3 Speed Circ Control Automatic

[jebatty]

An idea to automatically control a 3 speed circ. Mine has a manual switch for L-M-H. I haven't pulled the switch apart yet, but it seems to me the following would work to automatically "modulate" the circ from L to M to H depending on water temp with the following simple circuit. You could use any temperature controllers, from strap-on aquastats to something more sophisticated.

Example: When boiler output water temp reaches 160F, the first switch closes to activate L on the circ. When output reaches 175F, the second switch closes, cuts power to the first switch, and activates M on the circ. When output reaches 185F, the third switch closes, cuts power to switches 1 and 2, and activates H on the circ. As output temp falls, the switches open in reverse order when the differentials are reached.

What do you think? Does this have merit? Pitfalls?

 

[muleman51]

That would seem to have a lot of benefit, especially with storage. There is no need for the pump to circulate at high speed when the fire is out, on the other hand there is residual heat in the boiler and you also what to keep it warm. I think you need to keep the pump running on low speed all the time. Then as the boiler heats up, the change in speeds would remove the heat efficiently. Great Idea. Would you use water heater tstats or klixon. Now I'd have to buy a new pump, more expense for the money pit. Jim

 

[chuck172]

That's a great idea Jim. I'd really like to control the circ. speed automatically.
We need to find out what temperature controllers would work.

 

[jebatty]

Almost any controllers would work, from line voltage to low voltage + switching relay; aquastats, set-point controllers, etc.; possibly a multi-stage boiler control.

Right now I have 2 circs on my boiler, with the second "on" at 185F controlled by a separate aquastat to boost water flow as boiler output rises. I think the above circuit is better than a multi-pump setup to achieve variable flow. An advantage of a multi-pump setup, though, is that if one pump fails, the other still provides flow to prevent overheat.

 

[Northwoodsman]

I have been using a three speed Taco 010 all winter and through the use of trial and error, I have determined that I get the best heat removal from my EKO40 system w/ 1,000 gallons of storage with my pump on the low setting. It is my understanding that the desired velocity through the piping to the boiler is 2-4 F/MIN (per the factory Taco bulletin) regardless of water temperature. Thus, this summer I plan to put a "T" fitting before and after the pump on my boiler return piping and insert a flow meter at each location to check the actual flow rate.

When I originally installed my system last fall I had my pump on the high setting (because this is what everyone told me to do) only to have my boiler rapid cycle on a regular basis. Once I performed the head calculations of my piping system I determined that the pump needed to be on the low setting. When I switched the pump from high to low I never experienced the rapid cycling again for the entire winter (and rarely was able to hit 195 F on my boiler) due to the fact that I was maximizing the heat extraction from the boiler and putting this heat into my storage tanks.

Thus, what I am wandering is, why I (or any one else) would want to very the speed/flow setting on the pump knowing that the deisred flow rate is 2-4 Ft/Min?

Let me know what you think.

Brian

 

[jebatty]

I agree generally with you on the L speed setting. What I find, though, is that as storage water temp rises to 160F+, the L speed will allow boiler output to rise to idle point. If I increase the circ speed, I can prevent idling. I am able to bring my 1000 gal storage up to 190F, and the higher circ speeds are important to eliminate or at least minimize idling. Do you see a downside to this?

 

[jebatty]

The Tarm boiler fittings are 1-1/4" = 14 gpm, and 1" pipe = 8 gpm which feeds my storage. Even on High speed I don't exceed 8 gpm, so I think so far as flow is concerned, there should not be an issue.

 

[Northwoodsman]

I have not experienced my boiler getting to the max temp since I put my pump on the low setting. However, I typically tend to charge my tanks up to 170-175F max and thus I guess if I were to charge them higher (which I plan to do next winter) than maybe the higher speed setting would be beneficial.

I also have a 10F difference between my controller/digital readout on my boiler controller and the analog gage readout on my supply side plumbing on my boiler. The digital readout on my boiler reads approx. 10 F higher than the analog gage which is measuring the water temp after it has been through the boiler and is on its way to the storage tank. I am thinking about putting my sending unit for the boiler controller on the pipe where my analog gage is and seeing if this makes a difference.

This is probably another reason I don't get my tanks much above 170/175.

NWM

 

[Gooserider]

For whatever it's worth, Nofossil did something similar to do an autoswitching setup on a Grundfos three speed pump... He had a good thread either here or on his website about the innards of the switch and how he did his mods. Worth doing a search on it IMHO...

I think that if I were setting up something like that, I'd be seriously looking at his controller setup, relatively low cost, can take info from sensors placed anywhere, and control pretty much any sort of needed output, all with a fairly simple web-interface logic setup...

Gooserider

 

[WoodNotOil]

Here is nofos thread: https://www.hearth.com/talk/threads/15270/

I also have a 10F difference between my controller/digital readout on my boiler controller and the analog gage readout on my supply side plumbing on my boiler.
NWM

Is the analog in a well? Is the digital in a well? That is strange that there would be such a difference. I usually only experience differentials like that between strap-on vs. wells. Strap-on readings are generally 5-10* lower than well readings.

 

[jebatty]

Thanks for that link, I don't know how I missed it. My idea had the Tarm in mind which seems to have a more simple controller than than the Eko. My idea also is electro-mechanical, not computer based, takes no programming, and I think is as safe as a strap-on aquastat can be, in its most simple configuration.

The ideas that come up are excellent -- many thanks to many contributors.

 

[Gooserider]

Far as I understand it, NoFo's setup doesn't touch the boiler controller at all - it looks at the inputs and outputs, but it gives the boiler itself the "black box" (or green as the case may be :lol: ) treatment. I like the computer based setups because they seem more flexible to me, both in terms of what you can look at, and the extreme ease in changing the "logics" of a setup in order to experiment with different approaches.

However, whatever you feel most comfortable with...

Gooserider

 

[Nofossil]

For whatever it's worth, Nofossil did something similar to do an autoswitching setup on a Grundfos three speed pump... He had a good thread either here or on his website about the innards of the switch and how he did his mods. Worth doing a search on it IMHO...

I think that if I were setting up something like that, I'd be seriously looking at his controller setup, relatively low cost, can take info from sensors placed anywhere, and control pretty much any sort of needed output, all with a fairly simple web-interface logic setup...

Gooserider

I called it the 'poor man's variable speed pump'. It's been working just fine ever since. It might be a little difficult to control directly with aquastats - there are two control inputs and four possible states (off, low, medium, and high). I did reverse engineer the Grundfos speed control switch, and that should provide a good starting point.

 

[jebatty]

Far as I understand it, NoFo’s setup doesn’t touch the boiler controller at all - it looks at the inputs and outputs, but it gives the boiler itself the “black box” (or green as the case may be LOL ) treatment. I like the computer based setups because they seem more flexible to me, both in terms of what you can look at, and the extreme ease in changing the “logics” of a setup in order to experiment with different approaches.

I misspoke, as I looked at the schematic too quickly. No disagreement on computer based logic control system. At this time I don't have that and probably should take the time to learn some computer based control hardware and software. Until that point, I'll have to stick with what I have and can do.