I suspect each chiller has input for âload limitâ. This can be analog (0-10 VFD, 4-20ma) or communicated via BACnet, Lon, etcâĶ Ideally, the BAS would start lag chiller and limit running chiller, hold both with limit at say 50%, then slowly ramp limit so machines load together. Take a look at schematic and see if there is terminals for load limit signal.
Are both chillers designed to run together? Your chilled water entering is 46F -48F. You have no load in the building or your bypass is having an issue.
@@HVACLife I think whatâs happening is with both running or both running with no load in the building. Itâs causing the CHW loop to go wild. Even the discharge pressure was low and suction pressure higher. Like you lost mass flow of refrigerant. Try running the condenser water to 80F see if that makes a difference.
Are the 2 comnected by a COM bus , T-Lan Or something? Like does Ch1 know that Ch2 just kicked on or are they completely independent from one another ? Like another commenter asked , cause if they're connected then it could be that whenever Ch2 kicks on , Ch1 goes into a ramping down phase and goes back to minimum load in order to jave both chillers at the same load , and then they can manage the heat load on the Chilled water loop together equally by ramping up and down with very minimal increments . If that is the case then maybe the parameters regarding the ramping down need to be looked at maybe it's been setup in a way that it's to "violent" too sudden . But it all depends on that one If though so maybe I've been rambling about for nothing ð Oh and they might not be physically connected by a bus but it might be the BMS ordering one Chiller to ramp down whenever the other one kicks on too ...
Does the sequence load limit the running chiller when starting the second?
What is sequence loadâĶremember Iâm a VRF dude not chillers
I suspect each chiller has input for âload limitâ. This can be analog (0-10 VFD, 4-20ma) or communicated via BACnet, Lon, etcâĶ Ideally, the BAS would start lag chiller and limit running chiller, hold both with limit at say 50%, then slowly ramp limit so machines load together. Take a look at schematic and see if there is terminals for load limit signal.
Are both chillers designed to run together? Your chilled water entering is 46F -48F. You have no load in the building or your bypass is having an issue.
Yeah they areâĶyeah I think thatâs true but why such vastly different operating conditions ðĪ
@@HVACLife I think whatâs happening is with both running or both running with no load in the building. Itâs causing the CHW loop to go wild. Even the discharge pressure was low and suction pressure higher. Like you lost mass flow of refrigerant. Try running the condenser water to 80F see if that makes a difference.
Are the 2 comnected by a COM bus , T-Lan Or something?
Like does Ch1 know that Ch2 just kicked on or are they completely independent from one another ?
Like another commenter asked , cause if they're connected then it could be that whenever Ch2 kicks on , Ch1 goes into a ramping down phase and goes back to minimum load in order to jave both chillers at the same load , and then they can manage the heat load on the Chilled water loop together equally by ramping up and down with very minimal increments .
If that is the case then maybe the parameters regarding the ramping down need to be looked at maybe it's been setup in a way that it's to "violent" too sudden .
But it all depends on that one If though so maybe I've been rambling about for nothing ð
Oh and they might not be physically connected by a bus but it might be the BMS ordering one Chiller to ramp down whenever the other one kicks on too ...
Wonderful idea! I had not considered that but I think you may be onto something there!!!
im the last one who can say something here, probably its stupid, maybe water pump head of ch2 is too much and its starving of water ch1?
No, that is a really good thought! I mean, it is the only thing that I can think of, but itâs weird that itâs so specific to one of the two ðĪ