Oil Pressure

[NorthSeaTech]

Hi all,

This is my first post on the site and its got me scratching my head, any assistance would be greatly appreciated.

I have a recurring fault with a chiller system namely a Trane CRHM200 (water cooled) with an LCG200 starter panel. This chiller is tripping on Oil Pressure, the problem is that everything seems to be fine with the system. My pressures are all in line with the manufacturers recommendations, the compressor has a healthy oil level which lead me to suspect the Oil pressure switch so i changed it out with a new one and the system still trips on Oil Pressure. There is 2 bar diff between LP and OP (4bar LP 6bar OP) as stated in manufacturers guidelines.

The only thing i can think of now is the TEV causing liquid surge........Anyone any ideas??

Thanks in advance

[Magoo]

Sounds electronic to me, fit power filters to primary control power supply for a start. If on a rig, gen sets do weird things, not in the manual but happens, power spikes screw processor cards, usually when no-one is there.
magoo

[lowcool]

if you have an oil level sightglass on compressor check for foaming especially at reaching set point and you are not overcondensing.as i dont know the plant your working on but 28 psi pump pressure is rather low but would still be above oil trip point bloody manufacturers dont leave much room do they.dont suppose someone lowered cut out point

[Gary]

Have you seen it trip?

[Peter_1]

...and you are not overcondensing.
Please explain what's overcondensing.

[NorthSeaTech]

Sounds electronic to me, fit power filters to primary control power supply for a start. If on a rig, gen sets do weird things, not in the manual but happens, power spikes screw processor cards, usually when no-one is there.
magoo


I did suspect an electronic fault as the starter panel looks older than i am lol. Again the problems offshore with power spikes etc as you stated are common. Then agian the TEV does look in a bad way very corroded etc so i will change it out and then if i still have the same problem then i would almost certainly expect it to be a controls fault.

As for your post Lowcool i have observed the oil in the compressor and there is no foam in the sightglass.

[NorthSeaTech]

Have you seen it trip?

Hi Gary,

I have observed it trip. The conpressor starts up and unloads ok, as previously stated all pressures are within spec. The compressor then trips after 2-3mins of running a manual reset of the OP is required.

[Gary]

Hi Gary,

I have observed it trip. The conpressor starts up and unloads ok, as previously stated all pressures are within spec. The compressor then trips after 2-3mins of running a manual reset of the OP is required.

That pretty much narrows it down. If the net oil pressure is good as you are watching it trip, then the control is not sensing the net oil pressure. You have replaced the control, so that narrows it down to the sensor.

Keep in mind that both oil pressure and crankcase pressure must be sensed by the control. You could have a faulty oil pressure sensor, or possibly a plugged line from the crankcase.

[bill1983]

" The compressor then trips after 2-3mins of running "

are you monitoring the oil and lp pressures when it trips.
can you definately rule out low oil pressure due to flood back?
does the trip always occur 2-3 minutes after initial start up or is it random. does it occur after defrosting as well?
have you checked the obvious, ie oil filter in the compressor, condition of oil pump and internal pressure release. check also the superheat setting and tev operation
or is the oil quality as good as it should be? too thin an oil from overheating will also cause a low oil pressure.

[Magoo]

I am not familiar with the chiller /Trane system. But fault would sound like a blocked / restricted pre-strainer fitted in the sump, most electro/mechanical oil protection switches have 60 sec. 90 sec . 120 second delay trip settings.
magoo

[icecube51]

had the same problem a wile ago,but wonders if anyone now how the sensors can be checkt for good or bad one. is it by pressure or electronic??

[NorthSeaTech]

Thanks for all the advice guys.

Looks like the problem was down to the TEV/superheat settings. I replaced the TEV and the system has ran without problem since.

[lowcool]

Please explain what's overcondensing.
operating condition of the high side of the system being under the design condition,a good way of upsetting superheat across the evaporator causing narrowing of the superheat,narrow superheat lots of refrigerant in evap.
dont really like getting technical hope this covers it