? on Mt Vernon stove, manual vs automatic mode

[UpTheHill]

I bought the MT Vernon this fall and so far have liked it. But recently with colder outside temps, I have come up with either a problem, or a design feature (depends on opinion I guess).

in automatic mode it will go from Low to Medium heat output depending on how much heat is required, but I've never seen it 't go to high heat output.
I've called the place I bought it and they came out to look, they then called the tech support people who said it was running as designed.

Here's the scenario.
I have the thermostat set for 70 degrees with a temp differential of 1 and normally it keeps the house between 69 - 70 no problem.
BUT, it it's 20 deg or less out, the stove never goes above medium and the actual temp slips down to 66 degrees, and basically runs forever on medium never able to get the temp up higher.

WHEN I change from automatic mode to manual mode, and select high or even medium high, within 30 - 40 minutes the house is back up to 70 degrees and maintains the 69 - 70 degree range easily.

Mt Vernon tech support says this is normal as it only goes into high mode, when the temp differential is larger, but I think that if the stove has been running for 3 - 4 hours and STILL can't get the house to 70 degree, then it needs to know enough to increase the heat output itself.

any thoughts on this?

TIA, Dave

 

[tsmith]

Dave, in auto mode the stove is designed to ramp down as it gets closer to the set point. if you have it at 70, when it reaches 68 it will ramp down. You can fix this by setting the temp 2 degrees higher than you actually want. I found the following settings to work well for me.

Auto mode, hardwood pellet, set at 76 degrees with an offset of 3.5 degrees. The stove will reach 74 degrees and then maintain that temp until it does autoclean after about three hours running. After autoclean it will shut down until the temp drops to 70.5 degrees then start back up again. This allows me longer run times with less start ups which are hard on the ignitor. The other alternative is to just run it on manual med high or whatever works for you. You will need to try different settings to find what works for you. Hope this helps.
Happy Thanksgiving
Troy

 

[smoke show]

I use auto mode.
I agree with tsmith.
You should just bump up your set temp.
design flaw? maybe.
eats too much fuel on hi anyway.

 

[tsmith]

I don't know that it's a design flaw. I believe it is meant to be like stoves that have a high/low setting. Where as other stoves run at higher speeds to obtain desired temp then drops to low setting until heat is called for again. The Quad does basically the same thing only it doesn't reach set temp, it lowers itself before it reaches it, usually at 2 degrees below set temp. Therefor once again if you just set it 2 degrees higher than what you want, it will reach the temp you desire and maintain it.

 

[smoke show]

I thought the op suggested it was a flaw.
But after rereading the post I see he says design feature.
I personally like it that way.

 

[tsmith]

This is the first year I tried auto and I too like it. I am getting longer runtimes and my home is staying at an even temp. Just started snowing here. Nice and warm inside.

 

[vgrund]

Opinions vary on auto versus manual. Some people feel their stoves use more fuel in auto mode. I have not done a scientific comparison between the two modes, so I'll withhold comment.

 

[Countryboymo]

The stove might use more fuel in auto vs manual but if it keeps the room or house closer to a comfortable temp without a bunch of swings it might be worth it.

I would think it would use less fuel in the long run because through the night the stove usually needs turned up and if no one is there to turn it down if it warms up in the morning it would just get warmer in the house. The auto temp could either trim the fuel down or shut the stove off completely depending on the features.

I have a thermostat on mine but it stinks so I just flip the lever all the way to turn it on and the other and kick it off. I will be getting a digital and checking into this.

 

[UpTheHill]

Auto mode, hardwood pellet, set at 76 degrees with an offset of 3.5 degrees. The stove will reach 74 degrees and then maintain that temp until it does autoclean after about three hours running. After autoclean it will shut down until the temp drops to 70.5 degrees then start back up again. This allows me longer run times with less start ups which are hard on the ignitor.
Troy

yeah I could see how this would work, but if it's not cold as a witches .... body part outside, then I'd be heating the house warmer then my wife or I like and therefore wasting the pellets.

I guess I'll leave the auto mode setting the way I have it it, since it does keep the house at a temp that's comfortable for us most of the time, then just switch it to manual on cold stormy days / nights to give it the added boost it needs, since it only requires a 1/2 hour or so for it to heat the house up on nasty cold mornings.

I still think it's a rotten design, since the stove isn't heating the house to the temp set, when it could easily have some piece of software inside to say something like
"if (stove running for more then 1 hour and temp not rising)
then (increase heat output)
else (keep doing what your doing)"

seems simple enough for a 10 year old to code this in, but maybe QuadFire only hires 9 year old engineers
(OK OK Sarcastic joke in hopes of getting Quadfire's attention if they happen to read this)


thanks for all the answers and opinions.
Dave

 

[ernest99]

For what it's worth my Mt Vernon will change its heat output proportionally with the difference between the room temperature and the temperature setpoint, and I believe that's how it should work.

In other words, if the room is at 70° and you've set the thermostat to 71° its heat output will probably be "L" (if it's on at all).

If the room is at 70° and your thermostat is set to 90° then the heat output will probably be "H".

In between these extremes the heat output should change from "L" to "ML", "M", "MH" then finally its maximum of "H".

It is possible that your fan setting could prevent a high heat output - I'm just guessing, but try changing your fan speed from "quiet" to "normal".

seems simple enough for a 10 year old to code this in, but maybe QuadFire only hires 9 year old engineers
(OK OK Sarcastic joke in hopes of getting Quadfire's attention if they happen to read this)

You're probably right, unfortunately I don't know anyone at QF/HNI who understands some of these basic concepts. Maybe their engineers are kept locked away and are prevented from interacting with anyone else at the company.

 

[UpTheHill]

In other words, if the room is at 70° and you've set the thermostat to 71° its heat output will probably be "L" (if it's on at all).

If the room is at 70° and your thermostat is set to 90° then the heat output will probably be "H".

In between these extremes the heat output should change from "L" to "ML", "M", "MH" then finally its maximum of "H".

and according to Quadfire that's how it works.
my point is that if it's only 2 - 3 degrees off, and it's working at LM or M and it's been been doing that for say 2 hours and not getting any closer to the desired temp. meaning it's still 2 - 3 degrees low, then it should know to kick it up to a higher heat output, like MH or H

 

[jtakeman]

In other words, if the room is at 70° and you've set the thermostat to 71° its heat output will probably be "L" (if it's on at all).

If the room is at 70° and your thermostat is set to 90° then the heat output will probably be "H".

In between these extremes the heat output should change from "L" to "ML", "M", "MH" then finally its maximum of "H".

and according to Quadfire that's how it works.
my point is that if it's only 2 - 3 degrees off, and it's working at LM or M and it's been been doing that for say 2 hours and not getting any closer to the desired temp. meaning it's still 2 - 3 degrees low, then it should know to kick it up to a higher heat output, like MH or H

UpTheHill,

Are you in quiet mode? Like earnest99 stated above. Maybe thats what is limiting the stove from going into MH or H?

 

[ernest99]

... my point is that if it's only 2 - 3 degrees off, and it's working at LM or M and it's been been doing that for say 2 hours and not getting any closer to the desired temp. meaning it's still 2 - 3 degrees low, then it should know to kick it up to a higher heat output, like MH or H

The controller could easily be designed to do that but yes, it appears QF hasn't put the effort into designing it that way.

The wall unit appears to act strictly as a proportional control: it modifies heat output as a function of the difference in room temperature vs. setpoint. As the room gets closer to the desired temperature, the stove's heat output is reduced in steps. The problem with that is the room may never exactly equal the temperature you set - it approaches the setpoint asymptotically.

The way to design a controller to do what you want would be to integrate the temperature difference over time: this would effectively take the sum of the temperature error (the difference between set vs. actual) over time, and adjust the heat output accordingly. It's not difficult to do, but I'd imagine the engineers who designed the thing thought they were doing pretty good with the simple proportional control it has - a pretty advanced idea for a heating appliance.

If the room you're heating weren't as large as it probably is, the stove might overshoot the setpoint every time it came on, causing it to shut off and repeat with needless frequency. Instead, it gets close to the temperature you want, and essentially stays there at a low heat output, right? With a tiny bit more engineering effort, QF could have made the stove exactly equal the setpoint and stay there too. The tradeoff might have been some overshoot of the desired setpoint, but this too could be compensated for by incorporating a derivative function in the wall unit.

All three of these parameters - proportional, integral, derivative - comprise what's known as a PID controller:

where u(t) is the wall unit's output to the stove. All it's doing though is the first term. For something as advanced as the Mt. Vernon, it's kind of a disappointment. It's not difficult to code the rest in software; I've done it.

Compare this to an electric (or gas or oil) heater controlled by a simple on/off thermostat. The heater runs until the room temperature reaches the setpoint, then it shuts off. Consequently, the room's temperature is never constant - it's always wandering in a range of a degree or two above and below the thermostat's setting (electronic "adaptive" thermostats better at this than others). On the other hand, with its ability to vary its heat output your Mt. Vernon is capable of keeping the room at a constant temperature. A couple degrees below what you've set, sure, but at least it's constant. Given the alternative of frequent startup/run/shutdown/clean cycle demands required for a pellet stove, it's not a bad idea.

 

[tsmith]

Again, the simple solution is to just set the thermo 2 degrees higher than you actually want, works great for me, nice constant even temps.

 

[smoke show]

Again, the simple solution is to just set the thermo 2 degrees higher than you actually want, works great for me, nice constant even temps.

me too.
if it hit the set temp relatively fast every time it would decrease ignitor life even more than it is already.

 

[smg64ct]

This is my second season with the mt vernon. I run it on auto and set the temp at 73. I don't like when the stove cycles on and off to much. When it gets really cold I put it on manual.

 

[ernest99]

In other words, if the room is at 70° and you've set the thermostat to 71° its heat output will probably be "L" (if it's on at all).

If the room is at 70° and your thermostat is set to 90° then the heat output will probably be "H".

In between these extremes the heat output should change from "L" to "ML", "M", "MH" then finally its maximum of "H".

and according to Quadfire that's how it works.
my point is that if it's only 2 - 3 degrees off, and it's working at LM or M and it's been been doing that for say 2 hours and not getting any closer to the desired temp. meaning it's still 2 - 3 degrees low, then it should know to kick it up to a higher heat output, like MH or H

UpTheHill,

Are you in quiet mode? Like earnest99 stated above. Maybe thats what is limiting the stove from going into MH or H?

I just checked mine and it appears changing the convection blower speed from "quiet" to "normal" has no effect on this characteristic. I also tried changing the temp differential - I didn't think it would have any effect either, and it doesn't.

This could all be fixed by uploading new firmware to the wall unit. The thing already has a fairly robust algorithm - improving it can't possibly be that difficult, unless it's completely out of memory (which is hard to imagine).

Bummer!

 

[UpTheHill]

In other words, if the room is at 70° and you've set the thermostat to 71° its heat output will probably be "L" (if it's on at all).

If the room is at 70° and your thermostat is set to 90° then the heat output will probably be "H".

In between these extremes the heat output should change from "L" to "ML", "M", "MH" then finally its maximum of "H".

and according to Quadfire that's how it works.
my point is that if it's only 2 - 3 degrees off, and it's working at LM or M and it's been been doing that for say 2 hours and not getting any closer to the desired temp. meaning it's still 2 - 3 degrees low, then it should know to kick it up to a higher heat output, like MH or H

UpTheHill,

Are you in quiet mode? Like earnest99 stated above. Maybe thats what is limiting the stove from going into MH or H?

nope it's in normal mode

 

[mainegeek]

I've had my Mt. Vernon AE for three seasons now and I always run it on manual / medium-high with a 1.5 degree swing... that seems to work well. I also found auto ran longer and never really got to the set temperature.

Keep in my mind using Auto mode will lead to "dirtier" burns

 

[Gweeper64]

I've had my Mt. Vernon AE for three seasons now and I always run it on manual / medium-high with a 1.5 degree swing... that seems to work well. I also found auto ran longer and never really got to the set temperature.

Keep in my mind using Auto mode will lead to "dirtier" burns

Aren't you restarting frequently though? How many ignitors have you replaced?

I tend to leave mine in auto mode with a 2 to 2.5 degree differential. Temp is usually set somewhere around 74 keeps the family room around 70 and the bedrooms about 67+/- . When it is really cold out (teens and below), I put it in manual mode on medium/low or medium.

mainegeek is right about "dirtier" burns in auto mode though. It isn't so much the fact that it is auto, it is that it runs on "low" more which makes it "dirtier".

[edit: auto mode dirtier, not manual]

 

[rona]

how many people have tried running it using the 12 volt cord and a 12volt battery. It will not reach the highest fan setting wut it will burn steady for between 6 and 8 hours thus eliminating the annoying habit of start run stop over and over all day causing premature burn out of the igniter.
I do agree that Quadra fire is hiding the capability of this stove. The dealers should be able to reprogram it with different software much like the Bixby owners can do.

 

[Gweeper64]

how many people have tried running it using the 12 volt cord and a 12volt battery. It will not reach the highest fan setting wut it will burn steady for between 6 and 8 hours thus eliminating the annoying habit of start run stop over and over all day causing premature burn out of the igniter.
I do agree that Quadra fire is hiding the capability of this stove. The dealers should be able to reprogram it with different software much like the Bixby owners can do.

The 12v capability for emergencies was one thing that was attractive to us when we were shopping. We've never used it so far though. I need to buy a cable and deep cycle battery to have on hand.

I think the software in the control unit is upgradeable, but only by authorized service techs.

 

[ernest99]

how many people have tried running it using the 12 volt cord and a 12volt battery.

The Mt. Vernon is essentially a 12v stove, everything but the igniter runs on 12 v dc, so when you use a battery not much changes.

I have mine connected to a 12v battery full time as a backup. The battery is on a trickle charger. The ignitor will not operate while on battery so you have to light the fire yourself - a propane torch will do, or soak a handful of pellets with some alcohol-based gel hand cleaner. After the fire is lit it runs normally except the highest fan speed and highest heat output are not available while on battery. When the setpoint temperature is met the heat is reduced to minimum and the wall controller will annunciate "maintenance burn" which means it's just keeping the fire lit. Eventually it will shut down due to the need to clean the pot, and you have to light it again.

In my case the battery backup is mostly for occasional power failures. If the AC power is interrupted even briefly, it forces a shutdown and auto-clean cycle so that gets annoying.

I do agree that Quadra fire is hiding the capability of this stove. The dealers should be able to reprogram it with different software much like the Bixby owners can do.

The firmware is updatable with a laptop that attaches to the wall unit with a proprietary USB connector and a laptop running Windows-based software, but QF hasn't updated their firmware anyway. I have a description (somewhere) that describes it, but they won't release those tools to anyone but a dealer. I'll see if I can find the description and I'll post it here.

I don't think QF even knows how their stove is supposed to work anyway - see this post: https://www.hearth.com/econtent/index.php/forums/viewthread/63962/

Their dealers didn't know much about the battery backup feature either.

 

[ernest99]

Keep in my mind using Auto mode will lead to "dirtier" burns

Why?

 

[mainegeek]

A low burn is always a dirtier one