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Sourcing a variable water pump controller for RMH heat capture  RSS feed

 
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This may have been covered, but can't find.

I have built my second rocket mass heater, and both work extremely well. I didn't change anything from suggested size formulas or details. Including metal where the fire is in the burn pot-tunnel and riser.  Plus insulated with mineral wool in required places.

My question is, has anyone found a controller for a water pump, that would allow (control flow) minimal gpm when fire is starting, ramping up to much higher flow rates, when fire is at full bore, and then even shutting down completely when fire runs out of fuel and goes out.   (few hours after burn start)  

Would be nice, I am thinking, of being able to maintain final flu temp of 80-90 degree, and scrub as much heat as I can before this final reading.

Don't worry, this WILL NOT be a closed system, so no steam concerns. And this is NOT intended anywhere in the actual stove, like so many have tried to do.  Rather just in the exhaust tunnel area, which in my case is 12' long. The pumping action of the stove/air/fire will have taken place and I won't be cooling any of that area to quick to cause problems.

Just trying to scrub as much heat as I can with water- instead of carrying in 4500-6000 lbs of rock/stone/sand/cob  to a hard to get to location.

thanks in advance.

ps... 35 years ago, I used to be able to buy a controller that did just this, for the solar panels I installed, it had capability of 5 sensors, with the first one being simply, if heated water was 5 degrees warmer than stored water, pump would start, and then the same if below the set 5 degrees it would shut off.   Plus all the variable speeds (up)  as temp spread increased.  I can't find such a controller in todays world. But I suspect something is out there.

Scott
 
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Sure, you could couple a Taco 705-2 (or a 705-3) PLC controller with a Taco 007-F5 "mixing valve". The latter is a misnomer because it is actually a variable speed circulator pump and why I put it in quotation marks. You vary the inputs on the PLC of course, and you can control the pump via various temperatures too. Just set the parameters and it will automatically start...as well as ramp up to the percentage that you need based on what the plc is reading for temps.

What you are asking for is required for hydronic heat (radiant floor heating). Pex supply and other places online should get you want you need.
 
Scott Weinberg
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Just a quick update from the time of last suggestion- 12-24-16   By Travis J.    The suggestion is certainly on the right track.  And the local big box store had the items listed, but of course NO ONE that had any idea on how to set up.  So some reading/research is in order to go this route.      That never hurt anyone.

It also got me to do a "search" for PLC's with temp sensors-  and got a huge feedback.  This may prove the best yet, for the money, but doubtful for the least work as there seems to be companies that have done this for you.  So the classic "one hand vs the other"   Again I will post if I come up the solution that worked for me.

Back to the collection part- even before the controller is figured out.     I wrapped 60' of 1/2 copper fairly tightly around my horizontal flue piping- this filled with water and pumped at slowest volume possible- while I would say the flue temp before the wrapping was hotter than post wrapping, the temp gain in the water was discouraging.    But the cost was minimal to try...and much was learned.  Basically the volume of heated air (flue gas) was zipping by faster than what I could collect...  But what was learned was that I could inter-connect 2- 55 gal barrels, even 10 with great ease and low cost.

Forward progress.
 
Travis Johnson
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Scott Weinberg wrote:Just a quick update from the time of last suggestion- 12-24-16   By Travis J.    The suggestion is certainly on the right track.  And the local big box store had the items listed, but of course NO ONE that had any idea on how to set up.  So some reading/research is in order to go this route.      That never hurt anyone.

It also got me to do a "search" for PLC's with temp sensors-  and got a huge feedback.  This may prove the best yet, for the money, but doubtful for the least work as there seems to be companies that have done this for you.  So the classic "one hand vs the other"   Again I will post if I come up the solution that worked for me.

Back to the collection part- even before the controller is figured out.     I wrapped 60' of 1/2 copper fairly tightly around my horizontal flue piping- this filled with water and pumped at slowest volume possible- while I would say the flue temp before the wrapping was hotter than post wrapping, the temp gain in the water was discouraging.    But the cost was minimal to try...and much was learned.  Basically the volume of heated air (flue gas) was zipping by faster than what I could collect...  But what was learned was that I could inter-connect 2- 55 gal barrels, even 10 with great ease and low cost.

Forward progress.



My boiler system is so high tech that I cannot find people to work on it. Last year I added a zone to the system which upset the balance of the system and ultimately I ended up balancing it out myself. It just takes some adjusting of the parameters. So if you are inclined, do not be put off by the complexity of it. I read the instruction manual (okay, maybe a few times to really understand it), then adjusted the parameters. Through trial an error I got my boiler to work very efficiently. I am sure you could do likewise, but I would stay away from big box stores. Surely there is a local plumbing supply store near you where you get much better help (and probably better prices too)?

As a side note, I wonder if maybe a simple flow control would work for you?

I have to have these on my radiant floor heat because pex loops in the floor vary in length. When the heating system is first "balanced", I have to adjust these flow controls. You are getting too much flow by the sounds. The slower the flow of water, the more heat transfer that takes place, which I am sure you know. On longer pex loops in my floors, I have to slow the flow, and on shorter runs, I have to speed it up so I get the ideal Delta T of 15 degrees. I am talking 1/8 of a gallon per minute here, so when I say slow, it is very slow. I also use 3 speed Taco circulator pumps for my main loops through my floor loops (which is a different circulator then the PLC variable speed circulator called a "mixing valve"), to give me greater control. That might work better for you, but I am thinking a cheap flow control manifold might work best.

I did not search a lot, and could not find a single manifold, but here is a two zone manifold after a super quick search just to give you an idea of what I am talking about.
Manifold

Another cheap option might be to go to a auto parts store and get a thermostat for a cars heating system. In that way the water flow would be blocked off until it reached its set temperature then it would flow, though 160 degrees may be too hot. That is about the temp the bi metal spring opens at.



 
Scott Weinberg
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A few answers or perhaps better said- What I ended up doing.

by having barrels (55gal) used as storage, you can basically have a separation between heated and ready to heat water.    i.e.  if you have six barrels in a line, pulling off the bottom of each going to the top of the next (laid flat) The last barrel to receive water from the RMH is the hottest, and the one being drawn from is the coldest.    This does several things.

1) Allows a very low cost solar controller, do the start/stop of the water pump as the temp difference between inlet and outlet is enough different to be used to turn pump on and off.  12 degrees
2) is as low cost as I could find
3) gives 2630#'s of mass, so that each one degree of temp rise equals 1 btu stored.  give or take a bit.
4) gives easily expandable or move-able mass.
5) keeps the system open with the last receiving barrel having a open fill hole (no steam stop point or pressure build)

I have found with just one barrel, it doesn't take long, for the water going into stove vs coming out, can get much closer to  about 5 degrees apart, thus not really storing much or allowing the controller to do much.  (on/off a lot)  slower water movement equal higher temps, but less efficient --

Everything is a trade off, but this really pulls the heat off beyond the initial burn chamber, thus allowing the stove to do its thing, and the water jacket to do its thing as well.   No different than a COB mass, but perhaps allows less things (rocks and cob mix) to be carried in. Again a trade off, but a workable one.

cheers all and stay warm!

Scott
 
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