Announcement

Collapse
No announcement yet.

Chiller doesn't like to run when cold - Any advice?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Chiller doesn't like to run when cold - Any advice?

    We have an older 10 ton chiller mounted on our roof that has been working decently for the past 5 years. We recently replaced the compressor (not cheap) and upgraded to a new refrigerant - R407A. Now, it seems that when the temperatures get below 10F it gets a little testy.

    Basically, if the compressor is working, it will continue to operate to lower temperatures, but once the glycol gets to the set temp and it shuts off, it won't come back on. The local tech indicated that "it wasn't designed for this temp" and he said that if we insulate it, it may help keep the internal temps warmer and help it continue to run when the outside temps are a little colder.

    So... we insulated it and put a heat tape around compressor. Last night it worked till about -10 F outside temp which is good, but once shut off, wouldn't come back on till it reached 10F outside temp. When it wouldn't re-start, I felt the compressor and it was still warm, so it apparently isn't the temperature of the compressor that is causing the issue. Should we be insulating the R407A reservoir as well? Is there anything else that we can do to keep this running at lower temps? We are getting some pretty cold weather here in NY and I can't have my chiller shut down every night.

    Any advice from refrigeration gurus would be greatly appreciated.

    Thx.

    Tom

  • #2
    Do you have the model? Or do you know how the controls are configured? Is it set to come on from pressure or temp?

    Comment


    • #3
      This happened to us after we had our compressor replaced. Everything worked fine until the first winter day, the compressor wouldn't stay on, it kept triggering the low-pressure shutoff. On our system, there is a pretty significantly sized receiver that holds refrigerant. That receiver has a sort of variable capacity in that in warmer environments it will require less refrigerant to maintain system pressure than it will in cooler environments. So on that really cold day, there was no longer enough refrigerant in there to maintain the pressure needed to get past the low-pressure shutoff. This was fixed by simply topping off the system with some more refrigerant.

      In your case, I suspect your hunch is correct. If you insulate/heat-wrap the receiver, it might warm it up enough to get you through the weather.

      Comment


      • #4
        We also had a problem similar to this, except we found that the glycol percentage in our coolant wasn't high enough. The mixture was freezing on the heat exchanger for the refrigerant, keeping the refrigerant from picking up heat and causing low pressure alarm trips. Make sure your glycol mix is adequate for the correct suction pressure of the refrigerant.
        Linus Hall
        Yazoo Brewing
        Nashville, TN
        www.yazoobrew.com

        Comment


        • #5
          Here's a few tips that might help....

          Insulating and heating the Refrigerant Receiver is one of the steps we take on our systems supplied with our extreme low ambient kit option. In addition we incorporate some forced run bypass timers, discharge pressure control valves ("headmasters"), etc.
          You can also partially block off a portion of the air cooled condenser fin surface to minimize air flow across the coil.
          As Linus said, make certain your glycol percentage is correct for this ambient.

          The main reason for cold ambient issues is that the refrigerant wants to remain in the coldest part of the system, in this case it's in the condenser. The challenge is getting the refrigerant flowing on startup, before the unit cycles off on a low pressure alarm.

          Since this unit is R407, it unfortunately wasn't built by us, in a pinch you could still call one of our tech support guys and they'll likely give you a few tips (as expected this has been a big topic of service calls this past week). They can be reached from our main telephone line at 253-735-2631.

          Good luck to you, and everyone else that's enduring this storm- hang in there.

          Jim

          Pro Chiller Systems

          Comment


          • #6
            Thanks for everyone's help... And thanks Jim for offering advice/services on other manufacturers' old equipment. When we can afford a new system, we will certainly be contacting you.

            I moved the heat tape over to what I believe to be the condenser/reservoir and insulated that as well. Along with insulating the individual components, the whole outside unit is now insulated and has a flap on the back that opens when the fans come on and falls shut when the fans are off to help conserve heat. Regarding the covering up of a portion of the condenser fin in the front - along with preventing the unit from cooling down once the compressor kicks off, I suspect that it would make the whole unit run a little less efficient, which in and of itself will help the unit keep running throughout the night. I was wondering whether that would work or not. We have found that if we have beer to crash cool, the unit stays running longer, since the compressor is running more often, thus generating heat, etc etc.

            The worst part is that when the compressor kicks off in the middle of the night, the pump creates enough heat to warm the glycol up, thus warming all of the beer up. Always a bit of a schedule changer when you arrive to that in the morning.....

            I have resorted to just isolating the important tanks in the evening, so when the compressor kicks off during the night, I can still package product in the morning. Then I wait till the air temp warms up to about 10F for the system to kick back on and try to play catch up.

            Looking forward to spring!

            Comment


            • #7
              One thing to take into consideration is the refrigerant change. Some cooling systems operate on a pressure switch since refrigerant temp is directly correlated to pressure. When I was in the field we would have to set these switches to the proper pressure so it would operate the refrigeration condenser at a certain temp in the cooler. If this system works on a similar switch and the setting was not changed or set properly after the refrigerant change over that might be the culprit. For example at 20F R22 is 43.1 PSI and then R407 wont get to 43.6 PSI until the temp raises to 26F. So if the switch is set to turn on at 43 PSI the temp would have to raise 6 more degrees now.

              I could be way off but if it is cooling fine and comes down to temp but then wont come back on in cold ambient temps I would look there.

              Comment


              • #8
                ""The worst part is that when the compressor kicks off in the middle of the night, the pump creates enough heat to warm the glycol up, thus warming all of the beer up""

                This has happened several time to us. Jim have you ever considered adding control that would shut off the circulation pump when there is a compressor failure?
                Joel Halbleib
                Partner / Zymurgist
                Hive and Barrel Meadery
                6302 Old La Grange Rd
                Crestwood, KY
                www.hiveandbarrel.com

                Comment


                • #9
                  Jim have you ever considered adding control that would shut off the circulation pump when there is a compressor failure?

                  We definitely can and have, adding a t-stat that senses reservoir temperature and shuts down the Process pump if temperature exceeds a certain setting is a relatively easy add-on.

                  If you'd like I can have our engineers pull the wiring diagram off your unit Joel and show how this could be field wired in.

                  It's not a standard feature, but looks like we should maybe at least offer as a factory option on all systems. Thanks for the feedback.

                  Jim

                  Pro Chiller Systems

                  Comment


                  • #10
                    Jim have you ever considered adding control that would shut off the circulation pump when there is a compressor failure?

                    Yea, I have often wished for that, along with an alarm feature - IE - send me a text/email when the glycol temps are above a certain threshold...

                    Comment


                    • #11
                      Originally posted by fa50driver View Post
                      Jim have you ever considered adding control that would shut off the circulation pump when there is a compressor failure?

                      Yea, I have often wished for that, along with an alarm feature - IE - send me a text/email when the glycol temps are above a certain threshold...
                      We do have built in alarm features, with email notification, on our larger systems (CA series and larger), just not one tied in to shut off the glycol pump. The chiller controller, with these features, can also be incorporated into our smaller HP Systems- but the cost adder is pretty high.

                      There are aftermarket temperature alarm systems that I've seen customers utilize that are either web or phone driven. Don't have any firsthand units to recommend- but did quick Google search and there is plenty of them to consider.

                      Hope this helps,

                      Good Luck,

                      Jim

                      Comment

                      Working...
                      X