ACRD602P Low Suction Pressure

[BillP]

Hello dears,

I have three units of ACRD602P working as HACS, the three units located in one Datacenter.

Before 29 OCT the units were working as InRow, one of the units (CB1) gives Low Suction Pressure at 10:00 AM, and all the cooling system stopped working, the DC temp become very high.

First Question, why if one unit has a fault, the others unit become not working?

2- Why the unit gives Low Suction Pressure?

All the two units charged by 32kG and the third 33kG of Gas due to these calculations:

5.5kg+7.7kg+12.4kg+(18.6*0.28)kg=30.8kg + 2valve =32.8kg

For unit 3 about

 5.5+7.7+12.4 +(20.93*0.28)= 31.46kg + 2valve=33.46kg

The Supply Air temperature before install the flood receiver was 15c, now and after the flood receiver installing and charge the unit with 20kG gas in addition to the 10kG existed, the supply air temperature become 14c and some times 13c.

What is nominal supply air temperature?

What is the main function of the flood receiver?

What is the minimum suction pressure for the unit?

What is the nominal suction pressure for the unit?

What is the nominal discharge pressure for the unit?

What is the nominal suction temperature?

[BillP]

Hello Rami. The normal suction pressure for R410A is between 120 and 140psi and the discharge pressure is between 250 and 270psi. The unit will go off on low suction once the suction pressure reaches about 90psi. There are many reasons that this unit could have gone off on low suction. There could be a leak somewhere. It could be a low load issue. Do you have the load on this unit? As to why the other unit did not come on, there are a few variables to this. Are the units in a group and linked together or are they separate? What mode (type) are the units set to? Are the units all set to "On" or are the units in "Standby"? For the receiver, this is to store extra refrigerant. This is needed as the temperature changes throughout the year, the amount of refrigerant needed changes. In the winter, the refrigerant will pool in the condenser as it is the coldest place in the circuit. The extra refrigerant in the system will be needed to keep the pressures in the system up for the unit to operate. In the summer the extra refrigerant is stored in the receiver. 

Thank you

[BillP]

Hello Sir,

Thank you for your information

I don't think that we have leak in the units, because the unit is working Ok for a long, but sometimes it give this alarm.

The Datacenter load is very low, because of that I made the new configuration to HACS and turn on unit on and make the rest two units in Backup mode.

Are the units in a group and linked together or are they separate? 

Yes they are connected via A-Link and we have two Units of AFC

the units connected like this: Terminator - AC1-AC3-AFC-AC2-AFC-Terminator.

What mode (type) are the units set to? 

They was InRow, I made them recently HACS (because Ihave hot aisle)

 Are the units all set to "On" or are the units in "Standby"? 

All Were On

what do you suggest to test the Gas quantity in the units?

How can I log the Suction pressure on the units?

[BillP]

Hello Rami. The best things to do form here is first check the sight glass to see if there are any bubbles in the refrigerant that would indicate a low charge. Also pull the data logs off the network card (they can be found under the web interface under logs-data-log.) This records the suction pressure for the unit along with other values. You can set the interval from 10 min down to 1 min if it is not catching the low suction pressures. Also check the load values on the data log. We would like to see at least 15kw load on the unit. If it is getting below this, the low load could be causing the low suction. As you have a HACS system, make sure there are no open spaces in the racks or in the rows to help increase the load.

Thank you

[BillP]

Dear Sir,

I'm attaching the Events and Datalogs, I will also take them out tomorrow and back to you

[BillP]

Hello,

I'm attaching updated log files

by the way, the unit didn't gives low suction press alarm in the days when the log recorded 

[BillP]

Hello Rami. From the logs provided, I would put this on the low load in the room. The unit 1 is running for 30  to 40 min then shutting down as it has satisfied its cooling demand. It will then sit off between a half to one and a half hours. Are there plans to add more load to the room? When the units are off the refrigerant will migrate to the coldest place in the system. This is usually the condenser outside. When the unit starts back up it will sometimes take a couple of tries to get the refrigerant moving through the entire system again. More heat load will keep the system on longer and keep the refrigerant from migrating to the condenser.  we can try putting the units back to inrow mode until more heat load is added if they were working before changing it to HACS.

Thank you

[BillP]

Dear Sir,

The customer is planning to install extra equipments the Datacenter, I tried to make the units to be InRow, but the three units will be ON, and not one On and Two backup, what do you suggest to make them in the write configuration?

Also I found that the supply air humidity is more than 82%, what I should do?

what are the best parameters and set point for my case?

[BillP]

Dear Sir,

The customer is planning to install extra equipments the Datacenter, I tried to make the units to be InRow, but the three units will be ON, and not one On and Two backup, what do you suggest to make them in the write configuration?

Also I found that the supply air humidity is more than 82%, what I should do?

what are the best parameters and set point for my case?

[BillP]

Dear Sir, I'm waiting for your kind reply

[BillP]

Hello Rami. The return humidity is showing between 58% and 75% for the units. This is pretty high for room humid. The supply humid will read higher as relative humidity is dependant on the temperature. As we are outputting cooler air on the supply side, the relative humidity will go up. The cooling units will dehumidify a little while cooling but are not able to keep the entire room humidity down. To help out the humidity levels, you can raise the supply air temperature setpoint and make sure the reheat is enabled on the cooling units. This will help a bit but if there is humidity coming in from the outside, the only way to get the humid down would be to either seal the room or supplemental de humidification.

Thank you

[BillP]

Dear Sir,

There are no out humidity, I will increase the supply set point to 24C, by the way it is now 23C

[BillP]

Dear Sir,

Please check the attached Datalog 

The Supply humidity is 100% in CB3, CB1 and CB2 are Backup units.

I have made the supply air set point to 24C, and the coolant set point to 25C

By the way, I found water in CB3 radiator

[BillP]

Hello. When the unit does turn on to cool, it is cooling very fast and the supply air is getting lower then the dewpoint is is causing the supply humid reading to spike to 100%. To assist this unit in the low load situation, is the reheat enabled? Also what is the setpoint for the reheat? Try setting the reheat to 18 or 19C.

Thank you

[BillP]

Dear Sir,

The Reheat and Heat assistant are enabled, The reheat is 14C, I will make it to 19C due to your recommendation.

By the way, today I got new warning from one of the units, it is Low Superheat warning 

Please check:

11/13/2017 13:15:43 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 13:15:34 Device Low Superheat Warning. 0x40BA

11/13/2017 12:55:42 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 12:55:34 Device Low Superheat Warning. 0x40BA

11/13/2017 12:35:59 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 12:35:50 Device Low Superheat Warning. 0x40BA

11/13/2017 12:15:50 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 12:15:41 Device Low Superheat Warning. 0x40BA

11/13/2017 11:36:23 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 11:36:15 Device Low Superheat Warning. 0x40BA

11/13/2017 11:16:31 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 11:16:23 Device Low Superheat Warning. 0x40BA

11/13/2017 10:56:48 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 10:56:39 Device Low Superheat Warning. 0x40BA

11/13/2017 10:37:22 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 10:37:14 Device Low Superheat Warning. 0x40BA

11/13/2017 10:18:05 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 10:17:56 Device Low Superheat Warning. 0x40BA

11/13/2017 09:58:05 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 09:57:56 Device Low Superheat Warning. 0x40BA

11/13/2017 09:19:22 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 09:19:13 Device Low Superheat Warning. 0x40BA

11/13/2017 08:59:30 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 08:59:21 Device Low Superheat Warning. 0x40BA

11/13/2017 08:20:12 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 08:20:03 Device Low Superheat Warning. 0x40BA

11/13/2017 07:41:12 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 07:41:03 Device Low Superheat Warning. 0x40BA

11/13/2017 05:44:37 Device Low Superheat Warning Cleared. 0x40B9

11/13/2017 05:44:28 Device Low Superheat Warning. 0x40BA

I tried to understand the problem, I found that at the times which the unit give the low superheat warning, the superheat become lower than -16.6C, and the Output load is going to Zero!

I summarized the datalog for you, please check it

I make the time with problem occur in red  

[BillP]

Hello. What is the firmware version on the web interface for this unit? There should be an aos and app version.

Thank you

[BillP]

firmware version on the web interface of this unit:

Factory Information

Hardware Factory

Model Number

0N-9580AC

Serial Number

JK1712002547

Hardware Revision

06

Manufacture Date

03/30/2017

MAC Address

00 C0 B7 F5 F6 26

Management Uptime

0 Days 4 Hours 41 Minutes

Network Management Card

Serial Number

JD1713001244

Application Module

Name

acrd2g

Version

v6.3.3.g

Date

Apr 13 2016

Time

11:23:18

APC OS (AOS)

Name

aos

Version

v6.4.0

Date

Dec 18 2015

Time

15:10:21

APC Boot Monitor

Name

bootmon

Version

v1.0.8

Date

Apr 8 2014

Time

11:00:33

[BillP]

Mahmoud,

Please try upgrading to the latest firmware version, AOS 6.4.4/ACRD2G 6.3.4

I have attached it for you.

Thank you.

[BillP · Accepted solution]

Ok, i will upgrade firmware.