Differential Controller

[Robby]

I am about to install Diff/Controller between my boiler and 1200 gal sorage tank. (In past topics I thought it was 1100 gal but I measured it) and would like some input from you experts. There is an analog Boiler Diff/controller Solar Diff/controller both same unit that you can set the difference between 8F and 24F and it turns on a relay 120 volt. Couple of other features, bypass to run pump, power lights etc.

There are also digital "Solar" diff/controllers that appear to do exactly the same thing, same temperatures, etc. except they have a readout where the temperature is displayed. I would like the temperature readout, saves buying thermometers. Three readouts, boiler, top of tank and bottom of tank. The display would show boiler as solar collector.

Anybody see a problem?


Thanks,

Robby

 

[steam man]

I essentially do that on a smaller scale with a solar controller. It will work fine.

Mike

 

[sdrobertson]

Only thing I would do is get a reading at the middle of your storage as this tells you how much more usable water you have left in the storage. If you get excellent stratification then you get a better read on how much water you have left at a usable temp as once the middle starts to get colder, you will be able to figure out how many hours you have left, or how many hours you'll have to burn to recharge.

 

[Robby]

Yes your right. I can mount in long well and read the temperature in mid tank. I assume I will get reasonable stratification, the tank is 4 1/2 feet tall (and 11 ft long). I know it would be best vertical, but with insulation to tall and real heavy. Tank alone weighs in excess of a ton. It has four 3" inlets and I was going to use 3" inside and T return lines to try and prevent circulation. I intended to return from heating zone into mid tank.

Robby

 

[sdrobertson]

When I first fired up my tanks I had the return from the house to the middle with the same thought as you have. What I ended up with as totally mixed tanks and no stratification. I ended up moving the return to the bottom and it helped allot. One of the reasons I mixed was that my house zone ran all the time so when the zone was not calling for heat, the return would be in the 170 range and I thought returning it to the middle would keep the hot water at the top. Didn't work as I thought so I moved it to the bottom. I installed a controlled circ that would speed up and slow down so now I can keep the return at 125 and I have excellent stratification. You can try to return to the middle and see what your results are, but you may want to figure out a way to switch it to the bottom later if need be. My fix was a pain to redo and it might be easier if you planned in the event you have to switch.

 

[Robby]

That's real interesting. My system uses 1" copper and I thought that when I up-size to 3" into the tank that would slow down the speed of the water. The tank has a hatch so someone skinny, not me it's only 18" wide, can enter and plumb interior. Maybe I would be best to just put a T a few inches into tank on the return. To drain the tank later would be a hassle and cost a few bucks. All water treated, etc. The inlets (outlets) are on opposite sides and toward each end. Any thoughts on taking hot out of the top, left end, and returning to bottom, right end. Boiler to tank the opposite. Also I am installing 100' off soft copper coil into tank for a heat dump for the solar system. 60 evacuated tubes. There are six 3/4 threaded, three on top and 3 on the end. Two for copper coil, and 2 for immersion well's.

I do appreciate the info. I just hate re-inventing the wheel and then being wrong.

Robby

 

[sdrobertson]

With your tank being 4 1/2 ft tall the difference between the middle and bottom would not be that much. I'm thinking that you might be right about the 3" pipes not mixing much. My thought is that if you go all the way to the bottom, then its 4' from the top which would make it farther for the water to move which would slow the flow between the inlet and outlet as there would be more water between the two. With the 3" pipes you shouldn't get allot of "force" but I really don't know on the piping on opposite ends as this may swirl the water but I don't know if it would be different than if they were in the middle with "t"s. Hopefully someone who knows allot more on this than myself will help.