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  1. #1
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    VARIABLE PRIMARY FLOW OF CHW

    Friends, I am involved in a work that evaluating the proposal from an energy saving company, in the proposal they have claimed to install the VFD for primary chilled water pump and water-cooled condenser pump. We have many centrifugal chilled water systems.we know the benefit of installing vfd for secondary and tertiary pump. I spoke with their engineer the logic of vfd which control the primary pump. As I know in variable primary, it will increase the pumping (increasing the motor frequency) and maintain higher delta T . But hear the engineer told me that who will decrease the pump speed. What you thin think?

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    Quote Originally Posted by moideen View Post
    Friends, I am involved in a work that evaluating the proposal from an energy saving company, in the proposal they have claimed to install the VFD for primary chilled water pump and water-cooled condenser pump. We have many centrifugal chilled water systems. ..........
    What you thin think?
    Contact the manufacturer(s) of your equipment & see what they have to say about altering the water flow rates on their machiene(s).
    Eric

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    Quote Originally Posted by ESokoloff View Post
    Contact the manufacturer(s) of your equipment & see what they have to say about altering the water flow rates on their machiene(s).
    the chilled water delt Twill be low at low cooling load, then how again would be decreased the water flow to chiller. As I understood, usually increasing the water flow at low load in order to decrease the low delta T syndrom.

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    variable speed on the chilled water side of the chiller has a lot of benefits...the same benefits we see VFD technology being used elsewhere...it works. the difference here is the "rate of change" of the flow rate. if the flow rate changes too quickly, the chiller will not respond well. most HVACR systems are slow to begin with, however, some building automation programmers barely know how to program let alone how it affects a system. there needs to be A LOT OF TALK between the BAS company, the manufacturer and yourself so that everyone involved is on the same page. everyone will blame everyone else and say it is the other guys fault if something goes wrong...so get it in writing first.

    don't install VFD's on the condenser water side of the chiller. i am unaware of any chiller manufacturer that is ok with this. if they are using the VFD as a "soft start", then that will be ok, but it is an overkill for the cost of the starter.
    Don't step on my favorite part of the Constitution just to point out your favorite part.

    Political Correctness is forced on you because you have forgotten decency.

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    hmmm why no vfd on condenser pumps vs bypass actuator? I take it youre referring to centrif chillers Jay?
    Keep it simple to keep it cool!

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    Quote Originally Posted by jayguy View Post
    variable speed on the chilled water side of the chiller has a lot of benefits...the same benefits we see VFD technology being used elsewhere...it works. the difference here is the "rate of change" of the flow rate. if the flow rate changes too quickly, the chiller will not respond well. most HVACR systems are slow to begin with, however, some building automation programmers barely know how to program let alone how it affects a system. there needs to be A LOT OF TALK between the BAS company, the manufacturer and yourself so that everyone involved is on the same page. everyone will blame everyone else and say it is the other guys fault if something goes wrong...so get it in writing first.

    don't install VFD's on the condenser water side of the chiller. i am unaware of any chiller manufacturer that is ok with this. if they are using the VFD as a "soft start", then that will be ok, but it is an overkill for the cost of the starter.
    thank you, what is your concern about variable flow for primary pump. secondary is ok.agreed. when you reduce the flow rate of primary, what will be the effect on chilled water delt T and whole performance of the system.it may cause to low delt T system. i have seen some presentation for the variable primary, that is increasing the flow rate and maintain delta T.
    Attached Files Attached Files

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    Quote Originally Posted by stanbyyourword View Post
    hmmm why no vfd on condenser pumps vs bypass actuator? I take it youre referring to centrif chillers Jay?
    Bypass actuator (when piped Correctly) does not alter flow rate through condenser.
    Eric

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    That report is more then 10 years old (January 16 2007).

    If this procedure had such benefit I would think it would be (more) mainstream (known/used) by now.

    Have this conversation with the manufacture(s) of your equipment.
    Eric

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    Variable flow primary chilled water systems have been around for some time. I am fairly sure that the innovator of that system was Tom Hartmann and his system is called the Hartmann LOOP. Peruse his company's website and see if you don't get the information you are seeking.

    I initially was against varying condenser water flow, but after seeing the results I begin far less of a skeptic. When CHW demand is down, it isn't necessary to have design condenser water flow at extremely low condenser water temperatures. My mantra for condenser water temperature on York centrifugals with VSD was "the lower the better". After witnessing a Hartmann LOOP in operation on a chiller plant I maintained I saw that when primary CHW demand was low it was possible to reduce flow in the condenser and raise the set point as well and still see the performance from the chiller VSD.

    I will add this one caveat. Every major control company has tried to jump on this bandwagon and I have seen some disastrous results. I think it's important that the correct company by chosen because it isn't a simple "plug and play" solution. I guess what I'm trying to say is at least check to see if the innovator of this technology can help.

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    yes every chiller plant and type/make differ and everyone chiller tech , controls, consultants all need to be on same platform and know limitations of all to end up with a strategy
    Keep it simple to keep it cool!

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    Quote Originally Posted by ESokoloff View Post
    That report is more then 10 years old (January 16 2007).

    If this procedure had such benefit I would think it would be (more) mainstream (known/used) by now.

    Have this conversation with the manufacture(s) of your equipment.
    no, this is not from these energy company. it was with me given from one senior engineer in Dubai. i am thinking about the logic. which is the prper method that increase or decrese the water flow in primary. energy company say they will decrease the water flow. when i asked them the logic, they dont have even manufacture data! hence, i think they dont have much knowledge about that.

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    Quote Originally Posted by KnewYork View Post
    Variable flow primary chilled water systems have been around for some time. I am fairly sure that the innovator of that system was Tom Hartmann and his system is called the Hartmann LOOP. Peruse his company's website and see if you don't get the information you are seeking.

    I initially was against varying condenser water flow, but after seeing the results I begin far less of a skeptic. When CHW demand is down, it isn't necessary to have design condenser water flow at extremely low condenser water temperatures. My mantra for condenser water temperature on York centrifugals with VSD was "the lower the better". After witnessing a Hartmann LOOP in operation on a chiller plant I maintained I saw that when primary CHW demand was low it was possible to reduce flow in the condenser and raise the set point as well and still see the performance from the chiller VSD.

    I will add this one caveat. Every major control company has tried to jump on this bandwagon and I have seen some disastrous results. I think it's important that the correct company by chosen because it isn't a simple "plug and play" solution. I guess what I'm trying to say is at least check to see if the innovator of this technology can help.
    If you have any performance data, improved the cop, please share hear after providing the VFD for condenser pump. It will be a reference. How do you prove it with refrigeration cycle that the theory is while decreasing discharge pressure it increasing the COP

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