19XRV compressor surge/low speed trips

[axe05]

I have 2 400 ton 19XRV's that are about 3 months old. Lately I cannot keep both of them online for more than an hour before one will trip on compressor surge/low speed. Not using CCN; BAS only controls start, stop, lead, lag. I believe CHW setpoint is around 42 (is that too low?). High temp here in Dallas is in mid 90's everyday and I just about need both of them by noon. Per Carrier startup tech I run tower water at 65 degrees and we just did baseline eddy currents and brushed tubes so everything looks good there. At last trip chiller readings were CHW in 51.6, CHW out 42.0, CDw in 78.2, CDW out 84.1, EVAP ref 41.4, COND ref 86.3 and AMPS% 64.9. According to my cheap after market pressure guages there is about a 7.5 psi pressure drop across the condenser. I have VFD's on my Marleys but obviously they run full out with no hope of reaching 65 degree water when it's 93 degrees outside. Any thoughts?

[freonrick]

they should still be warranty. call carrier out to look at it. 42 setpoint should be ok. he may need to adjust it to speed up on low loads. dont make any changes while it is under warranty.

[chillered]

do you have your surge protection set up correctly. i have been adjusting mine for over a year finally got them to run surge free. it looks like everything is doing well on your readings. your delta t1,p1 ,t2 , p2 can be set to correct surging i can help you set them up if you want. i have some graphs that i have made that really helps you determine where you are running and where you should be

[overhaulin]

It is still in warranty, won't they help? Your problem looks like chilled water flow. 10DT evap @ 64% and 7DT on cond. What's the design and was it set at start up?

[axe05]

Good point about the warranty as I have one for 5 years. My service tech is coming out this week so I will have him looking at these things. I would be interested in seeing your graphs. If you like you can email them to me at madkins@geico.com. I'll have to look at the surge protection parameters and see what they have set up.

[hvacr]

Chillered
Those graphs would be great
Thanks

[matt8085]

65 degree tower water sounds low. 42 CWT also sounds low. You're probably logging oil in the barrel.

[chillered]

the chilled water is fine at 42 we run 43 and somtimes as low as 40 . your tower water will do lucky to get to 75 in dallas . i can run 4 -1000 towers and 1 -800 ton chiller and only get 75 in the summer. remember when you have the carrier tech look at your machine they are only going to fix what is going on then. i basically had to start over from factory and graph everything and just constantly adjuct surge protection. if you will also set your min run speed above 80 percent that will also help you until you can figure out the surging problem . i will put it this way it helped me .

[rscamaro]

The 65 degree water is what all of the engineers will tell you to set the condenser water at, period. What are your actual flows across the cooler and condenser vs. what they are spec'd at?

...Ron

[chillered]

delta"t"ltd designed ours at 80. if you run your condenser water at 65 i think that is to cold . carrier will tell you thats too cold . i have had my water to 65 in feburary and it ran great but i noticed that the refrigent temp and pressure got way low almost tripped

[Shophound]

If I recall correctly, my 19XR literature said to set entering condenser water temp no lower than 70 degrees and no higher than 85.

When wet bulb and tower approach go to pot here in Cowtown, I'm lucky to get 80 degrees supply with two towers. When wet bulb is down, like right now, my reset schedule does a decent job bumping the supply condenser water temp down toward 75.

It's probably a bit different on the 19XRV's, but I know my 19XR's are about to surge when the delta P between condenser and evap gets close to 85 psi (typically when there's a tower or pump problem). Low building load with high condenser water temp can also contribute to a surge, but that doesn't sound like your problem. I hope you post back your outcome as I'm curious as to how the XRV's differ in these respects from a constant speed XR.

[chillered]

i have 2 -500 ton xrv's and 2- 800 ton xr. there isn't a whole lot of diffence. although mine are not constant speed i guess that would have a little diffence in the surge protection. it is kind of nice to have a new plant where everyhting is vfd driven huh

[referteacher]

Chillered has you going in the right direction. Like he says, it will take a year to get an accurate surge map made up for your specific conditions at all loads.

If you don't have the origional design conditions, get them from Carrier. As an owners representative they have to give it to you. Sometime they're reluctant to give them to us independents. The specs should show full and especially, part load parameters. Hopefully every 20%, sometimes only every 25%. You will find that anything less than 60% load requires 65 degr tower water. Believe me, it works!!

Of course, this time of the year you won't get that tower temp. So now you are essentially running a fixed speed machine at 60 hz.

Make absolutely sure your water flows are within the specs. These things are that critical. The old days of sloppy installations don't cut it anymore these days.

Remember, it's all about "lift". If that wheel slows down, it looses it's lift big time. That's why the tower temp has to come down. You can also help reduce the "lift" by reseting the chilled water temp higher. You can get any chilleed water temp you want as long as you stay within the "lift" ability of the wheel.

[subcooledone]

Design,design,design. You can't t/s these units without design info. Whats the latest, I hate no fallow up so we can all learn.
With the 19xrv you need to know the speed at said conditions. I'm glad to see someone gets the speed thing (refertearcher). Speed is square to lift (leave out gas density). lets say you had 50* lift and your min speed was 70% (factory default)- .7*.7* 50 = 24.5 your new lift.
you must lower your cond wtr temp or raise your chw spt.
thats why you will see the mp speed up in a surge condition,trying to get more lift.
You can adjust your surge protection set points or raise your min speed but thats a killer-hp is cubed to speed.