# Backup Power for Pellet Stoves



## Mr. Heat Miser (Feb 6, 2011)

A potential problem with some pellet stove installations is that the stove may backdraft in the event of a power failure, possibly filling the living space with smoke. My Mom's Whitfield Advantage II T Insert has filled her house with smoke several times over the 20+ years she's owned it, fortunately her power rarely goes out.

The one time that really stands out in my mind is one New Years Day morning a few years back. We had all stayed up until well after midnight ringing in the new year, and finally passed out about 1:30am. I awoke about 5:30am to the sound of smoke alarms and a house full of smoke. It was freezing cold outside and the power was out. The only thing we could do was open some doors and windows and try and air out the smoke. Needless to say, the entire house was freezing cold in a very short time. The power did not come back on for several hours and the smoke was slow to exit without the help of some fans. That was an experience I didn't want to repeat anytime soon.

For a while after that we would shut down the stove if we felt that there was the possibility of the power going off becuase of an approaching snow or ice storm, but this was precisely the time we wanted to be sitting in front of the nice warm fire. So I began to research backup power options for the pellet stove.

The ultimate solution of course would be to have a stationary, whole house generator, that would automatically come on and keep all of my appliances running. But I was most interested in a quick, inexpensive solution to preventing the house from filling with smoke during the infrequent, short power outages. Being an IT person I immediately thought of the battery backups used to keep computers on long enough to shut them down properly during a power outage.

As a quick experiment, I measured the electrical consumption of the pellet stove with a P3 Kill A Watt EZ Meter http://www.amazon.com/P3-Internatio...1?ie=UTF8&s=electronics&qid=1297024532&sr=8-1 (see my other post - electrical consumption of pellet stoves), and compared that to the specs given on several different APC battery backup units I had. I selected one of the larger units, a Backups 650, which should have enough power to run the stove for long enough to shut it down and prevent the back draft problem. I connected the unit to the stove, and with the stove burning, pulled the power cord of the backup unit out of the wall outlet to simulate a power outage. The stove kept burning with no problems. I plugged the power cord back in and the backup unit switched back to wall power without a hitch. Everything seemed good, as long as the battery would last long enough for the stove to shut down, this was a possible solution.

But what about the power quality of the APC backup unit? How does it compare to what comes out of a wall outlet? Is it safe to run my pellet stove electronics from this power source? If it can power the sensitive electronics of a computer it must be okay to run my pellet stove for a few minutes right? Not necessarily! These same questions could (and should) be asked about generators as well. I did some investigating into the output power quality of various backup power devices and was surprised by what I found. What is okay for the DC electronics of a PC to run on, might not necessarily be okay to run the AC motors of your pellet stove.

Ultimately, you would like your backup power device to output a power signal that looks as close as possible to the waveform that is delivered by your utility company. In the U.S., for standard 120 volt wall recepticles this waveform is a fairly smooth sine wave, with a consistent amplitude and frequency of 120 volts and 60 hz.

Here's a great article I discovered in my research that compares the outputs of several common backup power devices, and shows pictures of their output waveforms on an oscilloscope for comparison. I hope this information will help others to select a quality backup power source for their stoves, and avoid potential costly problems caused by using poor quality power devices. No one wants to replace motors and control boards unneccesarily.

Power Quality Produced by Various Backup Devices
http://www.jkovach.net/projects/powerquality/ 

Anyone else here in the forum care to share their pellet stove backup power solution? I'd love to see them!


----------



## ChrisWNY (Feb 6, 2011)

I posted a thread on this last month, basically asking who had successes using the less expensive "computer UPS's" to run a pellet stove (at least so it could shut down properly) during a power outage...

https://www.hearth.com/econtent/index.php/forums/viewthread/67447/

Of course, many UPS solutions are only practical if you're present and conscious during the outage (or you have a whole-house generator that automatically kicks on within a short time frame), unless you invest in an enormous amount of batteries to keep your stove running for several hours. Some guys did that, they daisy-chained marine or car batteries together, enough to run their stoves for several hours during an outage. I was considering investing in a PFC pure sine wave UPS (best to use with electrical motors), but decided against it because my furnace passed the "smoke test", exhaust is properly vented even without power due to the 6' rise in my PL vent, as well as having an OAK that is installed physically lower than the exhaust vent.


----------



## THE ROOSTER (Feb 6, 2011)

Here's mine, 36V EZ-GO golf cart rewired to 12V, Harman's battery backup that will run the stove 10 hours easy... I'm lucky, my basement is right under the stove, just drilled a hole and dropped a line down to it...


----------



## rideboard147 (Feb 6, 2011)

so would this backup power just be able to run the fans and blowers and not start a new burn cycle? I am looking for something to do just that and not start a new fire when power is switched to battery or restored. Just enough to run the smoke out and shut down


----------



## Ro3bert (Feb 7, 2011)

I (still) have a mod F 503A Stabylex mounted on the a wall in the living room. The dealer I got the stove from had them and said they were made for pellet stoves.

As our power outages are infrequent it wasn't used very often so out of sight out of mind (hidden behind a large chair) so seldom checked the liquid level in the battery. And so goes the battery, never replaced it. It was a 12V marine battery that was so heavy it took two of us to move it into and out of the house. It was supposed to power the stove for 23 hours, but we've never had an outage for more that 3 to 4 hours.

I don't have an oscilloscope so have never been able to check the output. Wish I did, I could use it for other things (I'm insatiably curious-electronics background).


----------



## Mr. Heat Miser (Feb 7, 2011)

rideboard147 said:
			
		

> so would this backup power just be able to run the fans and blowers and not start a new burn cycle? I am looking for something to do just that and not start a new fire when power is switched to battery or restored. Just enough to run the smoke out and shut down



Exactly... this was my goal as well. I don't usually leave my stove running when I am not home, so that's all I am looking for now. Your fires burning, your home, the power goes out, you walk over and shut down the stove as usual immediately, the battery backup keeps the stove going for long enough to shut down normally, no smoke in house!

My Harman P35i insert is vented through a 4" liner up to the top of my chimney. Theoretically this should not back draft, but I have not yet tested it by pulling the cord on my stove. I think I will wait until the end of the season, when the warmer weather comes around before I test it. My Mom's Whitfield Advanatge II T insert on the other hand is direct vented, and is more prone to back drafting.

But yes, a larger computer battery backup with a nice sine wave output will run your stove and enable you to shut it down safely in the event of a power failure.


----------



## Vinelife (Feb 7, 2011)

Since mine has a horizotal draft I will be getting an apc 1/2 hour back up surge for mine.  That way if I'm home and power goes out it will give me sometime to turn it off without any smoke back..  of course this will not work if i'm not home.  But power goes on here in the winter atleast once a year.  If the power does go out I have a wood stove in same room and I have about 1 cord in the garage ...so will fire that up and boy that gets hot, almost too hot.


----------



## arnash (Feb 7, 2011)

I think the least expensive method might be to just have a strong battery and a power inverter connected to it, ready for use.  Since you have to be present anyway to shut the stove down, it isn't any big bother to unplug the stove from the wall and plug it into the inverter and restart the combustion/exhaust fan, and also the circulation fan if the stove is too warm to not use it.  Not having an electronic stove, I don't know if you can start the fans without using the igniter as in a normal start-up.  I have a 400 watt inverter and a spare battery that I think I should station near my stove just in case.   Come to think of it, alternatively, one could use a tank vacuum (like my Bisell carpet clearner) that allows attaching the hose to the air output port and plug it into the inverter and blow its air into the air intake pipe of the stove.  It seems that that would provide forced air just like the combustion fan does.  
    The real question is "just how much air is needed to vent the stove gases"?   Could a strong computer cooling fan attached at the end of a horizontal exhaust pipe provide enough suction to draw out the combustion gases?  It certainly couldn't provide the strong air flow for clean combustion, but if it moves the combustion gases out of the stove at a decent speed, that might be enough to prevent the gases from entering the house.

   Someone should invent a fan, that attaches to the end of the exhaust vent, that is driven by hot air pushing against its vans. I saw a version of that at the local stove store, but it stands on top of the stove and uses its rising heat to turn the fan and blow warm air forward.  That would be a perfect solution to venting stove gases without power.


----------



## FordMastertech (Feb 7, 2011)

The power went out the other day while I was at work, wife was home, and my Quad MT Vernon AE's backup battery ran the stove just like the power never went off. It does drop down one heat setting to save/prolong battery life and then goes into a maint burn to keep the fire going until it auto cleans or the battery drops below 10.0 volts then shuts it's self off normally. I haven't tried pulling the plug to see what happens with the smoke if the battery backup wasn't there but I think it would vent it self due to the 15 foot straight up the chimney vent. The down side to the AE's battery backup system is, first it will not start the stove with the igniter but it will give you instructions on lighting it manually in the thermostats display, second it will not charge or maintain the battery. I have my backup battery mounted on the wall in the basement over the oil tank.


----------



## pete324rocket (Feb 7, 2011)

arnash said:
			
		

> I think the least expensive method might be to just have a strong battery and a power inverter connected to it, ready for use.  Since you have to be present anyway to shut the stove down, it isn't any big bother to unplug the stove from the wall and plug it into the inverter and restart the combustion/exhaust fan, and also the circulation fan if the stove is too warm to not use it.  Not having an electronic stove, I don't know if you can start the fans without using the igniter as in a normal start-up.  I have a 400 watt inverter and a spare battery that I think I should station near my stove just in case.   Come to think of it, alternatively, one could use a tank vacuum (like my Bisell carpet clearner) that allows attaching the hose to the air output port and plug it into the inverter and blow its air into the air intake pipe of the stove.  It seems that that would provide forced air just like the combustion fan does.
> The real question is "just how much air is needed to vent the stove gases"?   Could a strong computer cooling fan attached at the end of a horizontal exhaust pipe provide enough suction to draw out the combustion gases?  It certainly couldn't provide the strong air flow for clean combustion, but if it moves the combustion gases out of the stove at a decent speed, that might be enough to prevent the gases from entering the house.
> 
> Someone should invent a fan, that attaches to the end of the exhaust vent, that is driven by hot air pushing against its vans. I saw a version of that at the local stove store, but it stands on top of the stove and uses its rising heat to turn the fan and blow warm air forward.  That would be a perfect solution to venting stove gases without power.



Yes....inverter, large deep cycle battery and proper wiring and ends and a plastic box to put it all in..and a charger...under 400 bucks and get 6+ hours depending on the battery


----------



## Whimpster (Feb 7, 2011)

My little pellet stove back up power 

Three cylinder Lister with a 13.5 KVA generator.


----------



## SmokeyTheBear (Feb 8, 2011)

I'm surprised you were allowed to put such an item in a building.


----------



## Indiana (Feb 8, 2011)

I put them inside buildings all the time.  Just have to have exhaust vented out like a chimney.  No different than your stove or furnace.


----------



## SmokeyTheBear (Feb 8, 2011)

I didn't exactly see where that exhaust went in that picture.


----------



## Ro3bert (Feb 8, 2011)

Whimpster said:
			
		

> My little pellet stove back up power
> 
> Three cylinder Lister with a 13.5 KVA generator.



I could be wrong but that item on the wall near the muffler looks suspiciously like a crank handle. Emergency starter maybe.


----------



## Whimpster (Feb 8, 2011)

SmokeyTheBear said:
			
		

> I didn't exactly see where that exhaust went in that picture.




The exhaust is vented out through a 10 inch chimney liner,all to local code.
Generator setup came out of a lighthouse, they were used for backup power systems to keep the light running in a power failure.
This generator setup was very common in my area most of the government maintained light stations were run with this system until they changed over to solar power.
Most of the gen-sets went up for auction that's how I acquired mine.System is fully automated with a auto transfer switch.
Lost power for 3.5 days before Christmas in winter of 2009 system ran for 14 to 18 hours a day it was sure handy to have it, burned about 6 gallons of diesel.


----------



## Whimpster (Feb 8, 2011)

Ro3bert said:
			
		

> Whimpster said:
> 
> 
> 
> ...



LOL...very observant my friend...your right!
Works well.


----------



## exoilburner (Feb 8, 2011)

My pellet furnace is connected to a pure sin wave UPS which is connected to one of my house 120v circuits which is hooked to a transfer switch that can transfer that house circuit to my back-up generator.  Works very well when power gets dicey.  The UPS cleans up intermittent winter power and automatically transfers from itself to generator or utility power if they are present.  The UPS will keep my pellet furnace going for around 45 minutes if I set the furnace for minimum burn preventing the igniter from drawing power.  Plenty of time to get the generator (inverter) hooked up and running.

APC is one of the oldest and leading UPS companies.  Here is some pretty good information from them about pure sine wave and stepped approximated sine wave UPS.
_APC's Back-UPSÂ®, Back-UPS OfficeÂ®, Back-UPS ProÂ®, and PowerCellÂ® all output a "stepped-approximated" sine wave when the unit is On Battery. While this kind of waveform is ideal for computers and computer-related equipment, it may not be compatible for other types of loads like motor loads. If you are using non-computer loads with one of the above-mentioned UPSs, consult the manufacturer's specifications to determine if the equipment can run off of a "stepped wave". If it can't, then it will require a UPS that outputs a pure sine wave when On Battery. APC UPS models that do output a Pure Sine Wave include:  Smart-UPSÂ®, Matrix-UPSÂ®, and the SymmetraÂ® Power ArrayÂ®._


----------



## smalltown (Feb 9, 2011)

Mr. Heat Miser kudos on a well written post. Loved the "O" scope pictures.
Thanks smalltown


----------

