# Poor man's variable speed pump



## Nofossil (Feb 13, 2008)

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...


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## Nofossil (Feb 13, 2008)

...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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## Nofossil (Feb 13, 2008)

...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.


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## Eric Johnson (Feb 13, 2008)

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.


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## SteveJ (Feb 13, 2008)

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


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## wdc1160 (Feb 13, 2008)

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


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## Nofossil (Feb 13, 2008)

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.



> I think the switch on this one is a little cheesy.



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



> Are you controlling from the 7260 through the 9700?



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.



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



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.



> Did you choose to put thermal overload infront of the contactor on the circ?



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.



> I am not sure why this is the poor man variable circ.  Can’t it be titled “The poor mans controllable variable speed circ”?



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.


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## wdc1160 (Feb 13, 2008)

> $60 on eBay.



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


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## Jersey Bill (Feb 13, 2008)

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.


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## slowzuki (Feb 13, 2008)

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.


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## steam man (Feb 13, 2008)

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.


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## Sting (Feb 13, 2008)

nofossil said:
			
		

> 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 look forward to that
Thanks for sharing your work


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## Nofossil (Feb 13, 2008)

Jersey Bill said:
			
		

> 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.



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


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## Jersey Bill (Feb 13, 2008)

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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## Nofossil (Feb 13, 2008)

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.


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## solarguy (Feb 13, 2008)

nofossil, you really are a mad scientist lol


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## raybonz (Feb 13, 2008)

nofossil said:
			
		

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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


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## Nofossil (Feb 14, 2008)

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.


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## raybonz (Feb 14, 2008)

nofossil said:
			
		

> 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.



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


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## Nofossil (Feb 14, 2008)

raybonz said:
			
		

> 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



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 ;-)


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## raybonz (Feb 14, 2008)

nofossil said:
			
		

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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


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## Eric Johnson (Feb 14, 2008)

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?


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## raybonz (Feb 14, 2008)

Eric Johnson said:
			
		

> 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?
> 
> ...



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


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## Eric Johnson (Feb 14, 2008)

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.


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## raybonz (Feb 14, 2008)

Eric Johnson said:
			
		

> 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.



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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## Eric Johnson (Feb 14, 2008)

"Relative" moron in technical matters. My talents lie elsewhere.

I'm in awe of you guys.


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## raybonz (Feb 14, 2008)

Eric Johnson said:
			
		

> "Relative" moron in technical matters. My talents lie elsewhere.
> 
> I'm in awe of you guys.



Eric we all have our talents and you certainly have yours!! I will be picking your brain I guarantee it!!

rAY


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## Nofossil (Feb 14, 2008)

Eric Johnson said:
			
		

> 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?
> 
> ...



Ray has it exactly right - my relays replace the manual switch. It's still a three speed pump, but now it can be controlled by the computer in response to inlet and outlet temps.

It does in fact default to the boiler's controller if my controller goes down. In that case, it runs at high speed when the EKO applies power. That's what I mean by 'failsafe'. I've been pretty careful to design everything that way. If my computer went down, everything except storage would continue to work fine - just like it came from the factory, so to speak.

Part of my makeup is that I'm really cheap. This pump with mods is cheaper than the industrial SCR speed control that Jersey Bill was kind enough to reference. I'll be buying one of those for my fan, where I need a lot more control than just three speeds, but I'm more happy with this cheap pump solution. I get a lot of satisfaction in figuring out inexpensive but technically sound solutions to this kind of problem.

To be even more specific, my controller will work fine without the network - all I'll lose is datalogging. Coming from an aerospace background, I'm a little obsessive about thinking of failures and how to minimize the effects.


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## raybonz (Feb 14, 2008)

nofossil said:
			
		

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I'm sure 3 preset speeds will suffice with circulator operation...

Ray


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## steam man (Feb 15, 2008)

I came across this site while researching variable drive stuff for my own project. Looks interesting but I have never seen any of it used. Probably more of a rich man's thing. I'm cheap too-or so they say.

http://www.controlres.com/ac.htm


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## Nofossil (Feb 15, 2008)

steam man said:
			
		

> I came across this site while researching variable drive stuff for my own project. Looks interesting but I have never seen any of it used. Probably more of a rich man's thing. I'm cheap too-or so they say.
> 
> http://www.controlres.com/ac.htm



Looks really cool, but no prices or purchasing info. If you have to ask, you can't afford it.


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## termite (Feb 15, 2008)

Could something like this be utilized to control a pump?  My idea was to replace the pot with a thermistor/resistor network to control pump speed.  I've tried to attach photos of the pertinent pages of the manual.  If they aren't readable I also attached the link.  These are $5 on ebay, by the way.  I bought some for R&D;.  If anyone has any ideas let me know and I'll butcher some of these up.

http://www.kbelectronics.com/catalog_fan_dist_panel.htm


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## Nofossil (Feb 16, 2008)

termite said:
			
		

> Could something like this be utilized to control a pump?  My idea was to replace the pot with a thermistor/resistor network to control pump speed.  I've tried to attach photos of the pertinent pages of the manual.  If they aren't readable I also attached the link.  These are $5 on ebay, by the way.  I bought some for R&D;.  If anyone has any ideas let me know and I'll butcher some of these up.
> 
> http://www.kbelectronics.com/catalog_fan_dist_panel.htm



I think these would work for manual speed control. The Taco is a PSC (permanent split capacitor) motor, ifI remember correctly.

The problem with these is that I don't have enough circuit design experience to figure out how to adapt them to computer based control. If anyone wants to chime in, I'll try it.


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## wdc1160 (Feb 16, 2008)

Solid state switching is ideally suited towards applications in the HVAC world. 
I am not certain the model your espousing for your system.  But, it is going to depend on your circ. 


I am also hazy on how you propose your going to use this in conjunction with thermisors.  But, you definately are hitting on a technology that runs parallel or over what we deem as the "poor mans variable speed pump"


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## Nofossil (Feb 16, 2008)

ABGWD4U said:
			
		

> Solid state switching is ideally suited towards applications in the HVAC world.
> I am not certain the model your espousing for your system.  But, it is going to depend on your circ.
> 
> 
> I am also hazy on how you propose your going to use this in conjunction with thermisors.  But, you definately are hitting on a technology that runs parallel or over what we deem as the "poor mans variable speed pump"



I suspect that termite was thinking about replacing the pot in the KB controller with a thermistor and resistor so that the pump speed would vary with temperature. That probably would work within a range of temperatures. Thermistors are wildly non-linear and you have to limit current to prevent self heating, but it's an interesting idea.

What I want is the same circuit, but with an electrically isolated 0-5V analog input so I can control it directly with my computer.

The Crydom controller mentioned earlier is very close to what I want. It handles a lot more current than I need, the input voltages don't quite match my outputs, and it costs more than the pump. I'll still probably get one unless I can figure a way to use this cute little KB unit.

If anyone can suggest a way to modify the KB to fit my needs, I'll test it and post a writeup on the mods.


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## raybonz (Feb 16, 2008)

nofossil said:
			
		

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You are correct that the Taco 007 is a PSC motor so no speed control can be used on that model pump.. Check out this bad boy they make: http://www.taco-hvac.com/en/product...Circulator/products.html?current_category=194

Ray

Sorry I messed up you CAN use speed control with this motor.. Think I'm going brain dead..

Ray


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## raybonz (Feb 16, 2008)

nofossil said:
			
		

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This may interest you.. check out the spec sheet..

http://web4.automationdirect.com/adc/Shopping/Catalog/Process_Controls/Signal_Conditioners/FC-33

Ray


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## termite (Feb 16, 2008)

raybonz said:
			
		

> I think these would work for manual speed control. The Taco is a PSC (permanent split capacitor) ....



They work manually.  I've played around with that.  The current draw goes up a little when you slow the pump way down.  I'm not sure if the speed control unit is soaking that up (the triac heat sink does get warm) or if the pump motor does.

Nofossil:  If you want one to play with I'll mail you one.


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## raybonz (Feb 16, 2008)

termite said:
			
		

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5 dollars was a real bargain on those speed controls! Were they brand new? You can buy heat sinks for those to protect the speed control from heat failure, if you do add heat sink compound to enhance heat transfer to the heat sink from the control..

Ray


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## Nofossil (Feb 16, 2008)

raybonz said:
			
		

> You are correct that the Taco 007 is a PSC motor so no speed control can be used on that model pump.. Check out this bad boy they make: http://www.taco-hvac.com/en/product...Circulator/products.html?current_category=194
> 
> Ray
> 
> ...



I looked at Taco's variable speed pump. It was around $600 three years ago. That's more than all three circulators in my system PLUS the 7260 controller, A/D boards, additional digital I/O board, relays, and wiring.


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## sled_mack (Feb 16, 2008)

Nofossil,
There are two ways for you to replace the speed pot on that drive.

First is to use a high speed PWM output from your computer.  I'd say 5kHz is the min freq that will run smoothly.  Most high speed outputs are low voltage/current, so you may need a high speed isolating relay (must be solid state, not dry contacts) between your output and the drive.  That works very well, becuase the computer output is isolated from the drive voltage.  The high speed relay is probably going to run about $50.

The second way is to use an analog isolator.  These are common in process control industry when an instrument has it's own power source and needs to be isolated from the computer input.  But, they are generally a bit pricey.  It would work like a champ, taking your analog output (0-10 V, 4-20mA, 0-5V, etc) and converting to the drive's voltage of 0-5V.

Generally speaking motors not designed for variable speed use will get quite hot if run less then 60% of rated full speed.  I don't know if that applies here or not, as I don't know enough about these motors.  But, I would set the min speed on the drive to something like 60%, then use the analog signal to control between that and full speed.  Use a separate relay to stop the drive completely.


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## raybonz (Feb 16, 2008)

nofossil said:
			
		

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Yikes that's an expensive lil devil eh? I could practically replace my oil fired boiler for that much! External speed control is definitely the way to go..

Ray


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## wdc1160 (Feb 16, 2008)

nofossil said:
			
		

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I should have seen that- thanks nofo.

Some of these approaches seem like they are very doable.
I am a fan of having the computer make the final say so(and logging) I have never used a sensor to directly control anything, but having some controls distributed could be a good thing.   

I am not at this stage of development with the control, but I have in the past used Omron brand solid state switches aka "solid state relays" 
by design they made to order when if comes to controling capacitive and inductive loads.  
Depending on the input V and output V you can getem for as little as $3 and unless you have to control obscene loads no more than $15

I think most importantly they are made for applications such as these.  Some of the other electronics listed here may not have been(I haven't checked).  Consequently, you'll find that these will last as long as your boiler.

This is something we defineiatly need to explore more to find the pros and cons of certain equipment, to the pros and cons of distributing the control of these pumps, solenoids and sensors.

Keep up the good work guys.


On my timeline is March 15, I will be doing the tests involving the Omron 3m line of SIP switches.    Hopefully it will be help for next season.


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## termite (Feb 16, 2008)

raybonz said:
			
		

> 5 dollars was a real bargain on those speed controls! Were they brand new?
> Ray



Yep, brand new.  Search for "Solid State AC speed Control for Blower motors" in Ebay.  I paid $4.95@ for mine.  He has jacked the price up to $5.95.  He had a bunch of them when I got mine.  He has three up right now.  They are the KBMC-13's.


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## raybonz (Feb 17, 2008)

termite said:
			
		

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At KB's site they sell them for $19.00 so you indeed got a bargain.. As long as you can desolder the speed pot you should be able to use external speed control once you determine what voltage they're using at the pot you may be able to use 0-5v or 0-10v or even 0-2.5vdc reference all of those being common. It's too bad that KB doesn't make one of those with external reference as an option.. I have used KB DC drives and they work pretty well and are very compact.. Will be interesting seeing who figures it 1st.. My money is on Nofossil..

Ray


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## raybonz (Feb 17, 2008)

termite said:
			
		

> Could something like this be utilized to control a pump?  My idea was to replace the pot with a thermistor/resistor network to control pump speed.  I've tried to attach photos of the pertinent pages of the manual.  If they aren't readable I also attached the link.  These are $5 on ebay, by the way.  I bought some for R&D;.  If anyone has any ideas let me know and I'll butcher some of these up.
> 
> Termite,
> Have you considered R1 as your point for speed control? Once you know the value you could replace R1 with an external resistance if it is standard such as 1k, 5k, 10k, etc. . Being 2 wire it would be simpler to do.. Just a thought..
> ...


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## termite (Feb 17, 2008)

raybonz said:
			
		

> Termite,
> Have you considered R1 as your point for speed control?


No I haven't, but that's a good idea.  That would be a lot simpler mod.  The functionality of the speed pot would be preserved as well to help fine tune for the application.  
Sled_mack mentioned not letting the speed drop below 60%.  The R2 pot would be the place to make that adjustment.


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## raybonz (Feb 17, 2008)

termite said:
			
		

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Looking at the schematic I am wondering what voltage your dealing with. Looks like it will be AC not DC so you gotta be sure that your control device is rated to handle the voltage.. You sure have me thinking!

Ray


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## Nofossil (Feb 17, 2008)

raybonz said:
			
		

> As long as you can desolder the speed pot you should be able to use external speed control once you determine what voltage they're using at the pot you may be able to use 0-5v or 0-10v or even 0-2.5vdc reference all of those being common. It's too bad that KB doesn't make one of those with external reference as an option.. I have used KB DC drives and they work pretty well and are very compact.. Will be interesting seeing who figures it 1st.. My money is on Nofossil..
> 
> Ray



Nofossil is a mechanical engineer, unfortunately. Looking at the schematic, I see three problems:

1) The voltage coming off the pots is AC
2) That voltage is referenced to the 110vac ground - toxic for delicate analog outputs
3) I can't really read schematics

I'm hoping an electrical engineer will look at this and post a simple solution - "You just need to desolder the pot and stick in an AD-97532 optically isolated fribblespatzer."


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## BrownianHeatingTech (Feb 17, 2008)

nofossil said:
			
		

> I'm hoping an electrical engineer will look at this and post a simple solution - "You just need to desolder the pot and stick in an AD-97532 optically isolated fribblespatzer."



If you do that, you'll need to remove the standard capacitor from the PSC motor and replace it with a flux capacitor.  Make sure it's a 5 microfarad unit, though - the 10 microfarad flux capacitors will send your circulator back to the 1950's...

Joe


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## overshot (Feb 17, 2009)

How do the Grundfos change speed? Are they PSC motors with additional windings? I never took one apart.


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## Nofossil (Feb 18, 2009)

OverShot said:
			
		

> How do the Grundfos change speed? Are they PSC motors with additional windings? I never took one apart.



They appear to be just as you say - PSC with multiple windings. Interesting that this thread resurfaced one year later to the day from its last posting. The circulator has been working fine since I started this thread.

I'm now playing with a commercial variable speed controller that looks like a very cost effective way to provide a high degree of control for PSC circulators as well as most fans. Reports to follow at some point in a new thread.


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## Ugly (Feb 18, 2009)

I assume the point of this is to have automation control? I mean computer controlled via digital or analogue interfaces? For a manual speed control I just use the quadrac off a cheap dimmer and add a 40W resistor and a triac and I'm off and running. Depends on the draw of the device as to what components you use. I even made a remote control for the old man using this method . In our case it controls the big blower motor that vents the compressors outside. It responds to the same remote control we use for the gas pumps. It literally interfaces by changing the position of a cog up or down to change the output to the blower. He can't handle a computer worth beans but a two button remote is right up his alley (up, down). I could use the same method to control it from anything with a hard wire interface. I know the approach depends entirely on motor type and tolerances.


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## overshot (Feb 18, 2009)

nofossil said:
			
		

> OverShot said:
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> 
> 
> ...



After doing more research. A common way of controlling a PSC motor for multiple speeds is using different tap locations on the capacitor winding. Makes sense. 

Another way to control it is voltage. PSC can go down to 50-60% in voltage and still run well. I wonder, multiple speed settings combined with variable voltage at each setting - sounds like a controller to me. I think the EKO fans do something similar.


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