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wood heating and "smart thermostat"

Started by mf40diesel, February 20, 2015, 01:15:14 AM

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mf40diesel

Hello All,
We mostly heat with wood, but have a very nice Buderus Propane boiler for forced hotwater through our cabin.  Long story short, but our great room was an addition added before we owned the house, and was built on sonatubes, the rest of the house has a full basement.  We have a very small Jotul woodstove which we love in the great room and try to keep it going most nights when we are in there.  Years ago, when we first moved in, during a sizeable cold snap, we had the woodstove roaring nicely, went to bed and woke up to find that room freezing, the then relatively unprotected pipes had frozen.  Since then we have been really dillegent about frequently cycling the heat, and I have wrapped and insulated the pipes.  With the subzero temps we have been seeing in Maine this winter and my getting too relaxed they froze again during one particularly cold night.  Luckily I caught it before they burst, and was able to thaw and get everything rolling again, until 0200 in the morning! but no damage. The space under the addition is just a crawl space, it is wrapped all the way around with flashing, and I have insulated all the pipes.  There are no drafts under there, but it is not warm there either.

My whole question is: Is their a thermostat available that is "smart enough," that it will automatically cycle to keep pipes warm, regardless of whether the zone is calling for heat? Seems like others must experiance this.  I don't really want to attach heat tapes to the pipes, seems like the regular heating could cause problems to the heat tapes, and insulation is good, but with the woodstoves going, I could therotically go days without using that zone for heat, no insulation could keep the cold out forever. I'd like a smart boiler that would monitor the temperature in the zones and not allow the temp to fall below 50, or on the other hand a thermostat that would call for heat every couple hours for a few minutes just to heat the pipes up again.

thanks in advance, not sure it was the best written question.
John Deere 5055e, mfwd. Farmi JL306 Winch. Timberjack 225 Skidder. Splitfire splitter & Stihl saws.

beenthere

Should be able to buy a thermostat to place in the crawl space that will have set points at whatever deg temp you want it to start a pump (i.e. maybe 35° F). They come in 120v which you can plug into directly.

Is that what you have in mind? 

I have a thermostat on my wood boiler system that will kick on my propane boiler if the water temp falls below 100°. Meant to kick the gas on if the wood fire goes out and I don't want the water to freeze, or the house plumbing to freeze up.

south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

bandmiller2

Rewire your present or add a constantly running small circulator to keep the water moving when the boiler shuts down. Frank C.
A man armed with common sense is packing a big piece

dave_dj1

Is the addition floor insulated? If not,I would start there. I would think if you hooked a t-stat to a timer you could make it do what you want. If the t-stat called it would fire or it would fire at a given time too.

jueston

any programmable thermostat you could set it to 90 degrees for 15 minutes every night at midnight.

that would mean at midnight you boiler would kick on, pump hot water through all the pipes and then turn off 15 minutes later.

this would ensure that once a day your insulated pipes received fresh hot water and assuming your insulation is good enough, that would prevent them from ever freezing

Hilltop366

Some thermostats learn your settings and then repeat them, I guess that would require you turning up and down the thermostat at night long enough to teach it.

I'm guessing you are talking about the heating pipes freezing.

Perhaps a less energy consuming setup would be a surface contact control on the pipe installed where the pipe freezes first. Wired to turn on that zone when the pipe temperature drops below a set temperature.

jwilly3879


mf40diesel

Thank you for all the great responses.  I have alway thought about the option with Antifreeze, which would be nice, however I hear that isnt good for the longterm life of the boiler.  With that said, we put antifreeze in our vehicles?

I'm curious about the surface contact control?  Is that a specific device?

We do have a programable thermostat now, and by massaging that I could therotically do the 15 min run 4 times a day.

It's funny, you would think that a function like that would be built into the boiler, without having to make modifications.

Thank you all, I'll keep you posted.
John Deere 5055e, mfwd. Farmi JL306 Winch. Timberjack 225 Skidder. Splitfire splitter & Stihl saws.

pabst79

 Using a surface mount aquastat or low temp air stat to start your pump would be the cheapest way to go, however any controls are prone to failure. Pumping Non toxic glycol into your system would be inexpensive as long as your capacity in gallons isn't too much. As far as glycol being bad for your boiler, I've pumped 1000's of gallons into many systems and had very little trouble with sludging or system failure. NEVER use auto antifreeze in your heating system, its not the same. If it was my house and I couldn't be sure of the temp under a crawlspace, I would go with glycol  ;)
Not sure which came first, but I have chickens and eggs.

beenthere

My surface contact control is a White Rodgers.

Here is a link to look at the variety they have for pipes.

White Rodgers hydronic surface contact control devices


Quoteyou would think that a function like that would be built into the boiler
The controls for the circulation pumps are external to the boiler, so wouldn't expect it to be a built-in function. It is a system design problem, and seems you are on the right track to get the system fixed.  ;)
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

dave_dj1

One thing to keep in mind if you decide on glycol, it's very inefficient to heat it, it takes about 30% more fuel to get it to temp.
I'm not a fan of anti freeze in a home system for that reason alone.
taken from here: http://www.dow.com/heattrans/pdfs/DispellingTheMyths.pdf

System Performance
• Adding antifreeze to water negatively impacts
system performance
– Must trade performance for freeze protection
• Reduced heat transfer efficiency
̶ Antifreeze decreases thermal conductivity & specific heat
̶ How much will system performance be reduced?
̶ Regrettably there is no "one size fits all" answer
• Increased power consumption
– Antifreeze increases viscosity  affects pump
horsepower and fluid flow

beenthere

When I put in my indoor wood boiler in 1980, I added about 3 gal. of a boiler anti-freeze to the system. Don't know what loss of efficiency has been, but have never had a problem heating the home with either the wood or the propane part of the system.
Nor any zone pump failure (same pumps since 1993 when I switched from oil backup to gas backup).  I have a spare circulating pump still sitting on the shelf collecting dust, and never dreamed I'd get the life out of them that I have so far.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

pabst79

Quote from: dave_dj1 on February 20, 2015, 08:46:41 PM
One thing to keep in mind if you decide on glycol, it's very inefficient to heat it, it takes about 30% more fuel to get it to temp.
I'm not a fan of anti freeze in a home system for that reason alone.
taken from here: http://www.dow.com/heattrans/pdfs/DispellingTheMyths.pdf


Most every brand of glycol has a 90% or better transfer rate of heat, 30% increase in fuel consumption? Maybe 20 years ago with a 100% solution. At a 50/50 or 60/40 mix with a gas fired boiler, running high temp perimeter baseboard it would be hard to notice.
Not sure which came first, but I have chickens and eggs.

pabst79

 Not sure how that got in quote form.
Most every brand of glycol has a 90% or better transfer rate of heat, 30% increase in fuel consumption? Maybe 20 years ago with a 100% solution. At a 50/50 or 60/40 mix with a gas fired boiler, running high temp perimeter baseboard it would be hard to notice.
Not sure which came first, but I have chickens and eggs.

pabst79

Here is a link from a competitor to the previous link, just to compare facts, no harm in that  :)


http://www.oatey.com/doc/cryotek.pdf
Not sure which came first, but I have chickens and eggs.

beenthere

pabst79
I'm pretty sure that cryotek is the brand name that I used. 


And your response that ended up inside the quote, just means you put it before the "end quote".
You can go back to that post and click "modify" to see where it sits inside those bracket symbols.

You can also use the "modify" button to edit a post and then use the "Preview" button to check that your post is how you want it to show up. Just computerese to keep us on our toes.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Holmes

  Buderus does not recommend anti freeze in their boiler. They already have problems with corrosion and the antifreeze makes them corrode faster.   I Believe there is 1 type of antifreeze that is allowed and it's $$.  A strap on aqua-stat would be the easiest way to make the circulater cycle on and off.
Think like a farmer.

Hilltop366

Quote from: Holmes on February 20, 2015, 11:43:26 PM
   A strap on aqua-stat would be the easiest way to make the circulater cycle on and off.

That was I was thinking of Holmes, I would think a switch in the circuit would be handy to disable it for the warm season.

I use one like this http://www.emersonclimate.com/Documents/White-Rodgers/Catalog_2010/2010_Cat_pg_108.pdf to turn on and off a circulator for domestic hot water I also have a timer in the circuit so it only comes on during the day.




beenthere

Hilltop
That strap-on shown in your link looks identical to the one I have attached to the 1½" pipe in the circulation system. That is wired into the gas boiler to kick on whenever the temp. gets below 100° F.

Seldom ever reach those conditions but it only for backup if the wood boiler doesn't maintain 100° plus temp.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

John Mc

The problem with putting a sensor on the pipe is that you only are measuring in one place. If there is variation, you'll need to determine the coldest spot to place it. If that spot changes (for example with different prevailing winds, or whether or not you are heating an adjacent part of the house), you may be out of luck.

A couple of years ago, I helped a neighbor clean up from the aftermath of a burst pipe on their baseboard heating system. They had been heating with their woodstove, which is at one end of the house. It kept things warm enough at their centrally located thermostat that their heating system never came on. Unfortunately, the opposite corner of the house got cold enough for the pipes to burst (even though they house is over a full basement). compound that with the woman of the house home alone recovering from foot surgery (not supposed to be walking), and not knowing where her water shutoff was located, it became quite a mess.

They addressed it by adding a timer in parallel with the thermostat. When the outside temps go below 0˚F, they turn on the timer. It forces they system on for several minutes every few hours, regardless of whether the thermostat is calling for heat.  They could make this fancier, and add an outdoor temperature sensor to enable the system anytime outdoor temps drop below a certain setpoint, but haven't felt they needed that for now.

I suppose someone out there has got a programmable controller that would let you control a heating system like this automatically, but I haven't really looked for one.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

mapleveneer

You could build your own "smart thermostat" with  a raspberry pi microcomputer ($35), a SainSmart relay board ($20), some thermocouples (DS18B20 $2 each in a pack of 10), some ethernet wire and various bits and pieces.  Find a local high school kid with some basic programming skills to help you.  It is really quite simple for someone with the basic skills.  Monitor whatever locations you want with the thermocouples; pipes, space, inside, outside, wherever and program the pi to activate the relay that is connected to your circulator pump controller when your target temperature is reached.

There are several tutorials out there that cover the basic temperature monitoring setup.  Here is one:  http://www.danielhansen.net/2013/03/raspberry-pi-temperature-logging-using.html

Another is webiopi.  Google that.  That  is an interface that allows you to take inputs and control outputs, set alarms, etc.

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