Me again!
We have a 110 ton McQuay air-cooled chiller on campus serving a classroom/office building that trips on low flow or low evap temp fairly often. I've learned quite a bit from you guys about hydronics piping since I started working here, but this on is a little different than most of our other systems. Seems to happen at fairly random times and I've only observed it last fall and now in the last couple weeks. From viewing the trend data in the BAS, it appears to usually not make it through an entire day.
I'm currently waiting on O-rings to pull the strainers on the pump diffusers (as I'm sure it has never been done before), so I thought I'd come on here to try and understand the piping of a system like this better.
Little history:
5 years ago the building had a major overhaul where most everything in the CHWS was replaced except for the piping (including the chiller and pumps). Sounds like the chiller has been an issue pretty much since then. A co-worker mentioned something about the chiller control board being changed out and a strainer being cleaned multiple times. Have no records to look at from this time period, so pretty much starting from scratch here.
In looking at the system, the piping seems to be different than what I'm finding on piping examples from various sources.
Here is what we have:
![]()
I honestly can't remember right now which side of the chiller the light green strainer is on. I'm not even sure right now what kind of strainer it is exactly. I think this is the one that my co-worker was talking about being cleaned out because the insulation has obviously been redone since it was installed.
The B&G SRS has a compression tank fitted with an airtrol fitting attached to the air removal port. Instructions for the SRS show it as needing to be installed just before the pumps, ours has the chiller between it and the pumps. Is this set-up OK or should it be changed?
The pumps currently pump "away" from the chiller. Every piping diagram I can find on variable primary systems with a bypass show the pumps pumping "into" the chiller. Which way is best (does it make a difference)? In my head, the by-pass would work better if the system was pumping "into" it instead of "pulling" it through the chiller and this could possibly be part of the flow issue. Or am I over-thinking it like usual?
From what I've read, it seems like the system should flow this way and the SRS should be moved:
![]()
Here is the SoO for the system.
![]()
Chiller minimum flow is 170 GPM
It is a McQuay AGZ125CHSNN-ER10
S/N: STNU100300221
Sticker on unit says it has Benshaw controls. Our BAS is Siemens Apogee and it communicates with the chiller VIA BACNET.
Being primarily a classroom building, there can be a very low heat load in this building at times during the day. A couple times that I noted a few times in the alarm history was around 1130am and 230pm. Might coincide with classes letting out and the building more or less being empty, but I haven't looked that far into it yet.
Am I right to suspect the piping to be an issue or do you think the strainers and low heat load are the most likely culprit? If it's mostly due to the low heat load, any suggestions on a work-around? The only reheat in the building is VAV's supplied from heat recovery our data center Lieberts.
We have a 110 ton McQuay air-cooled chiller on campus serving a classroom/office building that trips on low flow or low evap temp fairly often. I've learned quite a bit from you guys about hydronics piping since I started working here, but this on is a little different than most of our other systems. Seems to happen at fairly random times and I've only observed it last fall and now in the last couple weeks. From viewing the trend data in the BAS, it appears to usually not make it through an entire day.
I'm currently waiting on O-rings to pull the strainers on the pump diffusers (as I'm sure it has never been done before), so I thought I'd come on here to try and understand the piping of a system like this better.
Little history:
5 years ago the building had a major overhaul where most everything in the CHWS was replaced except for the piping (including the chiller and pumps). Sounds like the chiller has been an issue pretty much since then. A co-worker mentioned something about the chiller control board being changed out and a strainer being cleaned multiple times. Have no records to look at from this time period, so pretty much starting from scratch here.
In looking at the system, the piping seems to be different than what I'm finding on piping examples from various sources.
Here is what we have:
I honestly can't remember right now which side of the chiller the light green strainer is on. I'm not even sure right now what kind of strainer it is exactly. I think this is the one that my co-worker was talking about being cleaned out because the insulation has obviously been redone since it was installed.
The B&G SRS has a compression tank fitted with an airtrol fitting attached to the air removal port. Instructions for the SRS show it as needing to be installed just before the pumps, ours has the chiller between it and the pumps. Is this set-up OK or should it be changed?
The pumps currently pump "away" from the chiller. Every piping diagram I can find on variable primary systems with a bypass show the pumps pumping "into" the chiller. Which way is best (does it make a difference)? In my head, the by-pass would work better if the system was pumping "into" it instead of "pulling" it through the chiller and this could possibly be part of the flow issue. Or am I over-thinking it like usual?
From what I've read, it seems like the system should flow this way and the SRS should be moved:
Here is the SoO for the system.
Chiller minimum flow is 170 GPM
It is a McQuay AGZ125CHSNN-ER10
S/N: STNU100300221
Sticker on unit says it has Benshaw controls. Our BAS is Siemens Apogee and it communicates with the chiller VIA BACNET.
Being primarily a classroom building, there can be a very low heat load in this building at times during the day. A couple times that I noted a few times in the alarm history was around 1130am and 230pm. Might coincide with classes letting out and the building more or less being empty, but I haven't looked that far into it yet.
Am I right to suspect the piping to be an issue or do you think the strainers and low heat load are the most likely culprit? If it's mostly due to the low heat load, any suggestions on a work-around? The only reheat in the building is VAV's supplied from heat recovery our data center Lieberts.
