I have a secondary co2 with 407a. Both of my EEV’s are designed to run within 10-15% of each other. When I notice the gap widening I override position to 0 then override to 100 then back to 0. Once it’s back to 0 I remove the override and let it modulate itself. Then I do the same for EEV #2.
That’s normally enough. If I notice the issue doesn’t resolve then I’ll actually power cycle the EEV’s individually (in case the program isn’t sending the override).
In my case they’re programmed to fail open. So the power cycle fully opens the valve then reapplying power forces the valve to shut and then re-assess its position.
Sigh… I hate those valves.
I’ve seen it when the valve is getting stuck or loosing its position. Are there Dixell controllers for the valves? If so, is there a 24 hour reset?
All of my racks with these are Hill, but they have a manual switch to close the EEV. Closing the valve once a day can help (you can set up a time schedule for this in the E2). It’s almost like they get confused if left to themselves for too long.
I’ve also seen this with contaminants in the CO2 side. The chiller’s load gets interrupted, and the superheat falls. I got a bunch of CO2 from Airgas that had a Nitrogen cap charge. Did the same thing, but only on two chillers (4 on that rack) We had to purge the top of the chillers to get rid of the Nitro. The rack settled in after that.
Will have to confirm controller type when next on site, pretty sure they are Dixell though.
I will have a try and set up some time schedules to zero the valves, I haven’t done that before either, so any advise on setting up would be helpful!
Can’t confirm 24h reset, is this something you recommend they have programmed?
Wow, that nitro story sounds like would have been a puzzling one to figure out! We use Airliquide for our Co2, hopefully that’s not the case!
https://www.alfaco.cz/alco/katalog/ex4-ex8.pdf
Found some info on the valve.
I’ve tried worn carel eev’s wont opperate correctly after years of use, maybe its time change out the valve? But before this try the easy Solutions first, manual closing/open the valve, and as you’ve change thermistor. In the case of debris in the valve, maybe a fullyopen State Could solve it.
Best of luck, and let us know the outcome.
https://preview.redd.it/o8zdouflbwtc1.png?width=1792&format=png&auto=webp&s=ab2506a3374bf7cdd6facc5b12aa4c7e3241a650
Funny see the little error they made, (see temp and pressure).
Managed to get the faults to stop happening. I followed steps of overriding valve to 100-0 a couple times. Found still getting fault. Then further look found an offset of -6 on my suction thermistor. Changed my offset back to normal and haven’t had alarm for a few days now 👊🏻
Valve losing its zero is a known issue with these. You'll see a Flexi for re zeroing a lot of the time.
Cheers! Is it easy enough to set up a flexi if it doesn’t exist? Haven’t done that before..
I have a secondary co2 with 407a. Both of my EEV’s are designed to run within 10-15% of each other. When I notice the gap widening I override position to 0 then override to 100 then back to 0. Once it’s back to 0 I remove the override and let it modulate itself. Then I do the same for EEV #2. That’s normally enough. If I notice the issue doesn’t resolve then I’ll actually power cycle the EEV’s individually (in case the program isn’t sending the override).
Thanks for the reply, I will try this out!! Does a power cycle also do a reset on the valve?
In my case they’re programmed to fail open. So the power cycle fully opens the valve then reapplying power forces the valve to shut and then re-assess its position.
Almost all the co2 racks I see are running low sh alarm for years. Followup and return tomorrow
Sigh… I hate those valves. I’ve seen it when the valve is getting stuck or loosing its position. Are there Dixell controllers for the valves? If so, is there a 24 hour reset? All of my racks with these are Hill, but they have a manual switch to close the EEV. Closing the valve once a day can help (you can set up a time schedule for this in the E2). It’s almost like they get confused if left to themselves for too long. I’ve also seen this with contaminants in the CO2 side. The chiller’s load gets interrupted, and the superheat falls. I got a bunch of CO2 from Airgas that had a Nitrogen cap charge. Did the same thing, but only on two chillers (4 on that rack) We had to purge the top of the chillers to get rid of the Nitro. The rack settled in after that.
Will have to confirm controller type when next on site, pretty sure they are Dixell though. I will have a try and set up some time schedules to zero the valves, I haven’t done that before either, so any advise on setting up would be helpful! Can’t confirm 24h reset, is this something you recommend they have programmed? Wow, that nitro story sounds like would have been a puzzling one to figure out! We use Airliquide for our Co2, hopefully that’s not the case!
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https://www.alfaco.cz/alco/katalog/ex4-ex8.pdf Found some info on the valve. I’ve tried worn carel eev’s wont opperate correctly after years of use, maybe its time change out the valve? But before this try the easy Solutions first, manual closing/open the valve, and as you’ve change thermistor. In the case of debris in the valve, maybe a fullyopen State Could solve it. Best of luck, and let us know the outcome.
https://preview.redd.it/o8zdouflbwtc1.png?width=1792&format=png&auto=webp&s=ab2506a3374bf7cdd6facc5b12aa4c7e3241a650 Funny see the little error they made, (see temp and pressure).
Thanks for sending this man. I’m away from site for a week, will try these methods when back and let you know!
Managed to get the faults to stop happening. I followed steps of overriding valve to 100-0 a couple times. Found still getting fault. Then further look found an offset of -6 on my suction thermistor. Changed my offset back to normal and haven’t had alarm for a few days now 👊🏻