you are a wizard. It had to have taken lots of patience and skill to fit up. Much better than the junk they throw together on the discovery channel. Much more like 'Norm Abrams' style. It should live longer than the water heater.

randen · 10-26-13, 11:42 AM

The unit is up and running. Its using 5.4A at 110V so about 590W. Temperature start was 12 Deg C @11:30 am looking for 45 Deg C The tank is 175L . The Copper Cork-screw HX is working extremely well Temp in 58 Deg C out is 20 Deg C. So far no frost problem. Propane is the refrigerant of choice.

Randen

NiHaoMike · 10-26-13, 02:43 PM

That amperage is a little high for a 5000 BTU unit at the condensing temperature you indicate. What are your high and low pressures and suction line temperature?

BTW, since the load on the fan motor is now about half, you might find that switching it to low would use less power but not slow down the fan by much. In that case, leaving it set to low would likely improve overall efficiency. Also, if you cut away part of the foam insulation so that it discharges air from both sides, efficiency is also very likely to improve. Also insulate the compressor and discharge line to avoid unwanted heat loss, just make sure the discharge line temperature stays below 90C or so.

randen · 10-26-13, 04:41 PM

Well 4.5 hrs in we hit 41 Deg C. As I only brazed on a low side schaider for the fill and very quickly put a charge of propane in, Yes its drawing a little more current than it should. The compressor hadn't run for a number of months so it started drawing about 6.7A on the first half hr. on start-up. Tomorrow we'll start again this time looking at the charge and current draw vs. temp

All looks really good!!

Randen

NiHaoMike · 10-26-13, 05:23 PM

It's probably overcharged. Without a high side reading, you won't know how much subcooling you're getting. Also, trying to pull a vacuum through the expansion valve won't work.

randen · 10-26-13, 08:30 PM

NiHaoMike

Mike the unit is indeed over-charged but there are no leaks in either the water side or refrigerant side. The sizing of the 22' x 5/16 of copper cork-screw HX seems more than adequate. Its such a small unit and it took just a crack to charge and it hadn't been run for such a long time. The cold oil was causing some problems. Now that everything is flowing we can adjust the charge more accurately. The unit is such a small inexpensive unit a TXV was not in the formula, it sports a cap. tube. I would think after 1/2 hr. the vacuum should have worked nicely with the cap. tube.

The tank temp rose to 53 Deg C. Nice. Tomorrow after it cools we will adjust the charge and run it again. With the spare time while watching the tanks performance I will start the copper work for the solar collector in the "solar heat for the shop"

Randen

10-14-13, 07:03 AM	#32
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	Can't really tell from the photos. The tubing isn't discolored at the fittings, though. Either the tubing is solid through the tank fittings (i'm assuming) and compression fittings hold in water, or there is a break in the piping at each fitting (I'm hoping not) and the compression fittings hold in refrigerant and water. Only HV23t knows for sure. Whether or not it was done that way this time, this is far too common an amateur mistake! High pressure lines like refrigerant and hydraulic lines do not act like a garden hose! You can't just use a barb fitting or a zip tie on them, they must have high pressure fittings and be crimped, flared or brazed/welded together. Pipe fittings won't work either, they must not have tapered threads. Teflon tape or pipe dope cannot hold back the pressure forever, either. Quick-disconnect type fittings may or may not develop leaks right away, but if the connections are vibrated or moved, it can be assumed with certainty that they will eventually leak (this happens commonly in cars: brake and a/c lines and fittings are replaced during routine maintenance as cheap insurance against repeated failure). As with any homemade design, you are better off over-building your contraption the first time through to eliminate Murphy's Law from having its way with your creation. If you err in your judgement, it will be revealed to you sooner or later. Trial and error is how many machines are perfected after the architects are done dreaming. Real-world results always beat blueprints and simulations. Last edited by jeff5may; 10-14-13 at 07:04 AM.. Reason: words

10-25-13, 07:11 PM	#33
randen Uber EcoRenovator Join Date: Apr 2011 Location: Strathroy Ontario Canada Posts: 657 Thanks: 9 Thanked 191 Times in 129 Posts	another hot water tank heat pump Well so far so good. I wound a tighter more neat cork-screw type HX. The copper cork-screw was wound into the threaded bung hole. It proved to be a little on the difficult side but the end product was good. It is a neatly placed HX in the bottom of the tank where it will perform the best. It required an extra manipulation through the top threaded holes to keep the coil from walking up the inside of the tank. With a flashlight in one hole steel rod in another and an eye looking down the third I managed to keep it where it needed to be. Tomorrow we'll braze up the Hacked air-conditioner fill the tank with water and see how it will function. Randen Attached Thumbnails Last edited by Daox; 10-26-13 at 11:14 AM..

10-26-13, 07:39 AM	#35
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	AHA! So that's how you get a golf ball through a garden hose! Seriously though, you are a wizard. It had to have taken lots of patience and skill to fit up. Much better than the junk they throw together on the discovery channel. Much more like 'Norm Abrams' style. It should live longer than the water heater. Last edited by jeff5may; 10-26-13 at 07:52 AM..

10-26-13, 02:43 PM	#37
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	That amperage is a little high for a 5000 BTU unit at the condensing temperature you indicate. What are your high and low pressures and suction line temperature? BTW, since the load on the fan motor is now about half, you might find that switching it to low would use less power but not slow down the fan by much. In that case, leaving it set to low would likely improve overall efficiency. Also, if you cut away part of the foam insulation so that it discharges air from both sides, efficiency is also very likely to improve. Also insulate the compressor and discharge line to avoid unwanted heat loss, just make sure the discharge line temperature stays below 90C or so. __________________ To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...

10-26-13, 05:23 PM	#39
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	It's probably overcharged. Without a high side reading, you won't know how much subcooling you're getting. Also, trying to pull a vacuum through the expansion valve won't work. __________________ To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...

10-26-13, 11:42 AM	#36
randen Uber EcoRenovator Join Date: Apr 2011 Location: Strathroy Ontario Canada Posts: 657 Thanks: 9 Thanked 191 Times in 129 Posts	The unit is up and running. Its using 5.4A at 110V so about 590W. Temperature start was 12 Deg C @11:30 am looking for 45 Deg C The tank is 175L . The Copper Cork-screw HX is working extremely well Temp in 58 Deg C out is 20 Deg C. So far no frost problem. Propane is the refrigerant of choice. Randen

10-26-13, 04:41 PM	#38
randen Uber EcoRenovator Join Date: Apr 2011 Location: Strathroy Ontario Canada Posts: 657 Thanks: 9 Thanked 191 Times in 129 Posts	Well 4.5 hrs in we hit 41 Deg C. As I only brazed on a low side schaider for the fill and very quickly put a charge of propane in, Yes its drawing a little more current than it should. The compressor hadn't run for a number of months so it started drawing about 6.7A on the first half hr. on start-up. Tomorrow we'll start again this time looking at the charge and current draw vs. temp All looks really good!! Randen

10-26-13, 08:30 PM	#40
randen Uber EcoRenovator Join Date: Apr 2011 Location: Strathroy Ontario Canada Posts: 657 Thanks: 9 Thanked 191 Times in 129 Posts	NiHaoMike Mike the unit is indeed over-charged but there are no leaks in either the water side or refrigerant side. The sizing of the 22' x 5/16 of copper cork-screw HX seems more than adequate. Its such a small unit and it took just a crack to charge and it hadn't been run for such a long time. The cold oil was causing some problems. Now that everything is flowing we can adjust the charge more accurately. The unit is such a small inexpensive unit a TXV was not in the formula, it sports a cap. tube. I would think after 1/2 hr. the vacuum should have worked nicely with the cap. tube. The tank temp rose to 53 Deg C. Nice. Tomorrow after it cools we will adjust the charge and run it again. With the spare time while watching the tanks performance I will start the copper work for the solar collector in the "solar heat for the shop" Randen Last edited by randen; 10-26-13 at 08:35 PM.. Reason: punctuation