The efm 520 stoker boiler has been in production since 1951

We stopped manufacturing the 350 and 3 larger sizes in the 70's when coal was nearly phased out with inexpensive and low maintenance heating oil. The 520 unit was suitable to cover the heating needs of a wide variety of homes, from small to fairly large. This is the reason we kept this particular model instead of completely dropping coal units completely.

There is likely a very slim chance that we will ever produce the 350 again. If we were to manufacture anything, it would be the larger units.

There is also a possibility that soft coal stokers may be manufactured for the Western US due to the request of an aggressive efm dealer in the West.

stoker-man wrote:There is also a possibility that soft coal stokers may be manufactured for the Western US due to the request of an aggressive efm dealer in the West.

Could it also handle western Pa bituminous?

I don't know. The pot would have a rotating head because of the clinkers. It's only in the idea stage now.

I vote to bring back the 350!!!! Reason is that most newer homes are very well insulated and require very little heat. We have 2800+sq.ft. of home, 6 years old, 3 stories including finished basement, and actually not really well sealed compared to our last home (also newer, but only 1500sq.ft. ranch).

Even at that, we only have a 90k BTU input 90% natural gas furnace, and it will keep the house at 68F even when it's howling wind and -15F. Granted, it's running almost flat out, but it's doing the job.

So, for any new home under 3000sq.ft., a 520 is almost overkill. The 350 would be more suitable and probably have higher efficiency due to running more in the middle of the design curve.

I'd also love to see the bituminous stokers brought back - give Will-Burt a little competition. They are getting $4500 for the S30 stoker - that's alot of $$ for JUST a stoker - then you still need the boiler to put it in.

Better yet, bring out a bituminous stoker AND boiler combination, maybe two sizes - one around 20# hour max rate and another at 30# max. You could set one design up for the western coals with the rotating ash ring, and one for the eastern coals with the refractory hearth around the pot to allow the ash to clinker.

stoker-man wrote: that soft coal stokers may be manufactured for the Western US due to the request of an aggressive efm dealer in the West.

Bring it on....

We're actually working on something right now at the lowest level of ideas.

If you ran the 520 at 4 teeth, the gross/net is 85/76K btu. This is also a desirable feed rate with the quality of the coal available today.

The 350 used the same stoker and pot, but with a slightly smaller burner ring. Also, if the S22 burner ring is used with the 520, you can get more heat output than with the standard S20 ring.

Who knows, with enough demand, there is always the possibility. I, for one, would like to see the return of the WCB-24 efm wood/coal boiler, which I have in my house. I can heat 2200 sq ft at my desired comfort temperature of 75 degrees and the rating on that unit was 60K.

what yrs were the af100 and the af150 produced? and were any larger hot air stokers produced?

stoker-man wrote:If you ran the 520 at 4 teeth, the gross/net is 85/76K btu. This is also a desirable feed rate with the quality of the coal available today.

The 350 used the same stoker and pot, but with a slightly smaller burner ring. Also, if the S22 burner ring is used with the 520, you can get more heat output than with the standard S20 ring.

Who knows, with enough demand, there is always the possibility. I, for one, would like to see the return of the WCB-24 efm wood/coal boiler, which I have in my house. I can heat 2200 sq ft at my desired comfort temperature of 75 degrees and the rating on that unit was 60K.

Fisrt you need to come up here and get some good Quality Anthracite coal that will Put out 13.000 to 13.600 BTU's Per lb tested at the Breaker's once a month or weekly if they sell to the state the lowest around here would be 12.500 to 12.900 Per lb Second would you like another WCB-24 if so PM me

I'd like to go into the mine to inspect. In my younger days, I worked for two years in a deep mine. Once you get below 6 feet, it doesn't matter how deep you go. I worked at the 1500 foot level most days.

I vote to bring back the 350!!!! Reason is that most newer homes are very well insulated and require very little heat. We have 2800+sq.ft. of home, 6 years old, 3 stories including finished basement, and actually not really well sealed compared to our last home (also newer, but only 1500sq.ft. ranch).

Even at that, we only have a 90k BTU input 90% natural gas furnace, and it will keep the house at 68F even when it's howling wind and -15F. Granted, it's running almost flat out, but it's doing the job.

So, for any new home under 3000sq.ft., a 520 is almost overkill. The 350 would be more suitable and probably have higher efficiency due to running more in the middle of the design curve.
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I agree with this assessment By: europachris.

I heated a 3200 sq ft house with the EFM 350 (three zones). With zoning you can cut the unit size down 20% since not all zones are calling for heat all the time. EFM biggest draw back is it sales model, aggressive marketing and financing of the coal units would skyrocket sales. Instead of waiting for the current outdated sales distribution system to produce effective results.

I'm not sure that there is a need for a 350. I've seen both sized units. There is little difference size wise. Mechanically the 350 uses most of the same stoker parts as a 520. The main mechanical difference being that the 350 can run up to a 7 teeth rate and a 520 can burn up to a 10 teeth rate. That can be changed by simply changing 1 part on the linkage. So,,,,, a 350 running at 85k btus(4 teeth) is running the same as a 520 running at 85k btus (4 teeth). Actually the 520 has a very slight advantage because of the difference in heat exchanger surface. A slight advantage only. I think the 350 was a smaller design for space considerations. There isn't that much difference really. Scott

I've brought this concern to the higher ups before. There may be some changes coming.

Even if we supplied a smaller boiler, you would still have the same S20 stoker. The only difference would be less water jacket capacity.

I've inquired about this efficiency question quite a few times with quite a few people.

Their answer is: It's not an oil system. You don't have inefficiency at start-up or shut-down. All you have is a blower going off and on and the coal burning or not. I have to agree. With my training in the oil end of the business, I know full well about combustion efficiencies. With coal, I don't see it.

If you're talking system efficiency, you are correct. 40 gallons of water is not necessary for a modern house. I keep my house at 70-75 all winter with a 60K wood boiler, heating over 2000 sq. ft. and I don't even fire it that hard. But, with coal, the fire either stokes or rests. I don't see any combustion efficiency improvement by constant running.

I will listen to any opposing opinions.

The other point to a smaller unit (physically) is many newer homes have finished or partially finished basements with limited room for a large unit. In our home, I have no access to the outside from the mechanical room of our finished basement, therefore I was forced to install a direct vent stove in the finished media room. I would rather have installed a boiler with a hot water coil in the forced air and a plate exchanger for the DHW (or just use the coil). But, that space is quite limited and really something any larger than a KAA-2 Keystoker would not have fit (and also I don't need any more BTU's than that).

But, I love the design and construction of the EFM units. Bulletproof.

stoker-man wrote:I've inquired about this efficiency question quite a few times with quite a few people.

Their answer is: It's not an oil system. You don't have inefficiency at start-up or shut-down. All you have is a blower going off and on and the coal burning or not. I have to agree. With my training in the oil end of the business, I know full well about combustion efficiencies. With coal, I don't see it.

If you're talking system efficiency, you are correct. 40 gallons of water is not necessary for a modern house. I keep my house at 70-75 all winter with a 60K wood boiler, heating over 2000 sq. ft. and I don't even fire it that hard. But, with coal, the fire either stokes or rests. I don't see any combustion efficiency improvement by constant running.

I will listen to any opposing opinions.

Combustion efficiency for any fuel is the highest when the correct amount of air, i.e. oxygen is available. In coal appliances there is no provision for adjusting the amount of combustion air except, depending on design, an on/off control. There is a fundamental problem of determining the correct amount of air when the fuel (coal) input is so variable. Current coal appliances have no way to determine this.

Since air contains large amounts of nitrogen and nitrogen is not part of the combustion equation it just passes through the appliance. You want to limit the amount of extra air, because it takes heat with it, by heating the nitrogen in the air. That's one of the purposes of a barometric damper.

Some day when coal becomes expensive, coal burning appliances will be re-designed to measure flue gases, with a sensor similar to an O2 sensor in an automotive exhaust system. That sensor will provide the feedback to adjust the combustion air to the ideal amount. Until then we just waste fuel.