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  1. #14
    Join Date
    Nov 2011
    Location
    North sweden, Umeĺ, Where the birches growing without limits.
    Posts
    95
    It sometimes trippin at set point, but often at freeze guard. The pressures is stable and vaporize is following the water temp as it should do. Nothing uncontrolled. My REFCO 4-way manifold has vapour and liquid scales. Checking the gauges several times per year against a digital reference gauge.

    But yeah sure it's flow issues, a colleauge of mine is maybe going to clean the plate exchangers. All depends on the customer.

  2. #15
    Join Date
    May 2002
    Location
    evansville indiana
    Posts
    943
    What's your evap approach?
    assuming the charge is correct per manufactures guidelines.
    Leaving water minus sat suction temperature. You said sat suction was +37 ,what's your leaving water ? 45????

    Example
    45
    -37
    = 8 approach

    Compare both circuits .

    If the approach is normal suspect low flow ,if the approach is high suspect fouling.
    mikeacman

  3. #16
    Join Date
    Nov 2011
    Location
    North sweden, Umeĺ, Where the birches growing without limits.
    Posts
    95
    Faulty circuit
    Evap +37f, leaving water +38,3f app=1,3f

    Correct circuit
    Evap +37f, leaving water +41f app=4f

    what is a correct approach?

  4. #17
    Join Date
    May 2002
    Location
    evansville indiana
    Posts
    943
    That approach doesn't sound out of line .

    The normal approach is something you could find in the machines or heat exchangers design / build documents as it can vary.

    I've seen approaches on fouled coolers upwards of 20 degrees !

    I have another question (s)

    Why is your water getting down to 37? is that setpoint ?

    What is your water temp setpoint? if your running water and not antifreeze your asking for trips at 37, in my opinion.

    Are you controlling temp by leaving water temp or entering water temp?

    What is the freeze trip setpoint ? See next question

    Are you running glycol/antifreeze or plain water?
    If antifreeze can you configure the machine as so and lower the trip setpoint

    I am used to seeing trip points in the area of 36 for water which you are very close to.
    mikeacman

  5. #18
    Join Date
    May 2002
    Location
    evansville indiana
    Posts
    943
    Also re-reading your posts I doubt you are fouled, but it is something to eliminate out of the equation.

    You have a 9 degree td across the "good" circuit and 12.5 across the "fail" circuit

    Read my above post and answer those questions if not only to yourself .

    you may have flow issues, but I still wonder why you are running a chiller so close to the freeze trip point . In my opinion your asking for nuisance trips .

    I would like to see your answer to my questions.
    mikeacman

  6. #19
    Join Date
    Nov 2011
    Location
    North sweden, Umeĺ, Where the birches growing without limits.
    Posts
    95
    Set point is 46f, starts at 53f. It's starting and stopping on inlet temp. Pure water, no antifreeze, no filters or anything like that

    Anyhow, putted some loggers on both circuits. Correct circ having parallell curves, faulty circ having uneven curves, directly the machine starts the outlet is dropping to 37-38f and lays there until inlet temp is correct, or trips on freeze guard.

    Mikeacman: Everything about the set temps etc... is written in previous posts.

    The company that I'm doing the job for have several systems with this type of system and chillers. Just clean freshwater.

  7. #20
    Join Date
    May 2002
    Location
    evansville indiana
    Posts
    943
    Hmmmmm.

    looks like a flow issue but

    Can measure a pressure diff and calculate gpm and compare both circuits ?

    Is your flow fluctuating ? VFD ramping up and down the pump?

    I guess for a temp measure you could raise the setpoint a few degrees until you figure it out.
    mikeacman

  8. #21
    Join Date
    May 2002
    Location
    evansville indiana
    Posts
    943
    Also ,I don't understand why your entering water setpoint has to be that low ....

    What supply temp are you shooting for ?

    Comfort cooling or process cooling ?

    Many ewt controlled systems I see don't have 46 degree setpoints

    Yours may require that but in my opinion that setpoint is begging for nuisance trips when running water and the safety trip setpoints are configured as such .

    When we push that envelope we often run glycol so we can configure for lower temps ... And the fact many of our machines and or piping coils etc... Are outside
    mikeacman

  9. #22
    Join Date
    Jul 2007
    Location
    The Hot South
    Posts
    1,315
    Being that it is controlled to entering temperature, the temperature controller should be a proportional controller (as opposed to a PI or PID controller). A proportional controller has a throttling range which means the setpoint will raise as the load increases. So if the setpoint is set at 46, then at no load or load load, the entering water temp will be close to setpoint. As the load increases, the entering water temp will drift upward. If the temp controller is set up properly for the flow rate you have, the leaving water temp should stay close to setpoint under all load conditions. Most older chillers controlled to entering water temp this way because we didn't have the advanced technology for leaving water temp control which uses PI or PID control. Proportional–Integral–Derivative (PID) control will keep the controlled water temp from drifting upward when the chiller loads so it is used for leaving water temp control.
    If you are setting your entering water temp setpoint at 46 and the leaving water temp is reaching 37, than either you have extremely low water flow, or your temp controller isn't set up properly or isn't working properly.

  10. #23
    Join Date
    May 2002
    Location
    evansville indiana
    Posts
    943
    Good point ,I think he hit it right on the head ........ I would figure being a York chiller configurable for ewt control they would consider that in their control algorithm....

    R123 has a valid explanation that's worth looking into ....

    May be a configurable setting....
    mikeacman

  11. #24
    Join Date
    May 2002
    Location
    evansville indiana
    Posts
    943
    another thought ,,,I have a hard time wrapping my head around things in a text only setting with no live discussion or hands on ...

    Is your compressor loading and unloading properly?
    mikeacman

  12. #25
    Join Date
    Nov 2011
    Location
    North sweden, Umeĺ, Where the birches growing without limits.
    Posts
    95
    You mean starting current etc?

    Anyhow. It's just on/of by a contactor. No magnet valves etc... Circuit just straight basic with condenser, evaporator, txv and comp. Pressure controls... High Pressure and low pressure control.

    No abnormal sounds when it's starting or stopping.

  13. #26
    Join Date
    May 2002
    Location
    evansville indiana
    Posts
    943
    So no unloading ....at all...
    mikeacman

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