killing our scrolls? help

[Gary]

What troubles me is that everyone would rather take a wild guess than take an accurate measurement. I would rather figure out what's wrong than compile a list of possible problems.

[ENERGY KNIGHT]

ok 90 degree air going into condenser 110 degrees leaving but the at bottom of the coil (in what i think is the 7 degree subcooling circuit) the temp is about 103 degrees. you can really feel the temperature difference. the pressure going into condenser was 320 and leaving was 290 the pressure going into reciever was also 290 so no drop in line. the dryer has just been replaced when we put in new compressor and new r-22. only an hour of run time on it. the pressure just before compressor runs 55-60 and we have 40 degree water running through chiller barrel. I have slowed the water pump down to maintain a 9 degree delta-t so we either run pumps fast and have low delta-t or run pumps slower to get good delta-t either way we have 55 - 60 psi on low side. the condensers are outside and compressors ,reciever , and chiller barrel are inside all about the same elevation.

[Gary]

ok 90 degree air going into condenser 110 degrees leaving but the at bottom of the coil (in what i think is the 7 degree subcooling circuit) the temp is about 103 degrees. you can really feel the temperature difference. the pressure going into condenser was 320 and leaving was 290 the pressure going into reciever was also 290 so no drop in line. the dryer has just been replaced when we put in new compressor and new r-22. only an hour of run time on it. the pressure just before compressor runs 55-60 and we have 40 degree water running through chiller barrel. I have slowed the water pump down to maintain a 9 degree delta-t so we either run pumps fast and have low delta-t or run pumps slower to get good delta-t either way we have 55 - 60 psi on low side. the condensers are outside and compressors ,reciever , and chiller barrel are inside all about the same elevation.

The condenser delta-T is 110-90=20F. This should be no more than 30F dT... so there is plenty of airflow for the current load. No problem there.

In situations where the receiver is in an area that is warmer than the outdoor temperature, the pressure in the receiver can exceed the pressure in the condenser, causing liquid to back up into the condenser... a big problem in cold weather. This can be resolved with an equalizer line from the top of the receiver to the top of the condenser. Supermarket people are very familiar with these. An alternative is to put the receiver outdoors.

Your condenser is filled with liquid. This system is waaaaaaay overcharged. I would remove refrigerant until the saturated condensing temperature (SCT) is no more than 35F above the ambient temperature.

Here is a pressure/temperature chart:

http://www.refrigerants.com/pdf/URI-0342_PT%20FINAL.pdf

For R22 at 320psi, the SCT is about 136F. This is about 136-90=46F TD. Way too high.

After removing the excess refrigerant, take new temperature and pressure readings and let's see how it all looks. We also need to know the line temperatures leaving the condenser, leaving the receiver and entering the TXV.

Will removing the excess refrigerant resolve the problems? No. Hopefully it will tell us what needs to be done next.

[Gary]

the pressure going into condenser was 320 and leaving was 290 the pressure going into reciever was also 290 so no drop in line...

And what was the pressure after the receiver?

[Gary]

In situations where the receiver is in an area that is warmer than the outdoor temperature, the pressure in the receiver can exceed the pressure in the condenser, causing liquid to back up into the condenser... a big problem in cold weather. This can be resolved with an equalizer line from the top of the receiver to the top of the condenser. Supermarket people are very familiar with these. An alternative is to put the receiver outdoors.

I should add that an equalizer works by gravity. So in order for it to work properly the condenser must be at a higher elevation than the receiver.

The better fix would be to move the receiver outdoors, under the condenser... and if this condenser has a subcooling circuit, the receiver may not be needed at all.

[ENERGY KNIGHT]

it does look and feel like we have a 7 degree subcoolin circuit on our condenser. today i was looking at our sporlan txv and the numbers on it show it is for 40 tons. we have 25 tons. also they are adjusted wide open. it looked like when the valve was closing i would get a clear sight glass and it looks like it opens too fast or too much and instant bubbles. still very confused im trying to get more info thanks for help hope we can get to the bottom of it.

[Gary]

It is possible that the flow is restricted at the condenser exit. The telltale symptom for this is the exit temp being lower than ambient temp.

[Gary]

it does look and feel like we have a 7 degree subcoolin circuit on our condenser. today i was looking at our sporlan txv and the numbers on it show it is for 40 tons. we have 25 tons. also they are adjusted wide open. it looked like when the valve was closing i would get a clear sight glass and it looks like it opens too fast or too much and instant bubbles. still very confused im trying to get more info thanks for help hope we can get to the bottom of it.

Generally, a TXV is able to control down to about 1/3 of it's rated capacity.

As to the adjustment, the TXV controls liquid flow. In this case, there is no liquid at the TXV inlet for it to control, so adjustment is futile.

Set all of the TXV adjustments at the midpoint. You won't be able to get an accurate adjustment until the other problems are resolved.

[Gary]

The flow is restricted somewhere between the condenser exit and the TXV inlet. Temperature readings at various points along this path will tell the story.

I'm thinking pictures would help, too.

[mad fridgie]

Over sizing the valve is now very common with R4*** refrigerants to allow for the bubbles forming. "Glide"
What we are seeing is classic hunting of the valve. hence the clear then wild bubbling. How ever we now come to an old argument (sorry Gary) about sub cooled liquid in a reciever. If we have a dedicated sub cooler with 7K sub cooling, how can we have vapour in a flowing reciever. I think we can not. It must be choker with liquid and is likely to be backing up into the cond, giving you high head pressure "so gary is correct it does look overcharged" I think this is occuring because you are trying to charge to a full sightglass. Which maybe be an issue due to the glide.

[mad fridgie]

[QUOTE=Gary;233598]The flow is restricted somewhere between the condenser exit and the TXV inlet. Temperature readings at various points along this path will tell the story.


I'm thinking pictures would help, too.[/QUOTE
More temp and pressure readings

[Gary]

For all we know, the receiver could be piped backwards. We can't see it from here. We can only "see" it through the description and the temperature/pressure readings.

[ENERGY KNIGHT]

95 deg outside 305psi 140 deg leaving comp. 265psi 122deg leaving cond. (fans obviously maxed.) same 265psi 122deg at ove40 vcp-100 sporlan valve. 55-65psi suction at 52-50deg. 25ton copeland scroll zr300kce-twd-250 with R-22 and mineral oil. I have drawn a nice picture but am not smart enough to get it on here yet one of our IT people even failed me but i am still trying.

[ENERGY KNIGHT]

here is a drawing that might help

[serviceman]

which is the sh and sc? by reading you have in the machine the problem is the vet.

[Gary]

here is a drawing that might help

At the right side in the drawing, it says, "135 deg". Is that the leaving air temperature?

What size is the discharge line?

[mad fridgie]

Discharge temp looks vey low, for the operating conditions "ignore this for the time being". All other high temps seem to matchup with saturation, so seems to be no sub cooling, only pressure drop.
Dare I say "non condensables" just sitting inthe top rows of the condensor, effectively reducing the cond size.

[ENERGY KNIGHT]

Yes 135deg f is what I got coming through the coil I think the line size is 1&3/8 and about the non-condensables I am very confident that we pulled the entire system down for a long time after we put the new compressor in and we used new r22

[texas64]

One has to assume the manufacturer made the proper size condenser. Just from reading these posts, I believe you have poor heat rejection in the condenser coil. So, the coil is clean, not damaged from previous overcleaning or damaged from hail or age? All the condenser fans are on for the particular section of coil? What brand/model # of chiller? What are the temps entering and leaving the condenser coil? Have you cleaned these coils? I really think the refrigerant hasn't subcooled through the coil, hence the vapor/liquid mix through the sight glass. Of course, I am assuming here....

[Gary]

Yes 135deg f is what I got coming through the coil I think the line size is 1&3/8 and about the non-condensables I am very confident that we pulled the entire system down for a long time after we put the new compressor in and we used new r22

"coming through the coil" isn't very clear. If this is leaving air temp, please say "leaving air temp". Is 135 deg the leaving air temp? If so, there is insufficient airflow through the condenser. 135-95=40F dT. The dT should be no more than 30F.

It seems very strange that the temperature did not drop between the condenser outlet and the receiver inlet, especially since the condenser is outside and the receiver is inside... and especially since the TXV is getting enough liquid to control the superheat. I assume these are actual pipe surface temperatures, right?

Discharge line size of 1 3/8 seems small for 25 tons, but the 5psi pressure drop is not excessive. Perhaps others would have a better idea of proper discharge line sizes.

[mad fridgie]

Sorry old age must be getting to me! How many compressors are on this chiller? first post you said 4 out of the 8 comps have failed, Is there 8 compressors on the chiller.

[mad fridgie]

"coming through the coil" isn't very clear. If this is leaving air temp, please say "leaving air temp". Is 135 deg the leaving air temp? If so, there is insufficient airflow through the condenser. 135-95=40F dT. The dT should be no more than 30F.

It seems very strange that the temperature did not drop between the condenser outlet and the receiver inlet, especially since the condenser is outside and the receiver is inside... and especially since the TXV is getting enough liquid to control the superheat. I assume these are actual pipe surface temperatures, right?

Discharge line size of 1 3/8 seems small for 25 tons, but the 5psi pressure drop is not excessive. Perhaps others would have a better idea of proper discharge line sizes.

Size of the discharge line looks OK if only a single comp.

If the condensing is still occurring (which it seems to be doing) then you would not see a drop in temp in the drain leg (cond to reciever)

He has assured us that there are no condensables, not ovecharged.

Physical surface area has been idicated as very similar to others, without a problem. Air off is very warm!

Are you sure the fans are rotaing in the right direction?
Are the blades mounted the correct way on the shaft?
Do the moters have the correct number of poles (are they spinning at the right speed)? Hence the correct airflow

[Gary]

Now that the superheat is in the ballpark, I would adjust the water flow to raise the evap dT up to 10F.

[Gary]

Discharge temp looks vey low, for the operating conditions...

Discharge temp is directly related to compressor inlet superheat. I suspect the 12F superheat shown in the picture is measured at the compressor inlet rather than the evap outlet. The low discharge temp can be simply remedied by tweaking the TXV adjustment. One turn clockwise should be just about right.

[mad fridgie]

Discharge temp is directly related to compressor inlet superheat. I suspect the 12F superheat shown in the picture is measured at the compressor inlet rather than the evap outlet. The low discharge temp can be simply remedied by tweaking the TXV adjustment. One turn clockwise should be just about right.

Under the conditions given I would expect the discharge to be well over 200F, if the measurement was right, then flood back would be occurring, Discharge temp is directly related to suction SH, internal SH, compression ratio, efficiency and comp heat loss

[Gary]

Under the conditions given I would expect the discharge to be well over 200F, if the measurement was right, then flood back would be occurring, Discharge temp is directly related to suction SH, internal SH, compression ratio, efficiency and comp heat loss

And the adjustable variable is...

[mad fridgie]

And the adjustable variable is...

If he has 12F SH at the compressor, then thats OK, so he has either no suction superheat or his temperature discharge reading is wrong.

[Gary]

We are missing one of the key indicators, i.e. the liquid line temperature at the outlet of the receiver.

[sfnz]

check TX valve element, particularly it the valve is welded on , had a few "from new"failures and partial failures there

[chillerman2006]

We are missing .

Your not wrong

This is like the best book I ever read

But some-ones ripped out the back pages !

Do hope Energy Knight returns so you guys can finish

[ENERGY KNIGHT]

sorry. its been a while. I am thinking that the company that "custom built" these condensers (with a strange subcooling circuit) goofed up. just look at the pressure going into condenser and pressure leaving condenser. looking at 265psi and 122deg. with r-22 looks like 0 sub cooling. but if I still had my 300psi and 122deg we would have a lot of liquid correct? the condenser manufacturer is looking back at the condensers and have mentioned that they should have that subcooling circuit. hopefully they will get us a different condenser that works. otherwise we get out the lawyers or the tourch and repipe condenser somehow.

[Yuri B.]

Energy knight, just concerning the mentioned by Mad fridge low discharge SH: does the compressor have a liquid injection line for its cooling?

[Gary]

sorry. its been a while. I am thinking that the company that "custom built" these condensers (with a strange subcooling circuit) goofed up. just look at the pressure going into condenser and pressure leaving condenser. looking at 265psi and 122deg. with r-22 looks like 0 sub cooling. but if I still had my 300psi and 122deg we would have a lot of liquid correct? the condenser manufacturer is looking back at the condensers and have mentioned that they should have that subcooling circuit. hopefully they will get us a different condenser that works. otherwise we get out the lawyers or the tourch and repipe condenser somehow.

That's the real question: Do we replace the condenser?... or do we make it work?

[ENERGY KNIGHT]

there is no liquid injection line. and i goofed i said the condenser manufacturer said we should have that subcooling circuit and i mean to say we should not have that circuit. I really want to re-pipe the headers on the end of the condenser but am not 100% shure on how to do it right.