EFM, Keystoker, or AHS

Coal is in and oil is out. I need a solution to my household needs. I'm torn between spending more for the EFM DF 520 (with the convenience of an auger) and the price of a Keystoker (KA-6). The AHS 130 looks like a good boiler and is also in consideration.

Can any Keystoker users give me an idea of loading/ash removal frequencies?

Which boiler is best for summertime domestic hot water supply?

Which boiler is more convenient for cleaning?

Is there any boiler with an outstanding efficiency?

Is the EFM really worth the extra cost?

Any information on auger/fan noise will also help split the decision. I live in PA so coal size supply should not be an issue

the efm is built like a tank they will last forever if you take care of them cleaning them is rather simple.. as for noise it is not as loud as a oil burner it is well worth the cost in my opinion plus it is asme certified

Coal guzzler, welcome to the forum! I'm a bit discriminating about coal boilers. Having only used an EFM it is hard to find a fault with it. Being an older (1960) with the heat exchanger section worried me about the cleanout until it actually happened. The boiler itself came clean very easily without alot of trouble. A quick scrub inside to knock the flyash off, then around to the cleanout door where it was a quick scrub to clean the heat exchanger sections. A pass with the vacuum and the boiler was finished. On the other hand, the stove pipe was full of fly ash. After disassembling it , and knocking off all the ash, it was put back together using the trick that Richard ,the administrator, showed on his cleaning thread. Instead of using 90's, use tee's and caps. That way the pipe doesn't have to be removed. Just remove the caps and vacuum.
This is my first year of coal burning and REALLY,,, this EFM has made the transition to coal a real cool experience. It heats everything I can find to heat. The oil backup for me isn't an issue. The only reason that it has been shut down is to change some of the piping to a more friendly use.
As much as it's the boiler, the coal plays a big role in the whole coal burnin' thing. My advice would be to read the forum. Especially the older threads, when the real coal burners were the main posters. Good luck on the boiler choice! Have fun! Scott

Hello Coal Guzzler.. all of the boilers you list are good units.. one consideration will be do you need the BTU capacity of the EFM and Ka6 ? They all will do a fine job making domestic hot water..
The amount and freqency of adding coal and removing ash is directly proportional to heat needs.. For example with my Axeman Anderson 260, right now, I'm heating DHW, and burning only aobut 20# a day. This translates to emptying the ash pan about once a week... in the winter with 0* weather, I'm looking at 150-200# a day, and emptying the ashpan every day or two...

None of the boilers you mentioned are very noisey at all..

Anyone of the three will do a very good job.

What is the BTU of your current boiler? and what is your monthly or seasonal use of oil ??

Greg L

Greg L,

My current oil boiler is 105,000 BTU/hr so it would seem that the KA-6 and EFM are overkill. I've questioned the need to go to those sizes myself since the oil burner keeps up just fine. My home is 3400 sq. ft. but it is fairly well insulated. This winter was my first winter in the house. I went through 180 gallons in December, even though it was relatively mild that month (southeast PA) and one of my zones was completely turned off (about 1000 sq. ft). That terrified me so I put in a used Saey coal stove in my fireplace in January. It worked real well but didn't do a good job at heating the bedrooms. Burned about between 1.5- 2 tons for the remainder of the season but still burned some oil (at a greatly reduced rate).

Eventually I will finish the basement and plan to use the boiler to heat that space. Therefore, it makes sense to go a little bigger with the coal boiler.

I'm leaning more toward the Keystoker. This is due to the cost and the option to backup the coal with an oil burner. The EFM is next only due to the cost. The auger feed seems very appealing to me. The AHS has the disadvantage of not having an oil burner option.

I've considered piggy backing the coal boiler to the oil boiler but I only have 1 chimney flue available. I hear that you could use the same flue for the coal and oil boiler but for some reason that doesn't sound right or safe.

Hi CG, there are numerous threads on the forum about the identical subject,, using the existing boiler as a backup and adding a coal boiler in series.. Personally I'd do this. I'd buy the AHS,, it is a very good unit, and sized right for your house.. put it in series with your current oil boiler, and you can wire and set up the aquastats so that you will have seamless uninterupted tranfer from coal to oil heat if you are not home to 'flip the switch' for converting back to oil..

OR, try to find a good used EFM, Keystoker, or Harman stoker boiler.. But used coal appliances are going to be like finding hens teeth this season.. not easy..

Good luck, Greg L

You might look at the AA ( Axeman Anderson) too. Auger feed, less money than the EMF. (but more than a Keystoker) The AA should be more efficient as it has a self cleaning fan feature that forces more heat into the heat exchanger.

Coal Guzzler wrote:Greg L,

My current oil boiler is 105,000 BTU/hr so it would seem that the KA-6 and EFM are overkill. I've questioned the need to go to those sizes myself since the oil burner keeps up just fine. My home is 3400 sq. ft. but it is fairly well insulated. This winter was my first winter in the house. I went through 180 gallons in December, even though it was relatively mild that month (southeast PA) and one of my zones was completely turned off (about 1000 sq. ft). That terrified me so I put in a used Saey coal stove in my fireplace in January. It worked real well but didn't do a good job at heating the bedrooms. Burned about between 1.5- 2 tons for the remainder of the season but still burned some oil (at a greatly reduced rate).

Eventually I will finish the basement and plan to use the boiler to heat that space. Therefore, it makes sense to go a little bigger with the coal boiler.

I'm leaning more toward the Keystoker. This is due to the cost and the option to backup the coal with an oil burner. The EFM is next only due to the cost. The auger feed seems very appealing to me. The AHS has the disadvantage of not having an oil burner option.

I've considered piggy backing the coal boiler to the oil boiler but I only have 1 chimney flue available. I hear that you could use the same flue for the coal and oil boiler but for some reason that doesn't sound right or safe.

A EFM 520 Set at 5 Teeth feed will give what you need to heat your house Remember you can adjust the feed rate for what you house need a 520 can burn at 21.490 BTU's to 214.690 BTU's all you do is change the feed rate & Air rate very
simple look at the link then look at the chart http://www.efmheating.com/manuals/DF520%20Manual.pdf

After reading this forum for the last few months, 1 thing that stands out to me when folks are comparing boilers, is that a lot of people want the EFM but can't justify the cost over the Keystoker or Harman if they don't need the extra BTUs. Yes the EFM can go slower but why pay the extra $3K to go slower? It would be nice if EFM would offer say a model 300, smaller than the old 350, to compete with the Keystokers and Harmons. Instead of selling it for $7500 like the 520 sell it for $6000. Still more than a Keystoker or Harman but I bet it would sell if they could cut the manfacturing costs to get down to that price.

My gut tells me EMF uses the same stoker on all the models. The only difference is the amount of boiler above the fire. The difference in price to make a smaller water section wouldn't be much at all. I'm sure they've crunched the numbers!

Well I am sure they could down size everything if the boiler was smaller.

Downsize everything?

Freddy is correct, the same stoker is used for any sized boiler. Why mess with something that has been bulletproof for 57 years? Add to that, the cost of engineering, casting and machining new parts. Easy to suggest, but not at all profitable for such a small market.

I take the concerns of the people on this forum directly to upper management and the engineers. Whatever changes are being brewed up will use the time-proven S-20 stoker.

The auto market has always been big enough to support all types of models, from the Neon to the Mercedes along with a wide variety of choice.

There's nothing to stop anyone from building the smallest, strongest, cheapest, most efficient coal boiler on Earth. Feel free! I'm sure if anyone builds a boiler that is truly better, yet cheaper, you'd eventually see EMF, Axeman Anderson, AHS, Keystoker go out of business. It hasn't happened to EFM in the last 57 yrs, so I figure they're doing something right.

Of course I am not saying there is something wrong with the EFMs or they are on the verge of going out of business I would just like to have a dollar for every person on this forum that is looking for a boiler, likes the EFM, and then says I bought a KA-6.

Freddy wrote:My gut tells me EMF uses the same stoker on all the models. The only difference is the amount of boiler above the fire. The difference in price to make a smaller water section wouldn't be much at all. I'm sure they've crunched the numbers!

The 350 had a smaller pot the boiler held 30gal of water the water coil was 3.5 gals the fed rate went
from 1 to 6 teeth 2.5 Lbs a hr to 15lbs a hr. this was a S-15 stoker The air was 1 3/4 to 6.5 later These where the early models 350 later ones went to a S-20 stoker like the 520 with a 5 gal water coil The 520 Highboy Made from 1948 to early 1954 held 73 gals of water The water coil was 7gal the feed rate went from 1 to 10 teeth 2.5 lbs a hr. to 25lbs a hr stoker was a S-20 The air went from 1.3/4 to 9.5 The standard 520 held 40 gals of water with a 5 gal water coil they also use the S-20 stoker 14.5" Pot ring They made a S-22 witch was 15.5" and gave you a extra 5000 BTU's The 700 used a S-30 Rotating Pot 7gal water coil max feed was 30lbs of coal per hr. The 900 used a S-35 Rotating Pot max feed was 35lbs of coal a hr. 3.5lbs Per tooth 10 teeth max. feed 7 Gal water coil boiler held 102gals of water The 1300 used a S-45 Roatating Pot 7 Gal water coil Not Sure of water capacity of boiler Here are the Dimensions on the Different models

EFM - 350 Boiler 27 3/4 Tall X 23 5/8 wide X 32 1/2 deep Boiler weight is 575 lbs
Base is 24 1/8 tall x 24 1/8 wide x 32 1/2 deep Base weight is 135 lbs
Stoker weight 214 lbs Jacket weight is 105 lbs Total weight 1029 lbs

EFM 520 Boiler 28 3/8 Tall x 25 1/4 wide x 36 1/2 deep Boiler weight 750 lbs
Base is 24 1/8 tall x 26 1/8 wide x 26 1/8 deep Base Weight 142 lbs
Stoker 214 lbs Jacket weight 109 lbs Total Weight 1215 lbs for older Round door model's 520 with tube heat exchangers
New Sq Door DF 520 are 1250 lbs with Flat heat Exchanger

EFM 700 Boiler 33 " Tall x 29 1/2 wide 42" deep Boiler weight 1100 lbs
Base is 23 1/2 Tall x 29 3/4 wide x 42 3/4 deep Base weight 226 lbs
Stoker 375 lbs Jacket 132lbs

EFM 900 Boiler 38 1/2 " Tall X 30 1/2 Wide x 52" deep Boiler weight 1465 lbs
Base is 23 5/8 tall x 31 1/4 wide x 52 deep Base weight 283 lbs
Stoker 395 lbs Jacket 167 lbs

EFM 1300 Boiler 40 3/8 Tall x 32 wide x 56 1/2 deep Boiler weight 1850 lbs
Base is 25 1/4 tall x 32 wide x 56 1/2 deep Base weight 330 lbs
Stoker 400 lbs Jacket 175 lbs