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Old 10-05-2021, 15:16   #1
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Which direction to bend isotherm evaporator (does it matter)

I am about to bend the 54" by 12" evaporator plate which comes with a Isotherm Compact 2013 system and the manual says you can bend "either" direction (across the short dimension obviously). I have a question as to the "preferred" direction to bend. I will be covering the top half of three faces of the insulated box. Two independent systems one for the "nominal deep freeze" and one for the "nominal refrigerator"

As I will be using one for a deep freeze application and one for a refrigerator application (and as a backup freezer) and understand there may be issues with things like leafy greens freezing if against the evaporator. I will have a third dedicated fridge which is held at appropriate temperatures for vegetables, most likely the unit with a dedicated blower :-)

The question I have is if the "bumpy" side of the evaporator should be toward the wall, there appears to be a "more smooth" side and a "more bumpy" side. If I bend the evaporator to have the "more smooth" side toward the interior of the box the tubing will be between the evaporator and the wall of the insulated box, if I bend the evaporator to have the "more bumpy" side toward the interior of the box then the tubing will be on the interior of the refrigerated space away from the wall.

I suspect it does not make much difference, perhaps the "more bumpy" side can conduct a bit more heat? Perhaps the "more smooth" side is much easier to clean? Perhaps having the tube between the evaporator and the wall protects it better and is worth the extra struggle to get it all through the hole existing the box.

Any thoughts from the assembled masses is most appreciated :-)
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Old 10-05-2021, 15:26   #2
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Re: Which direction to bend isotherm evaporator (does it matter)

Look at the install diagram, the piping orientation is more important.
Think in terms of that and the act of feeding the lines to where they need to exit the box.
I use a short length of pvc tube to act as a mandrel/form to bend around.
The side with the sensing tube clamp is usually faced away from the inside of the box.
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Old 10-05-2021, 17:41   #3
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Re: Which direction to bend isotherm evaporator (does it matter)

Quote:
Originally Posted by Coolerking View Post
Look at the install diagram, the piping orientation is more important.
Think in terms of that and the act of feeding the lines to where they need to exit the box.
I use a short length of pvc tube to act as a mandrel/form to bend around.
The side with the sensing tube clamp is usually faced away from the inside of the box.
Good advice above, be careful forming bends slowly and avoid kinking. We always folded 'bumpy' side in as that side has already been stretched, and therefore thinner, during evaporator manufacture.
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Old 11-05-2021, 10:20   #4
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Re: Which direction to bend isotherm evaporator (does it matter)

Well, the guys at isotherm were extremely responsive to my questions

The answer is that bending either way is fine and there is no significant difference in the efficiency of thermal transfer. When they bend these plates to make an oval the tube set is on the "outside" which would make for the "bumpy side" on the outside or toward the wall of the box.

While having the tube set connection toward the inside does make installation easier but if possible it is preferred to have the tube set connection to the wall for protection which would result in the smooth side as the interior surface.

Also, they noted that bending a corner which does not have any channels in it is workable, stay at least 1cm from any channel and only make flat bends. Be careful to not cause the two side to attempt to pull apart. I suggested bending around a 1/2" wooden dowel attached to a workbench over the plate and then bend which they felt would work.

The one last question is if running the tubing set behind the plate for the entire length of the plate would cause any trouble... I will ask. i.e. since the tubing set runs down the plate until bent around is it better (assuming extra tubing available) to immediately exit the insulated volume (making a smooth 180 degree bend) or run the tubing behind the evaporator plate all the way around the three sides...

Hummm...
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Old 11-05-2021, 10:55   #5
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Re: Which direction to bend isotherm evaporator (does it matter)

Quote:
Originally Posted by Coolerking View Post
Look at the install diagram, the piping orientation is more important.
Think in terms of that and the act of feeding the lines to where they need to exit the box.
I use a short length of pvc tube to act as a mandrel/form to bend around.
The side with the sensing tube clamp is usually faced away from the inside of the box.
Great thought using a piece of PVC tubing to form the tubeset of the evaporator. What diameter of PVC do you use for the purpose? I seem to remember that there is a recommendation of a 6" minimum bend diameter (i.e. a 3" minimum bend radius...
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Old 11-05-2021, 10:56   #6
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Re: Which direction to bend isotherm evaporator (does it matter)

Quote:
Originally Posted by OzeLouie View Post
Good advice above, be careful forming bends slowly and avoid kinking. We always folded 'bumpy' side in as that side has already been stretched, and therefore thinner, during evaporator manufacture.
Interesting thought... The choice becomes protect the tubeset connection from someone doing something bad to it or bending the easier way.... (Although it appears bending either way is ok...

Thanks!!!
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Old 11-05-2021, 11:48   #7
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Re: Which direction to bend isotherm evaporator (does it matter)

It appears from isotherm that having the tube set touch the evaporator, even for an extended area of the tubing is not expected to cause any trouble.

I can do any one of the following:

1) Make an immediate (appropriately radiused tubing) turn out of the insulated volume of the box, i.e. since the tube runs back down the plate this would result in a 180 degree turn with a radius of about half of the evaporator plate width (or about 3" radius, 6" diameter) and then out of the box. - results in 10" of tubing inside the box

2) Run for a distance along the evaporator plate while tending downward to get down near the "bottom" of the evaporator plate and then make a 6" radius (12" diameter) 180 degree turn to be able to exit in the back corner of the insulated volume near the top. - results in 30" of tubing inside the box

3) run behind the evaporator plate through both of the 90 degree bends between the wall of the insulated volume and the evaporator plate. This requires making about the same bend radius as the evaporator plate bending tool but gives a nice otherwise straight run - results in about 55" of tubing inside the box.

In all of the cases the tubing inside the box is sandwiched between the evaporator plate and the wall and so is nicely protected.

Option 2 is pretty easy, Option 3 might be easy and uses up excess tubing nicely

Thoughts?
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