possable oil lock

enthalpy

What was going on with this system PRIOR to your recharging the system, I missed that one. Would like to see where you were before you started, and IF the coil is oil plugged did your diagnosis aid in the oil clogging of the coil in which you seem to think is there.

Kal Row

this one has me guessing...ooops fixd text...

so we changed the exp valve and high side drier, and no joy, but the distributor leaked so we swapped the exp valve again,


so here are the symptoms,


1)if you put more than 6.5 out of the 10.6 lbs of r22 in, it goes to 400 and trips out on high head

2)the liquid line temp at the exp valve to the bad stage is 20 degrees higher than the temp on the good stage

3)the evaporator is dry on one half – ie not filling enough – note we did blow nitrogen back from the distributor to low side gauge port on the suction line drier which is past it’s filter


my personal theory is that the evaporator is half full with oil even though it allowed the flow of nitrogen – I don’t think a gauge port past a suction line drier would allow enough nitrogen flow velocity, to carry the oil out to it


and if it is oil lock – what the best way for dealing with it, - recover, remove suction line drier, disconnect distributor from exp valve and blow, hoping for the best – or drlll holes at end of evaporator and drain under pressure


any takers?

Rodney Summers

Eugene Silberstein 3

Don't Run For the Drill!

The fact that the liquid line of the circuit that is not working pproperly is higher than the other is normal. Since you mentioned that you only partially charged the system, the condenser subooling should be low, meaning tha that the liquid line temperature and the condenser saturation temperature will be close together. Low condenser saturation temperature (and pressure) and high liquid line temperature will lead to low subcooling.

What are you concluding that the evaporator is dry in the second half of the coil? Did you take a superheat reading?

Please provide the follwing info:

Suction line temperature at the outlet of the evaporator

Suction pressure (evaporator saturation temperature)

Liquid line temperature at the outlet of the condenser

Liquid line temperature at the inlet of the metering device

Temperature difference across the liquid line drier

It seems like you have a flow problem, but I doubt the evaporator is oil-locked. Where is the evaporator coil located with respect to the compressor (above, below and how far). Is there a refrigerant trap at the outlet of the evaporator coil and, if so, where is it with respect to the thermal bulb on the TXV (between the evaporator and the bulb, etc)?

So, before you start driling holes, let;s check a few things out. You'll most likely be glad you did.

Kal Row

here is a few...

it's had to get temps while the unit is going since if you pull the covers to get those readings you loose the airflow over the coils,

-Suction line temperature at the outlet of the evaporator

NEAR ROOM TEMP MUCH HIGHER THAN NORMAL

-Suction pressure (evaporator saturation temperature)

SLIGHLY LOW BUT CLOSE TO NORMAL

-Liquid line temperature at the outlet of the condenser
-Liquid line temperature at the inlet of the metering device
-Temperature difference across the liquid line drier

ALL THE SAME


evap 3ft above compressor/condensor - its a vertical packaged unit

12" refrigerant trap at right angle to the return line where tvx bulb and equalizer is


fyi: when i opend the cover just to put my bare hands on both sides of the liquid line drier - the condensor fan motor tripped on thermal followed closely by boths compressors - clearly we are running too hot in there - going to acid wash the condensor first - just because it looks clear through aint enough - maybe that all it is - whan i get my sub cooling back - i will get my capacity back

don_144

I believe

the professor has allready given the correct advise here.

No way we can help Kal without more infro.Kal drill some holes,install your sensor where they need to be and gets
your temp reading.Anything else is nothing more then a guessing game.

Remember the customer is paying you by the hour,so do what you have to do so you can diganose the system properly the
first time.

If I may ask a question..will you be charging the customer for those expansion valve,or will it be something you have to eat?

Kal Row

not quite by the hour...

more like a commercial service contract of a whole building and just happens the be the building where my office/shop is.

anyway, it all started a year ago with a compressor with a bent valve, (was spinning an making very little pressure) those type of failures tend to dump a lot of oil into the system

after the compressor change out w/suction/discharge driers – the high side was 25lb higher than normal – so we cleaned the condenser coil, got 10psi drop but still high, and got higher still over time, even after a second cleaning, so I changed the exp valve, better but not enough, and the rest is history

the temp/pressure relationship of different points in this system don’t make sense – usually for a given pressure, you have a given temp, except if there is a lot of velocity or changing state, this acts like a foamed up glob of oil in the evp – moves, so it’s hard to pin down –

trouble is, this is a computer machine room and is mission critical – (my access to the “wall” runs through it) so I cant just take it down, before it gets really cool, otherwise I would have taken it apart at every fitting a long time ago, and blew and sucked it to death

I will be adding more units to the room to allow for some downtime as the original designer did not install 150% like I would have in this env

Need to cut small access doors in the panels so that I can point an IR temp gun at points
While the system is running without tripping it out

This unit was installed in 1989 – so the insides of the coils could be varnished from burnt oil – happens

I wasn’t expecting an easy answer – I even called in another service company – in case I overlooked something stupid – no joy

don_144

Yikes

service contract,even more so to comb it,However I do understand down time.

Personally I would have thrown in the towel and say look my freinds now it becoming costly to the both of us,not only in down time but inconvience as well.

We have come along way in todays technology and with the new energy bill being pass,it would benenfit the both of us
to install new equipment.

Thanks Kal for your reply and believe me I know all to well how the service contract will hold you up from making a sell.

Thanks again and I wonder if the unit are front discharge.
If so I've seen them run higher head then most top discharge,just the nature of the beast with very little coil surface.

Good luck Kal.

Kal Row

condensor rear,rear evap rear in, top out...

it's being acid washed as we speak before it gets to hot outside

Kal Row

ok people..this is embarrassing...

once again it was just basics!!!
The condenser coils may have looked clean , but after a caustic wash out of many years of crud – the high side dropped from 320 to 200 and the low side to 30 – there then, is the room for the missing three pounds for r22 – I am glad I listened to the doc and didn’t drill holes

In fact they had tightened up the vari-pulley for a faster condenser fan speed, and it had to be lowered – that why the condenser fan motor was so close to thermal trip, as it was pushing more air than it was designed to

Eugene Silberstein 3

Whew!

Basics are good!

I stress to all of my students to NEVER take severe action (Replacing compressors, altering refrigerant charge, replacing metering deivces, etc) until you have measured and evaluated ALL system operating parameters.

It pays off in the long run and you look like a hero ALL THE TIME!

Kal Row

still gona need some tweeking...

for starters - i need to adj the exp balve back to org pos - the alternate tech messed with it, but at least he recorded turns and direction - and he added some r22 also, so i am going to recover it and charge it by weight - to be sure - thank god it's a scroll - which can handle all sorts of sins, except electrical, and negative suction pressure ones - copland ought to put a neg suction internal release valve in to keep the scroll from binding up on a pumpdown