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Evaporator water flow too low alarm keeps happening.

Evaporator water flow too...

Evaporator water flow too low alarm keeps happening. Recently cleaned coils now this. The pumps are running fine. The pressures are good on the approach. The water strainer is clean. What is this a cause of?

Contractor's Assistant: How long has this been going on? And how severe is the problem?

The system shuts down after 3-5 minutes. For about 7 days now

Contractor's Assistant: Do you plan on doing the work yourself?

Yes

Contractor's Assistant: Anything else we should know to help you best?

There was a power outage a week ago, then the fan vfd vfd's went into fault. I did a hard reset then fans started working. Then evap water flow too low alarm

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Answered in 32 minutes by:
8/7/2017
Brian HVAC Guy
Brian HVAC Guy, HVAC Technician
Category: HVAC
Satisfied Customers: 1,019
Experience: I have been an HVAC/R mechanic/technician for 30+ years.
Verified

Hi Ham, I'm Brian, the same tech that helped last year. Is this on the same Trane CGAM chiller you're having the problem? And, could you explain in more detail what you mean by "The pressures are good on the approach." Please?

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Customer reply replied 10 months ago
The manufactures specs is 5-10 degrees. I have 8.
Customer reply replied 10 months ago
Evaporator approach.
Customer reply replied 10 months ago
thanks for last year. You solved that issue...

You're welcome, glad I could help.

Since your approach is good chances are the refrigerant level is proper so that's good. I haven't pulled the manual because I wasn't sure what chiller you had but most modern chillers use a flow switch for proof of flow and the chiller's LWT and RWT temperature sensors for a FLOW TOO LOW alarm. I think I would first check both sensors for accuracy to rule in/out a faulty temperature sensor.

I'm also thinking about the VFD issue and whether it's just a coincidence or not. I can't really think of anything related unless the drive lost a parameter or setpoint and isn't running at the proper speed. Just thinking out loud here but if your chilled water pump and piping got jarred during the power issues, could a pocket of air have moved into the chilled water barrel? That could cause some low temperature or high delta T issues between the sensors. Maybe a good idea to check the chilled water barrel for air.

Offhand, I can't really think of anything else. I'll put some thought into it though and if I come up with something else, I'll post a new response.

Thanks,

Brian

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Thanks, ***** ***** chiller. Ok, I'll fetch the manual and see if I can see anything more...

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So, I guess I would need to know a little more about the conditions. Have you been there when you caught it going into this alarm? Since you say the approach is ok, I'm having a hard time wrapping my head around this. It appears the chiller is looking at the leaving water temperature against the saturated suction temperature for that diagnostic but that's the approach so I'm a bit confused since you say the approach is normal. What are the suction pressure and entering and leaving temperatures? What is the Delta T across the evap? What percent loaded was it? What was the outdoor temperature? Having these numbers may help me understand things better and point you in a better direction.

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Customer reply replied 10 months ago
Fixed it. Bad temp entering water sensor.. thanks
Customer reply replied 10 months ago
It was 10 degrees out of range and rising.

That's great news! I hope I was some help. I'm really glad you got it up and running. They can be a bear to fix sometimes.

Thanks much for using Just Answer. Please remember to rate your service with me before leaving!

Best regards,

Brian

Brian HVAC Guy
Brian HVAC Guy, HVAC Technician
Category: HVAC
Satisfied Customers: 1,019
Experience: I have been an HVAC/R mechanic/technician for 30+ years.
Verified
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