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cwwilson721

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Reply with quote  #21 
Wouldn't it be simpler/cheaper to have a temp-controlled flow gate? Temp probe, hooked to a controller, and have the controller change a variable-opening gate valve?

That way, you set the output temp, and to raise the temp, the valve closes some...To drop it, opens it up.

Easier/cheaper than a variable pump. Pump runs the same , you throttle the water flow instead with existing tools

Something to think about

Garage_Hermit

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Reply with quote  #22 
@KEN

Hi, Ken, thanks for the input !  That PCB controller of yours looks very affordable !

I read you for the relay drive method, rather than PLC (guess I was just going for the  Big Dream System [redface] ).

Couple of questions: I guess your PCB controller works by issuing a variable frequency output to the pump motor ?
However, what is the card *input* ?

Looks suspiciously like "manual speed adjustment" over on the right there...
If this is the case, I figure it looks kind-of "no-no" re "automatic" speed control ??

So the question is, would this card take a temperature sensor ?  I guess not...

As I see it, the temperature being sensed is the *differential* temp (or more precisely, a derivative temp...) between the *store* output temp, and the *collector* output temp...

(because we don't want to be sending precious hot water from our store, to the collector, if the latter is not able (due to solar heat level...) to make it any *hotter*).
 
(I am assuming that the store temperature is homogneous (due to circulating of water through it...) , but this might not necessarily be the case, there could be some stagnation in there...).

Still, this is good food for thought !
=============
Also get what you mean about project saturation !
When I did my logic diagram, I was on the one hand trying to respond to the orignal post about the need for variable speed pumping, and on the other hand, get my ideas sorted for my own hydronic set-up, which threatens to be a monster !) and which is still evolving (on paper at least) (I am still reclaiming my Crawlspace for the moment...).

I guess I had not thought of an alternative control method to motor speed, namely, variable flow through valving...
which brings me on to

@CARL

Nice idea on the valve !  Guess it could be controlled by PWM, like on an automobile air throttle...

Which opens up a whole new can of worms here, namely, looking at BORROWING off automobiles, and adapting to solar, à la AIR COOLING FAN !

Going to have to drag out my old course notes and swat up on these things !

more later !

G_H

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KenD

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Reply with quote  #23 
The card uses an imcluded thermocouple as the input. The adjustment you see is for a maximum speed you want the driven device to run ( think of it as a calibration pot). I have ordered one of these and a 15 kHz step less motor controller that will handle up to 5A to see if I can use this to run a larger pump. I have the next 4 days off (I work 96 hrs on, 96 off). If I can find a little time I will see if I can't come up with a scheme that uses cheap commonly available parts to do what we are discussing and put it to paint and post it.
Garage_Hermit

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Reply with quote  #24 
Great news, Ken, thanks for the info !
That is the icing on the cake, then : and  all for 13 dollars !

Look forward to see the results of your labors !

Best regards,

G_H

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cwwilson721

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Reply with quote  #25 
@Garage_Hermit

Yes. A PWM, or stepper actuator for the flow control.

Since we're DIY, and car parts are generally cheap, I don't see why not...lol

This way, you set the temp for the collector output you want, and the actuated flow valve does the rest.

Of course, then your carefully setup pump might be doing less, or more, gpm than you thought you needed.

But, I figure that a actuated valve would be simpler to control than a continuously variable pump. Plus, would save 'wear and tear' on the pump itself.
Garage_Hermit

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Reply with quote  #26 
Er...

FWIW, just thinking aloud, re salvaging of automobile parts...

- opting for proportional valving (CARL), we are looking at an automobile cooling system (a bit like Gary at BIS is/was using in his greenhouse...), because it contains the thermostatic valve we want...

- if opting for proportional pumping (KEN), we are looking at a variable-speed coolant pump...

  • The problem with the VALVING approach, is that generally these thermostat valves are *temperature-controlled* - bang-bang / ON-OFF (coolant temperature below (say) 80°C = valve CLOSED: coolant does not go thru the radiator; coolant temperature above 96°C = Valve OPEN: coolant goes thru radiator) etc.
  • Therefore impossible to proportionally control the thermostat valve: it controls *itself*, depending on the temperature it senses.
Translation: thermostat valve not suitable for our application

  • For the PUMPING approach, we would need to find an electric water pump (& not a mechanical one, driven by an accessories belt off the motor...)

or this one , which is similar... 24V Brushless Electric Car Water Pump single speed or a 24V  Variable Speed Pump

These things cost around 60 USD.

CONCLUSION:  Taking the AUTO SALVAGING route, the variable-speed pumping approach looks easier than the valving approach.

==============

to be continued

G_H
=============

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Garage_Hermit

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Reply with quote  #27 
I had an afterthoght about the VALVING (rather than pumping ) approach...

As I see it, valving is actually extraneous (it means adding an extra item into the circuit...).
(sorry, Carl...) [frown]

In effect, the hydronic circuit demands a pump, but it does not demand a valve...

Therefore in purist terms, variable-speed pumping ought to be the way to go for our desired application.

Nonetheless, just for the exercise, I looked around at other valving possibilities, FWIW...

Since AUTOMOBILE is (apparently) no-go, I looked first at central heating...

with this...

http://www.upperplumbers.co.uk/images/Text/central_heating/Thermostatic-Radiator-Valve.jpg

This is already pointing the hydronic installation towards space heating, rather than DHW...

A similar unit is available for hydronic floor heating.

A variant could be sourced on a fan-coil unit (FCU).
=================
For a DHW application, most thermostatic valves seem to be employed for mixing and scald-protection... Read: ON/OFF... therefore no-go for our purposes...

What is required is a slide valve, solenoid controlled via a PWM package.
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQfmvRaeb9TNafVUnpsSeW96whJdPFn11ZYWt7dm4h5FAJIy3E3
However, the more I go down this road, the less I like the idea - I want to keep coming back to the PUMP, because logically this is where this level of kit belongs, IMO...


CONCLUSION: for proportional flow control in an hydronic circuit, we should be looking at variable-speed pumping, and not valving.

But that is only my opinion...

G_H

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Ky-Jeeper

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Reply with quote  #28 
http://www.amazon.com/Grundfos-Alpha-59896833-Variable-Circulating/dp/B004MSON4U Would this be of help?
Garage_Hermit

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Reply with quote  #29 
Thanks, Ky-Jeeper.

I dug out the technical datasheet for this - here:  http://ca.grundfos.com/content/dam/GCA/Data%20Sheets/ALPHA/ALPHA_General_Data_0311.pdf

It looks like we are getting there, but it is not exactly what's needed, as I can't see how it is fully proportional - it employs 3 fixed speeds and 3 constant pressure settings.

They don't say much about the "auto adapt" feature; I guess it plays with (modulates...) the pressure and the speed; but where is the temperature detection ?

Mebbe this is where Ken's printed-circuit comes in...

Thanks for the pointer anyhow, I  hope this will draw more comment.

G_H

P.S. Answering my own question: temperture detection is not necessary: the temperature is determined by the man in the loop, turning the thermostat setting down; the circuit pressure therefore goes UP... tis would be bad, because the pump is now pushing against a closed valve... However, this smart feature senses the pressure rise, and alters the mpum peed accordingly - "self-adaptive control"

Cf. video at Item #55 below ...


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cwwilson721

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Reply with quote  #30 
PWM controlled, variable 12v 2000L/h pump:
http://www.ebay.com/itm/Brushless-Dc12V-Magnetic-Drive-Pump-528Gph-Motor-Speed-Variable-0-100-50C-1240-/390818548093?_trksid=p2054897.l4275

Ain't REAL cheap, but comparable to a good topsflo.


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