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  1. #14
    Join Date
    Aug 2002
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    Southold, NY
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    Quote Originally Posted by R123 View Post
    3 GPM per ton is average for water cooled condenser. 2.4 GPM per ton is nominal for chilled water which will give you a 10 delta T At full load. Many new sites have lower flow rates and higher delta T but I agree 30% on VFD is way too low.


    The flow rate is not linier to speed, it’s squared so 30% = 18 HZ which means there is about 5% flow going through the chiller if the pump was sized correctly.


    You’ve been asked this question twice and seem to be dodging it. Are you a chiller tech or maintenance?
    Agreed 2.4 GPM.

  2. #15
    Join Date
    May 2018
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    Thread Starter
    Thank you for all of the inputs to date.

    I'm overseas and I am reliant on locals to perform tasks. If you have been overseas then you know what I face. It is like an electrician walking into a plumbing supplier looking for conduit connectors...who knows, he might get lucky!

    I wish this was simple as water flow but I'm looking for someone who's actually had a similar issue with a York Latitude and/or someone who found something odd to check. This is one of the few forums where I have learned from someone else's headache. My original question was "Something that ISN"T in the troubleshooting guide". Subcooling and superheat point to leaks but no oil signs and especially all four compressors says it is something else. The pumps are fine and even pumps locked at 30% cause no issues with other chillers of same make, size and load. That doesn't say there isn't a restriction. Highers are looking for a quick fix but my gut says they're "f*&ked" with this unit and GC knew it (or someone did or why was unit turned off?

    If anyone comes across something, I'm all ears. As far as the rest, 15+ years as a commercial HVAC-R Tech and 15+ years in commercial/industrial facilities to include ammonia. Not like any of that matters here.

    Absorption units, where the future in is in the past!

  3. #16
    Join Date
    Jul 2007
    Location
    The Hot South
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    How about posting a full log including GPM and full load delta T?
    The 2nd most important amendment is to protect the 1st...

    Free Air Conditioner Sizing Chart

  4. #17
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    Hard to accept that all four compressors are locking out on low suction (they are locking out..correct?) and that all four lockouts are caused by low refrigerant charge. It smacks much more of chilled water flow volume, and/or capacity control concerns with the chiller itself (i.e. It is not unloading quickly enough when load declines) or...and this one is often overlooked but it's a doozy....there is not enough water volume in the entire chilled water loop per ton of chiller capacity. The chiller manufacturer should state what is an adequate level of water volume per ton of capacity.
    Building Physics Rule #1: Hot flows to cold.


    Building Physics Rule #2:
    Higher air pressure moves toward lower air pressure


    Building Physics Rule #3:
    Higher moisture concentration moves toward lower moisture concentration.

  5. #18
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    May 2018
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    Thread Starter
    Yep, everything keeps pointing to low flow. I am most interested in the unloading issue because the system has no true bypass correctly setup. Only thing correct are two 3 ways at the furthest AHUs but they only account for 200 GPM. There are gauges everywhere but not one evap or but or large coil have a single piped to both sides. "A man with two watches never knows the correct time". We are recommending some form of reservoir tank (that will facilitate with bypass) But we remain on the outside looking in while GC, warranty, O&M all point fingers at each other. If I ask any of them what the design DP should be at the furthest point I get a blank stare. The more we peel the onion back the more things we find that just aren't kosher with this install.

    Side note, Any recommendations on a DP gauge. I know we can just pipe two sides together with valves old school way but anyone found a DP gauge that has worked well in providing a simple DP reading? We need to correct about 30-40 in order to start getting accurate pump flows via DP.

  6. #19
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    May 2018
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    Thread Starter
    That would require properly places gauges across inlets and outlets in order to create some sort of log. That is such a novel idea. Too bad GC and Eng have never worked on a chiller to know what they should have on them. Note-we have backflow in the other chillers during Chiller 1 runtimes. There are NO backflow prevention in this system. Flow is from pump>chiller>back flow to other chillers>backflow through other pumps but the majority of the flow goes into the structure. Top it off, every connection points are "Ts" and "Ys" so we also have back pressures and deadheading at some connections. I would imagine fluctuations in flows and demands can exasperate these issues.

  7. #20
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    May 2018
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    Thread Starter
    Correction

    Ts and NOT Ys

  8. #21
    Join Date
    Jul 2007
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    The Hot South
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    I use a Fluke PV350 connected to my multimeter to check pressures. This is a tool, not a gauge left on the system.
    The 2nd most important amendment is to protect the 1st...

    Free Air Conditioner Sizing Chart

  9. #22
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    Quote Originally Posted by HDog View Post
    Rule of thumb. Doesn't work correctly with VSD compressors and pumps on VFD because demand and GPMs are supposed to fluctuate.
    Ah ha! If the chilled water system is variable primary and the compressors are variable speed, there's no guarantee the comps will unload holding hands and singing kumbyah with the chilled water pump unloading curve. If the pumps slow either faster than the comps can unload, or below the lowest turndown ratio of the comps, I would expect low suction trips or freeze lockouts.

    Are all valves at all air handlers two-way, three-way, or a mix?
    Building Physics Rule #1: Hot flows to cold.


    Building Physics Rule #2:
    Higher air pressure moves toward lower air pressure


    Building Physics Rule #3:
    Higher moisture concentration moves toward lower moisture concentration.

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