Galletti air to water heat pump again!

[nike123]

Hi!





I was today at intervention and finally find out that expansion valve of water heat exchanger is blocked and that is why that unit few days in role trips at low pressure alarm. That happens because unit doesn't defrost and low pressure alarm trips. Before, when I came, ice is already melted. Then, two days ago I changed parameter for alarm reset and set it to automatic reset.
This is result:

left side


right side



Question is, why both sides are not equally frozen?

This is refrigerant diagram:


And this is pipe layout:

[Gary]

A better question would be, why is the left side bottom frozen and not the top?

The coil isn't getting enough refrigerant.

Most likely the system is short of refrigerant, but if the charge is sufficient, then the TXV is underfeeding.

Most likely cause would be plugged inlet strainer. If the inlet strainer is clear, then the TXV is maladjusted or malfunctioning.

OR

If the coil has a distributor, the cap tube(s) feeding the clear section may be plugged.

The bottom line is: The clear section isn't getting enough refrigerant.

[nike123]

A better question would be, why is the left side bottom frozen and not the top?

The coil isn't getting enough refrigerant.

Most likely the system is short of refrigerant, but if the charge is sufficient, then the TXV is underfeeding.

Most likely cause would be plugged inlet strainer. If the inlet strainer is clear, then the TXV is maladjusted or malfunctioning.

OR

If the coil has a distributor, the cap tube(s) feeding the clear section may be plugged.

The bottom line is: The clear section isn't getting enough refrigerant.

That could mean that both of TEV are clogged, one almost totally and other partially.
Does partial blockage could explain left side partial freezing at bottom of exchanger?
Also what could be cause of this blockage. Could it be low quality exchangeable filter drier whose core falls apart or something else.
When I was visiting factory I saw that they use nitrogen when brazing parts so I suppose that brazing residues are not the cause.
Two month ago, when I was starting-up this unit everything was ok.

[Gary]

That could mean that both of TEV are clogged, one almost totally and other partially.
Does partial blockage could explain left side partial freezing at bottom of exchanger?

Also what could be cause of this blockage. Could it be low quality exchangeable filter drier whose core falls apart or something else.

The frost looks pretty even on the right side. It is the left side that has a problem.

I have no way to tell what is causing the blockage. You'll have to take the inlet screen out and see what you find in there... if anything.

[nike123]

The frost looks pretty even on the right side. It is the left side that has a problem.

I have no way to tell what is causing the blockage. You'll have to take the inlet screen out and see what you find in there... if anything.

Thanks
I shall post here my findings.

[paul_h]

So this has a single TX that feeds both coils?
That refrigerant circuit only shows one TX (4) splitting to two distributors. The l1, l2 ,l3, l4 section.

How does the liquid line split to feed the two coils, if not perfectly horizontal, the lower one will get most of the liquid, with the other one get mainly vapour if the unit is short of refrigerant.

[nike123]

So this has a single TX that feeds both coils?

That is right.

How does the liquid line split to feed the two coils, if not perfectly horizontal, the lower one will get most of the liquid, with the other one get mainly vapour if the unit is short of refrigerant.

Thank you Paul-h for that taught. I did not looked that way on problem till you mentioned it.



In this way pipes are placed after air heat exchanger TEV.
I presume, that because of blocked TEV of water heat exchanger, this TEV ( of air heat exchanger) suffers lack of refrigerant and not because shortage of it in the unit.

This is second case of same manufacturer and same model with same problem (and, to me, apear as same cause) only difference is that second unit has encountered this in sumer during cooling operation and high pressure safety valves are vented all 18 kg of R407 refrigerant.
On that unit I changed TEV (i didn't want riski of second call for same problem in case TEV is malfunctioning) of water heat exchanger and filter-dryer and now it works OK.

On that particular occasion, I founded something like rubber particles in TEV. As I recall, this TEV doesn't have inlet screen. TEVs are Danfoss TRE20.

Any comment appreciated!

[nike123]

Today, I was on site again. I switched on the unit (now it is defrosted) and first thing what i noticed is, that fan blows small amount of air, considering that outdoor temperature is relatively low (7°C). I checked pressures and suction temperature is around -10°C with tendency to fall. Also crankcase of compressor started to sweat. Then I connected fan directly to power supply and, voila , I got 0°C suction temperature, compressor crankase is heating up, condensation rises etc....
Then I checked controller (Carel Microchiller 2) parameters for fan control, and noticed that some parameters are not what I think that they should be.
I called manufacturer in order to send me the correct set of parameters for that unit and I found that almost 20 parameters are set vrong.
Then I changed those parameters but fan still doesn't run fast enough.
I checked presure transducer for fan control and he shows correct pressure.
Then I changed parameter for fan to go on on/off control instead of proportional to pressure, and after that, it still works on some minimum speed or off.
Than I measured voltage of controller output for fan and found that is 0V or 2,37V instead 0-10V.
And there it is, controller is faulty.

Now, I (and customer) need to wait week or two in order to get new preprogrammed controller (if we are in EU only two to three days).

And there it is, I was person who made startup of unit. Weather at that time is mild and minimum fan speed has been sufficient for that temperatures and everything appears fine at that time. I supposed (supposing is mother of all f+++ups) that factory delivered tested and valid unit. At least, that is what is suppose to mean, that stickers of quality control signed and sticked on unit.

Now, I am going to throw away that startup form made by factory, and make my own!

I hope this experience may help someone!

[The MG Pony]

Good job at hunting it down! Such things are frustrating indeed, as you pull your hair out trying to find fualt when the factory has told you it is good!


I hope for you to get the controller promtly! so you may rest!
Oh and thanks for the update! It is all ways nice to see the end!

[nike123]

Good job at hunting it down! Such things are frustrating indeed, as you pull your hair out trying to find fualt when the factory has told you it is good!


I hope for you to get the controller promtly! so you may rest!
Oh and thanks for the update! It is all ways nice to see the end!

Thank you for god wishes!

Did your year have 18 months instead of 12? I ask this because it seems that your thinking not corresponds with your stated age.