Retrofitting from R22 to R404a

Hi,

I just found a walk-in freezer retrofitted previously by a different company. It has an R404a condensing unit and an R22 evaporator. After not gaining the correct superheat (it was 34 at the condensing unit and 22 at the evaporator outlet), I took it apart and found an R22 expansion valve , with the screw on the top fully turned out.
The owner thought the reason for not cooling properly is because they are using it too often, but having a look at the evaporator coil, it wasn't even frozen only on the 1/3 section of the coil. I think a new expansion valve is needed, the question is, how do I choose it?
It has a CAJ2464Z compressor and a Danfoss TEX2 68z3209 q-71322 -40/+10 expansion valve.
Unfortunately that is the only information available of the system...
Any help would be greatly appreciated.

Thanks

Hi Johnny,

Yes you are right, a new expansion valve will be needed. The bulb temperature that feels the superheat still is with R22 so it can't counter balance the force exercised by the pressure side.

Buy a TES2, see what is the orifice used on the existing TEX2 and try to use that orifice on the TES2...probably it will be not enough...apply then the next orifice number. If you are out of the maximum orifice (orifice number 6 is the maximum for the TEX2) then you to buy the TES5 with an orifice such as can give bigger capacity than TES2 orif.nº6.

Thanks for the answer.
The problem is that they didn't leave that plastic label on the expansion valve with the information about the orifice size. Shall I just go for the TES2 with Nr. 6 orifice straight away?

I'd go with a n.3 in a TES2 giving about 4kw at 5C your unit is rated at 2.3kw at -10C, and a new drier.

Best bet would be to give Climate Center (or your prefered wholesalers) tech peeps a call and get them to size it for you. (thats what i do, then it someone elses fault if it don't work!)

If you get a catalogue then all the duties are in it for danfoss and L'unite stuff etc

Thanks, I think I will try Climate Centre tomorrow.

I am a bit confused, this should be a powerful freezer at -18/-20C. You say its 2.3KW at -10, 4KW at 5C, so this means its only about 1KW at -20?

Strip the orifice out, you need to check it for a blockage anyway, number is stamped on the orifice. Sandro has the best option, experiment. You can size it yourself using the box the tev is in, get your duty off the condensing units at your evaporating temperature and match it.

al

Quote:

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Originally Posted by Johnny Walker

Thanks, I think I will try Climate Centre tomorrow.

I am a bit confused, this should be a powerful freezer at -18/-20C. You say its 2.3KW at -10, 4KW at 5C, so this means its only about 1KW at -20?

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Chart in the book for expansion valves is at 5C, the duty will drop as the evap temp drops so thats why a bigger orifice than the unit. The chart for the cond unit starts at -10C and goes down to -35C evap temp because its a freezer unit. The unit will do about 1.5kw at -23C evap temp.

You could get the orifice number of the existing valve, convert it to kw for R22 then pick the nearest R404A orifice, likely it will be one size bigger.

Easier to just get it sized by tech dept!

Johnny,

When you make the experience please give us a feedback, okay?

Sure. I will go on Tuesday to check the orifice size and will fit the new one probably on Wednesday.

Hi all,

Yesterday I have changed the expansion valve, in climate centre they told a nr. 2 orifice will be the right one, so I took that.
Needed some adjustment, but now it is properly working, I get the right superheat and customer happy as well, he said they've never had the room this cold. Previous engineer told them the room gets max -4 instead of -18 because the room is in constant use day and night and they are opening and closing the doors too often :S
Gas was low as well and just before I left I had a look at the sight glass: indicates moisture, so I think I will have more work to do on the unit...


Thanks for all your help

Well done and more importantly, thanks for the update.
We all continue to learn eh!
Grizzly

Quote:

---

Originally Posted by Johnny Walker

Hi all,

Yesterday I have changed the expansion valve, in climate centre they told a nr. 2 orifice will be the right one, so I took that.
Needed some adjustment, but now it is properly working, I get the right superheat and customer happy as well, he said they've never had the room this cold. Previous engineer told them the room gets max -4 instead of -18 because the room is in constant use day and night and they are opening and closing the doors too often :S
Gas was low as well and just before I left I had a look at the sight glass: indicates moisture, so I think I will have more work to do on the unit...


Thanks for all your help

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Watch out the moisture it can blockage the expansion device and consequently lack of evaporator feed (high superheat), less capacity.