controllers

[Rickard]

What are people doing for controllers? I have a system with three heat sources (four when solar hot water comes) and 8 zones (including hot water). It is easy to find controllers that will take care of multiple zones but I haven't seen anything for multiple heat sources.

Between an oil boiler, a wood boiler and stored heat there are a lot of "and-or-if" circuits to make them integrate since each supplies heat in a very different way. I assembled my own with a combination of zone controllers, separate relays and transformers. It works well but it is very complicated and I would love to find a mostly all-in-one solution. Adding solar will bring another layer of complexity.

I have added a couple of controls since this picture.

Dean

 

[free75degrees]

I think my initial control was a lot like yours, basically a bunch of relays configured to give the desired and/ors/ifs, but I switched to an ARM based single board computer like the one that nofossil uses. All of the if/ands/ors can then be done in software. Plus it allows some neat custom stuff like:

- differential control on loading the tank. I only heat the tank if the boiler output temp is higher than the temp at the middle of the tank. if you don't have this you may be cooling the tank as the fire goes out.

- using house zones to prevent boiler idling. When my tank gets near the max temp, the temp delat between the boiler output and the tank water is not large enough to keep the boiler cool enough to prevent idling. I haven't done it yet, but soon I will be adding logic that says "If the boiler output is >= 190* and I have a house zone that is less than the zone set point + 5 degrees, turn on the zone circ. I am pretty certain that this will cool the boiler enough to prevent it from idling near the late-mid part of the burn.

- If I am heating with oil, decrease zone temp set points by 10 degrees. The only time when I heat with oil is when I am away or mis-judge the time I have until i need to make a fire. It would be nice to have a little lee-way before the oil kicks in.

- logging and graphing of system temps/states. This has been an invaluable tool for me to learn what my system is doing over extended periods of time - when the tank is charging, what portion of the time circs run as a function of tank temp, etc, etc. I can't overstate the usefullness of logging.

- custom hysteresis - I can adjust the hysteresis of my various temperature sensors so that, for instance the boiler circ comes on at 160, but doesn't turn off until below 150.

There are probably dozens of other cool things that you can do with a programmable computer doing the controls that I have not mentioned here. If you are good with computers and electronics you might want to consider a setup like this.

 

[WoodNotOil]

The STSS company that makes storage tanks (Bioheat USA formerly Tarm USA sells them as well as others) has a product that is supposed to help with that (broken link removed to http://www.stsscoinc.com/Products_EMC.aspx) . I have not looked at it in detail, but it is the only thing close to what you want that I know of (not that I know that much either).

I am starting to make controls out of an Arduino usb board and DS18S20 1-wire sensors with solid state relays. To start with I will use it as a differential control for loading the storage tank and later plan to add sensors for logging and graphing and possibly more relays as needed. The electrical/electronics side to the gasification and storage obsession seems to just be starting here on the forum (with the exception of Nofo and a few others that came to this with those expertise already) I think we will see a number of innovative ways to do this coming in the near future here in the boiler room.

 

[Rickard]

Hi free73degrees

Wow. I have been looking at the computer controls thanks to your suggestion. However I don't want a system that is dependent on having a computer running (and I'm afraid of the learning curve). It just seems like another potential point of failure. I want to have something that is dedicated and more simple yet will do the job. I know this is way too much too ask.

I looked at STSS and sent an email looking for more info. Their site could use a little help. The wiring PDF shows one circulator and the description talks about three so there seems to be something missing.

Thanks guys.

Dean

 

[free75degrees]

Dean,

If you are not already familiar with computers and programming, I agree that a computer solution is a bit of a stretch. I am not familiar with the stss controller but maybe it would work for you. I think the reason that there isn't already a nice comprehensive solution is that there are so many different ways that one can hook up these systems - series, parallel, primary/secondary... Then for each of those setups some people use zone valves, some use circs, then there might be differences with how people load the heat tank - i.e. do you charge and discharge in opposite direction and if so, how do you control that? Coming up with an out of the box solution that can deal with all of these combinations would be very tricky. I think nofossil may be working on such a solution, but I don't know if that is definitely happenning, and if so when it will be ready and how plug and play it will be. If I hadn't done the computerized solution, i think i would have wired up a more permanent controller with the relays and maybe added some kind of differential control on the tank loading and then put it all inside a box to make it tidy. Yes it is complicated, but I think complexity will be hard to avoid at this point. It seems like you have a good grasp on your own home-made controller, so I'm sure you'll be fine with whatever you end up doing.

Marc

 

[Rickard]

Hi Marc

I think you hit the nail on the head.

"I think the reason that there isn’t already a nice comprehensive solution is that there are so many different ways that one can hook up these systems"

There is just no way around it.

I'll keep looking though. nofossil's solution may be the one.

thanks

Dean

 

[chuck172]

I'll bet over in Sweden and other parts of the world where people have been using wood boilers for many years have more standard ways of controlling their boilers.

 

[Nofossil]

Hi Marc

I'll keep looking though. nofossil's solution may be the one.

Dean

I'm moving slowly in the direction of producing a productized version of mine. I'll continue to make all information and software available for those who want to roll their own, but I'll probably set up a low-profit corporation to sell assembled controllers and provide setup assistance. Not likely for this heating season though.

 

[Rickard]

I have been looking at the Tekmar units. I am also looking mostly for a solution to not cooling the storage when the wood boiler temp gets lower than the storage at the end of the cycle. It looks like the Tekmar 155, 156 or 157 would work for this. The 156 is the cheapest and would do the job but has only one output. The 155 has 2 outputs, but is a lot more expensive ( I guess because the outputs are relays?). The 157 looks good for not too much more $ and two 120 circulator outputs including one variable speed circulator out that would work with a Taco 007. Now that sound interesting.

 

[WoodNotOil]

- differential control on loading the tank. I only heat the tank if the boiler output temp is higher than the temp at the middle of the tank. if you don't have this you may be cooling the tank as the fire goes out.

Out of curiousity, why did you choose to compare the middle of the tank versus the top of the tank.

 

[free75degrees]

- differential control on loading the tank. I only heat the tank if the boiler output temp is higher than the temp at the middle of the tank. if you don't have this you may be cooling the tank as the fire goes out.

Out of curiousity, why did you choose to compare the middle of the tank versus the top of the tank.

Well, I figured that attempting to add heat would be effective so long as the input temp was greater than the average tank temp and the middle sensor is the closest I have to an average. Let's say the input is slightly less than the top but greater than the middle and bottom. Continuing to charge the tank might lower the top a little but raise the middle and bottom. In this situation I'd lose some stratification but add overall energy to the tank - a tradeoff I am willing to take.

Your question has made me think though - maybe I ought to actually calculate the average of the 3 temps and use that... I think I may try that.

Any thought or arguments on using the top or something else?

 

[chuck172]

I mounted the storage sensor on my return line from the tank to the boiler. I figure as long as I'm replacing the cold water from the tank with hot water from the boiler, I'm doing good.

 

[free75degrees]

I mounted the storage sensor on my return line from the tank to the boiler. I figure as long as I'm replacing the cold water from the tank with hot water from the boiler, I'm doing good.

I forget - do you have pressurized? Using the tank output temp would make sense for pressurized. Mine is open.

 

[free75degrees]

I mounted the storage sensor on my return line from the tank to the boiler. I figure as long as I'm replacing the cold water from the tank with hot water from the boiler, I'm doing good.

I forget - do you have pressurized? Using the tank output temp would make sense for pressurized. Mine is open.

I suppose that might make sense for open too - I'll have to think about that.

 

[Rickard]

I mounted mine to an unused fitting tap on the top of the tank. It is a foot away from the in or out fittings so it should be a good average.