View Full Version : Chiller fault

Daz man
19-04-2013, 07:30 PM
Hi guys,

in Lamen's terms what does the following alarm code mean?

on a water chiller with a Carel Pco2 control interface an alarm is showing AL075 'anti freeze alarm'

help would be appreciated


install monkey
19-04-2013, 07:47 PM
low water flow though evap or pump interlock not working or setpoint too low

Daz man
19-04-2013, 07:51 PM
Much appreciated, will check and post my findings. Thanks

install monkey
19-04-2013, 08:02 PM
also check water strainer isnt blocked,pump inlet pressure should be 1 bar - minimum, pressurisation unit isnt in alarm, setpoint shouldnt be set below 10deg, check displayed temperature is accurate with tested return water temp..may just req calibrating
check no air in evap- should be a manual bleed plug.

Daz man
20-04-2013, 08:31 AM
Install Monkey once again your the man! Your like a college of knowledge when it's comes to this game. On site now so will check

Daz man
20-04-2013, 04:38 PM
Install Monkey-

been on site today and carried out various checks.

chilled water pump is running.
There is two bar of water pressure in the system.
Pressurisation unit showing no fault.
Temp probes appear to be reading the same as my temp probes I clipped onto in/out of of plate heat exchanger.


the chiller runs fine cycling on/off temp this morning. But at midday when the ambient warmed up to 12 degrees the second stage compressor kicked in and after approx ten minutes operation time it faults out on this antifreeze gas evaporator alarm?

What about the strainer, a possibility?

install monkey
20-04-2013, 05:04 PM
ambient temp wouldnt affect your problem, you say on 1 comp it chugs ok, when the 2nd cut in then it tripped.
probably due to the increase in return water temp , controller will have a proportionate band and timer parameters. - for compressor start delay and minimum run time.
so theres still an issue with the fact that when the 2nd pot starts its out on frost protection, moniter the water leaving temp - if done on the carel controller- stop the chiller, run the pumps to see if they read the same as the return water sensor, if ok then run it and moniter the water out temp to see if it gets near its frost thresh hold- typically around 3-5deg, if the frost stat is a mechanical type- then this is adjustable but u need to determine if its controls affecting it or actual water flow issues
whats the make/model of the chiller

Daz man
20-04-2013, 09:21 PM
It's an Aermec RV chiller. Dates back to roughly 2003. It has a section at one end of the chiller which houses two chilled water pumps and a buffer tank. Think the correct term for this section is an accumulation unit. At first glance it looks like part of the chiller, same in colour (dark green) and sits inline. But after closer inspection there is a 10mm gap between chiller and accumulation unit. On R407c gas, two reasonably sized semi hermetic compressors. It has a Pco2 interface as the main controller. To me and you it's a standard Carel but this one has Aermec software in it.

install monkey
20-04-2013, 09:31 PM
The anti-freeze alarm is active as if the
machine is turned-off or if the machine
is in standby mode. In order to prevent
breakage of the plate exchanger due to
frozen water, the compressor is locked (if
the machine is under 4 C) and the resistance starts up (if standby below 5 C), if the
temperature detected by the probe in the
exchanger output the chiller is below +4 C

(Default defi ned) = 7C, ∆t = 5C
Cold Setting Water inlet temperature in cooling mode
MAX. 15C
Antifreeze intervention Antifreeze alarm intervention temperature on EV side (water
output temperature).
MIN. -9C
Total differential Proportional temperature band within which the compressors are
activated and deactivated
MAX. 10C

install monkey
20-04-2013, 09:32 PM

Daz man
20-04-2013, 09:36 PM
All I meant with the ambient temp, was when the day warmed up and the demand of the building increased (a lot of glass) the chiller supplied more capacity hence the second compressor kicking in.

Badly phrased - I know.

21-04-2013, 02:29 PM
Whats the set point ,is it P or PI control,has someone changed it to outlet water control.

Daz man
21-04-2013, 03:36 PM
Not sure. Will check on Monday. P PI? Is this the controller?

21-04-2013, 05:18 PM
p=proportional control p+i=proportional+integral I,ve had them over shooting the set point in p+i if the chiller brings the tempreture down quickly. pco,s usually give you the option.

21-04-2013, 05:30 PM
Hi Daz Man.
I may be a bit late but can you tell me whether the setpoint is based upon water on or off the chiller?
Basically if it's Return water temp controlled and not leaving.
Then the chilled water temp can take the various control temps / pressures to low.
Add what the guys are all saying about flows etc.
And theres your issue!

Daz man
21-04-2013, 08:01 PM
Cheers Grizzly, will check in morning.