Faulty Tx Valves??

[frazzel]

Hello just a quick question hopefully shouldn't be to hard at the moment we are working on a freezer rack with an enviroguard system we are having a problem with the 15door freezer, the end evap is fine pulling down to -25 the middle evap is sitting around -12 with the first evap sitting at 0. At the moment everything else on the same system is sitting at around -26 which is all ok it is just the 15door freezer that has the issue. We have a full sight glass and suction pressure is sitting at around 72kpa Gas is 404.
What it looks like is that we have always had an issue with the TX valve in evap number 2 which is the middle one and both end ones have been keeping the middle case down to temp (as it is all linked) and now that the first evap has a fault the middle one is starting to suffer. At first we did section off the first part from the middle hoping that they still would be able to use the other 2 but yeah it looks like the middle one has had this fault.
Long story short im just asking is there anything else i should have checked or could i just have 2 faulty TX valves? Also the working evap which is down to -25 is at the end of the line and the ones we are having problems with are at the start.
Any help or discussion would be greatly appreciated.
Thanks for you time

[chemi-cool]

Is the liquid line full?
If it is, I would suspect bad piping design.
can you take pressure reading before and after each TXV?

[RONB]

Have you had any high head pressure problems. If you have the SPR valve will start dumping liquid into the surge vessel in order to lower the head pressure and thus start starving the evaps. Also it may look like your liquid line is full but in the past I have had the same problem, and because the charge on an Enviroguard system is quite a lot smaller than a conventional system a small leak will give a lot of temperature problems. It may be worth checking before you start changing TX valves.

[taz24]

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If you prove your TEV's to be ok (change if nessesary) then I would look
at how it was piped.
Check the obvious first like the strainer inside the orifice being clean.

Also check any solenoids in the circuit for correct operation. Some mag valves
can be restricted and not show signs of pressure drop.

With some instals the liquid travels past earlier tees and travels right to the end evap
before it backs up and then supplies the earlier evaps in the line.

So if the sight glass is full and the TEV's are fine try shutting off other cases
on the same system and see if the effected evaps improve, that way you will
know if it is a lack of refrigerant, liquid starvation or simple faulty TEV.

All the best

taz

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[frazzel]

Thanks all for the help!! After a day of pulling my hair out it ended up being the solenoid was not fully opening and starving the first 2 evaps in the case (just as taz said). I had tryed shutting off the end case but as the previous mechanic that used to look after the supermarket decided to heat the living **** out of the valve it isnt able to be adjusted :S All up and running now and down to temp

[taz24]

Thanks all for the help!! After a day of pulling my hair out it ended up being the solenoid was not fully opening and starving the first 2 evaps in the case (just as taz said). I had tryed shutting off the end case but as the previous mechanic that used to look after the supermarket decided to heat the living **** out of the valve it isnt able to be adjusted :S All up and running now and down to temp

Yey..... GO taz................

All joking aside though It's a good feeling when you get to the bottom of a fault and resolve it.

I have found in the past that more often than not there are two or three smaller problems
that added together give you the one big headache.

This job for example had a known TEV issue and then when combined with the other fault
it became a bigger problem that was pointing somewhere else and that tends to be the case most times.

We jump in looking for the big fix and somtimes its the mundane niggly jobs that add up.

All the best and at least it is working fine now.

taz

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