Hansen HA4AS-100 not opening fully

Hi all,
I have a relatively new Hansen HA4AS-100 on an evaporator wet suction return acting as a defrost pressure regulator and evaporator pressure regulator. NH3, 65KpA suction, 400KpA pumped LP liquid, -10degC room temp. The evaporator pressure is regulated by a Danfoss CVQ installed on a pilot line and a EKC is used for control of air on temp.

What I'm experiencing is the Hansen valve will not open fully in normal operation. With the Hansen valve jacked open the evaporators perform as expected, once un-jacked the performance reduces, brining of the coil is witnessed, the evaporator pressure rises to near room temperature equivalent. The CVQ is at min temp/fully open

What I have noticed is the pilot line is connected upstream of the valve/strainer. This line is taken off the top of the 100NB pipe yet has ice/liquid in it during normal operation and disappears when the suction valve is jacked.

Is liquid on top of the suction valve piston ok for normal operation? Maybe the HEV are too far open?

Superfridge,

Does defrost pressure regulator work to correct defrost pressure?

Try lowering defrost pressure to act as evaporator pressure to see if valve modulated on that, this will verify if valve does work okay.

Maybe CVQ, or line is restricted.

Imagine it has a solenoid in this line as well, is there something wrong with it.
Can you just use a CVP, why complicated with CVQ that is redundant.

Full coil should not matter.

Hi RANGER1

Thanks for the feedback.
The Hansen M3 regular is newish the same as the valve, about 6 months old, has been operating fine until two weeks ago. I believe the valve was originally replaced due to similar issues and the old valve was opened and no problems found. Defrost pressure is correct. I will try running the evaporator on the M3 at minimum, good idea. The CVQ is not redundant, it is used when site adjust the room temperatures, it doesn't require a fridgy to come and adjust. I agree though, get rid of the CVQ and fit CVP and on/off via a solenoid valve as it's just a cool store and all product is packaged.

The pilot line has a small circular finned heat exchanger on the pipe before the CVQ then strainer/solenoid valve to the HA4AS, this got me to thinking that liquid in the pilot line and CVQ was designed out and therefore could be the problem?

Superfridge,
No problem, Danfoss usually mount CVQ directly on valve, no lines etc.
CVQ no longer made, replacement in CVE-LP/ICAD, so day will come eventually to replace.
Pilot line/solenoid could have debris in line.

Superfridge,
No problem, Danfoss usually mount CVQ directly on valve, no lines etc.
CVQ no longer made, replacement in CVE-LP/ICAD, so day will come eventually to replace.
Pilot line/solenoid could have debris in line.

Hi Superfridge,

HANSEN Valve... Replace the piston seal kit. Had a similar situation after +/- 1 week post commissioning and cleaning strainer process. The pressure drop across the valve was way higher than expected.

Keep us posted.

Hi Superfridge,

Reading your original post again it seems your pumped liquid pressure is too high. Was that measured at the V/Station? Only head required is to get the liquid through the orifice / HEV and 10kpa for coil pressure drop. If you "pump through" the coil will under preform and the liquid only start boiling once the pressure falls away and the sub cooling has dropped off.

Hey GrantD,

Good post, appreciated, it's kinda where I'm heading too. Pumped liquid pressure was read at the pumps, no way to measure at the evaporator. Site records are nil. Tending only goes back a month. The site suction pressure has been dropped due to one -18degC room and that room isn't performing that well too mostly due to the -22SSt but could have the same issues as the -10 room, haven't got that far yet!

Superfridge,
400 kpa pump pressure, is that gross or net pressure?
400kpa above suction, or 400 - 65= 335kpa.
Have been involved in a plant that consultant wanted all reg valves fully open, still worked, of coarse low pump pressure.
You could test by closing LLSV for several minutes.
-22 on -18 deg C sst most likely never work especially if a suction riser involved.
Try to simulate things with what you have.
Nice to have pictures of pilot line, what size is it, what type/model of solenoid valve in pilot.
Be good to see picture of it, as cannot find anything about it from Hansen.
M3E25 external pilot should have been used in valve, Danfoss ones do have provisions for orifice when using hot gas in pilot.
Hopefully that orifice is not installed.

RANGER1
400Kpa net pumped liquid pressure. Pilot SV is a HS6, pipe is 1/2". Closing the LLSV lowers the leaving air temp.
The valve works with the defrost M3 as the temperature regulator so valve ok.
Going to remove the CVQ and pilot line, install another M3 and SV directly onto the HA4AS as per the Hansen book!
No photos sorry, too time consuming getting them on here. Maybe later.

Thanks Superfridge,
So sounds like you have to adjust reg valves as well?

Update.
Pilot line, CVQ removed. The HA4AS is now as per the Hansen book, two M3 regulators and a solenoid mounted directly. Now working as expected. Investigation into the pilot line uncovered no real issues, the strainer was still see through, the HS6 plunger was fouled up a bit, no real restrictions. So no real conclusions other than the pilot line was not allowing enough pressure on top of the HA4AS to allow it to open fully.

Superfridge,
You mentioned turning off LLSV air off was lower temperature.
Are you now considering setting up reg valves?
Hansen should have a chart to assist in initial setting if you know size/type & rough evaporator Kw.