New Temp Controller

[EricV]

I'm in my 4th season with the Tarm 40 (the money season because it is paid for this year) and found a solution to a problem I've had right along.

It's a 140,000 btu unit and I used 1" p[ex to hook it to the tank and existing heating system in the basement. 1" is too small to carry 140,000 btu's as I now know. So I had installed a second pump (both Taco 007's) and that makes a lot of difference. But that has it's own problem. It moves so much heat that it cools too fast when the fire slows down so the boiler quickly becomes a radiator and cools the tank before I can shut it off.

I know the fix for that is a differential controller and that is next months project.

It also takes a long time to come up to temp with both pumps running..

So the solution I came up with is this temp control. I have the thermistor on the output of the boiler and it controls the second pump. I have it set to turn on at 175 and off at 173. Works like a charm. The boiler comes up to temp nicely on one pump, then at 175 turns on the second pump. As it cools it turns it off.

Just thought I'd share this in case someone has a similar issue.

I'm going to get the Eagle 2 Diff controller next week maybe so then I can turn them both off when the tank is warmer than the boiler.

I'm also tinkering with the Arduino but my learning curve is steep.

Here is a pic of the unit.

 

[jebatty]

Useful ideas come from creative minds. We think alike. I did what you discovered a long time ago to solve the same problem, only I set the 2nd pump at 185. As you have realized, and I expensively realized, 1" pipe does not handle the output of a Solo 40 very well.

 

[in hot water]

nice simple solution! Many of the solar differential controllers have variable speed functions. Consider replacing the dual circ with one high flow circ and use the variable speed function to modulate based on that boiler output temperature.

Ideally sizing up the piping would help, moving a lot of gpm through an undersized pipe can lead to noise, excessive wear, and problematic air removal. Plus the small additional operating cost with a larger pump/motor.

Make sure to find a controller with a battery backup built in. Some brands need to be reset after a power interruption, which could be a problem with a wood fired boiler, not so much with solar.

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