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  1. #1
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    Condensing pressure control



    Typically, in North America we have 2 types of condensing pressure controls for industrial refrigeration plants.
    1. Pressurestats. Each pump or fan controlled by its own pressurestat. This is not perfect control but it is cheap $1,000-2,000.
    2. PLC. Condensing pressure control is part of the PLC, but this PLC is not cheap $30,000 - 100,000.
    Does anybody use another approach to control condensing pressure which have costs $5,000-10,000?



  2. #2
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    Re: Condensing pressure control

    So what do you want to have controlled? fan or pump? 1 kw or 300kw?

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    Re: Condensing pressure control

    variable speed drive and pressure transducer, generally prefer Danfoss

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    Re: Condensing pressure control

    Hi Segei
    I totally agree with Magoo. Switching fans and pumps on & off causes pressure swings to the liquid supply line, this creates major instability to the whole system & costs a lot of money to try keep the system under control .
    By the use of speed control (VSD's ) the system is stable, and runs more efficiently, the fans and pumps last longer along with the electrical components as they are no longer switched on/off causing electrical surges as one of the benefits of using VSD's is the soft starter plus with pumps and fans with the VSD the electrical savings can be huge as the power consumption works on the cube rule ie run at half speed with only 12.5% of the power consumed a total win win solution. Most supermarkets in the UK are using VSD technology on the lead compressor on packs , condenser fans, etc to reduce their power consumption. Floating the discharge pressure with the ambient using a VSD further reduces their payback time. Most system controllers these days give out a 0-10 volt signal for use with VSD technology

    When upgrading to VSD usage especially on condensers where the head pressure is lowered or floated with the ambient it is necessary to make sure that the system control valves are compatible especially servo valves.
    One system I was called to sort out was on a Flooded NH3 system, where they used a Danfoss SV float with a PMFL main valve for the level control. They service company had fitted VSD's to the condensers and to the Screw compressors, and had slowly reduced the discharge pressure to reduce their running costs to the max. But they reduced it to a point that the servo action of the SV & PMFL valve become compromised to the point that on the slightly colder days the system failed to work with the lower liquid pressure. To overcome this a Capacitive level rod was fitted with a Motorised ICM valve which solved the problem, so always look at the whole system to make sure that it will still work under all conditions , as mechanical valves have limitations with servo requirements whereas motorised valves just need electrical power
    Last edited by Glenn Moore; 20-08-2015 at 03:42 PM.

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    Re: Condensing pressure control

    Johnson controls have a Quantum LX condenser controller.
    It would have to be at the price range your after

    http://www.johnsoncontrols.com/conte...e_10-08-09.pdf

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    Re: Condensing pressure control

    Quote Originally Posted by Glenn Moore View Post
    Hi Segei
    I totally agree with Magoo. Switching fans and pumps on & off causes pressure swings to the liquid supply line, this creates major instability to the whole system & costs a lot of money to try keep the system under control .
    By the use of speed control (VSD's ) the system is stable, and runs more efficiently, the fans and pumps last longer along with the electrical components as they are no longer switched on/off causing electrical surges as one of the benefits of using VSD's is the soft starter plus with pumps and fans with the VSD the electrical savings can be huge as the power consumption works on the cube rule ie run at half speed with only 12.5% of the power consumed a total win win solution. Most supermarkets in the UK are using VSD technology on the lead compressor on packs , condenser fans, etc to reduce their power consumption. Floating the discharge pressure with the ambient using a VSD further reduces their payback time. Most system controllers these days give out a 0-10 volt signal for use with VSD technology

    When upgrading to VSD usage especially on condensers where the head pressure is lowered or floated with the ambient it is necessary to make sure that the system control valves are compatible especially servo valves.
    One system I was called to sort out was on a Flooded NH3 system, where they used a Danfoss SV float with a PMFL main valve for the level control. They service company had fitted VSD's to the condensers and to the Screw compressors, and had slowly reduced the discharge pressure to reduce their running costs to the max. But they reduced it to a point that the servo action of the SV & PMFL valve become compromised to the point that on the slightly colder days the system failed to work with the lower liquid pressure. To overcome this a Capacitive level rod was fitted with a Motorised ICM valve which solved the problem, so always look at the whole system to make sure that it will still work under all conditions , as mechanical valves have limitations with servo requirements whereas motorised valves just need electrical power
    Hi, Glenn.
    I agree with you except one issue. I will not put VFD(VSD) for water pump of evaporative condenser.
    People usually invest money in something that they understand. For example, they invest in LED light. It is easy to understand, that this light use much less energy especially with motion sensors. Many people don'y understand energy savings in industrial refrigeration and they are very careful about investing in these savings. This is the reason I want to give a customer different options at different prices.
    For example. He can save 400,000 kWh but $200,000 should be invested or he can invest $20,000 and save 100,000 kWh. Sometimes people invest $20,000 and when they see savings they will invest more.

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    Re: Condensing pressure control

    Quote Originally Posted by RANGER1 View Post
    Johnson controls have a Quantum LX condenser controller.
    It would have to be at the price range your after

    http://www.johnsoncontrols.com/conte...e_10-08-09.pdf
    Ranger 1.
    Thanks a lot. This is what I need. I'm concern about the price but I will check it.

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    Re: Condensing pressure control

    Last edited by RANGER1; 21-08-2015 at 10:03 AM.

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    Re: Condensing pressure control

    Thanks Ranger 1.
    I'm just wandering. Did anybody use these controllers?

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    Re: Condensing pressure control

    Pressure controlled frequency converter for fans and temperature controlled frequency converter for pumps.
    I work with ABB products.

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    Re: Condensing pressure control

    http://effbox.com/

    This is a good product with proved savings on large brewery and dairy plants that I have worked with them on to deliver.
    I love the smell of Ammonia in the morning!

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    Re: Condensing pressure control

    Quote Originally Posted by Segei View Post
    Thanks Ranger 1.
    I'm just wandering. Did anybody use these controllers?
    Is it worth finding out price & a few contacts from M&M.
    Sounds like a big player in that region of USA.
    If you know exactly what you want & approached a PLC controls company, they could make one as simple or as complex as you like.
    We always stipulate that we pay them to develop it, so it belongs to us, no secrets, copy of programe etc.
    Is there someone like that in your region?

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    Re: Condensing pressure control

    Quote Originally Posted by RANGER1 View Post
    Is it worth finding out price & a few contacts from M&M.
    Sounds like a big player in that region of USA.
    If you know exactly what you want & approached a PLC controls company, they could make one as simple or as complex as you like.
    We always stipulate that we pay them to develop it, so it belongs to us, no secrets, copy of programe etc.
    Is there someone like that in your region?
    I will get information about M&M.
    Actually, I'd like to find simple PLC from the shelf. Usually, it is much cheaper than custom made PLC. It should have two set points of the condensing pressure. One for operation and one for defrosting. Additionally, sequence of the fans and pumps should be chosen. I ask one company in our region but their cheapest PLC is $30,000. We know how to ave energy but we need tools(not expensive) to implement that knowledge.

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    Re: Condensing pressure control

    Hi Segei.
    I fully understand your concern on costs of any improvements, but your client will understand any costs saving on energy outlays will involve spending money to achieve results. They will base spending on capital expenditure / improvements on recovery period of costs. Generally 24 months payback. Then savings going forward. Cheap options that may or may not achieve savings will reflect on yourself and put your reputation at for false advise. Put on the salesman hat.
    cheers magoo.

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    Re: Condensing pressure control

    Quote Originally Posted by Segei View Post
    I will get information about M&M.
    Actually, I'd like to find simple PLC from the shelf. Usually, it is much cheaper than custom made PLC. It should have two set points of the condensing pressure. One for operation and one for defrosting. Additionally, sequence of the fans and pumps should be chosen. I ask one company in our region but their cheapest PLC is $30,000. We know how to ave energy but we need tools(not expensive) to implement that knowledge.
    We could do it for under 5k PLC & programming included with small touch screen like Alen Bradley 600
    Installation & integration in the system is obviously on top of that.

    I think shop around a bit more.

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    Re: Condensing pressure control

    Hi Segei
    Have you looked at the Danfoss range of AK PC controllers. They are basically PLC's and are expandable to how many I/Os you require.The PC840 can do up to 12 compressors with up to 36 steps of unloaders plus multi fan outputs or a 0-10 volt o/p for invertor control of a mixture of fixed and variable speed fans they have a large range of pack controllers from a small unit the AK Pc 530 up to the PC 840 you then buy the IO modules to suit the job they are very flexible in their application

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    Re: Condensing pressure control

    Quote Originally Posted by Segei View Post
    I will get information about M&M.
    Actually, I'd like to find simple PLC from the shelf. Usually, it is much cheaper than custom made PLC. It should have two set points of the condensing pressure. One for operation and one for defrosting. Additionally, sequence of the fans and pumps should be chosen. I ask one company in our region but their cheapest PLC is $30,000. We know how to ave energy but we need tools(not expensive) to implement that knowledge.
    That seems wildly overpriced, we deliver high end controlpanels for freezing and RSW systems for less than half that price, with integrated condenser pressure regulation through VFD and valve actuators or both, depending on the application.

    Be it a fan or a pump you need to regulate, all you need is a VFD, danfoss, ABB or Vacon, doesn't matter.
    the VFD can be set to maintain a setpoint through a pressure sensor.
    If you require a higher, or different setpoint during defrosting, that is all available through a simple input on the VFD, where you set it to a different speed or a different setpoint.

    you don't need expensive PLC solutions, it can all be done in the VFD.
    -Cheers-

    Tycho

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    Re: Condensing pressure control

    Quote Originally Posted by Tycho View Post
    That seems wildly overpriced, we deliver high end controlpanels for freezing and RSW systems for less than half that price, with integrated condenser pressure regulation through VFD and valve actuators or both, depending on the application.

    Be it a fan or a pump you need to regulate, all you need is a VFD, danfoss, ABB or Vacon, doesn't matter.
    the VFD can be set to maintain a setpoint through a pressure sensor.
    If you require a higher, or different setpoint during defrosting, that is all available through a simple input on the VFD, where you set it to a different speed or a different setpoint.

    you don't need expensive PLC solutions, it can all be done in the VFD.
    Tycho.
    This is really good idea. However, new fan motors and VFD should be bought first. Hopefully, it will work for my customer.

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    Re: Condensing pressure control

    Thank you guys. A lot of info to think.

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    Re: Condensing pressure control

    Is it beneficial to use condenser fan speed control on a 5kW condensing unit, operating at -5C using 404a gas.

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    Re: Condensing pressure control

    Hi Mac
    It all depends on where the unit is placed inside or outside and how many condenser fans involved. If at present you have no fan control at all , or maybe use pressure switches to control fans then it would be beneficial to fit fan speed control, something like the Saginomiya RGE . If you use pressure switches then the fans cutting in and out disturb the system pressures which cause the expansion valve to open and close causing poor system duty, plus wear and tear to the fan control contactors etc. If there is no fan control at all then the variants in ambient air temperature could in the event of very cold winds or snow etc during the winter months cause over condensing and system LP problems due to low differential pressure across the expansion valve. Over the past few years the times I have engineers call me because the cold room temperatures were rising due to the system not running due to low ambients and no fan control with ambients as low as minus 5 deg C. With the cold winters we seem to be experiencing it would certainly be in your customers interest to have some form of condenser pressure control to keep the system working summer and winter

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