york chiller help

hi fellas this chiller is a millenium recip chiller model num-ycad6595650a and serial-13099 its on r407c and was made in 8/96 if this helps. Neway when i got to the unit it was tripping out on circ 1 on low oil pressur run for a few mins then go off circ 2 was runing fine, so i put the gauges on circ 1 and the pressures was fine when running for a few mins then also circ 2 started doing the same checked the pressures and that all was ok:confused::confused: so both circuits pressures was good but yet low oil pressure. i checked the site glass on both and they was nearly half way up on them both on the controller the oil pressure would start of at 2.2bar but then drop to 1.5 and then both cut out so iam wondering why would and how could they lose oil and how can i solve it do i just add oil or what??? any help please thanks alot any questions just ask

adam:D

Hi Adam,

This problem is due to liquid refrigerant in the crankcase, i.e. flood back during operation or refrigerant migration during off periods.

What happens is this :

When liquid refrigerant is in the crankcase it dissolves in the oil. When compressor starts the crankcase pressure drops and therefore, this refrigerant evaporates. This vapour refrigerant blocks the oil pump inlet and there will be no oil pressure.
On the other hand, liquid refrigerant is heavier than oil (opposite ammonia), so if liquid refrigerant is in the crankcase it raises the oil level and from the sight glass the oil level seems fine.

To prevent this, the system must be pumped down before compressor is cut off. Also you can use crankcase heater.
If the flood back is during operation then you have to find the reason.

Is there any oil separator in the system?

Hope this helps.
Cheers

This could be a number of things, from memory the "millenium" controller or "york sh1te" as i refer to it monitors the diff between suction and oil transducers from start up. it requires > 0.3 bar after 10 seconds , > 0.5 bar after 30 seconds and > or equal to 1.5 bar after 1.5 mins and thereafter to allow the pot to run, any less and it will trip.
if you press the "display system pressures" button and watch on start up it should give a clue as to what is going on as it should match your gauge readings.
if both circiuts are giving faults i suspect this may possibly be some kind of water flow issue resulting in liquid thinning of the oil, or maybe a "york sh1te" control board problem.
check to see if any strainers on the water are clean.

hope this helps.
sling.

hi thanks fellas iknow now that one of the pumps is also broke and not working so its running on one pump water side i mean, and lana there is no oil separator on the system:confused:

Hi Adam,

I asked about the oil separator to know about a problem which is related to oil separator. If there isn't any so no problem.

As singlbalde mentioned check the pressure difference between oil and suction pressure.
Connect one gauge to the suction valve and another gauge to the crankcase then they must read the same pressure. If there is more than 4 Psi difference then the oil filter or suction filter is blocked inside the compressor.

Cheers

Adam
water pressure differential between inlet and outlet should be minimum 20Kpa or better, if water flow is ok you may have to check for head damage or fecked oil pumps which were quite common on these compressors. oil pressure has to be above 1.7b diff between suction and oil delivery. it also may be blocked oil strainers in the sump.

al

thanks again will have to check that next time iam there with the presures thanks alot

adam

Hi Guys

I am getting a little confused.

If the problem is that it is locking out on oil pressure failure, how does water flow impact that?
A problem with evap water flow would give a low suction pressure.
A problem with condensor water flow would give high discharge pressure.

A problem with both stages (I am assuming that both stages are completely separate circuits) means a common problem, either design or situation.

A sustained low load situation, just above shut down temp/press will hang up oil in the evap...perhaps poor evap water flow would cause that?! It would simulate low load.
This circumstance would have the high side full of refrigerant, and leave the low side...low. Perhaps you woul dget liquid slugging, but the tx should be almost pumping system down.
This would not explain the high level of refrigerant in the crank.

It sounds like refrigerant migrating to the crank, on the offf cycle, washing oil out of crank...I like the idea of pump down cycle in this situation, but not too low, or you may freeze the barrel.
Is this compressor located in a cold place, compared to chiller barrel? You need to figure out why refrigerant is migrating to compressor, and why the oil is getting stuck. Is the suction trapped, is the tx functioning properly, is there an oil separator?

From what you have said, I cannot see it as being a control board trouble, there will be low oil pressure if the crank is full of refrigerant, and the control board is telling us what your eyes have verified.
I would empty the crank of refrigerant. Make certain that there is some oil in crank to start compressor. run it and watch it.

Watch for slugging, check SH constantly, simulate low load, see what happens, after it has run for while, shut it off and see if you get refrigerant migration into crank.

I guess I am gearing towards TX trouble, and needing pump down circuit.

thanks for your help again i thought it was going to be as easy as add oil:D but it never is that simple is it:mad: neway one circ would run for bout 5 mins then go of on low oil pressure now the other circ did run for over an hour then kept faulting like the other circ :confused:like i said the pressures on both sides are fine and yes 2 completely diff circs, the evap and everything is all out side so everything is together and also when the systems runs for say 5 or 10mins or should i say when it ran for an hour the water temp came down to 6 oc and room temps was also droping thanks alot

adam

Hi Adam,

Why didn't you try some of the points given here?

There is flood back in that system. Check it first.

Cheers

Quote:

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A problem with evap water flow would give a low suction pressure.

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Correct.
however, reduced water flow also reduces the amount of heat which can be extracted from the water and in turn results in not all of the liquid being evaporated, so it returns to the crankcase. this also gives a wide TD across the evap and a very low outlet temp. the "york sh1te" board only has an outlet temp. sensor and will shut the plant down if it drops above a certain rate (whatever is programmed e.g. 2 deg per minute).

Quote:

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Perhaps you woul dget liquid slugging, but the tx should be almost pumping system down.

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I think this is not the case, the txv will have a range of operation based on design conditions and if you introduce low flow or blocked strainers then it is outside these conditions and unable to operate correctly whereby you will get liquid return to the comp.

Quote:

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I cannot see it as being a control board trouble

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Given that it is now apparent that 1 circuit runs for an hour before tripping i am inclined to agree, but these piles of sh1te have cuased me lots of vexations in the past and i rate them the same as daikin a/c units, poor.

Quote:

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when it ran for an hour the water temp came down to 6 oc

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That sounds a little low to me, what % glycol mix is the water?

Quote:

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Why didn't you try some of the points given here?

There is flood back in that system. Check it first

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;)

The York J type recips are notorious for losing oil levels when running on part load for prolonged periods.

They usualyy run between 3.5 and 5 Bar diff, especially the R22 mineral oil ones.

Try and run each on full load and check the oil levels on both comps. It shouild be halfway up the top sight glass on full load, if not try adding some oil.

If probs persist drain oil and take off crank door, check strainer in sump and for white metal (bearing damage).

If all good try replacing oil pump.

Hello adam if you got compressor models jh, jl , check that there loading hydrulic pistons are not leaking .because when they load up , if the (o) ring is worn it will dump the oil in the crankcase and it will cause low oil pressure. to check this energise the coils individauly and see if the compressor loses oil pressure.

thanks alot fellas alot of good information ithink tho after what you have said it could be a problem with the water flow through the evap as ther is only one pump running:confused: but will have to check a good few things on what you fellas have said. I will let you know as soon as i find anything out,the reason why i havent been back to this unit yet is because its is a 5hour drive away and bang in the middle of london :mad::mad::mad::mad: but any more veiws please let me know thanks alot

adam:D

Hi,
York chillers from around 1996 don´t pump down when stopping, but pump down on start up. This can occasionaly give problems after a prolonged shutdown. However, if your gauges are showing good oil differential pressure at all times then the problem is probably on the micro controller (check transducers first). This is due to the sample rate of the board which corresponds to the motor frequency (50Hz) or a harmonic of it (problem doesn´t occur on American 60Hz units. Sometimes this can be overcome by locating the oil transducer remotely and connecting by 1/4" flexible hose of at least 1 meter in length. If this doesn´t work, and everything else has been tested, the only resolution is to chang the board and/or EPROM.
Good luck.

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