High Deferential Oil Pressure Alarm

[NNNNNN]

We have FES Ammonia compressor 200 HP, once a while we get "High Deferential Oil Pressure Alarm" and "Low Suction Pressure Alarm" together, the compressor stops for these alarms. We reset then works for a while may be few days. that happened two years ago then gone. Now again last week one time, and this week one time.

I appreciate if any can help for the reason?

[Josip]

Hi, NNNNNN :)


We have FES Ammonia compressor 200 HP, once a while we get "High Deferential Oil Pressure Alarm" and "Low Suction Pressure Alarm" together, the compressor stops for these alarms. We reset then works for a while may be few days. that happened two years ago then gone. Now again last week one time, and this week one time.

I appreciate if any can help for the reason?

For the first one could be a clogged oil filter;)

for second one: maybe clogged suction filter on compressor, obstruction in refrigerant delivery to evaporators, too small or no load...

Tell us something more about your system, please.

Best regards, Josip :)

[NoNickName]

How cold is these days?
Is it colder or warmer than last year?
How does it compare with two years ago?

[US Iceman]

Low suction pressure and high differential oil pressure sounds like a cold start.

Cool oil injection temperatures will cause the high differential pressure, and if the ambient is also cool enough to where you canot deliver liquid to the evaporators, the suction pressure will decrease.

[NNNNNN]

After the first time last week, we thought it was the filter, replaced it. We are going to change the oil.

Out side temperatures those days 0 Deg C +-

[NH3LVR]

Am assuming you have a Micro II or III 3E panel. If this is correct, check the calibration of the sensors first. Very simple procedure, which is in the Panel Manual.

[NoNickName]

After the first time last week, we thought it was the filter, replaced it. We are going to change the oil.

Out side temperatures those days 0 Deg C +-


I don't think the oil has anything to do with it.
I think it's a low ambient temperature causing too much subcooling and results in low suction pressure.
Either you've got too much refrigerant or there's no condensing control in the unit.

[NH3LVR]

Just looked at my previous post.
I left a couple of things out.
In addition to checking the calibration of the pressure and temperature sensors, as well as the calibration of the slide valve, check to be sure that the machine unloads properly. I am assuming that the correct set points are entered in your panel.
On occasion the older panels will become erratic. This is often caused by a power supply problem, which can be replaced.
Unless the panel has a problem, the two failures are probably not related.

[US Iceman]

What is the oil sump temperature on the initial start-up?

Changing the oil does not seem right and I would not expect any appreciable difference by doing so.

[NH3LVR]

Changing the oil does not seem right and I would not expect any appreciable difference by doing so.

Correct.
If the oil were in a condition it is causing this problem you would be in big trouble indeed. Most likely shipping the Screw off to FES for an overhaul!

[NNNNNN]

We have changed the oil today, every thing as before.

Oil Sep. temp. starts at 113.7 F after five min. go up to 120 F or 121 F.

Starting Oil Diff. Press. is 94.4 psi and after 5 min. reaches to 112.6 psi

Delta P for the oil pump is about 15 psi

[NH3LVR]

Did you check the Sensors?
You can verify the readings with the Gage ports under the panel. (You have not confirmed if it is a Micro Panel, so I am assuming.)
You can connect ports to these with a ***** hose connected to a Gage TEMPORARILY. Do not use a manifold. NH3 is hard on the brass.
Something is wrong if your oil pump is putting out 15 PSI and you are showing 100PSI differential. The figures do not add up.

[NNNNNN]

- Yes the panel is Micro III
- The defferential Pressure for the Pump is 15 psi (out-in)

- I will be getting ports reading and inform you

-Regarding calibration of the sensors (Kindly I would ask you about the sensors you are mentioning? which sensors?)

Thanks.

[NH3LVR]

- -Regarding calibration of the sensors (Kindly I would ask you about the sensors you are mentioning? which sensors?)Thanks.

The pressure sensors are located under the panel by the gage ports. They each have a cable that runs up into the panel to the terminal strip at the bottom of the main board. They are labeled as to their function.
Connect a gage to the ports one at a time and compare your readings to the panel readings.
The recalibration procedure is in the manual. Very easy to do.
I am concerned about the low pressure differential you are reading across the pump. This is quite low.
A quick test of the sensors is too shut off the machine. All pressure readings should be the same except the suction. (It is measured upstream of the suction check)
Another possibility is an erratic sensor, or the wrong type installed. The board can be adjusted via jumpers for voltage or Milliamp sensors.
Jan Clark at FES in York, Pennsylvania can assist you if you have questions regarding sensor types. Or you most likely have a Rep in your area.

[NNNNNN]

Hi NH3LVR,

We have checked the calibration. only 1/2 to 1 psi diff.
it seems OK

Readings are:

1- When the compressor is OFF:
Suction Pressure: 20.0 psi
Discharge pressure: 107.2 psi
Inlet Oil Pressure: 107.3 psi
Oil Filter Inlet Pressure: 106.8 psi

2- When Sterted to run (after three min.)
Suction Pressure: 20.1 psi
Discharge pressure: 132.2 psi
Inlet Oil Pressure: 126.2 psi
Oil Filter Inlet Pressure: 135.0 psi

3- When Sterted to run (after ten min.)
Suction Pressure: 18.8 psi
Discharge pressure: 116.0 psi
Inlet Oil Pressure: 126.2 psi
Oil Filter Inlet Pressure: 125.0 psi


Note: The Filter Diff. pressure was around 8.9 psi
The Filter, Strainer and Oil has been changed one week ago.

Oil diff. pressure. 98.2 psi

Thanks

[NH3LVR]

I am a bit confused here.
Not know your particular machine makes this a difficult problem. Although i work on FES machines (Mostly older) regularly I have not seen them all.
I am on the road at the moment, so have had little time to look at this.
Does your machine have a large Viking oil pump (10-15 HP) Is it set up to run full time? It appears you have almost no oil pressure.
Is this a older machine with the micro 3 added? If so I would look at the installation and verify the connection and setup.
I am willing to take a closer look at this when I get home, but as I suggested earlier calling FES might be your fastest solution.

[NNNNNN]

I am not sure regarding the HP will get you that when go to work Tuesday.
The FES is about 7 years old, got it new at that time. has 24800 hrs. two days ago I have called a person workes on Viking pumps, he opend it found every thing OK with the pump (No wear and clearance is OK).
I looked today again the compare between the ports and reading on panel (Comp. OFF) all the same different about 2 psi (I don't think that is a big issue).

Thanks

[NH3LVR]

A break at last!
In my experience with Micro3's they have always shown the oil pressure as net (35 to 45 lbs over discharge). You are showing gage pressure instead. Dip Switch 6 #3 can change the readings in some cases. It should be in the open position. Closed is service mode to run the oil pump without starting the compressor.
Software may vary, however, so you should not rely on my experience exclusively.
Be cautious about the Viking pump. Even if an inspection shows no problem,they still may not pump warm oil.
A while back I sent two in for repair to a reputable company. They could find no problem. But they needed to be rebuilt before they would function.

By the way, does anyone have a sure cure for a Mycom screw that does not unload when running, yet unloads when started? The machine unloads, starts, loads up and stays at 100% from then on.
Electrical seem normal, valve clicks, etc, but it stays at 100%. The unloading valve does not have manual operating stems. I have had this trouble before and ended up rebuilding the entire unloading system.

[NoNickName]

Loading solenoid valve leaking?. Infact only unloads when oil pressure is nil? Just my 0.02 for a thought.

[NNNNNN]

The oil pump motor is BALDOR 3 HP 3.4 A 3ph 1750 rpm
pump S/N 10996327 PN 290-002330-022
The pressures that we have got through IN and OUt gauges.

[nh3wizard]

Just secound guessing here, but had someone changed a transducer lately and maybe installed the wrong one?

Does the Mycom have an external oil pump?

[NH3LVR]

NH3 Wizard:
Good point about the sensors. Danfoss did have a bad run a while ago.
As to the FES NNNNNN;
I am still confused about your machine. FES has used many manufacturer's compressors over the years. (Coby, Mycom, Dunham Bush,and now ELZE. I have never seen one with that small a pump. Not to say that they do not exist, I just have not seen one.
Fricks use a part time oil pump on some machines. The oil pump is used stickily to unload and prelube before starting.
Does your oil pump run all the time?
I am failing to see how this translates to a High Differential Shut down.
Take some pictures of your machine and post them.

[NNNNNN]

No the oil pump does not run all the time.
Attached are some picture of our FES comp.

[NNNNNN]

Attached some more picture

[NH3LVR]

OK, I have to admit I am totally unfamiliar with the Compressor in the picture.
You apparently have a part time oil pump, used to prelube and unload the compressor before starting.
I do not recognize the Compressor you have on your package. It seems to have a extra section I am not familiar with.
What is the setting you have for Oil Differential shutdown? Is there a pre-shutdown alarm setting?

[NNNNNN]

Here are some more photos

[mcalko]

load valve leaking. the o rings start to wear anf this will cause it not to load or unload. the oil is being bypassed in the load unloas cylinder.

[Andy]

We have FES Ammonia compressor 200 HP, once a while we get "High Deferential Oil Pressure Alarm" and "Low Suction Pressure Alarm" together, the compressor stops for these alarms. We reset then works for a while may be few days. that happened two years ago then gone. Now again last week one time, and this week one time.

I appreciate if any can help for the reason?

Hi NNNNNN:)

I would expect the problem to be on the electrics or the electronics side. Most transducers show low say -50 deg c when they go open circuit.
I would check the connections and then think about a new transducer or input card.

Kind Regards Andy:)