Danfoss tx vales

[fuzzy]

I have a new store with 404a refrigerant in two different racks ,head pressure set at 190 ,back pressure set at 49 ,recievers 60 persent ,sight glasses full, eprs on both racks set one degree above setpoint to keep epr sorit open. Both racks are medium temp one controlling dairy the other controlling meat. computer operated rack. One rack runs fine one rack has mojor tx valve problems adjust superheat check screen only get have half coil feeding on evap. Change tx valve to a sporlan problem goes away is this enough info to tell customer that danfoss tx valves are not cutting it.The only problem I have is that rack that does not have any problems. My only thoughts are noncondensibles upon start up. I have issues in the past and have changed over to sporlan and problem has gone away. It always seem to take a long time for these valves to pull temp. I have heard of head pressures high enough would keep these efficiency down also. They are on Hill Racks with warren cases.

[Mark]

Fuzzy

Welcome to the forum.I have never had any major problems with Danfoss valves, install them set them up bingo.How clean is the system?
Why is the head pressure set at 190 psi?

With Kind regards
Mark

[fuzzy]

The system was installed by another contractor so I don't know how clean it was ,190 is what the customer wants the condenser set at. I tried lowering it to 140 but it was too hot outside to drive it down, that was part of my question , does Danfoss valves work better at lower head pressures. I would prefer Sporlan and not have to worry about pressure all the time since I am not at the store every day, the customer would also like to keep the calls down. I just don't have any faith in these valves you can't take them apart to inspect them and that is a very big minus for me.

[Mark]

Iam not aware of any deviatons in TEV operation depending on who manufactures them.The principles of operation is still the same.
Have you measured the superheat at the fixture, what evaporating temperatures do the manufactures specify will achieve your desired shelf temperature.

[fuzzy]

Iam not aware of any deviatons in TEV operation depending on who manufactures them.The principles of operation is still the same.
Have you measured the superheat at the fixture, what evaporating temperatures do the manufactures specify will achieve your desired shelf temperature.
If you open the valve or close it and no feeding occurs superheat doesn't come into play. My suggestion is the valves are slow in responding and can't be accountable in a supermarket enviroment. They are not user friendly. can not be taken apart in the field to determine the problem therefor they are inferior to what I am trying to accomplish, This is a great site for guys getting into the field good luck.

[taz24]

They are not user friendly. can not be taken apart in the field to determine the problem therefor they are inferior to what I am trying to accomplish, This is a great site for guys getting into the field good luck.

I'm sorry but I disagree,
Once a valve is correctley fitted and commisioned you will have years and years of continuous accurate controlled use.
The problem with systems is when you introduce the one unknown variable into the equasion.
The so called engineer is the worst enemy to a system.
We introduce moisture and noncondensables, we adjust valves and control settings.

Remove non-condensables, moisture, contaminates and set the thing to how it was designed and then leave alone.

taz.

[monkey spanners]

I mostly fit danfoss tev's and find them to work fine. If you are adjusting the superheat screw and this is not altering the superheat then i would check to see that there is about 1.5-2mm of sprung movement between the orifice and the body of the valve, if not the phial/belows has lost its charge, check the gauze filter for rubish. Also worth checking that its the correct temperature range for the aplication. The only danfoss valves i can remember giving "trouble" where the mop ones, which was an aplication rather than valve problem.
Why not just fit a sporlan one if they are what you are familiar with?

Jon

[fowlie]

are you using the correct size orifices and should the valves not be external equalized

[750 Valve]

Try running the HP closer to design...
If the TXV's were selected on a high ambient or a low condenser TD then they may have been selected for a PD across the valve of say 10 to 11 bar, by running at 190 you may be allowing the PD across the valve to drop low enough that they cannot keep their rated capacity.

Although the pressures you describe are nothing abnormal, could it be liquid line sizing related? Have you tried fitting a liquid line sightglass at the furthest case on the rack?

Are the transducers out? Do you have a condenser/ discharge line pressure drop that the transducer may be reading discharge line on rack and receiver maybe considerably lower (making liquid pressure lower than what you think)?

Do you have a suction line pressure drop?