possible expansion valve fault

[davepik]

hi guys im pretty new to this.... I work with air conditioning mainly and have been asked to look at a supermarket multi system, its pretty daunting!:eek:

I have a problem with one of the freezers iceing up, all the thermistors seem fine, the only thing that i can think of is the expansion valve, its a danfoss akv 10-3, its icey straight after the valve which makes me think its faulty?? Is there any way that the valve can be adjusted or will I have to replace it?? any help much appriciated!!!

thanks
davep

[Brian_UK]

Hi Dave and welcome to the site.

Can't help with your problem I'm afraid but someone will be along soon I expect.

In the meantime information is here regarding the valve.....

http://www.danfoss.com/United_Kingdom/BusinessAreas/Refrigeration+and+Air+Conditioning/Literature/RA_Documentation.htm?CatalogKey=RA-6110f877-1a86-416c-a538-685d2ebcbfd7-en-EN&DocumentType=All&FreeText=akv%2010

[nicolacozma]

Hi Dave and welcome,

Try to heat up the temperature bulb of the TXV and observe if the TXV is opening (SH will decrease ).
Otherwise there is a regulating screw on the body of the TXV. Opening or closing of this screw will modify the superheat. Try this in order to check if TXV is working. Be carefull, make little changes I mean 1/4turn or 1/2 turn of the TXV and observe the changes of superheat. Take a reference for the original position of TXV.
If you will not observe any changes means the TXV is broken and you have to change it.

regards,

[FEISTY]

Welcome to the best circle of friends you never met face to face. Try using a heat gun carefully on the valve to melt any ice crystals that may be in the system. If the valve clears and it looks like the problem is solved , I would suggest adding some Thawzone deice solutionto the *****. Follow the directions as a little is better than a lot. As I have said before...I hate to mess with setting on txv unless you have a new...out of the box...replacement handy. At least factory setting will be closer to needs than " I forgot how much I turned it ". Good luck . If you are lucky...Gary is on line and can give you more help. He seems to have forgotten more than most of us even know.

[Kaiser]

When you said the freezer is icing up, do you mean the coil is a blocked with ice and no airflow across coil? Defrost issue?

[al]

if its an akv do not heat it, the strainer inlet may just be dirty, pump down and remove using a 10m socket.

al

[Silhouette]

What controller is powering the valve? Is there a distributor on the evaporator? Have you checked the defrost and control setpoints against the commissioning data? Is the icing up of the evaporator doe to a blocked drain etc.....

[SteinarN]

hi guys im pretty new to this.... I work with air conditioning mainly and have been asked to look at a supermarket multi system, its pretty daunting!:eek:

I have a problem with one of the freezers iceing up, all the thermistors seem fine, the only thing that i can think of is the expansion valve, its a danfoss akv 10-3, its icey straight after the valve which makes me think its faulty?? Is there any way that the valve can be adjusted or will I have to replace it?? any help much appriciated!!!

thanks
davep

The valve cant be adjusted. It is controlled by the conected electronic regulator regulator. The regulator has a pressure sensor conected to it sensing the evaporator pressure and a temp sensor at the evaporator outlet.

Is the valve clicking in 5 sec periods? If it is, then the valve is regulating properly. Of course the electronic regulator can still be faulty. If the valve is not clicking, then it is either 100% open or 100% closed or should be at least. If the valve is sized properly it shall be clicking when the case is down to temp.

If the defrost elements is good, then I would have checked if the valve closes properly during defrost.

To do this do the following:
Start defrost, gain access to the AKV. Remove any excess ice from the valve. Heat the outlet of the valve with your hand. You shall be able to melt any remaining ice. If it is impossible to heat the outlet to above freezing even after the defrost have been on for say 10min then it is an indication the valve doesn't close completely in defrost and defrost is impossible. If the outlet can be heated the valve is closing 100% as it shall be in defrost.

[Brian_UK]

Hi Dave and welcome,

Try to heat up the temperature bulb of the TXV and observe if the TXV is opening (SH will decrease ).
Otherwise there is a regulating screw on the body of the TXV. Opening or closing of this screw will modify the superheat. Try this in order to check if TXV is working. Be carefull, make little changes I mean 1/4turn or 1/2 turn of the TXV and observe the changes of superheat. Take a reference for the original position of TXV.
If you will not observe any changes means the TXV is broken and you have to change it.

regards,


Welcome to the best circle of friends you never met face to face. Try using a heat gun carefully on the valve to melt any ice crystals that may be in the system. If the valve clears and it looks like the problem is solved , I would suggest adding some Thawzone deice solutionto the *****. Follow the directions as a little is better than a lot. As I have said before...I hate to mess with setting on txv unless you have a new...out of the box...replacement handy. At least factory setting will be closer to needs than " I forgot how much I turned it ". Good luck . If you are lucky...Gary is on line and can give you more help. He seems to have forgotten more than most of us even know.


Sorry Guys and Gals but the AKV valve is an electronic one.

[davepik]

Hi guys thanks so much I appreciate all your help! :D

It is icing up straight after the expansion valve when the unit is on fan only (the unit is running on a tektroniks controller) which makes me think the valve is passing when there is no current. There is a large silver knob on the side of the expansion valve with the details of the valve... does this make any adjustments?

Thanks again!!!!!

[SteinarN]

If the "silver knob" is the same as on other Danfoss valves it is simply the knob to attach the coil to the valve.

It seems that you have found the fault, a leaking valve.

You got some pump down and soldering ahead. Take care to cool the valve with wet rags when you are soldering.

[Brian_UK]

Yep, read the instructions, strip and check the valve internals.

Could be a missing strainer and some debris under the valve seat.

[PaulZ]

Hi Dave
You might be able to get a repair kit which consists of the plunger and a seat. These valves have a small strainer around the seat as well.
If this is an old valve it may have to be replaced as we had trouble getting kits for the early AKV valves.
You should be able to look at what the valve is doing through the AKA 21 control panel if it's connected to an AKC controller. You said the unit is controlled by a Tektroniks controller, is this controlling the TX? Have a look in the board for a long aluminum covered box this is the AKC and the AKA 21 plugs into this. You will need the instructions to work through all the menus.
Let us know how you go.
Paul

[Silhouette]

Hi Dave,
Do you have the info on the Tektronics controller? Let me know, I can e-mail it if you need it.

[davepik]

hi guys thanks for all your help. I took the valve apart and cleaned it up when I put it back together it works fine so something must have been keeping blocking it open. Cheers

[Peter_1]

...
Is the valve clicking in 5 sec periods? If
Isn't it 6 seconds SteinarN?

[Plank!]

Isn't it 6 seconds SteinarN?


3 or 6 seconds with the danfos controllers

[Plank!]

Hi Dave
You might be able to get a repair kit which consists of the plunger and a seat. These valves have a small strainer around the seat as well.
If this is an old valve it may have to be replaced as we had trouble getting kits for the early AKV valves.


Early valves had a different seat material.
Newer Ammonia valves have a titanium valve seat, takes only the smallest speck of dirt to stop them sealing.
These valves are great, but do need fine strainer in line, also avoid any flash gas as it will destroy the plunger.

Regards
Steve

[Peter_1]

http://www.mark-off.ru/fam/eqpmnt/other%20eqpmnt/danfoss/Danfoss%20Cat%202000/02English/RD8AB102.pdf page 11, 3th line

[Plank!]

http://www.mark-off.ru/fam/eqpmnt/other%20eqpmnt/danfoss/Danfoss%20Cat%202000/02English/RD8AB102.pdf page 11, 3th line


I can't find a working link to the manual at the moment, however the Danfoss EKC 315A controller can be set to cycle at 3sec or 6 sec intervals.
6 secs is usually prefered, but the 3 sec mode is better on non constant loads.

Steve

[SteinarN]

Isn't it 6 seconds SteinarN?

You are absolutely correct. Logged in on a system. PwmPer is adjustable in 3, 4, 5 and 6 seconds on the AKC controller at least.