# Maxim M-175 Outdoor Pellet Boiler - Not So Simple



## ronp (Jan 18, 2009)

We still have hopes for eventual success with the Maxim M-175 Outdoor Pellet Boiler (by Central Boiler). But -- Anyone considering the M-175 should expect to add some complexities to their life.

I would describe the support available from the dealer (Northeast Outdoor Furnaces - NEOF in Claremont, NH) and the manufacturer (Central Boiler) as "sparse". The installation / operating manual seems to lack a lot of necessary information. Way too much of the set-up and feed rate / air setting seems to be left to trial and error.

The Central Boiler web-site has good sales information and provides an opportunity to submit testimonials. But -- there is no on-line access to manuals, suggestions, forums, or opportunity to request support. 

Installation did go about as expected and documented. We connected directly to a (now) depressurized oil boiler in the basement.

We have experienced significant problems with creosote formation in the top boiler tubes. 

Pellet consumption has been much higher than expected based on the estimating factors provided in the "impressive" marketing brochure. Four tons of New England (NEWP) Premium pellets have been burned between October 18th and January 16th out of the 7.5 ton estimate for heat plus DHW for the whole year for this small 1200 sq ft 1950 Cape in Central New Hampshire (based on the conversion for 850 gallons of oil).

Cleaning has been more difficult, frequent, time consuming, and messier than anticipated from the brochures, web-site, and dealer visits. You will need old coveralls, and must be ready to kneel in snow or mud. The manual doesn't even explain the clean-out panel latch ( just underneath and out of sight).

The (steel?) areator degraded and finally broke in half. The Maxim would still operate, but with reduced efficiency. The areator was replaced under warranty by a "house call" from NEOF. There is a redesigned cast iron areator now in stock at NEOF. These will be used as more areators fail. So, watch the areator.

Another problem was the "bridging" or crust of pellets which created a void and loss of heat. Also, several times, gravity has not been sufficient to slide all pellets in the hopper to the auger chamber. Two or three bags of pellets remain on the sides of the hopper when pellets stop feeding.

Of course, the week long power failure required getting temporary power to two places. Inverters from cars almost worked.

SO -- Buyer's Remorse - "No Good Deed Goes Unpunished" 

I did the research, estimates, made the suggestions, and fronted the $'s to help our son purchase the Maxim last June when pellets were $250/ ton and oil looked sure to hit $5/ gal. We heated our 1790's farmhouse in Upstate NY for 25 years with wood we cut in a Defiant air-tight (plus some solar). Our daughter has had real good experience with a nice little Harmon on Long Island using a couple tons of pellets a year. 

The choice was a Harmon which would save a lot and heat much of the NH Cape or the Maxim which should heat the whole house plus DHW and save even more. The ideas of not having to lug pellets into the house, not having the fire inside, not taking up space, and not cleaning inside were all quite appealing. 

As the kids on Long Island pointed out after being copied on numerous e-mails, you can just look at their Harmon in the living room and know how well it is burning or soon notice a problem.

With oil now down to around $2.50 and more pellets up around $290, it looks as if all I've accomplished is adding complexity to some already busy lives.

After a couple of days skiing with the grandkids, it will be time for me to fly back to Florida (Frostproof that is) and get back on my bike.


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## MARTYO (Jan 19, 2009)

Maxim problems


I too have had the exact same results. Hooked it up sep 26. from sep 26-dec 26(3 months) I burned 6 tons of pellets.
The dealer D&R;country designs in palmerton pa, Basically told me "that I could not have burned that much." I use approx
1000 gal of oil a year. Even if oil was $5 a gallon($5000 a year)12 months.  I would spend close to that if I ran the maxim all year.
I too had my areator melt in half only after 3 months of operation! Yes they replaced it @ no cost, but what about down the road when it's not covered?  All money issues and cost comparisons set aside, these are my concernes...
1. What if the power does go out when you are not home? This outdoor unit will freeze, or at least some exposed part like a circulator or pipe. Then when the power comes on then what?
2. Another plumber(not the one who installed the unit), told me not to depressurize the boiler. And not to hook the maxim directley together. It has to do with the oxygen in the water corroding the boiler. They give you rust inhibitor to combat this problem. But not sure if that is the answer.
3. What if the circulator fails at the outdoor unit. I'm not worried about the house getting cold. You just turn your boiler temp back up problem solved. Inside Yes, outside no. You still have the risk of freezing and breaking.
4. Yes, the cleaning. This is much more of a project then they lead you to believe. And this is to be preformed weekly? Wouldn't mind, if I was saving $2500 a year.
5. Filling this bottomless pit with pellets. I purchased the external 43 bushel bin, at the advise of the dealer. This was suppost to allow me to fill it once a month. No problem right?  Actually more like every 2 weeks. Then to make matters worse when the tank gets low you have to scrape the pellets away from the sides with a shovel. So every other day of so I find myself checking to make sure I don't run out.
I could go on and on.
The message I'm trying to get across is: If you are told this is a big money saver...False.  If the machine can run for a month, without filling, or tending to it... False.  And If you don't mind lugging around twice as many pellets as you were told. Buy the maxim.
My whole experience is... Oil is automatic no mess no worry. If you have a problem, you can call 1 of 20 people that will fix it right away. While it's cheap get an extra tank and fill up then, don't get the maxim!!


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## harttj (Jan 20, 2009)

Sorry to see you guys aren't happy.   I have a M175.  I installed it in June and fired it up in November.  I have been running 100% corn.  I have been happy with it.  My savings this year will be over $2,500 over propane.  

Did you guys install the Thermopex pipe, or install another brand or DIY?

I found the settings to be straight forward.  The one thing the manual doesn't cover is what the flame should look like.  I haven't seen a description here, but iburncorn.com has some very good pics and descriptions of what it should look like.  The factory settings aren't all that bad either.

I haven't had issues with my aerator, knock on wood.  It appears to be a cast piece though.  

Since I haven't burn't any pellets I can't comment on the creosote issue.  I personally think pellets are way over priced right now, hence why I am burning corn (I bought my supply at $130/ton).  I am wondering if the creosote is from bad pellets or not burning it at a high enough air rate.

The weekly cleaning isn't that bad.  I don't think they could make it much easier.  Yes, you do have to either squat or kneel to clean the tubes and empty the ash, but it doesn't take much more than 20 minutes.  From what I have read most people with stoves clean every day or every other day.  I actually enjoy going out and doing it.

I also 2nd the notion of not depressurizing your current boiler.  I used a heat exchanger.  Less risk IMHO.

I put 24" concrete pavers around mine to avoid the mud issue.

Oil/Gas is easier.  I suspect there will be a lot of alternative fuel systems for sale this Spring.


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## MARTYO (Jan 20, 2009)

I guess I should say the maxim did heat my house(3700sqf). While it was running it seemed to perform well. My problem was the pellet consumption, Lack of service available, poor instructions. And NEVER depressurize your boiler and directly tie it in.  When I switched back to oil, I had an air pocket in my boiler from being depressurized. It's not as easy as they claim to switch back and forth. For example, if there is a problem with the maxim,(oh like a metal piece melting in half), or some other problem that causes your inside boiler to kick on. It's very nerveracking to know that they are connected. Something could freeze, break and empty your whole heating system into the yard. It's just not as simple as the company claims.


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## ronp (Jan 21, 2009)

MARTYO said:
			
		

> Maxim problems






> 1. What if the power does go out when you are not home? This outdoor unit will freeze, or at least some exposed part like a circulator or pipe. Then when the power comes on then what?



According to our dealer, the 90 gallons of water in the Maxim which he says is pretty well insulated and the ThermoPex should hold for a "long time", which I took to be at least a day. The weak link would be the valves and pump behind the rear access panel.




> 2. Another plumber(not the one who installed the unit), told me not to depressurize the boiler. And not to hook the maxim directley together. It has to do with the oxygen in the water corroding the boiler. They give you rust inhibitor to combat this problem. But not sure if that is the answer.



Theoretically, the Maxim and the Oil boiler are still a "closed" system, the water mixes and stays in the system, so the inhibitor should protect both the Maxim and the Oil boiler. From what I've read, it would be a very bad idea to pressurize the boiler.



> 3. What if the circulator fails at the outdoor unit. I'm not worried about the house getting cold. You just turn your boiler temp back up problem solved. Inside Yes, outside no. You still have the risk of freezing and breaking.



If that happened, you could isolate the Oil boiler and drain the Maxim. But, it would be a major pain.


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## harttj (Jan 21, 2009)

MARTYO said:
			
		

> I guess I should say the maxim did heat my house(3700sqf). While it was running it seemed to perform well. My problem was the pellet consumption, Lack of service available, poor instructions. And NEVER depressurize your boiler and directly tie it in.  When I switched back to oil, I had an air pocket in my boiler from being depressurized. It's not as easy as they claim to switch back and forth. For example, if there is a problem with the maxim,(oh like a metal piece melting in half), or some other problem that causes your inside boiler to kick on. It's very nerveracking to know that they are connected. Something could freeze, break and empty your whole heating system into the yard. It's just not as simple as the company claims.



If they are connected the Maxim will not freeze.  It will stay the same temperature as the inside boiler.


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## ronp (Jan 21, 2009)

harttj said:
			
		

> Sorry to see you guys aren't happy.   I have a M175.  I installed it in June and fired it up in November.  I have been running 100% corn.  I have been happy with it.  My savings this year will be over $2,500 over propane.
> 
> Did you guys install the Thermopex pipe, or install another brand or DIY?



We (in NH) used about 35 feet of Thermopex from the Maxim thru the cement block cellar wall, then about 20 feet of regular PEX to the Oil boiler. The regular PEX was insulated with foam pipe insulation. The install was DIY except for a plumber hookup to the oil boiler.

I'm beginning to think that, since Central Boiler is in Minnesota, they may have done much of their R&D;using corn. NH has much woods and few corn fields. But, it sounds as if a lot of the pellets produced by New England Wood Pellets actually come by train from insect killed trees in British Columbia.


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## ronp (Jan 21, 2009)

MARTYO said:
			
		

> I guess I should say the maxim did heat my house(3700sqf). While it was running it seemed to perform well. My problem was the pellet consumption, Lack of service available, poor instructions. And NEVER depressurize your boiler and directly tie it in.  When I switched back to oil, I had an air pocket in my boiler from being depressurized. It's not as easy as they claim to switch back and forth. For example, if there is a problem with the maxim,(oh like a metal piece melting in half), or some other problem that causes your inside boiler to kick on. It's very nerveracking to know that they are connected. Something could freeze, break and empty your whole heating system into the yard. It's just not as simple as the company claims.



From the, "While it was running..." and, "When I switched back to oil" , I get the impression that you may have taken the Maxim out of service. If so, what did you do with it? 

A couple of weeks ago my son wanted to shove the beast over the bank with his snow plow.


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## harttj (Jan 21, 2009)

Ron P said:
			
		

> harttj said:
> 
> 
> 
> ...



Since you used the Thermopex you probably aren't losing heat to the ground.

Do you have the heat load of your house?  If you don't try one of the online calculators.  This will help determine if the usage is high.  It can be eye opening once the load of the house is known.  This makes it easy to determine if the usage is reasonable.

Tim


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## ronp (Jan 21, 2009)

MARTYO said:
			
		

> Maxim problems
> 
> 
> I too have had the exact same results. Hooked it up sep 26. from sep 26-dec 26(3 months) I burned 6 tons of pellets.
> ...



Our dealer said he had burned more pellets in his Maxim in Vermont than he expected. But, then he claimed it was because the weather was 20% colder than last year. I've been checking http://www.degreedays.net/# and only see around 3% difference across the river in NH.

We also talked about the creosote problems and I got the impression that it was not going to be practical to try to keep the Maxim going for DHW during the summer months. That was one of the reasons the thing sounded like such a good idea when he pitched it back in June.


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## ronp (Jan 21, 2009)

harttj said:
			
		

> .......
> 
> Since you used the Thermopex you probably aren't losing heat to the ground.
> 
> ...



We got to the estimate of 7.5 tons using the factors provided by Central Boiler's brochure and checked other sites which were consistent. So, 850 gallons of oil should be replaced by 7.5 tons. And, 850 gallons has heated the house comfortably for the last several years. The oil boiler was new about 2003 - it might be much more efficient than the calculators give it credit for. But, that shouldn't be enough to explain the pellet consumption.

No heat load calculations were done. No other changes were made to the house beyond covering some windows with blankets. The thermostat setting were not changed. (Well one slight change was made - several incandescent light bulbs appear to have been replaced by compact fluorescents -- but it is inconceivable that the heat from a few bulbs could make up for the difference.)

The house is around 1200 sq ft. From the construction and old looking double track storm windows, I thought it was built in the 50's. But, my son was told it was built in the 70's. Maybe the windows were reused. People in NH are pretty frugal and don't like to throw perfectly good stuff away. We don't even know what is in the walls for insulation. We know the house needs better windows and insulation around the cellar walls. Those projects would reduce either oil or pellet consumption.

So, we know that the oil usage is much more than an efficient house would use. But, the Maxim seems to be much less efficient than claimed.


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## ronp (Jan 21, 2009)

I was in NH for several days and studied the Maxim. I visited the dealer before I even saw the Maxim in operation. I spent $110. $30 for a "snake oil" Ashtrol powder which the dealer recommended to reduce the creosote problems and $80 for the official Central Boiler / Maxim chimney cap.

I bought the cap because I didn't think my son had gotten one. It turns out he had bought a cap at a hardware store for $15. (On the recommendation from the guy who delivered the Maxim.) I compared them. His was very black from creosote and had spark arrestor mesh around it. The official Maxim cap had a larger open area and didn't have mesh around it. I checked on-line using the model number on the box and found them on-line for under $50. But, the pictures on-line all showed spark arrestor mesh. The barcode sticker on the Maxim cap had the words "with spark arrestor". 

So, I wonder if Central Boiler ordered some special "without" caps for their pellet boilers. If so, is it possible that the little bit of resistance from spark arrestor mesh could contribute to the creosote problems and / or the high pellet consumption?

We installed the official cap. I'd like to delude myself that there is less smoke during the idle mode.

Close reading of the manual indicates that, during idle mode, the blower only runs when the auger turns. It may be necessary to crank up the blower speed for idle mode to get as much air in. It does seem that smoke only happens when the thing goes to idle.

We left NH this morning and just watched our daughter dump half a bag into her Harmon Accentra on Long Island. Next, back to Florida. ("Third Generation Snowbird")

It seemed as if every fourth vehicle in NH was either a propane or oil delivery truck.


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## harttj (Jan 21, 2009)

If you have used 4 tons out of 7.5 I'd say your on track to use the equivelant amount of pellets.

By knowing your heat load at given outside conditions it is very easy to see if there is a problem.  1lb of pellets ~8500 btu's.  If the house load is calling for 25k btu/hr then you should be consuming about 88 lbs taking the 80% boiler eff. into account.

Take the chimney cap off and throw it away.  This may be part of the problem.  Let the beast breath.

Tim


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## MARTYO (Jan 21, 2009)

In response to Ron P.  My maxim is disconnected, drained and just sitting there. For sale by the way, if anybody is interested!

Marty


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## jdeere5220 (Mar 13, 2009)

This thread may have died but wanted to post my experience anyway.

I installed Maxim M250 on Jan 23. I started burning 100% pellets because I didn't have a bulk corn storage system (i.e. a covered gravity box), but on Feb 23 switched to corn. I calculated my BTUs and cost per Degree Day using propane, pellets, and corn. Just FYI my propane furnace is rated 93% efficient. I connected the Maxim to my propane furnace ductwork using 140K BTU HX, and also to DHW using sidearm HX.

These are my results so far:

My propane use for all of 2008 was ~20,000 BTUs per Heating Degree Day (HDD). Cost as $0.54 / HDD, total cost was $4,000. Just so you have an idea what I'm heating.

For the month I burned pellets, I burned ~24,000 BTUs per HDD. Cost was $0.26 / HDD, so I saved just over 50%. I explain the increase in BTUs/HDD by two factors: 1) We turned up the house thermostat the very day we installed the Maxim, and 2) The Maxim is not 93% efficient. I can't say exactly how it compares to propane furnace because we changed the house thermostat. Of course the cost depends on what you can buy pellets/propane/corn for. I was buying pellets for $155/ton.

For the last month burning corn, I burned ~26,000 BTUs per HDD, and cost was $0.38 / HDD. I don't think I'm really burning more BTUs per day, I think the corn is higher moisture or got wet in my gravity box or somehow not producing the rated heat. Anyway I'm not saving as much burning corn as I was saving burning pellets, at least at today's prices.

Other observations:

For me, the corn burns MUCH CLEANER than the pellets. Yes, I get more ash with corn (I hardly got any ash with pellets). But the firebox is very clean and there is no smoke When I burned pellets, my firebox was full of tar and I constantly had smoke. If corn were cheaper it would be a no-brainer. However at current prices I would have to say putting up with the tar/creasote is probably worth it.

So in the end, I look to save ~$2000/year using the Maxim at current prices, which is a little less than I expected but still a 5 year payback. I also had my stirrer melt and break off, but the dealer replaced it at no cost (this time). Apparently this is a wear item, there is not a metal made at reasonable cost that can stand up to the firebox temps (1300F) forever.

The big thing to me is now I have heating options. If propane goes sky high, I don't care I can grow my own corn. If corn/pellets are high and propane is cheap, I will burn propane. But I like burning locally grown corn, it just feels better than buying foreign oil. Just my 2 cents.


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## rowerwet (Mar 15, 2009)

I found turning down the air to match the feed rates got rid of the creosote with pellets, form iburncorn, it seems that corn requires higher air than feed which is why the stove is factory set that way. 

To save pellets, turn the feed in idle down to one, if the fire goes out turn it up one bar at a time until it doesn't go out (this will change with seasonal temps) 
Turn the middle bar down until the stove kicks into high every time the house calls for heat, then turn it up one bar. (the factory presets are all rather high I find)
turn the high setting down until the stove can't keep up with a large heat up in the house (for me this was the 6:45 AM jump from 60 to 66 on the programable thermostat) then turn it up one bar. 
The only adjustment you should have to make from then on is for the shoulder seasons when it gets up into the 50's and 60's during the day, then you may need to turn up the idle to keep the fire from dieing. 
Match air to feed for pellets.


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