12VDC controller board for home furnace & hot water heater

[briansmothers]

Hello All -
I'm new here but I did a pretty good search of existing questions and can't find this anywhere. 
We have a lot of storms where I live and power goes out quite often.  I have propane gas for both Heat (as a backup source... wood stove as primary) and Hot water.

What I'm looking for is a 12VDC controller board for either or both above appliances rather than the standard  110vac controller board.  This should allow me to run the appliances (furnace & HWheater) from a 12VDC battery that I just keep charged via a trickle charger. 

Alternatively, I could get a small power inverter from the battery to the existing controller board.  I can't imagine the controller boards draw much more than about 10mA... though the solenoid (if that's what is used for the gas flow) could draw more.

Has anyone done this?  If so, how?  Seems to make sense to me.

Thanks in advance

[thirteen]

Maybe call a portable generator shop some of them that are portable are controled by 12V systems that start or run the systems or even a trailer repair shop alot of trailers run a 12 system I know mine did. I sold it 2 years ago and everything was 12v. Just an idea.
13

[OperaHouse]

I detailed a project here on a UNO fridge control.  Same basic thing.  With this you can add a lot of smarts to the system.  Even a GHURD dump controller can be used as a temperature control.  Then again, ebay has a 12V digital one for only $14 shipped.

http://www.ebay.com/itm/Automatic-Digital-Temperature-Controller-Thermostat-12V-110V-220V-Control-Switch-/160809424363?pt=LH_DefaultDomain_0&var=&hash=item2570fd15eb

[Mary B]

small inverter on those circuits would be far quicker and cheaper

[thirteen]

Operahouse;  I am trying to find a temperature sensor that I can install in my pipe crossing a road and creek. It gets 10 - 20 below at times and I am going to installa 1 inch line (thinwalled) pipe in with my water line. So if the temp gets low (35)  it will activate thus turning on a 12 v fan which will take the air from the house and send it down thru the line and venting its self out of the disconnect box on the upper side of the road.  Thus warming the line over the creek and road. I can only bury the line 2 ft down on the road and the creek is 18 ft bank to bank. I have done this before but never installed a sensor inside the pipe. There will be three pipes going threw the 4 in pipe inside the center of the 12 in. culvert 1 = 1 1/2 in. water pipe, 1 = 1 1/4in  condeut, 1 = 1 in. warming line. So there is not a lot of room to spare. the distance is 82 ft to the center of the pipe (culvert). I heat with wood, cook with wood, no furnace. I will install an old fashion raidiant propane heater in the water shed as a backup for when I am gone.  Any ideas would be helpful. Everything I have run across has been too large to use or the distance has been to great. The nearest I could get is about 35/38 ft from the probes position. So I thought I would ask you. 13

[OperaHouse]

Small diodes in series are a convenient tem sensor.  Then something as simple as the 3 terminal LM431, the main component of the GHURD controller, can be used to power a relay coil.  That could also be done with an op amp but you would also need a voltage regulator chip for a temp reference.  The advantage of an op amp is you could seperate the turn on and off by several degrees with some feedback and prevent relay chatter.  A FET could also be used in place of a relay.  These solutions would be small but requiew some building.  There might be some pictures of the diode sensor I used with the UNO fridge thread.  I put some hot melt glue on the diodes and then stuck them in some heat shrink.  Heating that all together gave me a waterproof sensor that would survive in a damp environment.   I don't see a problem with this sensor being several thousand feet from controller.  There would have to be a capacitor at the sensor else it turns into ba big crystal radio and filtering at the control.  I have also had problems when I tried to extend China temp sensors that operate as R/C circuits instead ov voltage sources.

[OperaHouse]

I would consider turning on an electric valve at temperature and letting some water flow.  If water was scarce I would pump it back from one expansion tank into another. Something like that.  Heat transfer from air doesn't seem like it would go that far.  Pipe within a pipe, circulating has real possibilities.

[thirteen]

Letting the water flow is a good idea but I do not know what the water supply from the spring is at 20 below. I know it runs but not the volume. I've never been up there at that time. It is a gravity flow system and was put in at one time but all of that has been washed away twice from a plugged culvert. I will be putting in a whole new system this late summer. I have to put in a drain line back to the creek so I can drain my whole system anyway.  I've put several others in over the years and used small fans for the warm air. I had more room in the 4 in pipe but adding the conduit shrunk my space. But I also used a small light as an indicator then the fan was turned on manually. Since I may be gone I would like an automatic system. The reason for the 12v system I have 3 Surflow pumps 12v (1 new in the box 2 slightly used) and I will not have enough preasure in my gravity flow system to operate the ignitor for my ondemand water heater. So I need to use my pumps to add preasure. I have an older battery bank that will be 12v just for the pumps and for this warming fan. My big system will be 24v but will be new batteries and new panels. I'll trickle charge my 12v system from my other system plus it has it's own two solar panels.   Thought I would add some general information on why. In 2 years I will install a micro hydro system and the 12v system will be taken out and used in the single room cabin I plan on building away from everything.
Thank you for the info. 13

[mttrout]

If you are in need of a temperature reading  look into A  J style thermocouple wire My solar
water system hae them connected to a Watlow controller with a dc output. which controls a
ssr on 12 vdc.. I made  my leads all you need are j style wire  then using 1/4" tubing copper
 affix the two wires twisting + and - to copper tubing strip back insulation.insert into tubing say 4" pinch end and solder them together.
you will also need male and female connectors.
very accurate.

http://www.ebay.com/itm/Thermocouple-wire-Type-J-Special-limits-TFE-Teflon-insulation-1000-ft-spools-/140896288671?pt=LH_DefaultDomain_0&hash=item20ce12bf9f

Cheers,
 Chuck

[ghurd]

GHURD controller

Somebody a while ago used a 3-wire TO-92 direct temp-to-voltage IC (what he used was available in 2 types, output in F or C), and a couple resistors, in where the pot is.
Can't remember what he wanted to do with it, but it worked fine.
G-

[just-doug]

for moving heat,water is vastly better than air.on a off-grid cabin i did one  where three pex tubes where run and bundled together.they where cold ,hot and hot return.all bundeled and insulated.the hot went to the end and then returned threw a small ag pump ,like the surflow,and was plumbed into the hot water tank drain.pump was controlled by a thermoste from the hardware store.when the pump turned on the hot loop heated everything.since you have a demand type water heater,a 5 gallon camp trailer propane water  heater could act as your" boiler."

[madlabs]

Probably an LM34 or 35. Very easy to use, I have used lots of 'em. Outputs 10mV per degree, so simple to read, no lookup table.

JOnathan


[/quote]

Somebody a while ago used a 3-wire TO-92 direct temp-to-voltage IC (what he used was available in 2 types, output in F or C), and a couple resistors, in where the pot is.
Can't remember what he wanted to do with it, but it worked fine.
G-
[/quote]

[GaryGary]

Hi,
You might have a look at the myDTC controllers -- they are very flexible and not to expensive.

http://www.mydtcstore.com/

Gary