If your VC Merrimack uses too much wood

Shrek Ogre

Member
Mar 6, 2017
11
Chester Springs, PA
Hello everyone, I'm a newbie on this forum.

It seems that many are disappointed with their Merrimack inserts for burning too much wood or unable to sustain a burn overnight. We're on our 4th year with a Merrimack, we were initially disappointed for the same reasons but have fixed it.

The Merrimack introduces fresh air through the secondary air tubes at the top of the box which you cannot control. I disabled those secondary air tubes, now we can turn the air control all the way close and have beautiful licking flames that last for hours. We load it up half-full before bedtime, 8 hours later there still are flames. A few times I could re-establish a fire after 20 hours using kindling on the hot coals that remained. We now use 1/4 the firewood compared to the first 2 years for similar burn times.

This change likely affects the emissions if I assume that is the purpose of the secondary air.

Countering that, burning 1/4 the amount of wood for the same heat gain has probably less emissions than burning 4x more at lower emissions level. Factor in is the emissions from effort to collect, split, move and stack 4x more fallen trees, almost all of it involving using gas motors in my case (chainsaw, diesel tractor, splitter, truck etc.). We process our own firewood but if we purchased it from elsewhere, then we'd have to include the emissions of hauling the load also. Lastly, factor in heating with oil when the cleaner-burning Merrimack runs out of heat after it wasted its wood up the chimney, then I'm pretty certain that overall it's better for the environment also. It certainly is a lot better for me and my budget.

With that said, a few questions. Is that ethically OK to disable the secondary air tubes? If so, should I post the fairly simple process to do the fix?
 

begreen

Mooderator
Staff member
Nov 18, 2005
83,703
South Puget Sound, WA
The insert is designed to burn cleanly and not smolder. Decreasing the efficiency of the insert is not going to reduce fuel consumption unless the insert was run incorrectly in its unaltered state. What has been described sounds like reverting it to a 50 yr old design. Yes, it's possible to reduce fuel consumption, but at a much lower heat output. If 4x less wood is being burned, much less heat is being produced. Perhaps this insert was the wrong choice to start with? Is sounds like the appliance like operation of a cat stove is more desired for this installation.
 

Shrek Ogre

Member
Mar 6, 2017
11
Chester Springs, PA
Thanks for your input but perhaps you don't know the specifics of the Merrimack concerns: owners say that it is burning through a full firebox in a few hours, disappointed about the heat gain from fuel concerned. Having used VC fireplaces for over 10 years I know what to expect, and when I burned through my entire 11 cord stash in the first year with the new Merrimack, I knew it had a problem.

I run it just a hot as before, harvesting at the same rate as before because firebox temperature is the same with or without the afterburners. I never smolder a fire.
 

webby3650

Master of Fire
Sep 2, 2008
10,932
Indiana
Maybe I don't understand either? If you are burning the stove just as hot, how are you using 4x less fuel?

Removing the secondary combustion from the firebox does not sound like the answer. Could you rather come up with a way to meter the secondary air? Slowing it down can be a big help on certain installs, but eliminating it altogether doesn't seem like the answer.
 

moresnow

Minister of Fire
Jan 13, 2015
1,201
Iowa
Interesting. My previous stove had a "set" secondary air supply as well as a primary air supply that really would not close down well. I applied a manual override (think crumpled tin foil) to both supply locations as a air reduction experiment. Much longer burn times with increased STT over that time. Less wood. More heat. I was thrilled. Stock air supply would nuke a load in a blink. This was my honest experience. Not the same stove but it sounds like a similar problem.
 

webby3650

Master of Fire
Sep 2, 2008
10,932
Indiana
This is all thanks to our EPA. Before it's all over, non-cats will have have only med-high and cats will only have low-med. Customer satisfaction and usability does not matter, only low emissions...
 

Easy Livin’ 3000

Minister of Fire
Dec 23, 2015
2,668
SEPA
This is all thanks to our EPA. Before it's all over, non-cats will have have only med-high and cats will only have low-med. Customer satisfaction and usability does not matter, only low emissions...
I have this funny feeling that the EPA won't be bothering with this for a while. Or, perhaps because wood burning takes money out of the oil companies pockets, it'll become completely illegal. I guess we'll see...
 

webby3650

Master of Fire
Sep 2, 2008
10,932
Indiana
I have this funny feeling that the EPA won't be bothering with this for a while. Or, perhaps because wood burning takes money out of the oil companies pockets, it'll become completely illegal. I guess we'll see...
Maybe they are held at bay for a moment, but the damage has already been done. All the manufacturers have been scrambling to meet the new regulations, theybdonwhat it takes to stay in business. For non-cats, that means loss of controllability unfortunately. Now they backed off a little and some manufacturers are offering easier to use, more reliable units.
 

Easy Livin’ 3000

Minister of Fire
Dec 23, 2015
2,668
SEPA
Hello everyone, I'm a newbie on this forum.

It seems that many are disappointed with their Merrimack inserts for burning too much wood or unable to sustain a burn overnight. We're on our 4th year with a Merrimack, we were initially disappointed for the same reasons but have fixed it.

The Merrimack introduces fresh air through the secondary air tubes at the top of the box which you cannot control. I disabled those secondary air tubes, now we can turn the air control all the way close and have beautiful licking flames that last for hours. We load it up half-full before bedtime, 8 hours later there still are flames. A few times I could re-establish a fire after 20 hours using kindling on the hot coals that remained. We now use 1/4 the firewood compared to the first 2 years for similar burn times.

This change likely affects the emissions if I assume that is the purpose of the secondary air.

Countering that, burning 1/4 the amount of wood for the same heat gain has probably less emissions than burning 4x more at lower emissions level. Factor in is the emissions from effort to collect, split, move and stack 4x more fallen trees, almost all of it involving using gas motors in my case (chainsaw, diesel tractor, splitter, truck etc.). We process our own firewood but if we purchased it from elsewhere, then we'd have to include the emissions of hauling the load also. Lastly, factor in heating with oil when the cleaner-burning Merrimack runs out of heat after it wasted its wood up the chimney, then I'm pretty certain that overall it's better for the environment also. It certainly is a lot better for me and my budget.

With that said, a few questions. Is that ethically OK to disable the secondary air tubes? If so, should I post the fairly simple process to do the fix?
Does the glass stay clean now that you have removed the tubes?
 

Easy Livin’ 3000

Minister of Fire
Dec 23, 2015
2,668
SEPA
Maybe they are held at bay for a moment, but the damage has already been done. All the manufacturers have been scrambling to meet the new regulations, theybdonwhat it takes to stay in business. For non-cats, that means loss of controllability unfortunately. Now they backed off a little and some manufacturers are offering easier to use, more reliable units.
Please offer some examples of the easier to use, more reliable units!
 

EatenByLimestone

Minister of Fire
Jul 12, 2006
7,343
Schenectady, NY
Hello everyone, I'm a newbie on this forum.

It seems that many are disappointed with their Merrimack inserts for burning too much wood or unable to sustain a burn overnight. We're on our 4th year with a Merrimack, we were initially disappointed for the same reasons but have fixed it.

The Merrimack introduces fresh air through the secondary air tubes at the top of the box which you cannot control. I disabled those secondary air tubes, now we can turn the air control all the way close and have beautiful licking flames that last for hours. We load it up half-full before bedtime, 8 hours later there still are flames. A few times I could re-establish a fire after 20 hours using kindling on the hot coals that remained. We now use 1/4 the firewood compared to the first 2 years for similar burn times.

This change likely affects the emissions if I assume that is the purpose of the secondary air.

Countering that, burning 1/4 the amount of wood for the same heat gain has probably less emissions than burning 4x more at lower emissions level. Factor in is the emissions from effort to collect, split, move and stack 4x more fallen trees, almost all of it involving using gas motors in my case (chainsaw, diesel tractor, splitter, truck etc.). We process our own firewood but if we purchased it from elsewhere, then we'd have to include the emissions of hauling the load also. Lastly, factor in heating with oil when the cleaner-burning Merrimack runs out of heat after it wasted its wood up the chimney, then I'm pretty certain that overall it's better for the environment also. It certainly is a lot better for me and my budget.

With that said, a few questions. Is that ethically OK to disable the secondary air tubes? If so, should I post the fairly simple process to do the fix?

How does the chimney look after a season of burning?
 

webby3650

Master of Fire
Sep 2, 2008
10,932
Indiana
Please offer some examples of the easier to use, more reliable units!
The Lopi Rockport is a brand new stove that has been on display at the trade show for several years. Looks like a solid unit, was hybrid, then non-cat, then back to hybrid.. this is EPA driven. All the gas units were going with IPI, because of the new EPA mandates, they backed off, now the major players are offering milivolt valves again. IPI is very unpredictable, standing pilot milivolt gas appliances are bullet proof for the most part.
 

WoodyIsGoody

Minister of Fire
Jan 16, 2017
1,437
Pacific NW Washington
This is all thanks to our EPA. Before it's all over, non-cats will have have only med-high and cats will only have low-med. Customer satisfaction and usability does not matter, only low emissions...
I've been burning wood for 35 years and I wouldn't install a non-EPA stove even if it were given to me. And it has nothing to do with air pollution. Yes, non-EPA stoves could be turned as low as desired but, if not burned hot, efficiency was in the garbage because unburnt gases simply escaped up the flue. Except the emissions that bonded inside the flue waiting to burn your house down! Burning all the combustible gases respects the work I put in cutting, splitting, stacking and hauling all that wood inside and keeps my family and friends safe.

The situation is analogous to EPA regulation of automobile emissions. The need to meet the new standards ushered in the era of EFI (electronic fuel injection). Car "enthusiasts" predicted unreliability, breakdowns and drivability issues. They complained loudly and incessantly (often laced with profanity). Instead of the predicted disasters, we got improved MPG, better engine longevity, better drivability and reliability and more peak hp. Engine deposits were also reduced.

Some people are simply opposed to any change even when that change is a massive improvement.
 

WoodyIsGoody

Minister of Fire
Jan 16, 2017
1,437
Pacific NW Washington
All the gas units were going with IPI, because of the new EPA mandates, they backed off, now the major players are offering milivolt valves again. IPI is very unpredictable, standing pilot milivolt gas appliances are bullet proof for the most part.
Intermittent Pilot Ignition is actually more reliable overall vs. standing pilot ignition. Most people who have had experience with many gas appliances have cursed the old style ignition systems more than a few times! I like the IPI's that have small battery back-up so they continue to work during power outages. Before these were available a standing flame ignition was a no-brainer but now there are better choices. A standing pilot ignition uses around 700 btu/hour 24/7. Not good.
 

webby3650

Master of Fire
Sep 2, 2008
10,932
Indiana
Intermittent Pilot Ignition is actually more reliable overall vs. standing pilot ignition. Most people who have had experience with many gas appliances have cursed the old style ignition systems more than a few times! I like the IPI's that have small battery back-up so they continue to work during power outages. Before these were available a standing flame ignition was a no-brainer but now there are better choices. A standing pilot ignition uses around 700 btu/hour 24/7. Not good.
The idea of IPI is wonderful. However, the technology is still in need of improvement. You have to be living under a rock if you think IPI is more reliable than standing pilot. Even the manufacturers are realizing this and reverting back to standing pilot in the new units.
 

jetsam

Minister of Fire
Dec 12, 2015
4,720
Long Island, NY
youtu.be
This is all thanks to our EPA. Before it's all over, non-cats will have have only med-high and cats will only have low-med. Customer satisfaction and usability does not matter, only low emissions...
This is the same EPA that made the rules that resulted in us having what we all refer to as 'EPA stoves'... Which, in our lingo, means 'more heat, less wood, why would you even have a pre-EPA stove'.

I am sorry that it is due to die a gruesome death; it's really helped us out and was continuing to do so (unless you think the stove manufacturers will continue to spend all that R&D money voluntarily?).


Will some bad decisions and designs come out as manufacturers struggle to comply with new rules? Yep. Is likely to be awesome for us in the long run? Yep.

My BK is possibly the best available technology, but it still passes unburned fuel (go look at my chimney cap if you doubt me). On higher settings, it wastes a lot of heat up the flue. It is the best stove I have ever had- but I don't want to be using that technology in 20 years.
 
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jetsam

Minister of Fire
Dec 12, 2015
4,720
Long Island, NY
youtu.be
Also, be aware that there is probably going to be a large difference between a product from the company that goes to engineering and says, 'OMG make all of our old stoves technically compliant with these awful new rules by next month so we can keep selling them', and the company that goes to engineering and says, 'These are the upcoming rules, please figure out the design constants we need to make sure the next product line hits those targets'.

They both might crank out an awful stove on the first try, but company #1 will probably never make anything BUT awful stoves, and company #2 will probably come up with some cool stuff.
 

EatenByLimestone

Minister of Fire
Jul 12, 2006
7,343
Schenectady, NY
I think we'll be seeing catalysts that can light off earlier so they can catch more VOCs released in early burning.
 

webby3650

Master of Fire
Sep 2, 2008
10,932
Indiana
This is the same EPA that made the rules that resulted in us having what we all refer to as 'EPA stoves'... Which, in our lingo, means 'more heat, less wood, why would you even have a pre-EPA stove'.

I am sorry that it is due to die a gruesome death; it's really helped us out and was continuing to do so (unless you think the stove manufacturers will continue to spend all that R&D money voluntarily?).


Will some bad decisions and designs come out as manufacturers struggle to comply with new rules? Yep. Is likely to be awesome for us in the long run? Yep.

My BK is possibly the best available technology, but it still passes unburned fuel (go look at my chimney cap if you doubt me). On higher settings, it wastes a lot of heat up the flue. It is the best stove I have ever had- but I don't want to be using that technology in 20 years.
I assume you are well aware that I fully promote modern EPA approved stoves. That is not my point. My point is that they are making some unreasonable requirements, to comply, stove manufacturers do what they must. For now, that means giving the customer less control over the appliance.
 

Shrek Ogre

Member
Mar 6, 2017
11
Chester Springs, PA
Thanks for all your replies.

@jetsam - you hit it on the head: in my opinion the Merrimack is in your first category - an EPA emissions solution slammed on as an afterthought. Disappointingly so from VC, ruining an otherwise fine and beautiful insert.

@moresnow - exactly the same problem as you describe, my "fix" for the Merrimack is the same as yours by closing up the secondary air.

@ED 3000 - glass stays clean, sometimes a bit of white ash coating in the morning but that burns off with when the new batch of wood gets going. In the cold spell recently with temps around 15-F daytime, we turned off the geothermal heat pumps (they don't work well in that cold) and relied purely on the Merrimack in the living room and a Winterwarm in the basement to heat a drafty 3400 sq ft old stone house for 5 days straight. The glass was a bit glossed over after a week but cleaner than the Winterwarm which gets sooty in a day no matter what.

@EatenByLimestone - can't say at this time, we have it cleaned out every 2 years and have not done so since the fix of 2015 (due now). I don't expect a difference because it runs just as hot as before. I can't measure flue temp easily, not accessible.

@webby3650 and in general on this thread:

The primary air opening size is 2 square inches, damping it down closes this almost entirely, perhaps 1/2 sq inch open. The two secondary air openings on the other hand are about 3 square inches each with no ability to choke it down. (I'm going from memory about sizes when I had the thing apart, but the ratio is what matters, secondary about 3 times primary. And no control.)

Before the fix, it made NO difference when you close off the primary all the way. If it made a difference it was so small that you could not tell watching it for minutes before and after. Two cubic feet of fuel would be gone in 4 hours. I believed and proved that was on account of the secondary intakes that remained fully open.

After blanking off the secondary intakes, now when we close the primary it does exactly what you expect - within seconds the flames settle with a steady swirl like any other good firebox. Open it up and within seconds the fire responds.

So we are burning 1/4 the firewood simply because it is not wasting it up the chimney in uncontrollable flames. In my opinion, overall emissions is lower as I tried to explain at the onset.

Just measured the steady but small fires now which has been going since this morning, the Merrimack at 550-F, the Winterwarm at 600. They will idle along like this all day long with two small feeds each, then a large load at bedtime. Huge difference since castration.
 
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fibels

Member
Mar 18, 2016
115
Boston,Ma.
Hello everyone, I'm a newbie on this forum.

It seems that many are disappointed with their Merrimack inserts for burning too much wood or unable to sustain a burn overnight. We're on our 4th year with a Merrimack, we were initially disappointed for the same reasons but have fixed it.

The Merrimack introduces fresh air through the secondary air tubes at the top of the box which you cannot control. I disabled those secondary air tubes, now we can turn the air control all the way close and have beautiful licking flames that last for hours. We load it up half-full before bedtime, 8 hours later there still are flames. A few times I could re-establish a fire after 20 hours using kindling on the hot coals that remained. We now use 1/4 the firewood compared to the first 2 years for similar burn times.

This change likely affects the emissions if I assume that is the purpose of the secondary air.

Countering that, burning 1/4 the amount of wood for the same heat gain has probably less emissions than burning 4x more at lower emissions level. Factor in is the emissions from effort to collect, split, move and stack 4x more fallen trees, almost all of it involving using gas motors in my case (chainsaw, diesel tractor, splitter, truck etc.). We process our own firewood but if we purchased it from elsewhere, then we'd have to include the emissions of hauling the load also. Lastly, factor in heating with oil when the cleaner-burning Merrimack runs out of heat after it wasted its wood up the chimney, then I'm pretty certain that overall it's better for the environment also. It certainly is a lot better for me and my budget.

With that said, a few questions. Is that ethically OK to disable the secondary air tubes? If so, should I post the fairly simple process to do the fix?
It' always a wonderful feeling to be able to get longer heat times out of your stove.You done good.
 

EatenByLimestone

Minister of Fire
Jul 12, 2006
7,343
Schenectady, NY
How tall is your chimney?
 

Shrek Ogre

Member
Mar 6, 2017
11
Chester Springs, PA
25' feet for the Merrimack. The fireplace and SS liner were installed by our fabulous local pros, the Stove Shop in Phoenixville PA. They worked well with us during the initial period, once even disassembled the fireplace when we (and they) suspected a cracked firebox or some mechanical problem.

The other one in the basement is 33'.
 

WoodyIsGoody

Minister of Fire
Jan 16, 2017
1,437
Pacific NW Washington
You have to be living under a rock if you think IPI is more reliable than standing pilot. Even the manufacturers are realizing this and reverting back to standing pilot in the new units.
The manufacturers are not "reverting back" to standing flame pilots - they never quit making them! Yes, they cost a little less - just as a carbureted engine costs slightly less than EFI engine.

But if you think I'm "living under a rock" when I say IPI is more reliable than the old standing flame pilot, then you must think HVAC industry pro's who work with gas appliances day in/day out must be naïve as well:

http://hvac-talk.com/vbb/showthread.php?187567-intermittent-vs-standing-pilot

HVAC industry pro "Hearthman" shares his experience in post #2. Yes, overall IPI ignition is more reliable. Standing flame pilot lights have had more than their share of lemons and are the number one cause of service calls on gas appliances with pilots. I don't know of anyone with extensive gas appliance experience who believes otherwise.