reliability

I would go towards the XXV for the reason the controls are onboard and not from a remote that seems to be the MtVernons weakness. Cleaning will have to leave to others as I have never got down and dirty with the MtVernon

Have owned the MVAE for over five years now, with no issues EXCEPT that stupid thermostat. Terrible design in which they put half the brains of the stove in a thermostat that is flaky at best, proprietary to that stove (nothing else will work) and ridiculously overpriced. I'm on my third one in those five years. The MVAE is a great stove but for that one major flaw, but it's a big one. I would go for the XXV.

Love Harmans, but also haven't had any experience with the MV. I've heard several complaints about that temp control so if you're planning on trying to heat mainly with a pellet stove, you might want to really think about that. However, if it will be supplemental heat, then maybe it wouldn't be a big deal for you.

Robert Tee said:

New to pellet stove. In the running currently are Harman XXV, and Quadrafire Mt Vernon AE. Would appreciate all thoughts on this choice. Would rate reliability number 1 in importance to us, and easy to clean and maintain number 2. Thank you for any advice.

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I had one of the first Mt Vernan AEs and had a Harman PC45 . If you have problems with the AE you better have a dealer who knows that stove or you will have problems and no solution. Cleaning a AE is pretty easy as is the Harman. The AE had lots of problems with the control . Static electricity would mess things up. Igniters would need replacing once a year.
The bad points to me were when it dumped the pot it has to run until the pot is empty of hot material then it dumps and restarts. During this time the fire is out and the house will cool off. If you have a small house it may not bother but if you are heating a large house it cools off to much and during cold weather it wouldn't keep us warm. The other thing was the ash tray was very small. I was burning corn at the time which produces more ash then pellets.
With a stove that never shuts off you don't have this down time.
I also prefer to have a stove I can service myself without being at the dealers mercy. With the highly automated AE most of the issues will be the control, the igniter, or the main electric control.
One good feature the AE had was its motors are 12 volt DC meaning you can connect a cable from the stove to a 12 volt battery and keep warm

I have both a MT. Vernon AE and a Harman Accentra, both are great stoves but I have to give the edge to the Harman. I too am not quite sold on the AE operation of always shutting down to clean and reignite. I also like that the Harman has a maintenance burn in between calls for heat and does not always have to shut down and restart. I replaced several igniters on the AE and none on the Harman. Now the AE is 7 years old and the Harman only 3 but still.

I just got a xxv so I can't contribute to the reliability of it, but man it does heat and its pretty easy to operate. It seems pretty quite but I have heard the AE is the quietest stove.

Robert Tee said:

New to pellet stove. In the running currently are Harman XXV, and Quadrafire Mt Vernon AE. Would appreciate all thoughts on this choice. Would rate reliability number 1 in importance to us, and easy to clean and maintain number 2. Thank you for any advice.

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Here are my opinions.

XXV
PROS

• Harman patented feed system. Efficient, solid, doesn't EVER jam up, deals with fines, can burn any kind of pellet with pretty much the same results to the end user. Good pellets, bad pellets, low density, high density, dusty, clean, its doesn't really matter. The system works well with everything.
• Heavy, lots of cast iron, great radiant qualities.
• Easy to fill, hopper is located dead center top and us somewhat cool so setting down a bag on the rim won't melt and you wont blow out your back trying to hoist 40lbs out and away from your body such as a rear mounted hopper.
• Parts are reasonably priced though I cannot see needing any for some time
• has an option for a 6" stove pipe adapter for a true wood stove looking install and exhaust is true dead center off the back
• variable speed blowers the user can set
• Built in room temp sensor
• virtually nothing needs to be removed other than the ash bin to perform maintenance
• Quiet running
• Harman's maintain the highest resale value over time
• Simple error reporting
• lower price than Mt Vernon

CONS

• Very large foot print, especially if you are installing in a corner. Most corner installations will require a 48" pad to meet clearances as the rear corner must be 9.75" from walls
• Very heavy stove. Impossible to move by yourself and VERY VERY VERY difficult to get in and up stairs. There are really no hand holds and there is nothing you can really take off to lower the weight other than the door and I would suggest not doing that as it's very difficult to recenter.
• Door gaskets wear out quicker than any other stove in their line up and will cause the unit to miss ignitions. (this is what happens when the door is not put on the right way too)
• Enamel units, enamel chips easily and when it does it exposes the white gesso undercoating (do not attempt to move an XXV enamel unit yourself, hire a furniture moving company or the stove shop that sold you the unit
• Modulation of stove is lost (variable burn rates) if a regular programmable TSTAT is used
• Mirror glass is stock (I don't like mirrored glass)

MT Vernon AE

PROS

• Solid stove with super high heat output
• Very very efficient
• Very very quiet
• Room sensing thermo control and programmable time and day TSTAT
• Error reporting
• Beautiful cast look and radiant qualities
• stove can be taken apart to some extent to reduce moving weight
• Can be installed 3" to walls in a corner
• Built in 12v power relay for battery back up
• Can burn multiple types of fuel
• 70 lb fuel hopper!

CONS

• WAY WAY WAY TOO MANY SENSORS!! Sensors usually fail and parts do not
• Highly electronic dependent
• Super expensive replacement parts, though you may not need any anytime soon....but you may, who knows
• kinda a small fire in a very large viewing glass
• TSTAT to run the unit must be hard wired in your house OR it hangs around with an exposed cord near the stove

Wilbur Feral said:

Have owned the MVAE for over five years now, with no issues EXCEPT that stupid thermostat. Terrible design in which they put half the brains of the stove in a thermostat that is flaky at best, proprietary to that stove (nothing else will work) and ridiculously overpriced. I'm on my third one in those five years. The MVAE is a great stove but for that one major flaw, but it's a big one. I would go for the XXV.

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IF you have gone through a few TSTATS you may want to consider replacing the 3 pole TSTAT wire before you entertain a fourth. I've found that the wire they give isn't a very good shielded wire and the continuity somehow gets screwed up. In every one of the jobs where I have had to replace the tstat, cutting the wires down to about half that 50' length solved the issue.

Here is a similar thread from 2007 you can check out.

https://www.hearth.com/talk/threads/harman-xxv-or-quadrafire-mt-vernon.8652/

I only have an opinion for the Harman and it will go a few days without having to anything other than add pellets, maybe knock some ashes into the ash pan, takes 10 seconds. I don't think I would ever purchase anything other than a bottom feed hopper. Best thing to have IMO but as stated no experience with the Quadrafire. Mine has treated me well since owning with the only issues being pellets not auto lighting if I don't clean out the ignitor area every other month or so. Which is not really an issue. It is part of your monthly cleaning any stove would require.

Good luck in your choice.

Robert Tee said:

New to pellet stove. In the running currently are Harman XXV, and Quadrafire Mt Vernon AE. Would appreciate all thoughts on this choice. Would rate reliability number 1 in importance to us, and easy to clean and maintain number 2. Thank you for any advice.

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First have a good look at all the parts you need just to operate the burn pot and the self cleaning mechanism
Everybody knows that the more mechanics parts there is, eventually the more repair you will have to go thru.

smwilliamson said:

IF you have gone through a few TSTATS you may want to consider replacing the 3 pole TSTAT wire before you entertain a fourth. I've found that the wire they give isn't a very good shielded wire and the continuity somehow gets screwed up. In every one of the jobs where I have had to replace the tstat, cutting the wires down to about half that 50' length solved the issue.

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Good thought - Thanks, Steve! Have now changed it.

BTW, can you think of any way to find out the signaling protocol used between stove and stat? I could likely replicate the logic (and improve it) if I knew more about the data being exchanged between the two. I could then run the stove with, say, a Raspberry Pi or Arduino.

You can buy many parts on ebay or Amazon.com - internet - just price around - most items I've gotten under 100.00 FYI

Ya but wait a minute, isn't than an enamel XXV in the OP's avatar ?