Battery backup for wood furnace

[bicylindrico]

Hey guys. I am getting ready for heating season and after last year I really need to come up with a solution for last years dangerous power outage scare. I awoke one cold night to the smell of burning ductwork/furnace paint. I had a full firebox of Black Locust and the power went out on our street for no reason. I rushed outside where the furnace is and found smoke rolling from under the furnace shed roof. It was the paint burning off the sides of the Hotblast I believe. I frantically began pulling out as much wood and coals as possible but that thing was so hot it didn't make much difference. It took another 5 minutes to get the generator hooked up and the blower running again. Of course this just filled the house with more stink but I got the furnace cooled down. I did about melt the fan limit switch so that was replaced but everything else seemed to survive.

So now I need to at least know that that particular situation is covered. I have come up with a system of an RV switch, 12v d/c to 120v a/c power inverter, battery maintainer (Battery Tender) and a bank of large (6)12 volt car batteries. I have yet to purchase anything because I want to make sure there is not a better way to put this together. I can't seem to find info on these switches being automatic or manual. The websites that sell them have not been helpful in returning emails. I also found a product online that will produce an audible warning once power has been lost. This will just plug into an outlet in the bedroom and give me time to get the generator running.

Has anyone given any thought to this scenario and if so have you come up with any solutions. The wife has shut down the furnace until I come up with a solution. Thanks guys.

 

[Somesawguy]

Get yourself a used UPS from ebay, and wire up the batteries to it. They are usually 24v for the smaller ones. That way, when the power goes out it will automatically switch to the battery bank.

I just tossed out a few of them. I would have sent you one for the cost of shipping. :msp_unsure:

 

[bicylindrico]

Get yourself a used UPS from ebay, and wire up the batteries to it. They are usually 24v for the smaller ones. That way, when the power goes out it will automatically switch to the battery bank.

I just tossed out a few of them. I would have sent you one for the cost of shipping. :msp_unsure:

Great advice, thanks! I think I could even wire the batteries up series parallel for the 24 volts. I think these are exactly what I need if it can handle the 1000 watts or so to run the blower.

 

[Somesawguy]

Great advice, thanks! I think I could even wire the batteries up series parallel for the 24 volts. I think these are exactly what I need if it can handle the 1000 watts or so to run the blower.

There should be a current rating on the motor for when it's running. You'll want something that can handle the startup current. If you know someone with a clamp on current meter, they could give you the peak current to start the motor, or get a kill-a-watt meter from lowes.

 

[stumpy75]

So now I need to at least know that that particular situation is covered. I have come up with a system of an RV switch, 12v d/c to 120v a/c power inverter, battery maintainer (Battery Tender) and a bank of large (6)12 volt car batteries.

If you can find them, use 6v golf cart batteries. They are the deep cycle ones that you want for this application. Lot's of power, and they can be deep discharged. You can wire them to get either 12 or 24v. Lot's of RVs and backup power sites use something similar.

 

[Somesawguy]

If you can find them, use 6v golf cart batteries. They are the deep cycle ones that you want for this application. Lot's of power, and they can be deep discharged. You can wire them to get either 12 or 24v. Lot's of RVs and backup power sites use something similar.

I have Trojan T-105 batteries for my solar setup. They are a little pricey though.

 

[blackdogon57]

I bit the bullet a few years ago and hard wired all critical circuits to my generator. I can run everything but stove and dryer indefinitely. I have a manual transfer switch and have to manually start generator but if you want to spend the money you can automate everything.

 

[Chris-PA]

Yikes! :shock: I cannot even imagine having a system that requires grid power or a generator to keep from damaging itself. That's just way too reliant on technology and complex systems for me.

 

[CrappieKeith]

Outside of getting a draft regulator to slow down the burn rate which is what caused the over heating...over firing...and being that the hot blast is not ul listed to operate without power like the Yukon's are a heat dump might be a good fail safe to dump heat out of the unit when there is a lack of air moving through it...you may have a small blower and a heat dump could help.
A larger hot air plenum and larger runs could also help get heat away from that unit.If I recall they only have a small supply opening.

 

[Genius.]

Yikes! :shock: I cannot even imagine having a system that requires grid power or a generator to keep from damaging itself. That's just way too reliant on technology and complex systems for me.

:agree2:


The biggest worry of mine is what the OP is talking about. At the moment I only have a wood furnace downstairs, I am looking at a wood stove for the main floor just in case the power goes out my family can still sleep good at night.

 

[cantoo]

I have a Hotblast 1400, I used a grinder and ground the knobs off the ash pan damper. I can shut the air off the fire and smother it to kill it in case of power outage. I have a generator but it takes awhile to get it ino to position and run the fans. I have a little generator that will power it but somebody always borrows it when I need it.

 

[NCHornet]

I recently installed my first wood furnace in the basement of my house. prior to buying the Hot Blast 1557 I did a lot of reading and asking questions. I read that many never even use the blowers on the unit and just let the heat rise. This really got me interested, and so far I have not used the blowers at all. But after reading this I am a bit worried. I have not noticed any excessive heat by doing this, although it hasn't gotten real cold yet either. Anyone else just rely on the heat rising principle and leave the blowers unplugged? Thanks for the help.

 

[fields_mj]

As far as automatically controlling the power source, a simple 120V icecube relay should do the job just fine. Wire the control terminals to an extension cord, and then run your 12 or 24V power supply through the normally closed contacts. These would be the contacts that are closed when there is no power on the control terminals of the relay. So long as the relay has 120V supplied to the control terminals, the relay will keep the contacts open. When power to the control terminals are lost, the contacts close and now your batteries are supplying power to what ever it is you are hooking up. If you are using an inverter, just make sure that the inverter is not sending power back to the 120V control terminals on the relay. So long as you are able to isolate the control terminals so that the power from the batteries can't cause the relay to open back up again, it should work fine. If it becomes an issue, you could use a 24V DC relay. How it would have to be wired in is too complicated for me to put into words. I'd have to draw a picture

Just my 2 bits,
Mark

 

[timbrjackrussel]

Furnace power backup system

Furnace power backup system
I had a similar experience with my Surefire wood furnace last March, ice storm and loss of power. All this happened at 2 AM just after I loaded it full of White Oak, and was getting ready to leave the house at 4AM. I scrambled to get the generator going. But what would of happened if I was't at home? I made up an automatic power transfer switch good for 30 Amps. at 120 V.A.C.. It is safe that it can't connect the load (the furnace) to the power grid and the standby source at the same time. I use sixteen 8C6V floor scrubber deep discharge batteries in a series parallel connection to power a 1000 watt true sinewave inverter at 12 volts to produce 120v.a.c. to run the furnace. It is just like a LARGE computer back up supply. The batteries should run it about 60 Hours!! I have a telephone dialer that calls my cell if the power to my house goes off. When I get home if the power is still off, I pull the starter cord on the generator, load in some more wood and head out to help my neighbors.

 

[Patrick62]

my 2 cents worth

My history:
I have a shop and office that is run off the grid. The shop used to have a large collection of Golf cart batteries and assorted invece rters. Charging was mostly a small windmill. Lessons learned thus far:

Series connections are better. It is very difficult to make a parallel connection that will balance the charge/load evenly.
Golf car batteries are awsum, and if maintained correctly (I didn't) will last a long, long time.

size your system to your needs. I went nuts with the initial installation and had 14 batteries in there at one time.

The office now has a very modest system that consists of a single 12V AGM battery, and a solar panel and charge controller. AGM batteries are sealed, and the charge controller is the neetest thing since a bread slicer.

I really like the idea already presented here with a UPS system. How much does you fans draw? In comparison to a standard furnace blower?? I have a propane furnace in the shop... I can start and run that blower off a 1200 watt inverter!

The idea of using a 3 or 4 pole double throw relay. Great! (mostly) Switch the AC with two poles from the panel to the inverter. Switch the inverter on/off from the remaining contacts. The only possible issue is that you are transfering a running motor to a inverter that may be 180 out of phase electrically. might work, might not. A time delay would ensure that the motor slowed enough not to jolt the inverter badly.

My preference is for heating devices that don't care if the AC is on, or not.

When I get to reworking that system out at the shop my plan is to use 4 floor scrubber batteries in series for 24 volts. Then get a wind charger to charge them, and most importantly keep that water full !!!

-Patrick

 

[iowa]

My electricity went off today for an hour. I had just loaded my longwood furnace. Once the power went off my dampner butterfly shut. Snuffing out the fire. Nothing got overheated.

 

[robsco]

I'm not sure how your furnace operates but it seems to me you would be much better served by a damper that is held open by 120v and would therefore automatically close and shut off air supply to fire box when power goes out. All of the ups type systems still have the possibility to fail. Also if you are not home before the batteries run out you're still in same situation. Just an opinion

 

[zogger]

You want what is called an inverter/charge controller, plus your battery bank.

Battery banks should be placed in a sealed but vented battery box/case. they use a pusher fan, not a puller, to vent air that is piped to the outside world. the charge controller and/or inverter runs your stuff. Put a sub panel in and remove the circuit that normally runs your furnace. Now..you don't need solar panels or a windcharger, almost all of them I am aware of are also capable of being grid tied, so your battery bank can stay fresh. Instead of being either/or, you just always run your furnace from this now isolated circuit. You adjust-program-your inverter charger to pull grid power sometime, ususally late at night is how most guys do it. size it well enough you might could pull an additional circuit or two for your "must have" stuff in your home, your home officer/computer stuff is nice...

the power you get from this setup will not only carry you through a power outtage, but will be a lot 'cleaner" than normal grid supplied.

Your typical name brand industry gold standard is xantrex Xantrex | Power Inverter, Inverter Charger, Battery Charger Manufacturer for the electronics, and trojan Trojan Battery Company, or upscale into serious long range will work like you won't freekin believe, rolls-surrette Rolls Battery. One Mean Battery. batteries. They will need periodic maintenance as in adding *distilled* water.

Installation and whatnot is fairly straight forward, last connections in most areas of the reasonable civilized world will have to be done with an electrical contractor and inspected by the local officials with their hands out for the permit money.

You can build the battery box yourself, normal plywood like 3/4", use a layer of sintra on the bottom, say siz inches up, and liberal amounts of baking soda on the floor, that is for the highly unlikely event of a acid spill. helps with the inspectors and insurance goombahs.

The electronics controller will have full wiring instructions and setup instructions. You can check the site and see what all they have, small to large. I'd suggest going heavy on the batteries, it is way better to have too much and only ever shallow cycle than not enough and deep discharge them all the time.

Barring that, an autostart generator can be had cheaper, and those features are either built in or can be gotten right from the genny shop or online. They go from cheap to OMG expensive depending on your needs.

If you go the generator route, run that thing at least once a month for around 15 minutes. Leting it sit unused in between emergencies is ujust like those folks who let their saws sit one summer branch in the yard to the next and wonder why their saws don't work.

Here, all the big diesel gennies get run 15 minutes once a week. Five minutes without power = proly 1/2 million bucks or so worth of dead cluckers.

Those are a little overkill for most houses. but it is the same principle and they got them out there to buy, no need to reinvent and cobjob the wheel . Just buy one, sounds like for just that furnace the smallest autostart model anyone makes, plug it in, use dang fresh fuel with stabilizer. Power goes out, they come on, power comes back, they shut off. how they are supposed to work anyway. You may have to add a panel switch thing, depends on what you buy. too many models/names out there (talking small gassers) and I am some years not up to speed anymore, so have to google around for that.

Or a propane genny, those are slick too, propane lasts a long long time, and if you buy your own tank, and get it filled, you are golden. Less likely to grow legs either, build them right into a concrete pad.

I know of several folks who got started on alternative energy with just such a smasll scale project, just having enough backup juice to run their normal gas or oil furnaces, then it goes from there. kinda sorta fun. practical too, when you consider you are always going to want power the rest of your life, might as well work towards getting independent of the dang power monopolies. Like wood heat is a great start getting energy independent then it it your hot water, then onto the electricity.

small salad garden to a larger garden to a dang we just canned hundreds of cans and got two freezers filled. it's neat to get more independent on life's necessities.

 

[victoria stiles]

It is necessary to have a good battery backup for your comfort. Thanks for sharing.