What's UP with an UPS?

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CAHazard

New Member
Jan 4, 2011
7
New Hampshire
Well I am finishing up this week on an install of a small pellet stove (a New Englander 55-SHP-10 to heat a 600 sq ft enclosed patio'd room addition)

And I have heard horror stories about smokey back drafts during power outages or just a normal shutdown (say due to high winds on the vent side of the house).

Some pellet stove owners have purchased an UPS (UnInterruptible Power Supply).
This does not appear to be a complete solution.

My question (esp. to knowlegeable owners of the 55-SHP-10 and similar electronic controlled stoves) is :

Why connect the entire stove to a UPS?
When all one needs to do is to guarantee that the exhaust fan continues for a good 20-25 minutes after "any" power removal
(intentional or unintentional).

Looking at the basic schematic, I see that the exhaust fan is actually a combustion fan.

Does that pose a problem?
- to jury_rig the combustion fan (about 100Watts typical vs 600-800Watts for the entire stove)
to run an extended 20 minutes (no matter what) after power is removed?
aside from the obvious warranty problems

It would not take much of an UPS and a basic relay circuit to do this.


Is this a feature the next generation stove could use or am I off in right field...
Will prolonging the exhaust fan actually keep combustion going?
How do these things stop>?


Chris H.
NH (or real motto is - "Live, Freeze, Then Die")
 
My stove only uses 125 watts on high fan with aruger motor running can see no reson to not just plug it into a ups and let it run it also provided surge protection and power conditioning for the stove also.
 
Prolonging the exhaust fan will keep the combustion going by drawing air through the system and burning whatever pellets are left in the burn pot. If you were going to rig something up to keep the fan going no matter what for an extra 20 min or so, go for it if you wish. You are probably better off following the manufacturers installation recommendations for your vent pipe. By doing that, you will create a natural draft that will help pull the smoke out from whatever pellets are left burning should you experience a power outage.

I recently had the power go out on me for the first time in 4 years while my englander was burning. Most of the smoke exited the stove through the vent pipe due to having a proper set up. Some smoke, (enough to smell) however did get out of the stove. When my power went out, I simply scooped out the pellets that were in the burn pot, and put them into my covered ash can that I have next to the stove to alleviate any more of a smoke issue.

If your power does happen to go out on you often, a UPS might be worthwhile. My power rarely goes out, so I don't have one.

I've also never had any problem at all with a smokey backdraft on a normal shut down.
 
Thanks for the quick reply - guys
And yes we here in these hilly parts of NH get FREQUENT power outtages... <sigh>

I will really get bummed - if I have to deal with extraneous smoke/soot issues as we just had the room carpeted and stuff.

I have figured on using the simplest manufacturer's recommendation on venting.
As I have a split level (2nd floor) hookup it will be -
straight out the wall for about 30 inches total, past the overhanging eave, and then 10 feet straight up above the roof line and terminate with a shrouded cap.
As with most people - no one can estimate what the weather/wind conditions will be at the cap for a given day (but the shrouded cap was great find).
Hopefully that will take care of accidental blowback on stormy windy days during a normal shutdown.

The Power rating for Direct Vent stoves can be a bit misleading
depending on the mode....

The exhaust fan itself is a reasonably low and easy power draw (no $600 UPS needed to drive that)
Add the current draws of the auger motors,
and then if the stove is set to cycle on and off (you have automatic ignition which will really drive the current up)
and finally the room blower...
So an UPS driving the stove will at best give protection for an hour or two or three at most?
(before the combustion process eventually gets interrupted for a longer blackout).

So again if the entire UPS consideration is to avoid coming home (or waking) to <cough> <cough> smoke
during any blackout (short, medium or long).

It makes sense to force the combustion process to finish (ie stove off/augers off and burn off all the pellets in the pot)
wait a bit, then let the exhaust/combustion fan switch or die off.

so the Battery only needs to drive that fan for the length of time it takes to burn a pot of pellets plus say 15 more minutes (easily done without big bucks).

Being an Electronics Technician I will have to risk (ahem "try") this...
namely - upon detection of outlet power loss to the stove,
switch UPS to exhaust/combustion fan - only -
(and let the small UPS and battery run out till you arrive).

The stove will be off following a fully completed burn.


Ch (remembering Murphy's Law)
 
I think the hot ticket would be a ups with a relay to interupt the control circuit. With just a ups you would have to be there when the power fails or you just delay the problem.
 
Yep!
Basically

Tho' I would reconnect the fan to the COM contacts of a good quality 110VAC 2A DPDT Switching Relay energized from the same outlet as the stove.
With normal powered operation the fan would get its juice from the controller (as it should via the NO contacts).

Once that Relay drops out... the fan picks up from the NC contacts (or the UPS Output) and will run (based on the UPS battery size) till well after the burn chamber has been consumed.

When power comes back the pellets will be consumed, the fire out, the stove will be off and the UPS battery recharges till next time around.
 
No, I meant break the thermostat circuit, so it would just go thru a normal shut down. Power comes back, thermostat gets control again. That is if you have a stove that can use a thermostat that actually starts and stops your stove.
 
Excellent suggestion! - and it seems less intrusive.
Am not sure if I personally will go w/ a thermostat (for now) as I have two separate sliding patio doors to help heat the rest of the house
and in a power failure I'm going to want it off till I get back.

but it's still a great suggestion for the boards...

by the way, what did you do with all that money?
 
Gotcha - Reading about the thermostat option for my stove New Englander 55SHP-10,

I see an alternate way of controlling the stove on loss of power...
autoswitch to UPS (entire stove)
and open thermostat connection

it will shut down

nice!
 
True - And I have lost a lot of stuff <grin>
But at times these discussions are not aimed for or at the technically faint of heart.

With all modifications aimed at improvement, there are safety and warranty ramifications.
That was my basic question.

Perhaps some stove makers will improve next years model by reading some of these posts...

I am happy with the suggestions presented
and can end this thread

Thanks All!

C
 
this idea would work perfect with a top feeder. A harman needs the auger to turn a little during shutdown to prevent burnback into the screw.
 
I posted a thread on this a couple days ago asking "why not use a computer/electronics UPS?". After reading several other threads where guys had rigged massive amounts of batteries (car batteries, golf cart batteries, etc.) to run their stove for 6-10 hours+ in the event of a power outage, I was a bit perplexed as to why that much battery power would be needed. Read the context of those posts, many of those guys are banking on running their stoves for extended periods of time on those UPS's, if you have generator power, you don't need huge battery capacity (which makes a UPS expensive). Personally, I didn't need such a rig because (A) I don't run my Fahrenheit furnace when my wife or myself are not home, nor will we ever run it when we're away for more than an hour or two, and (B) if my power DOES go out, I can plug my 5500W gas generator into a receptacle in my garage which powers my entire breaker, flipping my entire house over to generator power requires less than 10 minutes.

So, I only need a UPS capable of operating my pellet burner for 15-20 minutes, either to allow myself time to get the generator going, or to put my furnace into power-down mode. Once I send the furnace into shut-down mode, the flame is out in 5 minutes, hot coal base is gone within 10 minutes. There are higher-end UPS's that will give your pellet burner "cleaner power", such as PFC UPS's, that is what was recommended by another forum user, the recommendation made sense because the power boards in modern pellet burners are sensitive to power glitches, but I don't need beefy UPS based on my requirements. I'll go with a PFC UPS with 1000VA or more (1000VA should give me at least 15 minutes of run time on the fans/auger), such as this one for $139:

http://www.amazon.com/CyberPower-Ad...N192/ref=sr_1_2?ie=UTF8&qid=1294234428&sr=8-2

My PL vent pipe also has a 6' rise to it, so in theory smoke/exhaust should continue to be pulled up the vent if my power goes out while the furnace is running.
 
CAHazard said:
Yep!
Basically

Tho' I would reconnect the fan to the COM contacts of a good quality 110VAC 2A DPDT Switching Relay energized from the same outlet as the stove.
With normal powered operation the fan would get its juice from the controller (as it should via the NO contacts).

Once that Relay drops out... the fan picks up from the NC contacts (or the UPS Output) and will run (based on the UPS battery size) till well after the burn chamber has been consumed.

When power comes back the pellets will be consumed, the fire out, the stove will be off and the UPS battery recharges till next time around.

I think that's a great idea that should be adopted by all the stove makers since it positively will eliminate any complaints of smoke backup no matter how you install the stove! DO IT!!!!!
 
This works great for me.........
 

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ChrisWNY said:
I posted a thread on this a couple days ago asking "why not use a computer/electronics UPS?". After reading several other threads where guys had rigged massive amounts of batteries (car batteries, golf cart batteries, etc.) to run their stove for 6-10 hours+ in the event of a power outage, I was a bit perplexed as to why that much battery power would be needed. Read the context of those posts, many of those guys are banking on running their stoves for extended periods of time on those UPS's, if you have generator power, you don't need huge battery capacity (which makes a UPS expensive). Personally, I didn't need such a rig because (A) I don't run my Fahrenheit furnace when my wife or myself are not home, nor will we ever run it when we're away for more than an hour or two, and (B) if my power DOES go out, I can plug my 5500W gas generator into a receptacle in my garage which powers my entire breaker, flipping my entire house over to generator power requires less than 10 minutes.

So, I only need a UPS capable of operating my pellet burner for 15-20 minutes, either to allow myself time to get the generator going, or to put my furnace into power-down mode. Once I send the furnace into shut-down mode, the flame is out in 5 minutes, hot coal base is gone within 10 minutes. There are higher-end UPS's that will give your pellet burner "cleaner power", such as PFC UPS's, that is what was recommended by another forum user, the recommendation made sense because the power boards in modern pellet burners are sensitive to power glitches, but I don't need beefy UPS based on my requirements. I'll go with a PFC UPS with 1000VA or more (1000VA should give me at least 15 minutes of run time on the fans/auger), such as this one for $139:

http://www.amazon.com/CyberPower-Ad...N192/ref=sr_1_2?ie=UTF8&qid=1294234428&sr=8-2

My PL vent pipe also has a 6' rise to it, so in theory smoke/exhaust should continue to be pulled up the vent if my power goes out while the furnace is running.

If the goal is to merely shut the stove down then following the manufactures venting instructions will be all that is required (yeah, I know rarely happens).

If the goal is to allow time for getting home from wherever to getting a generator running then a certain amount of battery is required.

If the goal is to provide backup for extended periods of time without a generator then you need a substantial battery package.

So it all depends upon what ones goal is.

Remember what might work for you may be the worst possible solution for someone else.
 
What's UP w/ an UPS?
- The Whole Picture -

well to reiterate my original post

There are times when smoke/soot blowback occurs and you are not there!

1. Power Outtages (and they are very frequent where I am... once or twice a month on the average).
and
2. On rare occasion when high winds momentarily hit the vent cap and pressurize that pipe just after the exhaust/combustion fan has been stopped by the stove's controller
(this 2nd case can be avoided by using a shielded or shrouded vent cap that does not have any open exposed sides to the wind). Along with good venting practices discussed throughout this site.

Either way - "the" solution is to maintain the exhaust fan well after power has been lost or well after a manual shutdown to guarantee the vent pipe is pressurized out
until the stove burn pot is cold dead and not still smouldering (about 20-30 minutes should work).

Many people have used a med. to large UPS (but length of a power outtage often cannot be determined)
so when that battery ultimately dies and the exhaust/combustion fan stops, blowback when you are not home is apt to happen.

We have discussed (2) possible improvements along with input on safety and warranty issues.
1. Aside from a general UPS for the stove (which will work for rather short outtages less than 2-3 hours)
2. Another setup is to detect power loss to the stove and just UPS the exhaust fan.
The stove and feed augers be off, the burn chamber and fans will continue to burn and work until the chamber fire dies and shortly after the UPS will go offline as the battery dies
(a far simpler cheaper and more efficient option but it requires rewiring the stove's fan :( ) <ouch>.

an even better option is to:

3. Detect power loss to the stove and disconnect/open the thermostat input (if using a suitable thermostat capable stove) and the stove will simply coast to a stop not feeding any pellets or even running the room blower
(as it is over room temp) till the burn chamber is dead. Some time later (depending on battery size) the UPS goes off line as the battery is dead and the stove is off until you return.

And in all three cases when power comes back the battery gets recharged thru the UPS until next time.


This last option may not even affect the warranty and will be the one I will try.
As when the power goes... I want to feel safe that the stove shutsdown on its own until I get back (with the exhaust fan going all the way to the end).

Thanks For The Input People,
The stove manufacturers only need to offer a thermostat disconnect on power loss option (to cure this small annoyance).
 
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