RTAC 450

[nun]

I have 4 RTAC 450s. They are 8 feet apart side by side. Started having some nuisance trips "high evap liquid level". That was @ 95 degree OSA and it seemed only to be the two inside chillers (2 and 3).Then when we hit 98-100 degrees OSA all 4 chiller went to 110% they started tripping on "high oil temp" . Measured temp between chillers and it was 135 degrees in spots. The job was value engineered and I believe they are a few ton shy(quite afew ton shy). I decided to check charges in chiller 2 and 3. everything looked ok except the subcooling on Circut 2 were both about 30 degrees. What should my condenser aproach be? Any of you guys thoughts will be appreciated.
BTW: MO design temp is 95 degrees.

[cw0682]

nun have ya done any diagnostic tests on your the liquid level sensors on the 2 with high evap level? Sounds like possibility of liquid level sensor sticking. Just something to check that and your AEV. There is test for both in Trane Publication rtac-svd01a-en. This is a must have for working on these units if you don't already have it.

As far as the high oil temp alarms the are definetly getting to hot, We have the same scenario at two differnt plants here we take care of just not as big of equipment.

The chillers in the middle get to hot due to the fact they are just sucking air off the other two.

One thing I would be very very sure to check would be my fans too though. With ambient temps like that dropping 3 or 4 fans on one of those units which is the circumstance that typically happens if you have one go bad. will deffinetly hurt ya.

One more thing I'm sure your not an Idiot but I am so i'm going to share from my expierience. Once I was checking the subcooling on one of these units with no guages, I was reading the Saturated Condensor Refrig Temp off of the ch530 and measuring my liquid line temp and doing the math from there. One word caution there is no Pressure Transducer on the liquid side of those systems. the transducer Trane calls that is the one located on top of the oil seperator on the discharge.

I can't wait till the day the engineers at trane start consulting me before making decisons. Any how good luck wish I could help ya more, but i'm learning on those machines too.

[Healey Nut]

RTAC Read the IOM those unit are to close together causing short cycling of air off the condensor. thats what those installation intructions are for. Thats the bit the installers forget to look at and read. Graham Trane tech.

[cw0682]

Grahm just curious what IOM manual you get that out of I am going to have to get me a copy because publication rtac-svx01c-en says 4 feet.

[duke of earl]

4 feet is ludacris! Trane has screwed up royally to print such nonsense. Take an air temp measurement away from the chillers and then air entering the condensers. If the temp is warmer entering the condensers than there is hot air recirculation. Someone should have questioned this before proceeding with the installation.

[cw0682]

I agree 4 feet isn't enough We have 3 here at a plant with exactly that between them and we too have been fighting this problem.

As far as an cheap fix garden hose and a some sprinklers.I
doubt nun's customer is going to like it to well if he goes in there and ust flat out tells him Trane is idiots the installers are idiots and well your going to have to shutdown for a few weeks so we can move these units apart some more.


Get the sprinkler and hose tell them to turn strategically position them to keep your coils wet and tell them to turn them on when its over 95. If they want to pursue the proper fix well this will be a temporary till it can be resolved.

[nun]

The sprinklers are all ready there. I had to keep them running when it was 102 degrees. I have not done the test for the level sensors because they have all tripped on it one time or another. The two in the center have tripped more often. I believe it is either part of the undersize problem or maybe the units running so much the exv is loosing calibration. I do have a SB on spacing of the RTACs. According to it I am loosing 1% capacity at 8 feet apart. Fans are all good. I found one blade cracked. The costomer is talking about putting a roof from chiller top to chiller top to stop some of the short cycling. CW, I do check everything with my gauges and my fluke 54. That is a good point though. Duke, you know the installers only put it in the way the engieer draws it up. Most are unaware of spacing. Occording to O&Ms spacing is correct.
Thanks guys

[acjourneyman]

A roof is going to make it worse because than you will restrict air flow, if anything , put 6' of exhaust plenum on them.

[Healey Nut]

RTAC yes your right the IOM does say 4ft but thats assumming very low wind speed . also are the units surrouded by any sort of wall or wind break. I have 4RTAA"S in a small area close together surrounded by a wall and every summer same problem low oil flow diagnostics due to hot air reciculating off the condensors, only solution is to move units further apart.

[gottawork]

Water on the coils? What about the calcium/lime and other minerals that will scale on the coil surfaces?

[scott123]

If you put water on the coils, they will get trashed. I wouldn't do it. Set the current limit down and try to keep them on-line until location changes can be made.

[duke of earl]

I agree with Scott. No water on the coils.

[nun]

The IOMs say To space chillers min 8ft apart when side by side the SB says do not put more then 2 chillers side by side and if you must to put them 16ft apart. Now, why didnt the IOM say that. How many contractors have SBs? I think moving the chillers is a major deal. First in cost next in space limitation. Scott I am limiting current right now. Im just worried we may not make Temp when it gets above 100 degrees. It will get a little more life out of the compressors and hopefully keep unit from shutting off on high oil temp.

[bertoh]

nun, maybe nothing wrong with liquid level sensors. if you are sending hp gas with little or no subcooling to exv, as soon as it enters evap at 30 saturation temp, it is probably cooling to a liquid state first before it flashes too a gas and stars refrig effect. just a thought, it sounds like you have enough other problems to handle first, good luck

[nun]

Well started to clean condensers today found a section on one chiller clean. Somebody pulled a wire off and neatly tucked it in the wires to the condenser fan motor contactor. Two fans were off due to it. I think that solved one of my High oil temp trips. Next we put a tarp in between two chillers. The high side dropped almost 30 psi. I think it solved our air recirculating problem. (Temp Fix) I still keep getting High evap liquid level alarms on one. I will wait til temps go below 90 degrees load it up and check SH and SC to make sure it is not overcharged. These chillers sit directly below a major highway. Can you say dirty? Does anyone know what cond approach I should look for? Rob are you still around? I did pay attention but cant recall you saying what temp to look for.