Expert help needed fast..PLEASE

[jstch00tme]

here is the situation, 5 ton heat pump package unit , first look we have shorted windings on a three phase scroll compressor, change the compressor and the contactor, evac and recharge back to factory spec., unit runs for an hr. or more cooling but not that great, pressures are not good, 200dis. 30 suction. shut down unit dbl check install, reverse two leads make sure running forward, check proper rotation of fans..the basics. OK, hook guages back up. pressures are equilized, start unit up, discharge goes from 200 to 250 suction SLOWLY goes down to about 80 BUT then goes back up to about 90, at this point you can hear a change in the compressor, its strugeling, and the amps confirm the sound, they go from 30 to sixty+ then the compressor shuts off, i assume on thermal overload because its EXTREEMLY hot and then you can hear the system equalize (hiss loud)... it does this in less than one min. of running cant even get superheat, subcooling nothing.... tried the reversing valve seems to work, can hear it click, when engaged the high side jumps to 350 but low side does same as before and unit shuts down....at this point i have reclaimed the refrigerant and cut the suc. and dis. lines just to see of the compressor will run....it does just fine with no gas! sounds good and only draws 9 amps.... any ideas?

[GXMPLX]

It is not convenient to change a compressor without doing first a tear down analysis of the failed compressor, this can give you the clues for system problems and solve them before they affect the replacement.
Compressor model?
The main suspect here is a faulty 4 way valve it is probably not moving the piston all the way and it is bypassing gas to the suction, this may be caused by metal debris from the first compressor or it could have been overheated. It seems the problem gets worse the more you use it.
Did you clean up the system before changing the compressor?
Can you install tap valves at the inlet of both coils and measure discharge and suction pressure simultaneously?

[jstch00tme]

cleaned up as good as i could, checked oil from old, clean and accounted for. changed dryers, evacuated for apx. 1 hr with 6cfm 2stage. if the valve was not seating properly wouldn't the pressures tell me something more? since the old oil was clean and the compressor was shorted, i assumed an electrical failure not mechanical.

[GXMPLX]

In order to distinguish between electrical an mechanical failure you must open the compressor there's no other way to tell. There's low probability any new component is cousing the trouble i'd rule out the filter unless it showed evident signs of temperature change (high pressure drop could cause overheating) .
If the 4W valve is bypassing gas you will measure a much higher suction pressure at the compressor than the one you have at the INLET of the coil conected to the suction at that moment because of the bypass. Or you chan hear the valve hiss.

[wambat]

I'm afraid you may have damaged the compressor running it backwards. it is so important to check for proper scroll compressor rotation up front! Reverse rotation for over an hour may cause the compressor to pump the oil out of the bearing pump. Of course running the unit without oil damages the unit. Verifying proper compressor rotation upon start up prevents this damage.
You can verify the proper rotation by observing the refrigerant suction pressure and the
discharge pressure when the compressor is energized. An elevated sound level or “odd noise” also indicates reverse rotation, but newer scroll compressors don’t rattle when run backwards. Therefore, sound is not the best
way to determine if you have a problem.

[jstch00tme]

the first time the unit ran the guages responded properly ( discharge increase, suction drop) sound was normal.....when i did reverse two leads and run it backwards the guages responed acordingly (no change in pressure) as i understand it this new copeland scroll has protection against running backwards and will only alow it for apx 1-2 min. before shutting itself down anyway so im confident this is not the case here.

[jstch00tme]

you have a strong point with the 4-way, going threw this in my head i am thinking a passing 4-way would feed liquid back into the accumulator, at wich point it would become full then the liquid would go back to the compressor, not so much changing the pressures but the non condensable liquid is now choking the compressor causing the sound change and the excessive amp draw untill it fails.....sound rite?

[nike123]

the first time the unit ran the guages responded properly ( discharge increase, suction drop) sound was normal.....when i did reverse two leads and run it backwards the guages responed acordingly (no change in pressure) as i understand it this new copeland scroll has protection against running backwards and will only alow it for apx 1-2 min. before shutting itself down anyway so im confident this is not the case here.

Thats not accordant with your previous statement!

shut down unit dbl check install, reverse two leads make sure running forward, check proper rotation of fans..the basics. OK, hook guages back up. pressures are equilized, start unit up, discharge goes from 200 to 250 suction SLOWLY goes down to about 80 BUT then goes back up to about 90, at this point you can hear a change in the compressor, its strugeling, and the amps confirm the sound, they go from 30 to sixty+ then the compressor shuts off

What was the case? If you had at first pressures as you said first hour, why did you changed rotation direction?
Or, you are saying that you reversed two leads and find out that compressor, with reversed leads, in fact, running backward, and then, you put back leads as they are before this reversal and that way you confirmed that first leads position was OK.
That make sense of your previous post!

[jstch00tme]

sorry for the confusion, I was talking with a friend about the situation and although i was a master electrician long before i started playing with refrigeration and was quite sure of the correct phasing,he suggested it, so i did it quickly to appease his curiosity, just to eliminate it from his list as he has more refrigeration experience than i.

[nike123]

you have a strong point with the 4-way, going threw this in my head i am thinking a passing 4-way would feed liquid back into the accumulator, at wich point it would become full then the liquid would go back to the compressor, not so much changing the pressures but the non condensable liquid is now choking the compressor causing the sound change and the excessive amp draw untill it fails.....sound rite?

If you have bypassing 4-way valve, you should have low amp draw (no high pressure) but compressor overheats because of too hot suction gas. There is no liquid when valve is bypassing.

If you have (as described before) low suction pressure (30psi) than you have low amount of gas to cool windings and in 1 hour of work, it may overheat motor.
That was your case, and this later high amperage (???) just added more heat to already overheated compressor.

Start again next day with cool compressor and search for restrictions or malfunctioning TEV. Also check 4-way valve temperature drops.

[jstch00tme]

the latter part of my description ( high suction, loading sound, high amp draw, shut down within 1 min.) is on a cold compressor! went back the next day and tried it again.

[nike123]

the latter part of my description ( high suction, loading sound, high amp draw, shut down within 1 min.) is on a cold compressor! went back the next day and tried it again.

I would remove (replace) 4-way valve and clean system thoroughly with nitrogen blowing before fitting new one. I would also open expansion valve and clean his screen and orifice and check his functioning and flow with nitrogen with cooling and heating of bulb, or maybe change it with new one. Also change filter dryer with new one.
Then commission system by brazing in nitrogen protective atmosphere, pressure test for leaks, evacuate, charge by weight and then check correct functioning.

[jstch00tme]

ah yes...the (shotgun) method! he he he... when in doubt...throw parts at it! ha... I am way ahead of you on that one..lol....I already ordered both items! but was lerious of investing more time and $ when I'm not a "pro" at this. so many variables, not sure of this one...know what I mean? but already have so much $ and time invested, hate to walk away.

Thanks for all your help guys.

[jstch00tme]

but just one more question how exactly do I "commission system by brazing in nitrogen protective atmosphere"?

[nike123]

ah yes...the (shotgun) method! he he he... when in doubt...throw parts at it! ha... I am way ahead of you on that one..lol.

It is cheaper than new compressor!

[nike123]

but just one more question how exactly do I "commission system by brazing in nitrogen protective atmosphere"?

You need to have bottle of nitrogen and pressure/flow regulator. Connect nitrogen on one side and you need to have open port on other side of brazing spot. Open bottle and adjust flow that only small amount of flow at other side is sensed with wet finger. Allow some time to purge air and after that start with your brazing.

P.S.
When purging air you could let some more flow to speed purging, but after that, reduce flow to hardly noticeable.

[jstch00tme]

never herd of that before, is it necessary? what does it accomplish?

[GXMPLX]

Yes, nitrogen is more than necessary not to form oxides in the pipe that won't be easlily cleaned and will eventually end up in the compressor. Check correct solering practices.
The different symptoms you were mentioned here on the 4W valve correspond to different states a fautly valve may be in, depending on where in its path gets stuck. It may be fully open where you won't get compression at all and low amp or it may be almost there where you will get compression, almost normal amps but abnormal high suction pressure and high superheat causing high discharge temperatures. This is the main suspect here. Change it but make very sure you are not overheating it and DO circulate nitrogen. The burnt flux inside the pipe could easily stuck the new valve in an intermediate position.

[Larry2]

here is the situation, 5 ton heat pump package unit , first look we have shorted windings on a three phase scroll compressor, change the compressor and the contactor, evac and recharge back to factory spec., unit runs for an hr. or more cooling but not that great, pressures are not good, 200dis. 30 suction. shut down unit dbl check install, reverse two leads make sure running forward, check proper rotation of fans..the basics.

I think your failed compressor is a consequence of an important problem in the system, perhaps an issue with the metering device or obstruction somewhere in the system. Or you could have water freezing in the metering device from a wet system. You would learn plenty by cutting open the original compressor. It takes five minutes and an .040 grinder disc on an electric grinder to do.

Was this system really clean an dry when you restarted it? Did it get all new driers, or just one added? Was the system acid from the burnt widing, or did the fuse protect the system from an important burn-out? Burned motor windings release a lot of insulation junk that is not easily cleaned out.

When you had 200 discharge and 30 suction, you should have pulled the disconnected and gotten serious about troubleshooting. Running the new compressor longer to see if the system will improve is just going to damage the new compressor and worse yet, you burn the windings on the new compressor, and will have even more contamination in the system.

When you had 200 discharge and 30 suction, there was no reason to swap the phase as an experiment, because the compressor was running the right direction to produce a good discharge pressure. Scroll will take reverse running a while, so hopefully you are okay there if it was only abused it briefly. Wambat is right, they can only take some amount of abuse. They have a planned oil flow that reverse direction may defeat.

I'm not an expert, so take my advice with a grain of salt or two asprins. I would run the system only long enough to look at pressure measurements, make some temperature observations, some observations as simple as feeling the ports on the reversing valve, listening at the metering device and then shutting if off while you go sit and ponder what you find.

An engineer where I worked used to say "problems are solved in the office, not at the bench". What he meant was once you have your measurements and observations, you write them down, you stop tweaking and tinkering and sit quietly in your office to consider your measurments, observations and design. You surely don't start swapping phase on a system that once worked.

You ask why you need dry nitrogen during brazing. First hand observation will teach you why. This should be a required lab experiment for every tech, because the temptation to skip this step is great to make the day shorter. Take some scrap copper tube and a few fittings. Braze them together out in the open air. When you are finished, plunge the assembly into cold water. You will see the burned oxidized copper flakes release from the assembly in large flakes. The same thing happens, creating oxidized flakes inside a system. Without the thermal shock, sometimes it just takes longer for them to turn loose.

Now consider that these bits are also produced on the inside if the tubing if you braze without inert gas to exclude air from reacting with the copper tube. These bits aren't very large. They are huge compared to a refrigerant metering device. They can be pretty hard too. Metal oxides are harder than the base metal they come from. They can be large enough to accumulate inside your metering device and cause a restriction. They can catch in the fine tolerances of the four way valve, where they prevent the shuttle from moving freely. Folks hear this in training "drift dry nitrogen through while brazing" , but until you run the experiment first hand and watch this junk flake off of copper heated to 1300 degrees, it seems like advice that might be skipped if one is in a hurry on a busy hot day. It can't be skipped when you braze. Murphy law says that flake of junk will land where it does the most damage. Skipping this step might be why you are servicing this unit now.

[Peter_1]

never herd of that before, is it necessary? what does it accomplish?

One f the most important steps while brazing.
If you braze without OFN on a Daikin unit, you lost all you warranty.

[jstch00tme]

UPDATE!!! we were all wrong! new TXV new 4-WAY ..... SAME PROBLEM!

[jstch00tme]

also, talking to quite a few pro's around these parts, and not 1 of them drifts OFN while brazing.

[nike123]

Are the symptoms identical or somehow changed now. Are you sure that you did not overheated new 4-way valve while brazing. Do you have check valves. If you have stuck open check valve, symptoms are similar as with faulty 4-way valve.
Also, do you have (or maybe you could draw) refrigerant diagram (like this one) to post here.

[Peter_1]

also, talking to quite a few pro's around these parts, and not 1 of them drifts OFN while brazing.

Well, if they don't use OFN while brazing, they're definitely aren't pro's.
Do once the test for yourself, solder a tube with and without OFN and you will see the difference for yourself.
If you don't use OFN for example with a Daikin AC, you loose all warranty. Just to say....

[Peter_1]

Also Mitsubishi http://www.bdt.co.nz/comfortmaster/info_r410a.asp at the end of the page
and also http://www.bbc-consultancy.com/Hydro...Guidelines.pdf page 27

[jstch00tme]

At this point we have converted this unit to straight AC eliminating the outside TXV, all check valves and the 4-way. the system has three new dryer/filters one liquid at the exit of compressor, one liquid just prior to the indoor TXV and one suction just prior to the compressor return. All of the oil from the old compressor was accounted for, the accumulator was removed and emtyed then re-installed and the system completely flushed with nitro prior to the install of the new TXV. And yet it exibits the exact symtoms : start unit up, discharge goes from 200 to 250 suction SLOWLY goes down to about 80 BUT then goes back up climbing higher and higher while the high side does not change, at this point you can hear a change in the compressor, its strugeling, and the amps confirm the sound, they go from 30 to sixty+ then the compressor shuts off!

[GXMPLX]

If you have no more valves that could bypass gas into suction, the only possibility is a damaged compressor.
What is the model number?