Qualitair icing tev

[Northy303]

R410a cellar cooler
10.7 degrees c superheat
17 degrees c subcooling

6 bar low side pressure
24 bar high side pressure
And the tev looks like this.
I think it's not operating properly
Any thoughts
Many thanks in advance

[frank]

Either low ambient with no head pressure control or sog
cellar cooling is normally around 10 -13 C so evaporating around 4 - 6C...no chance of frost that those temps
17K subcooling is excessive.
try blocking the condenser and see what happens

[monkey spanners]

High(ish) suction superheat and high liquid line subcooling point to underfeeding TEV, though also check air flow through evaporator coil/ coil cleanliness etc. Would expect lower superheat if the air flow was poor.

I'd probably try warming the valve and phial to with some water to see if things improve even if only temporary. Could be partial loss of charge from the phial and bellows, or moisture/wax or dirty blocking the seat in the valve.

[The Viking]

How far back does the frost go on your liquid line, before the TEV?

[Glenn Moore]

Is this an internally qualified expansion valve? , it looks like a Danfoss TUB type .Have you any better pictures showing the valve evaporator and valve bulb positioning and if it's an internally equalised version ?.

[Northy303]

Is this an internally qualified expansion valve? , it looks like a Danfoss TUB type .Have you any better pictures showing the valve evaporator and valve bulb positioning and if it's an internally equalised version ?.

Yes it is danfoss and does not have an equalising line just one in and one out
And a bulb for the super heat

[Northy303]

There is no frosting on the liquid line and I have high subcooling all up to the valve

[NH3LVR]

Not my specialty, however I see the frost lead up to the TXV.
Looks like a restriction in the liquid line. Solonoid valve or drier.

[Glenn Moore]

It is unusual to fit an internally equalised valve to an evaporator that has a distributor fitted . The distributor and leads will have a large pressure drop and the expansion valve will not be able to offset this pd and will run with a too high superheat. Even trying to adjust the tee will not help unless you fit a externally equalised valve to remove the pd from the distributor.
Fit a access valve to the expansion line to see what the pressure is there and then measure the suction pressure as well deduct one from the other to see what pd you have. More than a couple of psi difference change the valve to externally equalised

[Northy303]

It is unusual to fit an internally equalised valve to an evaporator that has a distributor fitted . The distributor and leads will have a large pressure drop and the expansion valve will not be able to offset this pd and will run with a too high superheat. Even trying to adjust the tee will not help unless you fit a externally equalised valve to remove the pd from the distributor.
Fit a access valve to the expansion line to see what the pressure is there and then measure the suction pressure as well deduct one from the other to see what pd you have. More than a couple of psi difference change the valve to externally equalised

Thanks Glenn
Think you are right all the other qualitair coolers I look after have an external equalising line on the tev.
This unit is only a year old and probably one of the last ones out of the factory as qualitair have gone bust heaven knows why this one has a different valve on it.
Anyway we have to honour our warranty and sort this out as we fitted although we bought it from dean and woods so see what they have to say first but as you say looking like a new valve.
Many thanks again.

[Glenn Moore]

I'm sure it will solve your problem,
Best regards Glenn

[NH3LVR]

My apologies and I feel like an idiot. When I looked at the picture I thought the liquid in was coming in from the lower part of the valve. I blew it up and saw my mistake.
Am glad no one listened to me!

[cadwaladr]

Change the valve for one with an equaliser New filter drier,but the mystery remains it worked at some point? Ah well the fridge job does have a habit of biting back sometimes guess that's why we love it varied thermodynamics!

[Northy303]

Change the valve for one with an equaliser New filter drier,but the mystery remains it worked at some point? Ah well the fridge job does have a habit of biting back sometimes guess that's why we love it varied thermodynamics!

I don't think it ever worked you can see where the customer has chipped away the ice as all the fins are bent or missing.
Think we are going to replace the coil as well.

[Glenn Moore]

Just for the record
An internally equalised valve should only be used on small single circuit type of evaporators or evaporators with only 2-3psi pressure drop between the expansion valve and the evaporator outlet.
Multi circuit evaporators that have distributors fitted must always use an externally equalised valve
to overcome the pressure drop from the distributor head plus the distributor leads , this can be anything between 14 - 30 psi "or more in some cases" this will cause a massive loss of duty and high superheats etc with the wrong type of valve fitted

[Grizzly]

Thanks for the valued input Glenn.
Sometimes we all forget the basics.
The sign of a true Engineer is being able to admit when you get it wrong.
Just like HN3LVR. (Who knew but misread a photograph.)
Our industry is so big and diverse, you cannot get it right all the time.

Which is why this forum is so good for all of us!
Grizzly