DF 520 question.

on EFM' s website it says that u can turn the 520 down to 21,470 btuh. and they claim that is 2.5 lb/hr. what i do not understand is if you have13,000 btu in a pound of coal that puts the DF 520 somewhere about 65% efficient.

what am i missing here? is the amount of ash in the coal figured in there somehow? Or is it way more complicated, and one can not easily deduce efficiency based on coal input and btu output?

Coal varies in BTUH depending upon where it is mined. I think it was a very general statement.

EFM does not assume the coal will be perfect, and there are other things to consider like efficiency and a pickup factor. The 2.5 lbs per hour of run time per tooth of feed is correct for rice coal. 13,000 btu's per lb is optimistic...12,000 is more like it. 4 teeth of feed with rice is 10 lbs per hour, allow 80% for the efficiency figure....96,000 btu's/hr.

I have setup three houses in Northern NY with 520's...it is a great boiler that can handle an average home with ease.

What are you looking to heat?

Rob R. wrote:What are you looking to heat?

I am heating a 1400 sqft ranch home. single story with full basement. it was built in 1987 so it is fairly well insulated. I use 54 ft. of fin tube baseboard, and there is a cast iron rad. in the basement that measures about 42" x 30" x 8". the oil boiler is rated at 134,000 btuh and my hand fired coal boiler is rated at 85,000'. they both heat the house fine. Also i look to add 2 rooms to the system that are currently not heated, and eventually my 1 car garage.

Sorry, i did forget to mention that it will also heat my domestic water

Boots wrote:Sorry, i did forget to mention that it will also heat my domestic water

Does that include dual rainforest shower heads and a car wash?

Rob R. wrote:

Boots wrote:Sorry, i did forget to mention that it will also heat my domestic water

Does that include dual rainforest shower heads and a car wash?

afraid not.

Boots, you will hear me say this more that once...and I know Rob and Scott will concur: Do NOT UNDERSIZE the boiler.
I know you will expand demand with a garage, workshop, addition...something that you neighbors can't do unless they replace their boilers.
When it is 20 below and there a 5 people taking showers, that small boiler will be like taking a knife to a gunfight! I would NOT risk it.
I have a dozen 260's running year round and they don't overheat. The basements are dry, warm, and comfortable...not a frigging dungeon like most cellars.
SIZE MATTERS!!!! Only people too small to admit it understand this concept.......

Boots wrote:

Rob R. wrote:What are you looking to heat?

I am heating a 1400 sqft ranch home. single story with full basement. it was built in 1987 so it is fairly well insulated. I use 54 ft. of fin tube baseboard, and there is a cast iron rad. in the basement that measures about 42" x 30" x 8". the oil boiler is rated at 134,000 btuh and my hand fired coal boiler is rated at 85,000'. they both heat the house fine. Also i look to add 2 rooms to the system that are currently not heated, and eventually my 1 car garage.

Ok, so the heat load is low...what kind of domestic hot water usage is expected? One or two people isn't bad, but throw a few kids into the mix and suddenly the coal boiler is working overtime. My personal opinion is that the "little" boilers like the KAA-2 and LL110 are ok for a light heat & DHW load when there are NO plans to add additional loads. Considering that you are already thinking of adding to the heated space, you should get a boiler with some headroom.

Tightly-sized stoker boilers are fine with everything is going right, but not much fun when you get a load of sub-par coal, or someone forgets a window cracked open on a night with a howling wind.

Rob R. wrote:Ok, so the heat load is low...what kind of domestic hot water usage is expected? One or two people isn't bad, but throw a few kids into the mix and suddenly the coal boiler is working overtime. My personal opinion is that the "little" boilers like the KAA-2 and LL110 are ok for a light heat & DHW load when there are NO plans to add additional loads. Considering that you are already thinking of adding to the heated space, you should get a boiler with some headroom.

Tightly-sized stoker boilers are fine with everything is going right, but not much fun when you get a load of sub-par coal, or someone forgets a window cracked open on a night with a howling wind.

I have a family of four. And in about a year my parents will be staying for extended visits every month or so. There will be lots of showers and laundry.