Trane cvhf770 eductor

[licensed to chill]

Walking thru mechanical room of new account with a pair of Tranes and saw ice on evaporator eductor on both machines.
Any ideas? appears to be returning more refrigerant than oil and bottom of compressor terminal cover sweating.

I logged machine readings and can post if needed.

[Nuclrchiller]

This is normal, if its not insulated.. That line is usually insulated, but I have seen many that are not. That area right there is actually the lowest pressure point on the chiller and will get cold enough to frost over to the point of building up a layer of ice. I've seen a ball of ice as big as a golf ball there. The only problem I've seen from it is it can cause rust to form on the oil tank where the condensate runs down. Like it's started doing on that one.

[Nuclrchiller]

I used to be concerned that the pressure of the ice buildup could create a problem, but I've never seen that happen.

[Nuclrchiller]

I don't believe this is related to the sweating on the compressor terminal cover.

[Healey Nut]

It isnt abnormal to see ice build up on the eductors , you need to keep an eye on your oil temp to make sure all that refrigerant isnt dropping the oil temp to low . How many turns open is the service valve on the evap where the eductor is drawing from . You may want to try closing the eductor valve down and see if the chiller loses oil , if it doesnt loose oil close it some more if you can maintain oil level with the eductor closed then close it off completely .

[tcy612]

When possible, I try to install isolation valves, a sightglass and strainer to be able to see ref flow and protect the eductor from plugging up. I was replacing one of these strainers on a running machine once and decided, out of curiosity, to check the pres on the branch of the eductor... I recorded pressures as low as 24-25in hg. P/T indicates a sat. temp well below 32° with R-123.

[tcy612]

I don't know what the load profile or the application of Licence to chill's
Machines are, but I would be concerned about oil loss/return if I closed off the evap return eductor line if the machine ran an extended time under light load... Whats say you Healey??

[Healey Nut]

I don't know what the load profile or the application of Licence to chill's
Machines are, but I would be concerned about oil loss/return if I closed off the evap return eductor line if the machine ran an extended time under light load... Whats say you Healey??

Like I said .......
if you can maintain oil level with the eductor closed then close it off completely .

And this means under all running conditions .

[Tech Rob]

It's normal for some machines, but it can also mean that the strainer is blocked. I don't have any that I have closed off completely like Graham said, although that is what the factory says "If you can maintain the oil level with it closed, keep it closed". I keep the valve open between 1/4 and 1 turn. If I can get away with 1/4, I think this is better. I think all machines lose oil, and oil loss is usually a matter of a lack of oil return. I suspect that more oil is lost through the vent line than most people think. The suction cover eductor is very important also. Every centravac since the early to mid 80s has a suction cover eductor, but not all of them have evaporator eductors.

[ga1279]

The eductor problem is solved, now about the sweating of the motor terminal box. There should be about an inch, to inch and a quarter of insulation on all 4 sides of the interior of the motor terminal housing sheet metal. The motor terminal plate should not need insulation as it has a low heat transfer rate, unless Trane in their infinite wisdom has gone to a metal plate instead of the material they were using. I know during annuals I find myself repairing the insulation on the inside of the terminal box and also the area around the outside of the motor, temp sensors box and motor information plate. That solves the sweating problem. -GEO

[Nuclrchiller]

There was a service bulletin concerning motor terminal box sweating. It involved adding a heater inside the box and how to wire it up. I never did that, so i don't recall any details. Maybe one the guys here can help with that. Also, regarding GEO's mentioning of insulation, even though he did not suggest insulating the motor terminal plate, if this is a 2300V or higher machine, do not insulate the plate. The glue can possibly create a current path. At least that's what a coworker was told once by tech support in LaCrosse. After a burnout. On a chiller with the terminal plate insulated.

[licensed to chill]

thanks for the replys.
Oil level in tank normal with no foam and oil temp. also normal.
service valve on evaporator opened 3/4 turn.

i guess i will keep an eye on it.
chillers are 4160 volt so i could not take terminal cover off without plant electrician present to see how much condensation if any is inside

[Nuclrchiller]

I wouldn't take that cover off regardless of who's present, without LOTO (locked out, tagged out). I realize you didn't say if it was running or not, I'm just trying to help you be safe.

[Healey Nut]

thanks for the replys.
Oil level in tank normal with no foam and oil temp. also normal.
service valve on evaporator opened 3/4 turn.

i guess i will keep an eye on it.
chillers are 4160 volt so i could not take terminal cover off without plant electrician present to see how much condensation if any is inside

The 4160V duplex I look after doesnt have insulated terminal boxes but it does have a couple of small 110v resistance heaters in the box instead .