my moneys on non condensibles

 

Kenneth199.
I think you will find he has mentioned he has a level sensor in the cooler which makes his chiller either phase 1. or 2 which probably didn't have cooler pinch control.
Depending on cooler water temp even B circuit looks high if close to setpoint, we have asked for a full log but to date he hasn't supplied one to let us see the full picture. Still for the cost of a return air ticket to Perth WA via Bali for a few days R&R including a nice hotel I am sure I could take a look and solve his problem.
Gibbo

 

Here's a picture of a 30HXC310 running.
As you can see the condenser temperature is close to the outlet temperature.

 

I can see in your first post that you have
water in 26c and out 32c
condensing temp a 49c
condensing temp b 41c

Water inlet is system A and water outlet is system A?

The usual difference between water outlet and condensing temperature is 1-3c with the type of condenser you have.

Clogged condenser, dirty water, faulty transducer, faulty probes water in/out. non condensables.
Could be one of the things ive mentioned above.

 

The issue is that circuit A is running 300kpa higher than circuit B discharge pressure . Occasionly getting hp faults but circuit A unloads or limits because of this high head pressure .gas 134a
Ie. circuit A 1280 kpa discharge at 70% load and limiting
circuit b 950 kpa at 100% load

 

What exactly is the issue with the system? Which alarm do you get?

The exv is controlled by cooler pinch, (difference between evap temp from pressure probe and water outlet)
Its default set to 1,1c or 2c. Not sure. The discharge superheat is also controlling the exv. If it gets to low the exv and compressors start to unload.

It's also possible to set a max working pressure for condenser, if the pressure gets above a certain point the compressor starts to unload.

Do you get high pressure alarms? 103, 203 etc? Which is supposed to be the high pressure switch with manual reset?

 

yeah 10 degrees celsius is what default setpoint on these are and im running at 18 degrees celsius .

 

Discharge superheat set-point default is 22f.

If discharge superheat gets too low, it'll start to unload to bring it up.

Chase







Sent from my iPad using Tapatalk

 

Hi again . Reattended site monday to check chiller operation.
Found pressure high again on circuit A. Logged both circuits but noticed circuit A running at 70% and B at 100% and circuit A still alot higher discharge pressure than B .
Suction pressure and temps both the same .Liquid temps both similar.
Exv both at around 24%.
The only way i think i can get discharge temp and pressure down is for the exv to open as exv looks at discharge superheat.
My discharge superheat on A is 18.
Cirrcuit b is 11.
There is a low discharge superheat setpoint but dont think a high setpoint.
Does exv on these chillers look at evaporator suction pressure /temp or liquid level?
Condenser water temps were ok.

 

Whats the cold water in/out?
Have you compared the water flow you have to max water flow through condenser?

I would reclaim gas (1-3kg) from top of condenser or evaporator, and check if the cylinder has the same pressure as the temperature.

 

The more I think about this the more I think you have non condensables.

 

Keep in mind if circuit A was running and circuit B was not during a period of condenser water problems (high conductivity or some other water treatment issue) circuit A could have developed scale while circuit B might not have since there was no heat in the circuit B area of the condenser. Just a guess without seeing a complete log sheet, but if you know condenser flow is correct then you likely have another heat transfer issue in the condenser which is normally fouled tubes. I think if you had an overcharge your valve would be pinched off more than that and your DGSH wouldn't be able to stay in a reasonable range. Non-condensables is certainly a possibility, but not likely on a high pressure machine and I think you would see erratic pressures, not just consistent hi discharge. The reason i say not likely on a hi pressure machine is the servicing technician before you would've had to try pretty hard to get that much air in the machine during repairs etc...

 

I know a couple of ac guys out there. Duncan Alexander and Mike Fletcher both worked out in Bermuda when I was there years ago. Both running their own companies now. Pretty sure Duncan worked for Carrier Perth for awhile.

 

Hi yeah im thinking the same possibly non condensables ,air , overcharged etc.
Im in Perth , Western Australia and the forecast for the next 3 days is 40c.. ouch.
havnt been back to site for a week but will def be popping in tomorrow.

 

i was thinking air in system as well

 

Where exactly are you ?

 

If the delta t on condenser is full load then its most likely overcharged or non condensibles not foul tubes, your subcool will tell you which

 

Hi , the tubes where cleaned 8 months ago , not by me but i will be doing them this year. Thought if tubes where bad it would affect both circuits.. depends where scale etc buildup is of course.
Since last post i manage to check exv steps and both circuits where limited to 1200 steps. I put them back to 1500 steps as the manual default states.
After i did that i noticed it did bring the head pressure down to 1050kpa and discharge superheat dropped to around 12k.
The exv position was still only at 34% and dont think what i have done affected it as before the valve only opened the same.
We have only looked after this chiller for 12 months and starting to suspect previous contractors may have worked on it and possibly overcharged or non condensables .
I will look at that liquid line strainer .
Its not the main chiller and on hot days it runs in tandem with a trane .
Will get full logs .
Thanks

 

Perhaps you could submit a full log of both circuits including subcool which would help.

 

Have you cleaned the tubes. It could have good flow. But not transferring good heat. Also has there been any refrigeration repairs made to that circuit? Check the liquid line mesh strainer . it's right before the TXV

 

Both , checked to make sure tranducers reading right using gauges .
since my last post i have managed to access service settings to find discharge superheat setpoint 10 on both .
Will be returning next week to try and find a exv min max drive steps and further tests..
I feel my exv should be opening up to bring discharge superheat down as this is what the exv looks at the manual states.
thanks .

 

How did you measure that high pressure reading?
Straight to the Prodialog high pressure transducer reading or your high pressure manifold reading...?