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Poor man's variable speed pump

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Nofossil, Feb 13, 2008.

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  1. Nofossil

    Nofossil Moderator Emeritus

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    For anyone who is so inclined, here are directions for modifying a Grundfos UPS15-58FC 3 speed circulator for computerized control. Note: following these directions is at your own risk. It may void your warranty, curdle your milk, and cause spontaneous defenestration. You've been warned.

    This approach is designed to be 'fail safe': If no power is applied to any of the relays, the pump will be under the control of the EKO controller.

    My control system is designed to drive 12vdc relays. Three relays are needed: two DPDT and one SPDT. Almost any will work - I used Potter Brumfield relays from Digi-Key, part number PB968-ND at $1.90. These are rated at 8 amps. At that price, you can use these for the SPDT relay as well.

    One relay - the 'Assert' relay - switches control from the EKO to my controller when power is applied. The other two relays replace the function of the speed selector switch on the pump, and add a fourth 'Off' position.

    1) Take the cover off and remove the screws holding in the switch / contact assembly. Remove this assembly by pulling it up gently. It is basically an 8 prong plug.

    2) Pry / cut the cover off of the switch / contact assembly. Discard the rotating switch component.

    ..continued...

    Attached Files:

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  2. Nofossil

    Nofossil Moderator Emeritus

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    ...continued...

    3) Reassemble. Install relays and wire according to the schematic below. The pins on the connector are numbered 1-8, with 8 being at the end where the power connectors are. Pins 3-4 and 5-6 are connected in the housing - you will have to provide a jumper for pins 1-2. Make sure you reconnect the capacitor.

    ...continued...

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  3. Nofossil

    Nofossil Moderator Emeritus

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    ...continued...

    4) When you're done, it might look something like the photo below. The neutral and ground wires can plug directly to the original spring clips. The hot (line) goes to relay A.

    You'll need to run 12v wires to the pump to control relays A and B, the 'Assert' relay should probably be in the housing on top of the boiler next to the boiler's controller. The table at the bottom of the schematic above shows the pump operation as determined by the state of relays A and B.

    If the 'Assert' relay is not energized, then A and B should not both be energized - that would prevent the boiler from turning on the pump.

    Tested and works great. If you don't care about failsafe operation, then the 'Assert' relay is not required, and the state table would make more sense if you swap the normally closed and normally open contacts on the A and B relays. That would mean that the pump would be off if neither relay were energized, and on / high if both were energized.

    Attached Files:

  4. Eric Johnson

    Eric Johnson Mod Emeritus

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    Thanks for that nofossil. I have one of those pumps as well as an older Grundfos 3-speed. I think the switch on this one is a little cheesy.
  5. SteveJ

    SteveJ Member

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    Nofossil - very cool! Thanks for the post.

    Are you controlling from the 7260 through the 9700?

    What signals are you keying on and are you going to post at www.nofossil.org?

    Thanks again for the great step-by-step breakdown,
    Steve
  6. wdc1160

    wdc1160 New Member

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    Nofo you animal. You have to have a team of engineers working around the clock.

    Did you choose to put thermal overload infront of the contactor on the circ?
    Nice choice of circs by the way. I am not sure why this is the poor man variable circ. Can't it be titled "The poor mans controllable variable speed circ"?

    Thank you for the info
  7. Nofossil

    Nofossil Moderator Emeritus

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    Thanks for the kind comments. Just trying to make life easier for the next person who wants to do this. Maybe I'm the only one, but I hope there are others.

    Yeah - Nice circulator, but cheesy is really the only adjective for the switch. It felt good to throw it out.

    The 7260 is the computer itself. The 9700 is an 8 channel analog input card that plugs into it. I have two of them to measure temperatures, either from thermistors or thermocouples. In addition to the digital I/O on the 7260 itself, I also added a 64 channel digital I/O board as well - the DIO64. It can drive 12v relays directly.

    At first, I'm going to try and match the speed of the pump to the output of the boiler by simply running the pump faster as the boiler gets closer to 180 degrees. I'll post this writeup and my control strategy on my site when I have a few minutes.

    I didn't do anything with or for thermal overload. There's a little circuitry that's attached to the capacitor leads that might provide thermal protection - I don't know. I left it as it was. All I did is replace the function of the rotary switch with relays.

    Semantics. In my mind, the Grundfos is a single speed pump with a selectable speed. Real variable speed pumps - the ones that can be externally controlled or that have their own controllers - cost fairly hefty bucks. This one was $60 on eBay. The relays are less than $2 each. If you're a cheapskate and want variable speed, this is a reasonable way to do it.

    I've edited the first post to include the relay part numbers.
  8. wdc1160

    wdc1160 New Member

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    love the idea, love the price. I can't wait to a graph of its performance.
  9. Jersey Bill

    Jersey Bill Member

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    Nice modification Nofossil. It was cool that you got the relays to fit inside the pump housing.

    I made a Taco 007 pump variable speed. Following the way that Tekmar controls their injection pumps, from Digikey also, I bought avariable SCR for a heater control. It had an analog 0-10 v input and a 0-120 v output.
    I tried to use it instead of a mixing valve for temperature by controlling the heat exchanger pumps. It did work, but not well enough for temperature control. I had to go to a 3 way mixing valve.
  10. slowzuki

    slowzuki Feeling the Heat

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    If you could get small 3 phase circulators this would be easy, variable speed drives that won't burn up motors are cheap for small applications. I've got a few on my sawmill. Easily programable for feedback control ramping of speeds etc.
  11. steam man

    steam man Minister of Fire

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    I have a Bell & Gossett 220v 3ph 1/6hp circulator and a Cutler Hammer VFD for it (Ebay<$200). I haven't used it yet but intend on installing it in my wood boiler systems primary loop. I have some three way valves and actuators. I planned on using some multi loop Siemens 353's for control. I am just not sure about wanting to go too complex. I came across an electronics manufacturer in Mass. that makes variable speed circuit board drives for small motors, especially for HVAC stuff. I just can't find the link. I'll post it when I come acrossed it.

    Nice job on the poor man's control.
  12. Sting

    Sting Feeling the Heat

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    I look forward to that
    Thanks for sharing your work
  13. Nofossil

    Nofossil Moderator Emeritus

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    Any chance that you have a part number for that Digi-Key SCR? I'd love to have fan speed control.
  14. Jersey Bill

    Jersey Bill Member

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    Its a crydom 10PCV2415. I think I got it from digi-key- either them or Newark electronics.

    Remember that a standard motor does not do very well if you drop the voltage. without getting into the math, the rotor speed is proportional to frequency, not the voltage. If you take a standard induction 1 hp motor and dip the voltage, it will pull more amps to try and output the rated 1 hp. If the voltage drop is too much it will trip the overload, or burn out the coil.

    These little pumps however are high impedance, so they will slow when the voltage drops, within limits. Universal motors are different also. Some small fans, vacuum cleaners, and other kinds of household devices use universal motors.

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  15. Nofossil

    Nofossil Moderator Emeritus

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    Thanks - very helpful. The EKO controller puts out fan voltages from about 90 to about 200 volts (after the stepup transformer), so I expect that this gem would be perfect. Just as with the circulator, I want to be able to control it directly, with a failsafe that reverts to EKO control.
  16. solarguy

    solarguy New Member

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    nofossil, you really are a mad scientist lol
  17. raybonz

    raybonz Minister of Fire

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    I'm impressed at your knowledge so I thought you'd like this link:

    http://web6.automationdirect.com/adc/Home/Home

    You can buy PLC's VFD's etc. at very good prices.. I have used many of their plc's and the software is inexpensive and easy to learn...

    There is a vfd that costs $99.00 that will use 120v input and give 3 phase 240v out!

    Ray
  18. Nofossil

    Nofossil Moderator Emeritus

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    Thanks for the link - it's in my bookmarks now. This stuff is hard to find online, and harder to find in the woods of Vermont.

    A few years ago, I built a 3 phase converter to drive my lathe and Bridgeport. 3 phase motor, some big caps, and a timer relay for engaging the start cap. Works like a champ.
  19. raybonz

    raybonz Minister of Fire

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    Your welcome! They sell serious stuff there. I designed and built an autofill hot melt system and controlled it with their $99.00 PLC including several failsafes.BTW you can download their programming software for free but it's limited to 100 words if I remember correctly.. Are you an electrical engineer or electrician? I am a licensed electrician and did industrial maintenance for 25 years..

    You are running a 3 phase motor with single phase and caps?? Are you sure you aren't just getting enough torque to start and then running it as a single phase motor? It would work but with reduced capacity.. Can you explain how that would work?

    Ray
  20. Nofossil

    Nofossil Moderator Emeritus

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    I'm a mechanical engineer by education, but I went over to the dark side in 1980 when I got my hands on a computer. Downhill since then. I can speak semi-fluent electronics, but I can't design any but the most simple circuits.

    My 'phase converter' uses a 3-phase motor and caps to create a reasonable facsimile of real three phase power. The three phases aren't perfect, but they're pretty close. See schematic below. I don't have a good way to capture a scope image, so you'll have to trust me on this one ;-)

    Attached Files:

  21. raybonz

    raybonz Minister of Fire

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    That's pretty deep stuff especially coming from a mechanical engineer! I assume what you're doing is using the caps to make the phase lead 180 degrees essentially causing phase rotation? I still wonder if the motor is running as a single phase motor with a start winding..It would be interesting to see how it looks on a scope to see what is really happening .. In all my years I have never seen anyone do something like that..

    Ray
  22. Eric Johnson

    Eric Johnson Mod Emeritus

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    Not to hijack the hijack, but I'd like a layman's description of what you've done with that Grundfos pump, nofossil.

    Would it be fair to say that you've replaced a three-speed switch with circuitry that allows an infinite number of speed settings, made by a computer, within the speed range of that pump?

    And if so, how is the speed regulated? Would it be analogous to a computer-controlled dimmer switch?

    What happens to your boiler if your computer network goes down? Does it default to the boiler's controller?
  23. raybonz

    raybonz Minister of Fire

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    It may be none of my business but what he did is control the individual speeds by relay control instead of having to switch the speeds by hand. The relays essentially do what the manual control did so no it's not infinite speed control. You could have infinite speed control by using a variable frequency drive (VFD) but you would have to replace the circulator with a 3 phase motor.. Gotta say that nofossil is one smart cookie! What the grundfos (sp?) is a multispeed motor with predesignated fixed speeds and he controlled them via relay contacts instead of the manual speed selector switch. FYI most vfd's will allow you to run a motor up to 200% speed and many times you can get away with that. The trouble with vfd's running at low speed can cause motor overheating unless a motor is designed with vfd's in mind.. With a low load situation you could probably get away with it though.. I would love to talk to nofossil and discuss my thoughts on this subject. He sounds like an open minded individual hence a great learner!

    Ray
  24. Eric Johnson

    Eric Johnson Mod Emeritus

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    I'll second that.

    Actually I have spoken to nofossil on the phone, but he didn't realize that he was dealing with a relative moron, so it was hard to keep up my end of the conversation.
  25. raybonz

    raybonz Minister of Fire

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    Eric you are far from being a moron in my mind one who assumes things is a moron! I hope I wasn't being intrusive as I was only trying to help...


    Ray
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