30RAP AquaSnap Control

[CentraVac1470]

Hi all, Have a 40 ton AquaSnap that keeps tripping out on A207. Both EWT and LWT thermistors are both reading correctly. Also have 15psi across the exchanger. Both of those are the listed diagnostics in the troubleshooting manual. What is happening is 2 stages are starting and continuing to run at 50% capacity without staging down. They cycled down in the past. Also noticed that even though the A1 compressor relay is "OFF", I'm getting an "ON" for the A1 compressor feedback. My control setpoint is 50°F. Unit keeps running until LWT is 33°F and then tripps. Any ideas? It's a glycol unit, digital scroll and the correct fluid is set in Option 2 of configuration. Control mode is set correctly also (0). My clsp1 is set for 50°F and my brine freeze set point is set for 32°F. It is running in Local Mode and not on CCN. Thank You!

[Dallas Duster]

How fast is all of this staging down happening?

[CentraVac1470]

Actually, they are not staging down at all. The unit starts 2 stages, one at a time, 1st. one, A1, then second one, B1 and they continue to both run constantly until the unit alarms with A207 at 33°F. The capacity or available capacity remains at 50%. Never decreases. I remember seeing it stage down earlier to 40, then 27% and so on.
Thank You....

[Dallas Duster]

Actually, they are not staging down at all. The unit starts 2 stages, one at a time, 1st. one, A1, then second one, B1 and they continue to both run constantly until the unit alarms with A207 at 33°F. The capacity or available capacity remains at 50%. Never decreases. I remember seeing it stage down earlier to 40, then 27% and so on.
Thank You....

What is the control point?

[CentraVac1470]

Control point is 50°F.

[Dallas Duster]

Control point is 50°F.

So the control point and set point are both set to 50 , how old is this unit? What does the load factor do during all of this?

[CentraVac1470]

Yes, both are 50°F. The unit is just a little over 2 years old. Was installed in early 2010.
As for the load factor, I'll have to check back with you. I'm not at the site right now.

[Dallas Duster]

Oh and another quick question. Does it shut completely off when your A207 happens? Is that the only alarm you get? Do your sensors have the correct voltage drop for the temperature? I'll check on some other info tonight. Checked your strainer lately?

[CentraVac1470]

Yes, shuts completely off including chilled water pump. I checked strainer this morning. Was perfectly clean. A207 is only alarm that comes in. I will check voltage drop on sensors in morning when I return. Didn't do that. Thanks again!

[AZ-]

Hi guys,

I know the unit is 2 years old...but - I wonder if this is a new situation, Is this a process application? Has anything changed with the process? Do you have a chilled water storage tank? Maybe not sufficient loop volume - if the load drops more quickly than the chiller can unload you could overshoot the control point and lose the chiller on this A207 alarm. This chiller requires 3 gallons/ton (120 gallons of loop volume).

[Carrene #2]

Have you called Tech Support?
Give that a try.
I'm not going to give out number, if you or your company works on this equipment, you should be able to come up with the number.

[CentraVac1470]

Well, after several hours trying to get this problem straightened out, I think all is corrected. We service and maintain all our own chillers in house and after getting in touch with tech support from our local rep, it looks like the issue is identified. The machine is actually working as programmed. The unit was going into and "oil return mode". (mode23 if I remember correctly. Not exactly sure right now as I have too many codes in my head from working on it all day) The machine was calculating how long the 1st. stage runs, and if unloaded for a specific amount of time, will start a second stage to bring oil back to the digital scroll no matter what the set point is. During that time, because of the cooler temps outside, it was just overshooting itself and tripping on the brine freeze set point. Not A207 as shown in current alarm. Personally, I think these AquaSnaps are over controlled. But I guess that's just the way it is. On the bright side, our local Carrier rep informed me that the version of software on my particular 2 year old machine has quite a few bugs in it (Carrier Confirmed) and is scheduled to come out next week to upgrade the software at no charge to alleviate this problem. (Incorrect A207 Alarm) Thanks guys for all the advice and help but it looks like we can close the book on this one. I'll update on the software upgrade and performance of the machine once it's been done. For now, until the new upgrade is installed, I've disabled the B1 and B2 compressors to keep it from over shooting and all seems to be running fine. (for now!) Thanks Again!

[Dallas Duster]

I'm not positive an upgrade will fix an oversized chiller problem.