Vermont Castings Merrimack

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Per my experiments in sound-reduction... it was a failure.

My plan was to replace the centrifugal blower with an array of axial fans. Unfortunately, the axial fans were not able to tolerate the static pressure induced by the heat exchanger and airflow path in the Merrimack. So, the prototype was quieter, but the airflow was significantly reduced.

I am abandoning that aspect of the project. I may look into more acoustic shielding / dampening material as the last resort, but I don't expect miracles.

Sorry guys, I would have loved to come up with a kit that could have been a simple retrofit that was significantly quieter. We will just have to wait and see if Vermont Castings ever comes out with a quieter blower.
 
white point, i checked the merrimack install guide and it doesnt say where to position the baffle, unless i am missing something. just odd that i am getting easier stable lights with like 90 percent less smoke. does it really matter? am i losing more heat in the firebox because i have it positioned in the middle?
 
I guess it is up to you where to place the baffle, but I thought I read it should be all the way back. (Mine is all the way back)

The reason you are probably doing better with it a bit forward is that allows the air to head straight up the chimney instead of having to hit the baffle plate, then travel forward over the secondary combustion air tubes and then split by the glass airwash dam and then half go back up through the heat exchanger and out of the chimney, the other half that splits when it hits the glass airwash damn goes down and then recirculates in the firebox for another trip around.

To reduce smoke escaping into the room, 1st I open the airflow lever all the way up (fully left as seen from the front) then I open the door a little bit at first, say an inch and let draft build up. Then I open both doors fully and the increased draft pretty much keeps the smoke inside and headed right up the chimney. One big puff usually escapes, but hey... that is life with a wood burning insert?

My guess is your wood isn't dry enough / seasoned enough. Mine isn't either and it is a major bummer. I am going to season a full 4 cords this year. You can tell the wood is too wet when you hear the hissing sound of steam escaping as it burns. Sometimes you can actually see water bubbling out of the end of the wood.

Another thing, since I am burning 24 hours a day I have found that I don't really need to open the doors that often. I open them, load a huge load, and then I keep them closed until I need to load another huge load (6-8 hours).
 
thanka sman yeah i did a search of the .pdf and i couldnt find anywhere where it says to position the baffle.

Anyway do you think im taking a dramatic hit on heat with the baffle being midway? i dont have it all the way to the front and the baffle does sit on all the tubes.
 
Musky...

If what you describe is the case that could pose a serious danger. I do doubt it would happen though because of the way the sheet metal surrounding the blower is configured. The intent of the blower design is definitely to suck air through the front lower intake grates.

The whole design is a little strange though because if you have every looked undeneath the center brick in the front, their is a steel plate with 4 screws and an air outlet at the point of the curve brick (sort of like the nose pointing into the firebox). If you remove the screws and look under that steel plate you will find 2 holes that lead right down into the blower area. Those are the holes that allow fresh air to flow up into the firebox. At first I was concerned that the slight negative local pressure generated by the blower could actually suck fumes out of the firebox and into the blower through those holes. But after 2nd thought, the draft suction from the chimney should be more than the blower suction and I belive it may be on the positive pressure side of the blower assembly. The bottom line is that it just isn't obvious to me and would require further investigation.

I am still happy with my Merrimack and I have gotten to know it pretty well. She behaves nicely and is keeping me cozy warm and I am getting decent burn times and there are always embers left after a long burn. I have let it go for 12 hours with no attendance and then stirred the embers and thrown in some new wood and it is back going again great in an hour or so. The noise from the blower is a bummer, but that is my only real complaint!
 
Thanks for you comments

.... but the sheet metal surround does not appear to be air tight. So if the blower is not pulling from the cavity, wouldn't house air exit through the leaky sheet metal enclosure. Also the installation manual said seal the unit and the only seal on my install is the sheet metal plate at the top of the chimney.

in adition to support your theory that the blower is not pulling from the cavity
Maybe it has something to do with the air behind the blower is hotter which naturally pulls cold air towards it. This might be greater than blower pressure so the blower draws the colder air from the room.
 
Where do you guys get kaowool from? does it go by another name? is this something u have to get special order from a fireplace store or could you get it at HD or lowes? i intend to insualte the top of the merrimack with it myself and i just dont want to burn the house down getting the wrong insulation. i have been told not too insulate the side of the merrimack also.
 
hello everyone again lol

anyway i am still confused on the primary air control and the the automatic setback control. i think the merrimacks instructions are piss poor on this.

anyway i took a picture of what i believe is the fully open position for the primary air control - see below.... am i correct on this?

second question - the automatic setback control? if u push further to the left it spring back and then according to the instructions ur supposed to hear a clicking sound of it closing? i never hear a clicking sound and what does it exactly close?

so basically my questions are is the pic below of the fully open position or should i go more to the right, exactly at the corner? also what the hell does the automatic setback control do?
 

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Mica,

Judging by the photograph that looks like fully open to me.

Now, what the automatic set back control does is this. When the stove is sufficiently cool, the set back mechanism can be used to set the damper to full open and hold it there while you adjust the regular damper control lever (pictured in your picture) back to the setting you would want it to be when the fireplace comes up to full temperature. Then the internal automatic setback control mechanism releases the internal damper control and you hear a little spring releasing as the damper then comes back under manual control and ends up at whatever setting you left the manual lever set at.

So here is an example of the operation. You let the fireplace burn over night, you wake up in the morning and it is pretty cool, you decide to re-load it and then go to work. So you reload the fireplace fully, slide the manual control lever all the way to the left (to set the automatic set back control in the full open position) THEN you set the manual damper control back to fully closed (all the way right). What will happen is that the damper will remain open because of the automatic set back control while the fire gets re-established and the fireplace heats back up. Then when it is burning nicely and the fireplace is heated, the spring will release and the damper will go back to the manual setting (fully closed), this will keep the fire burning nice and slow while you are away at work or whatever.

Without automatic setback control, you would have to leave the damper fully open to let the fire get re-established, then close it after an hour or two so you can prolong the burn. Sort of a bummer to have to drive home from work to adjust the damper on your stove.

Does this make sense?
 
i think i got ya,

so basically when starting a cold stove, pull the lever all the way to the left, past the pic i posted until you hear the spring then pull it all the way closed. after the stove heats up it then closes itself automatically and you will here a click - according to the manual?

If i am correct what temperature does it take for the setback control to close? the fan coming on?
 
To WhitePointBeach and your quest for a quieter fan:

I am a Montpelier owner and in the first year of ownership, felt the same as you do now about the fan noise. A couple of things I have learned over the past year:
a) Most woodstove insert fans are noisy and they all seem to be using the same style fan;
b) Running the fan on high doesn't produce a lot more heat than running the fan on medium - you're just getting more volume at a lower temperature with more noise;
c) You can find out about any technical bulletins issued by Monnesen here: http://www.insidemhsc.com/content/technical/bulletins/
d) Monnesen issued a technical bulletin that offered a repair kit to deal with the noise on Montpelier Inserts. Every Montpelier owner should contact their supplier to order this free repair kit. The kit provides some silicon tape strips to apply to the fan in areas that may come in contact with (and therefore vibrate against other) close by metal components. It is fairly effective, but I would have provided more tape for some other areas like the bottom of the fan;
e) if you pull the fan out of the stove and "bench" test it, you will find that the fan is very well balanced and very quiet. In fact it doesn't even hummm at the lowest level. Most of the noise produced when installed is a result of air turbulence and mounting vibration;
f) If you remove the fan, you have to pull the wires off the thermostatic control. You can then plug the wires together thereby bypassing the thermostatic control. Then you can run the fan anytime in order to experiment with ways to reduce noise. Also for those that complain that the fan takes a long time to turn on, can do this in order to turn it on anytime they want.... I think they will go back to using the thermostatic control.


If I was you, I would:
a) Ask your dealer to order the Montpelier repair kit for you (if you think it might help);
b) try simply pushing/shifting the fan while it is running to see if that has any effect;
c) try stuffing some non-flammable material under the fan/over the fan in areas that may contact metal...experiment...more stuffing is not always better;
d) make sure the electrical wire to the fan is not vibrating against the light galavanized steel shell;
e) run the fan at a lower speed...it doesn't really produce much more heat than the highest speed;

If you still want to design something, I think it should be an extension to the fan exhaust port, that fits into the cavity between the stove and the metal shell. This would reduce the air turbulence we hear directly from the fan, created by the lack of a positive connection between the fan and the heat exchange channel.

Hope some of this helps
 
Looks like the merrimack does not have the fan housing (I assume the intent of a fan housing was an acoustical shield). So the tape fix is not needed for the merrimack.

I had my unit serviced and all they did was put a styrofoam isolator between the fan and the sheet metal bottom pan.

Before he left he said "thats what they are supposed to sound like". What a cop out.

Not sure if I agree with your theory

Lower cfm = same room temperature rise since the discharge air from the low cfm will be hotter. Maybe in a closed system, but there is temeperature loss in the masonry cavity. But i do like the lower noise at 50% speed.

What do you mean by "lack of positive connection" fan to heat exchanger. Is there a gap?
 
Canboy and Musky...

So clearly Monesson understands fan noise is a significant customer complaint and has been for years. That is good to know.

I also agree that the blower design is almost identical to every other stove I have researched. So for those people who are looking for a fireplace insert and are worried about the Merrimack being noiser than other models, I doubt that is the case (they are all just loud). There is actually an interesting trade-off with one set of designs that put the blower in the back of the firebox... this insulates a lot of the noise, but if there should ever be a maintenance issue the entire stove needs to be removed, and that means detaching the flue pipe and man handling a 500lbs insert... not great. But in my opinion that is probably the superior design because a fan probably only fails once in 10 years or more whereas you live with the noise every second of every day that the stove is running.

Canboy, I do disagree with the statement that the noise is not due to the blower but the blower+housing combination. The blower is loud and it is what generates the vibration that resonates through the whole assembly... afterall, there are no other rotating or vibrating parts in the Merrimack. The blower is definitely the noise culprit. As for how much of the noise is "wind noise" vs. vibrational noise vs. electrical noise (electric motor hum) that is debateable and would require spectral analysis of the noise signature to determine. But at the flow rates the Merrimack is supporting (200 cubic feet per minute (CFM) or less) wind noise should be negligible. My HVAC system has a 1650CFM blower and it is almost silent even when I am sitting right next to it.

Musky, per your comments, I have removed the entire blower assembly from my Merrimack and indeed there is rubber-like tape on the bottom side of the blower assembly where it comes into contact with thin galvinized sheet metal bottom. If that is the noise reduction kit offered, that is pretty whimpy. If you look into my past posts, I insulated the entire "squirrel cage" section of the blower with Dynamat acoustic insulation specifically designed to eliminate vibration and noise and I only achived a 3dB(A) reduction. If you want me to send you 2 pieces of dynamat so you can wrap yours as well, let me know and we will work something out. I have 20 pieces.

If I get more interested and more time, I will be trying 2 more things. One will be to insulate the inside of the front intake grate with another type of Dynamat that is intended for under-hood applications in cars to quiet engine noise. It is an absorptive material instead of just a vibration dampener. Interestingly, only about 30% of the intake grate can be covered because there obviously needs to be a way for the air to get through. 2nd I would like to experiment with some sort of removable air filter to go behind the intake grate. We all know that fireplaces generate a lot of dust so why not add a little filtering to the system. If it was sink washable like those old window air conditioner filters, that would be convenient.

Otherwise I am just learning to live with the steady hum as it runs at 30%. By the way, I agree on the fan speed issue... more airflow at a lower temperature gives the same amount of heat as low airflow with air at a higher temperature. So I burn mine hot and leave the airflow low. So a big pocket of hot air forms on my ceiling (if you hold up your hands you can actually feel the difference) and then I turn on my ceiling fan at the lowest speed and it gently stirs it through the room.

In other news... I burned my Merrimack 24-7 in December and I just got my electric bill (I have a heat pump). I saved about 1200kWH which equates to about $150. If You figure it out, it comes to something like 2000W (~7000 BTU/h) for every hour it was burning when averaged across a whole month. Not bad given I was leaving it for 8 hour periods over night, etc.

I am happy with it... I just hope somebody makes a quieter blower system for it. Get me under 45dB(a) at 120cfm and I will buy it from you for $200.
 
i have more information soon on the thermal switch delay problem. there are edits to the install instructions for the merrimack that VC issued. The update comes from VC tech reps.

i would post now but it doesnt seem this site allows .pdf files. so when i figure out how to post the .pdf to another site and link it i will post it on this thread.
 
vector thanks ill try to have it up this weekend. its nothing groundbreaking but interesting for anyone that has a merrimack and is having slow response time for the blower.
 
I've had the Merrimack for about 2 months now and just spent the last hour or so reading through all 10 pages on this topic, so I just thought I'd share my findings and opinions.

First off I got some interesting info off of here, so thanks to everyone for posting. We got the Merrimack because of the large windows and large firebox, and it's just a beautiful insert...we've had many compliments on it. Got the insert and cast iron Northfield surround for $3000 and some change, and chimney liner and insulation kit for $700. Right at $3700 for everything and I installed it myself. Being a DIYer I figured, how hard can it be? It was some work, but it really wasn't that bad. Especially for never having done it before. This sucker is heavy though! Geez! Anyway, I just followed the instructions and took my time and did it in about 8 hours. I had a helper for bringing the thing in the house and running the liner down the chimney. Would I do it again? To save $500 installation fee, hell yes!

It seems there's been a lot of discussion on the windows getting dirty. When I first started burning I kept the air control fairly low and the windows got "sooty" pretty quickly. I've opened the air control up a little more (about an inch more to the left) and it made a world of difference. The fire's hotter and there's not as much smoke to cling to the windows. I also think that the increased draft makes what smoke is produced flow away from the windows, which is the air wash doing it's job. Also I will add that my firewood has only been cured for about 6 months, which is not ideal and probably adds to the problem. But anyway if your windows are getting dirty, increase the air control a little bit (move it to the left). We've had a hot fire burning for 3 full days now on the same air setting and in my opinion, the windows look pretty good for that much burning. I think there's always going to be some window cleaning to do, but overall I'm really impressed with this air wash system. And the water and ash method is the best way I've found to clean the glass. My 11 yr old daughter does it in about 10 minutes.

As far as starting a fire, I put the logs right on the floor of the insert, stuff a few pcs. of newspaper between them, open the air control all the way to the left and light the paper. I leave the right door cracked open about an inch to get lots of oxygen rushing in there. I'll have to add paper once or maybe two more times, but it usually lights pretty quickly like this. No kindling or anything. Leave the door ajar for 20 minutes or so until the woods burning good, then close it and set your air control and enjoy. The blower takes about an hour before it will get hot enough to come on. There's no way to turn the blower on manually. Once the fire's burning good and hot, I don't even change the air control when adding logs. Just open the doors slowly to keep smoke from coming out into the room.

I'll load the firebox up and it'll burn good for about 4-5 hours. I thought I would get longer burn times, but it seems others have had this problem too. While I don't load it all the way up to where the wood is hitting the tubes, they are pretty sturdy if you bump them. The baffle on top of the tubes, however, I am careful with. It seems somewhat fragile to me, but I don't really know. It reminds me of a grinding wheel type of material, but it's VERY lightweight. I don't know how much abuse it could take.

I'm going to try and put a few pics on here that I just took. One is of where I have kept the air control lever as this fire has burned for the last three days, and one is how the windows look with that setting. Another is where the blower cord is routed, just because there's been some discussion about that as well.

Sorry for being long winded, but maybe it'll help someone.
 

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I do not Know if this has been discussed but on the the reostat there is a adjustment screw by turning the screw you can take the hum out of the blower motor. I also agree that fans do not need to be run on high,the air temp on a high setting is lower then if it is set at 50%.
 
on the side of the reostat a small phillips sometimes painted white turn until humm goes away.
 
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