Another hot water tank heat pump

[AC_Hacker]

Originally Posted by NiHaoMike

I think the main difference is that the soldered joint turns the tube as it's being tightened, while the compression fittings do not. Use plenty of sealant (or Teflon tape) on the compression fittings since they tend to leak. That's especially problematic on the discharge line due to thermal cycling.

If you read the thread of the former attempt, you would see that in both cases (randen & Hv23t), tubes are being twisted inside the tank. The compression fittings that Hv23t used are for external connections, and have nothing to do with the tube on the inside of the tank

In the case of Hv23t, the the tubes did not collapse, in the case of randen, they did... what's the difference?

Using a threaded fitting to affix the copper tubes inside the tank is a very straight forward approach. Obviously, it can be made to work.

-AC

[NiHaoMike]

The tubes do twist around each other, but if they're soldered, they would twist themselves. While with compression, they would not.

He was using the compression fittings as seals. They would not grip the tubing until tightened.

[AC_Hacker]

Originally Posted by NiHaoMike

The tubes do twist around each other, but if they're soldered, they would twist themselves. While with compression, they would not...

This is an excellent point...



However, (and I am not referring to Xringer's airtap, I am comparing the attempts by randen and Hv23t) the twisting failure is taking place inside the tank.

Xringer's Airtap uses a custom fitting that would be difficult for most DIY people to make, unless they had a machine shop. It does turn out that both randen & Hv23t do have machining equipment at their disposal, but have chosen to use a more straightforward approach (that would be accessible to most DIY readers).

The Hv23t attempt worked, the attempt by randen didn't... what made the difference?

-AC

[Xringer]

You guys reminded me of that leak I had on my A7..
http://ecorenovator.org/forum/geothe...heater-33.html

I just picked up another 1-peice fitting (3/4" iron pipe to PEX adapter. ID=0.533").
Here's the two piece 'Swivel' that I replaced.. (Also comes in 1")
SharkBite 3/4 in. PEX Brass Female Swivel Adapter-UC530A at The Home Depot



I wonder if something like this could be used? Make a brass slug with
two holes for the copper tubes and braze the whole thing in place.?.
Add a brass nipple to screw into the tank..

If the tubes were too large, maybe the 1" adapter could be used?
And it that was still too small, maybe the ID could be bored out a bit..

[NiHaoMike]

The soldered fitting applies a torque to the tubing, while the compression fittings do not. I think that's the problem. The tubes twisting around each other can be compensated for by pretwisting them the other way.

[jeff5may]

OK, I can't help myself. Here's the difference:

The Airtap unit Xringer installed is a pre-engineered, somewhat drop-in unit. The Water heater fitting is made so you can assemble the whole shabang without much chance of anything bending very much. The Heat exchanger coil slides straight in, and can be positioned while the plumbing is somewhat dismantled. It has a swivel fitting, so assembling the plumbing presents no further twisting once the tubing is snaked into the vessel.

When HV23T made his heater, he snaked the exchanger coil through the rather large hole, leaving a few feet of tubing sticking out. He threaded these pigtails through the fitting, then tightened the fitting while the pigtails were still free to not spin the whole assembly inside the tank. If anything, the ends may have spiraled around each other a few revolutions. Once the through-wall fitting was tight, he then tightened the compression fittings for a waterproof seal.

The heat exchanger randy made is all one piece. Besides the wrangling of fitting the tubing through the bung hole, he had to twist the entire assembly multiple revolutions to tighten the through-wall fitting into the bung hole. Since copper is somewhat rigid, more so the larger the tubing diameter, when the exchanger contacted another surface inside the tank, it tried to crease rather than bend.

Rather than force it in and hope for the best, randy wisely decided to stop and re-bend his exchanger so it will fit. I would have done the same thing. Trial and error, man. That's what it's all about.

For what it's worth, I don't think it will make a whole lot of difference what shape the exchanger is, as long as it fits in the tank. Lanky snake or twisty slinky, as long as you put the thermostat down low in the tank it will sense cold inlet water arriving. Once the unit fires up, convection will mix the water pretty quickly.

[AC_Hacker]

OK... I think I see what has happened.

There are two kinds of fittings that rely on compression...

This one uses a small band that is compressed at both ends...

This fitting is used very often in plumbing, for instance to provide a small tube to supply water for refrigerator's ice-making function.

I formerly thought that a compression fitting was a compression fitting, and I used this kind of fitting in some of my early refrigeration experiments. It turns out that this kind of fitting does not stand up to the vibration stresses and extreme temperature cycling that is the everyday life of refrigeration equipment. I know this because one of these fittings failed me and bathed the clothing I was wearing with spraying liquid propane. To say the least, it was unpleasant... to be more honest, I could have died.

Since that experience, I never even allowed the idea of the former type of compression fitting to enter my consideration as a valid type of alternative when working with refrigerant.

It may be possible to make this type work if the compression ring is brazed on (not soldered) to the tubing... maybe.


The other type of compression fitting is a flare fitting...

This type will stand up to the rigors of refrigeration, both to vibration and to extreme temperature cycling. It is commonly used in refrigeration work.

From the looks of things, I now think that Hv23t) has used the former type of compression fitting.

Not a good idea.

-AC

[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.

[randen]

AC Hacker
The Flare and compression fitting both have their places. A lot of times I think the place for the compression fitting is to remain on the shelf at the hardware store. Their not very reliable. Any flex or vibration they start to leak. However a good flair fitting is golden.

I believe the success of Hv23t was because the tubing was thinner and therefore less rigid and not softening the tubing by soldering or heating the tubing removing its hardness.

I had thought of making up a fitting like Xringers A7 but with so many projects on the go I was wishing for a short-cut. I hope with the new cork-screw type HX I may have a winner. I will keep you posted. These could be relatively easy to make. We'll see how it works out.

Randen

[dremd]

Originally Posted by AC_Hacker

OK... I think I see what has happened.

There are two kinds of fittings that rely on compression...

This one uses a small band that is compressed at both ends...

This fitting is used very often in plumbing, for instance to provide a small tube to supply water for refrigerator's ice-making function.

I formerly thought that a compression fitting was a compression fitting, and I used this kind of fitting in some of my early refrigeration experiments. It turns out that this kind of fitting does not stand up to the vibration stresses and extreme temperature cycling that is the everyday life of refrigeration equipment. I know this because one of these fittings failed me and bathed the clothing I was wearing with spraying liquid propane. To say the least, it was unpleasant... to be more honest, I could have died.

Since that experience, I never even allowed the idea of the former type of compression fitting to enter my consideration as a valid type of alternative when working with refrigerant.

It may be possible to make this type work if the compression ring is brazed on (not soldered) to the tubing... maybe.


The other type of compression fitting is a flare fitting...

This type will stand up to the rigors of refrigeration, both to vibration and to extreme temperature cycling. It is commonly used in refrigeration work.

From the looks of things, I now think that Hv23t) has used the former type of compression fitting.

Not a good idea.

-AC

I'd like to say that I went from first type to second type on my Air compressor drain (7 hp 190 psi tat averages 3 hours/ day run time). I was cracking a copper tube every 6~9 months, and now the second style has been troubble free for just over a year.
Suddenly wishing that I had plumbed my pre-lube (pre-start engine oil) pump with 2nd type on my TDI.