I have a Carrier chiller, 30HL series. Now i have no info on the unit at this time, i know i should but i have a few questions. The chiller is 3 yrs old and is installed in a hot deck cold system. Now this chiller has been working fine all summer but just the other day after we fixed the 3 way valve the system tripped on T 133 and T 134 (low ref pressure Circ A and B). Now my question is did the alarms occur because of the 3 way valve? This 3 way valve is tied into a EMS and opens and closes the valve to the cold deck depending on demand for cooling. The system has been operating all summer with the 3 way valve disabled so they would shut the chilled water pump off if the building got too cold. It just seems a bit fishy given the fact we just replaced the valve. And the kicker is we just took over this account and no one has a clue if the system has ever worked properly. Monday someone will be at the site to check out the problem but i figured i would ask just in case someone else has run into this problem. Sorry for not having any info. Any ideas or suggestions would be a big help.
might check to see if the valve is install wrong. what i means is, if the valve is install backwards it will not bypass it wil stop flow.
is this a 3 way chill water valve and if so only one? the reason I say that is if the 3 way valve is allowing the water to go through the coil and ems tells the 3 way to bypass the coil then the chiller may not unload quick enough. If you take the load away too quick the chiller electronics will not shut it down quick enough. If you do have only one 3 way valve I would fix it open to coil and have ems reset the chiller temp to the desired cold deck temp.
There is only one three way valve. In my opinion the 3 way valve reacts slowly so i would think the chiller would have time to react to the change in the valve. The vavle is close to the chiller. Maybe there is something wrong with the chiller but it just seems odd to happen as soon as the vavle was fixed. The valve is working properly. Maybe i am over thinking this.
i doubt it is a problem with the chiller being that after the valve repair you are seeing this on both circuits...
sounds like you have a short loop and need to start working on system controls or chiller configuration help curb these errors... some times you have to get creative...
i would try and see if there was any thing that could be done with the programming on the chiller to speed up the controls... carriers are notoriously slow anyway...
it may be as simple as setting the chilled water setpoint up a little...
set your circuit loading to staged instead of equal and disable close control... things like that...
perhaps see if there is something that could be done with the remote start signal...
if you have a way to implement a chilled water reset... like said before... could help...
after rereading you post again... you mentioned that the ems shuts down the chilled water pump on demand...
ems control of the pump works fine on chiller start but on shut down not so good...
better off to start from the beginning and get proper ems control on the chiller and let the chiller control the pump...
just a few ideas...
It takes three people to do anything around here. Two do the work, one explains to the crowd of people who showed up when they seen smoke and flames.
Is it possible that the chill pump is being shut down on demand while the chiller is still running? This could account for the low refrig trips although I would expect to see freeze trips perhaps. Also, there should be a flow proving device, is there one and is it operating? The chill pump should be the first thing started and the last thing stopped.
you guys hit the nail on the head. The chiller is on "enable" and turns on and off when the pump does. And it all makes sense because if it shuts down due to a no flow condition it won't be able to pump down the system. But it doesn't have a problem on start up because for the first start of the day most of the alarms are reset automatically but if it happens more than once it will lock itself out. I think this should be obvious now, i think?
is there glycol in the loop?if there is make sure that the chiller is configed for brine.
this lowers the suction temp trip point,if your running waterconsider the glycol thing, just had my but bit by that config.
hope this helps
If you do consider glycol do your homework on capacity loss. If the system is close on capacity it could wind up undersized with glycol.
Was at the site again today
OK received a "no cooling call" later today. Went to site and unit was locked out on "T133 and T134". Restarted unit with gauges and tools ready.
I was there for 2.5 hours and no problems. I checked the unit when it was fully loaded. Info is:
Head 250 psi
Suction 76 psi
SH 15 F
SC 11 F
Now i only have the info for Compressor A and Compressor B i didn't write down because i will be back to do some other work in the building Tues.
I watched both circuits while I tested the system. I had it fully loaded with 100% of the bypass closed feeding all chilled water to the cold deck and had the system open the bypass 100% by itself and the chiller was able to unload on its own. The system cycled approx 4 times on its own and NOTHING!!! No rhyme or reason. But the part I love most is when i was about to get into my truck, the condenser is at ground level next to my truck, the unit turned compressor B off and Compressor A started at the exact same time. And guess what.....it freaking tripped. I spoke to someone from carrier and he believes it's a flow issue. Now there is only a pressure gauge on the discharge side of the pump so i have to come up with a way to get gauges on it. It seems ok because when the EWT is at 45 compressor B is running unloaded and pressure is about 70 but if it's loaded at that temp it is about 58. Which leads me to my next question what would the suction pressure have to be in order to trip this unit into T133 and T134? Also the history shows that the system trips in the afternoon when it seems the building is satisfied. Sorry this is so long.
Sorry, unit does not have glycol. The setpoint is 44 with the Zband set to 4. I bumped the setpoint to 48 and it tripped when I was getting into my truck.
you did not have this problem til you repaired the 3 way valve. if your set point is 44 or even 48 degrees, if the circuit is loaded and the 3 way valve decides to switch then you have the leaving water going into the chiller as entering water. if you have a 10 degree delta T, then your leaving water now is in the low to mid 30's depending what flow you have in bypass. this is not a good setup when you have delays built into the carrier controls. I would just fix the valve open to coil all the time and let the cold deck control the chiller temp by reset. this time of year you might get by setting the temp up on the chiller and leaving the 3 way open to coil. just watch your cold deck temp.