23xl cold tower startup problems

[bradysmill]

Hey guys,
thought Id put this one out there to kick around.
Have a 1 year old 23xl r-22 chiller installed where an old Carrier Centrifugal used to be.

Problem:
start up in spring and fall = oil loss faults.

Tower piping = no bypass, no lower sumps,just a tower and piping from pump to chiller and tower.

My interputation = when tower water temps are lower than say.....55 degrees f., faults occur due to low head pressure and screw cannot develop oil pressure fast enough to prove oil.(all screws without an oil pump are like this and rely on head pressure not an oil pump) tried changing ramp time and all but can' find anything that will really works short of a tower bypass valve, so......

NOW ---- When I called Carrier, they say that this screw can handle tower water to 45 or so degrees (I think thats what the guy said) I don't think I agree with that figure though.
By the way Carrier is the one that replaced the old Centrifugal with the screw with no tower water control.


What do you guys think---23xl tower water minimum temps???

[freonrick]

i read in one of the manuals that 55 is the lowest temperature to set it at. but it also says to refer to design specs. this temperature is also once the machine is up and running with the chill water temp down where you want it. so if you start the machine with say 70 degree chill water temperature and 55 degree tower water you will never build any oil pressure within 2 minutes and it will go down.

[gasnowman]

sounds like a good job for condenser flow control valve possibly. Let us know how you make out....

[old fitter]

I had a few of these when I worked for C, and I am suprised you also have not alarmed due to low cooler temp.This metering device looks like the raised slotted cover to a floor drain.A liquid line from the side of the cond runs down to underneath the slotted dome,and with pressure changes,lifts the assembly to allow flow into the flodded cooler.With low head pressure it is a race to see if you alarm due to no oil press or low cooler temp as the flow stacks.Its been about 12 years but I think I use to tie the condensor pump start to the optional fan control in the chiller control panel.SO the compressor starts,head rises,op makes and refrigerant flows into the cooler.The panel with its program starts the tower pump and you have it made.Tower fan control is via the sump,and the cond flow switch is time delayed.Also what a PIA watching the oil heater trying to get the sump up so you can restart!I found that if I removed the sump temp sensor wires and touched them across a spare relay coil,my panel thought I was up to temp,and I could restart.A good set of ear muffs and two aspirin made it almost ok.

[old fitter]

Almost forgot,I consider this a wiegh in charge.

[reefermadness]

The differential oil flow is not going to operate with low condenser water (already known)A bypass or flow control is the only reliable way you are going to keep that machine running.
The fan control deal sounds like it might work but the timing wouldnt be consistant at higher loads and such. They got to control head with something some how some way.

[twcpipes]

Since there is no heat source to warm the water up, has the idea of sump heaters been explored since you have a winter shutdown?

[bradysmill]

Can't believe Carrier did this in the first place. The idea of tying the cond. pump on a fan cyle is a thought but saw other chillers do this and was never a big fan of that because of the sudden shock (in this case and others)of the 45 or 55 degree water coming back and hitting the hot tubes. Have seen many tubes stress damaged from this.
My opinion still is the tower valve (that shoulod have been installed when the job was done.

Adding sump heaters would be an idea though. Oil press. would prove and the tower water would start cooling off (VFD Drive on two old MARLEY towers) by flow over the media only since VFD would have fan off until rise in water temp. happens. Tower water would then start warming up and not be as noticable to create any problems.

Hadn't thought of that.

[chiller mekanik]

As everyone has stated, you've got to get the cond. wtr. temp. up. I agree with most of what I have read so far, although that thing about controlling the pump with the c.t. fan output scared me a little. To be clear, I've never tried that before. I don't doubt it would work, I just worry that it would require constant manipulation @ different times of the year. One thing that comes to mind is this: entering condenser water should be 20* above leaving chilled water, period. Example: if the leaving chilled water temp is 45*, then the entering condenser water should be 65* or more, never to exceed 85*.